| Message ID | 20210820155918.7518-26-brijesh.singh@amd.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | Add AMD Secure Nested Paging (SEV-SNP) Hypervisor Support | expand |
On Fri, Aug 20, 2021 at 10:00 AM Brijesh Singh <brijesh.singh@amd.com> wrote: > > The KVM_SEV_SNP_LAUNCH_UPDATE command can be used to insert data into the > guest's memory. The data is encrypted with the cryptographic context > created with the KVM_SEV_SNP_LAUNCH_START. > > In addition to the inserting data, it can insert a two special pages > into the guests memory: the secrets page and the CPUID page. > > While terminating the guest, reclaim the guest pages added in the RMP > table. If the reclaim fails, then the page is no longer safe to be > released back to the system and leak them. > > For more information see the SEV-SNP specification. > > Signed-off-by: Brijesh Singh <brijesh.singh@amd.com> > --- > .../virt/kvm/amd-memory-encryption.rst | 29 +++ > arch/x86/kvm/svm/sev.c | 187 ++++++++++++++++++ > include/uapi/linux/kvm.h | 19 ++ > 3 files changed, 235 insertions(+) > > diff --git a/Documentation/virt/kvm/amd-memory-encryption.rst b/Documentation/virt/kvm/amd-memory-encryption.rst > index 937af3447954..ddcd94e9ffed 100644 > --- a/Documentation/virt/kvm/amd-memory-encryption.rst > +++ b/Documentation/virt/kvm/amd-memory-encryption.rst > @@ -478,6 +478,35 @@ Returns: 0 on success, -negative on error > > See the SEV-SNP specification for further detail on the launch input. > > +20. KVM_SNP_LAUNCH_UPDATE > +------------------------- > + > +The KVM_SNP_LAUNCH_UPDATE is used for encrypting a memory region. It also > +calculates a measurement of the memory contents. The measurement is a signature > +of the memory contents that can be sent to the guest owner as an attestation > +that the memory was encrypted correctly by the firmware. > + > +Parameters (in): struct kvm_snp_launch_update > + > +Returns: 0 on success, -negative on error > + > +:: > + > + struct kvm_sev_snp_launch_update { > + __u64 start_gfn; /* Guest page number to start from. */ > + __u64 uaddr; /* userspace address need to be encrypted */ > + __u32 len; /* length of memory region */ > + __u8 imi_page; /* 1 if memory is part of the IMI */ > + __u8 page_type; /* page type */ > + __u8 vmpl3_perms; /* VMPL3 permission mask */ > + __u8 vmpl2_perms; /* VMPL2 permission mask */ > + __u8 vmpl1_perms; /* VMPL1 permission mask */ > + }; > + > +See the SEV-SNP spec for further details on how to build the VMPL permission > +mask and page type. > + > + > References > ========== > > diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c > index dbf04a52b23d..4b126598b7aa 100644 > --- a/arch/x86/kvm/svm/sev.c > +++ b/arch/x86/kvm/svm/sev.c > @@ -17,6 +17,7 @@ > #include <linux/misc_cgroup.h> > #include <linux/processor.h> > #include <linux/trace_events.h> > +#include <linux/sev.h> > #include <asm/fpu/internal.h> > > #include <asm/pkru.h> > @@ -227,6 +228,49 @@ static void sev_decommission(unsigned int handle) > sev_guest_decommission(&decommission, NULL); > } > > +static inline void snp_leak_pages(u64 pfn, enum pg_level level) > +{ > + unsigned int npages = page_level_size(level) >> PAGE_SHIFT; > + > + WARN(1, "psc failed pfn 0x%llx pages %d (leaking)\n", pfn, npages); > + > + while (npages) { > + memory_failure(pfn, 0); > + dump_rmpentry(pfn); > + npages--; > + pfn++; > + } > +} > + > +static int snp_page_reclaim(u64 pfn) > +{ > + struct sev_data_snp_page_reclaim data = {0}; > + int err, rc; > + > + data.paddr = __sme_set(pfn << PAGE_SHIFT); > + rc = snp_guest_page_reclaim(&data, &err); > + if (rc) { > + /* > + * If the reclaim failed, then page is no longer safe > + * to use. > + */ > + snp_leak_pages(pfn, PG_LEVEL_4K); > + } > + > + return rc; > +} > + > +static int host_rmp_make_shared(u64 pfn, enum pg_level level, bool leak) > +{ > + int rc; > + > + rc = rmp_make_shared(pfn, level); > + if (rc && leak) > + snp_leak_pages(pfn, level); > + > + return rc; > +} > + > static void sev_unbind_asid(struct kvm *kvm, unsigned int handle) > { > struct sev_data_deactivate deactivate; > @@ -1620,6 +1664,123 @@ static int snp_launch_start(struct kvm *kvm, struct kvm_sev_cmd *argp) > return rc; > } > > +static bool is_hva_registered(struct kvm *kvm, hva_t hva, size_t len) > +{ > + struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info; > + struct list_head *head = &sev->regions_list; > + struct enc_region *i; > + > + lockdep_assert_held(&kvm->lock); > + > + list_for_each_entry(i, head, list) { > + u64 start = i->uaddr; > + u64 end = start + i->size; > + > + if (start <= hva && end >= (hva + len)) > + return true; > + } > + > + return false; > +} Internally we actually register the guest memory in chunks for various reasons. So for our largest SEV VM we have 768 1 GB entries in |sev->regions_list|. This was OK before because no look ups were done. Now that we are performing a look ups a linked list with linear time lookups seems not ideal, could we switch the back data structure here to something more conducive too fast lookups? > + > +static int snp_launch_update(struct kvm *kvm, struct kvm_sev_cmd *argp) > +{ > + struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info; > + struct sev_data_snp_launch_update data = {0}; > + struct kvm_sev_snp_launch_update params; > + unsigned long npages, pfn, n = 0; Could we have a slightly more descriptive name for |n|? nprivate maybe? Also why not zero in the loop below? for (i = 0, n = 0; i < npages; ++i) > + int *error = &argp->error; > + struct page **inpages; > + int ret, i, level; Should |i| be an unsigned long since it can is tracked in a for loop with "i < npages" npages being an unsigned long? (|n| too) > + u64 gfn; > + > + if (!sev_snp_guest(kvm)) > + return -ENOTTY; > + > + if (!sev->snp_context) > + return -EINVAL; > + > + if (copy_from_user(¶ms, (void __user *)(uintptr_t)argp->data, sizeof(params))) > + return -EFAULT; > + > + /* Verify that the specified address range is registered. */ > + if (!is_hva_registered(kvm, params.uaddr, params.len)) > + return -EINVAL; > + > + /* > + * The userspace memory is already locked so technically we don't > + * need to lock it again. Later part of the function needs to know > + * pfn so call the sev_pin_memory() so that we can get the list of > + * pages to iterate through. > + */ > + inpages = sev_pin_memory(kvm, params.uaddr, params.len, &npages, 1); > + if (!inpages) > + return -ENOMEM; > + > + /* > + * Verify that all the pages are marked shared in the RMP table before > + * going further. This is avoid the cases where the userspace may try This is *too* avoid cases... > + * updating the same page twice. > + */ > + for (i = 0; i < npages; i++) { > + if (snp_lookup_rmpentry(page_to_pfn(inpages[i]), &level) != 0) { > + sev_unpin_memory(kvm, inpages, npages); > + return -EFAULT; > + } > + } > + > + gfn = params.start_gfn; > + level = PG_LEVEL_4K; > + data.gctx_paddr = __psp_pa(sev->snp_context); > + > + for (i = 0; i < npages; i++) { > + pfn = page_to_pfn(inpages[i]); > + > + ret = rmp_make_private(pfn, gfn << PAGE_SHIFT, level, sev_get_asid(kvm), true); > + if (ret) { > + ret = -EFAULT; > + goto e_unpin; > + } > + > + n++; > + data.address = __sme_page_pa(inpages[i]); > + data.page_size = X86_TO_RMP_PG_LEVEL(level); > + data.page_type = params.page_type; > + data.vmpl3_perms = params.vmpl3_perms; > + data.vmpl2_perms = params.vmpl2_perms; > + data.vmpl1_perms = params.vmpl1_perms; > + ret = __sev_issue_cmd(argp->sev_fd, SEV_CMD_SNP_LAUNCH_UPDATE, &data, error); > + if (ret) { > + /* > + * If the command failed then need to reclaim the page. > + */ > + snp_page_reclaim(pfn); > + goto e_unpin; > + } Hmm if this call fails after the first iteration of this loop it will lead to a hard to reproduce LaunchDigest right? Say if we are SnpLaunchUpdating just 2 pages A and B. If we first call this ioctl and A is SNP_LAUNCH_UPDATED'd but B fails, we then make A shared again in the RMP. So we must call the ioctl with 2 pages again, after fixing the issue with page B. Now the Launch digest has something like Hash(A) then HASH(A & B) right (overly simplified) so A will be included twice right? I am not sure if anything better can be done here but might be worth documenting IIUC. > + > + gfn++; > + } > + > +e_unpin: > + /* Content of memory is updated, mark pages dirty */ > + for (i = 0; i < n; i++) { > + set_page_dirty_lock(inpages[i]); > + mark_page_accessed(inpages[i]); > + > + /* > + * If its an error, then update RMP entry to change page ownership > + * to the hypervisor. > + */ > + if (ret) > + host_rmp_make_shared(pfn, level, true); > + } > + > + /* Unlock the user pages */ > + sev_unpin_memory(kvm, inpages, npages); > + > + return ret; > +} > + > int svm_mem_enc_op(struct kvm *kvm, void __user *argp) > { > struct kvm_sev_cmd sev_cmd; > @@ -1712,6 +1873,9 @@ int svm_mem_enc_op(struct kvm *kvm, void __user *argp) > case KVM_SEV_SNP_LAUNCH_START: > r = snp_launch_start(kvm, &sev_cmd); > break; > + case KVM_SEV_SNP_LAUNCH_UPDATE: > + r = snp_launch_update(kvm, &sev_cmd); > + break; > default: > r = -EINVAL; > goto out; > @@ -1794,6 +1958,29 @@ find_enc_region(struct kvm *kvm, struct kvm_enc_region *range) > static void __unregister_enc_region_locked(struct kvm *kvm, > struct enc_region *region) > { > + unsigned long i, pfn; > + int level; > + > + /* > + * The guest memory pages are assigned in the RMP table. Unassign it > + * before releasing the memory. > + */ > + if (sev_snp_guest(kvm)) { > + for (i = 0; i < region->npages; i++) { > + pfn = page_to_pfn(region->pages[i]); > + > + if (!snp_lookup_rmpentry(pfn, &level)) > + continue; > + > + cond_resched(); > + > + if (level > PG_LEVEL_4K) > + pfn &= ~(KVM_PAGES_PER_HPAGE(PG_LEVEL_2M) - 1); > + > + host_rmp_make_shared(pfn, level, true); > + } > + } > + > sev_unpin_memory(kvm, region->pages, region->npages); > list_del(®ion->list); > kfree(region); > diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h > index e6416e58cd9a..0681be4bdfdf 100644 > --- a/include/uapi/linux/kvm.h > +++ b/include/uapi/linux/kvm.h > @@ -1715,6 +1715,7 @@ enum sev_cmd_id { > /* SNP specific commands */ > KVM_SEV_SNP_INIT, > KVM_SEV_SNP_LAUNCH_START, > + KVM_SEV_SNP_LAUNCH_UPDATE, > > KVM_SEV_NR_MAX, > }; > @@ -1831,6 +1832,24 @@ struct kvm_sev_snp_launch_start { > __u8 pad[6]; > }; > > +#define KVM_SEV_SNP_PAGE_TYPE_NORMAL 0x1 > +#define KVM_SEV_SNP_PAGE_TYPE_VMSA 0x2 > +#define KVM_SEV_SNP_PAGE_TYPE_ZERO 0x3 > +#define KVM_SEV_SNP_PAGE_TYPE_UNMEASURED 0x4 > +#define KVM_SEV_SNP_PAGE_TYPE_SECRETS 0x5 > +#define KVM_SEV_SNP_PAGE_TYPE_CPUID 0x6 > + > +struct kvm_sev_snp_launch_update { > + __u64 start_gfn; > + __u64 uaddr; > + __u32 len; > + __u8 imi_page; > + __u8 page_type; > + __u8 vmpl3_perms; > + __u8 vmpl2_perms; > + __u8 vmpl1_perms; > +}; > + > #define KVM_DEV_ASSIGN_ENABLE_IOMMU (1 << 0) > #define KVM_DEV_ASSIGN_PCI_2_3 (1 << 1) > #define KVM_DEV_ASSIGN_MASK_INTX (1 << 2) > -- > 2.17.1 > >
On 9/27/21 11:43 AM, Peter Gonda wrote: ... >> >> +static bool is_hva_registered(struct kvm *kvm, hva_t hva, size_t len) >> +{ >> + struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info; >> + struct list_head *head = &sev->regions_list; >> + struct enc_region *i; >> + >> + lockdep_assert_held(&kvm->lock); >> + >> + list_for_each_entry(i, head, list) { >> + u64 start = i->uaddr; >> + u64 end = start + i->size; >> + >> + if (start <= hva && end >= (hva + len)) >> + return true; >> + } >> + >> + return false; >> +} > > Internally we actually register the guest memory in chunks for various > reasons. So for our largest SEV VM we have 768 1 GB entries in > |sev->regions_list|. This was OK before because no look ups were done. > Now that we are performing a look ups a linked list with linear time > lookups seems not ideal, could we switch the back data structure here > to something more conducive too fast lookups? >> + Interesting, for qemu we had very few number of regions so there was no strong reason for me to think something otherwise. Do you have any preference on what data structure you will use ? >> +static int snp_launch_update(struct kvm *kvm, struct kvm_sev_cmd *argp) >> +{ >> + struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info; >> + struct sev_data_snp_launch_update data = {0}; >> + struct kvm_sev_snp_launch_update params; >> + unsigned long npages, pfn, n = 0; > > Could we have a slightly more descriptive name for |n|? nprivate > maybe? Also why not zero in the loop below? > Sure, I will pick a better name and no need to zero above. I will fix it. > for (i = 0, n = 0; i < npages; ++i) > >> + int *error = &argp->error; >> + struct page **inpages; >> + int ret, i, level; > > Should |i| be an unsigned long since it can is tracked in a for loop > with "i < npages" npages being an unsigned long? (|n| too) > Noted. >> + u64 gfn; >> + >> + if (!sev_snp_guest(kvm)) >> + return -ENOTTY; >> + >> + if (!sev->snp_context) >> + return -EINVAL; >> + >> + if (copy_from_user(¶ms, (void __user *)(uintptr_t)argp->data, sizeof(params))) >> + return -EFAULT; >> + >> + /* Verify that the specified address range is registered. */ >> + if (!is_hva_registered(kvm, params.uaddr, params.len)) >> + return -EINVAL; >> + >> + /* >> + * The userspace memory is already locked so technically we don't >> + * need to lock it again. Later part of the function needs to know >> + * pfn so call the sev_pin_memory() so that we can get the list of >> + * pages to iterate through. >> + */ >> + inpages = sev_pin_memory(kvm, params.uaddr, params.len, &npages, 1); >> + if (!inpages) >> + return -ENOMEM; >> + >> + /* >> + * Verify that all the pages are marked shared in the RMP table before >> + * going further. This is avoid the cases where the userspace may try > > This is *too* avoid cases... > Noted >> + * updating the same page twice. >> + */ >> + for (i = 0; i < npages; i++) { >> + if (snp_lookup_rmpentry(page_to_pfn(inpages[i]), &level) != 0) { >> + sev_unpin_memory(kvm, inpages, npages); >> + return -EFAULT; >> + } >> + } >> + >> + gfn = params.start_gfn; >> + level = PG_LEVEL_4K; >> + data.gctx_paddr = __psp_pa(sev->snp_context); >> + >> + for (i = 0; i < npages; i++) { >> + pfn = page_to_pfn(inpages[i]); >> + >> + ret = rmp_make_private(pfn, gfn << PAGE_SHIFT, level, sev_get_asid(kvm), true); >> + if (ret) { >> + ret = -EFAULT; >> + goto e_unpin; >> + } >> + >> + n++; >> + data.address = __sme_page_pa(inpages[i]); >> + data.page_size = X86_TO_RMP_PG_LEVEL(level); >> + data.page_type = params.page_type; >> + data.vmpl3_perms = params.vmpl3_perms; >> + data.vmpl2_perms = params.vmpl2_perms; >> + data.vmpl1_perms = params.vmpl1_perms; >> + ret = __sev_issue_cmd(argp->sev_fd, SEV_CMD_SNP_LAUNCH_UPDATE, &data, error); >> + if (ret) { >> + /* >> + * If the command failed then need to reclaim the page. >> + */ >> + snp_page_reclaim(pfn); >> + goto e_unpin; >> + } > > Hmm if this call fails after the first iteration of this loop it will > lead to a hard to reproduce LaunchDigest right? Say if we are > SnpLaunchUpdating just 2 pages A and B. If we first call this ioctl > and A is SNP_LAUNCH_UPDATED'd but B fails, we then make A shared again > in the RMP. So we must call the ioctl with 2 pages again, after fixing > the issue with page B. Now the Launch digest has something like > Hash(A) then HASH(A & B) right (overly simplified) so A will be > included twice right? I am not sure if anything better can be done > here but might be worth documenting IIUC. > I can add a comment in documentation that if a LAUNCH_UPDATE fails then user need to destroy the existing context and start from the beginning. I am not sure if we want to support the partial update cases. But in case we have two choices a) decommission the context on failure or b) add a new command to destroy the existing context. >> + >> + gfn++; >> + } >> + >> +e_unpin: >> + /* Content of memory is updated, mark pages dirty */ >> + for (i = 0; i < n; i++) { >> + set_page_dirty_lock(inpages[i]); >> + mark_page_accessed(inpages[i]); >> + >> + /* >> + * If its an error, then update RMP entry to change page ownership >> + * to the hypervisor. >> + */ >> + if (ret) >> + host_rmp_make_shared(pfn, level, true); >> + } >> + >> + /* Unlock the user pages */ >> + sev_unpin_memory(kvm, inpages, npages); >> + >> + return ret; >> +} >> + >> int svm_mem_enc_op(struct kvm *kvm, void __user *argp) >> { >> struct kvm_sev_cmd sev_cmd; >> @@ -1712,6 +1873,9 @@ int svm_mem_enc_op(struct kvm *kvm, void __user *argp) >> case KVM_SEV_SNP_LAUNCH_START: >> r = snp_launch_start(kvm, &sev_cmd); >> break; >> + case KVM_SEV_SNP_LAUNCH_UPDATE: >> + r = snp_launch_update(kvm, &sev_cmd); >> + break; >> default: >> r = -EINVAL; >> goto out; >> @@ -1794,6 +1958,29 @@ find_enc_region(struct kvm *kvm, struct kvm_enc_region *range) >> static void __unregister_enc_region_locked(struct kvm *kvm, >> struct enc_region *region) >> { >> + unsigned long i, pfn; >> + int level; >> + >> + /* >> + * The guest memory pages are assigned in the RMP table. Unassign it >> + * before releasing the memory. >> + */ >> + if (sev_snp_guest(kvm)) { >> + for (i = 0; i < region->npages; i++) { >> + pfn = page_to_pfn(region->pages[i]); >> + >> + if (!snp_lookup_rmpentry(pfn, &level)) >> + continue; >> + >> + cond_resched(); >> + >> + if (level > PG_LEVEL_4K) >> + pfn &= ~(KVM_PAGES_PER_HPAGE(PG_LEVEL_2M) - 1); >> + >> + host_rmp_make_shared(pfn, level, true); >> + } >> + } >> + >> sev_unpin_memory(kvm, region->pages, region->npages); >> list_del(®ion->list); >> kfree(region); >> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h >> index e6416e58cd9a..0681be4bdfdf 100644 >> --- a/include/uapi/linux/kvm.h >> +++ b/include/uapi/linux/kvm.h >> @@ -1715,6 +1715,7 @@ enum sev_cmd_id { >> /* SNP specific commands */ >> KVM_SEV_SNP_INIT, >> KVM_SEV_SNP_LAUNCH_START, >> + KVM_SEV_SNP_LAUNCH_UPDATE, >> >> KVM_SEV_NR_MAX, >> }; >> @@ -1831,6 +1832,24 @@ struct kvm_sev_snp_launch_start { >> __u8 pad[6]; >> }; >> >> +#define KVM_SEV_SNP_PAGE_TYPE_NORMAL 0x1 >> +#define KVM_SEV_SNP_PAGE_TYPE_VMSA 0x2 >> +#define KVM_SEV_SNP_PAGE_TYPE_ZERO 0x3 >> +#define KVM_SEV_SNP_PAGE_TYPE_UNMEASURED 0x4 >> +#define KVM_SEV_SNP_PAGE_TYPE_SECRETS 0x5 >> +#define KVM_SEV_SNP_PAGE_TYPE_CPUID 0x6 >> + >> +struct kvm_sev_snp_launch_update { >> + __u64 start_gfn; >> + __u64 uaddr; >> + __u32 len; >> + __u8 imi_page; >> + __u8 page_type; >> + __u8 vmpl3_perms; >> + __u8 vmpl2_perms; >> + __u8 vmpl1_perms; >> +}; >> + >> #define KVM_DEV_ASSIGN_ENABLE_IOMMU (1 << 0) >> #define KVM_DEV_ASSIGN_PCI_2_3 (1 << 1) >> #define KVM_DEV_ASSIGN_MASK_INTX (1 << 2) >> -- >> 2.17.1 >> >>
On Mon, Sep 27, 2021 at 1:33 PM Brijesh Singh <brijesh.singh@amd.com> wrote: > > > > On 9/27/21 11:43 AM, Peter Gonda wrote: > ... > >> > >> +static bool is_hva_registered(struct kvm *kvm, hva_t hva, size_t len) > >> +{ > >> + struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info; > >> + struct list_head *head = &sev->regions_list; > >> + struct enc_region *i; > >> + > >> + lockdep_assert_held(&kvm->lock); > >> + > >> + list_for_each_entry(i, head, list) { > >> + u64 start = i->uaddr; > >> + u64 end = start + i->size; > >> + > >> + if (start <= hva && end >= (hva + len)) > >> + return true; > >> + } > >> + > >> + return false; > >> +} > > > > Internally we actually register the guest memory in chunks for various > > reasons. So for our largest SEV VM we have 768 1 GB entries in > > |sev->regions_list|. This was OK before because no look ups were done. > > Now that we are performing a look ups a linked list with linear time > > lookups seems not ideal, could we switch the back data structure here > > to something more conducive too fast lookups? > >> + > > Interesting, for qemu we had very few number of regions so there was no > strong reason for me to think something otherwise. Do you have any > preference on what data structure you will use ? Chatted offline. I think this is fine for now, we won't want to use our userspace demand pinning with SNP yet. > > >> +static int snp_launch_update(struct kvm *kvm, struct kvm_sev_cmd *argp) > >> +{ > >> + struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info; > >> + struct sev_data_snp_launch_update data = {0}; > >> + struct kvm_sev_snp_launch_update params; > >> + unsigned long npages, pfn, n = 0; > > > > Could we have a slightly more descriptive name for |n|? nprivate > > maybe? Also why not zero in the loop below? > > > > Sure, I will pick a better name and no need to zero above. I will fix it. > > > for (i = 0, n = 0; i < npages; ++i) > > > >> + int *error = &argp->error; > >> + struct page **inpages; > >> + int ret, i, level; > > > > Should |i| be an unsigned long since it can is tracked in a for loop > > with "i < npages" npages being an unsigned long? (|n| too) > > > > Noted. > > >> + u64 gfn; > >> + > >> + if (!sev_snp_guest(kvm)) > >> + return -ENOTTY; > >> + > >> + if (!sev->snp_context) > >> + return -EINVAL; > >> + > >> + if (copy_from_user(¶ms, (void __user *)(uintptr_t)argp->data, sizeof(params))) > >> + return -EFAULT; > >> + > >> + /* Verify that the specified address range is registered. */ > >> + if (!is_hva_registered(kvm, params.uaddr, params.len)) > >> + return -EINVAL; > >> + > >> + /* > >> + * The userspace memory is already locked so technically we don't > >> + * need to lock it again. Later part of the function needs to know > >> + * pfn so call the sev_pin_memory() so that we can get the list of > >> + * pages to iterate through. > >> + */ > >> + inpages = sev_pin_memory(kvm, params.uaddr, params.len, &npages, 1); > >> + if (!inpages) > >> + return -ENOMEM; > >> + > >> + /* > >> + * Verify that all the pages are marked shared in the RMP table before > >> + * going further. This is avoid the cases where the userspace may try > > > > This is *too* avoid cases... > > > Noted > > >> + * updating the same page twice. > >> + */ > >> + for (i = 0; i < npages; i++) { > >> + if (snp_lookup_rmpentry(page_to_pfn(inpages[i]), &level) != 0) { > >> + sev_unpin_memory(kvm, inpages, npages); > >> + return -EFAULT; > >> + } > >> + } > >> + > >> + gfn = params.start_gfn; > >> + level = PG_LEVEL_4K; > >> + data.gctx_paddr = __psp_pa(sev->snp_context); > >> + > >> + for (i = 0; i < npages; i++) { > >> + pfn = page_to_pfn(inpages[i]); > >> + > >> + ret = rmp_make_private(pfn, gfn << PAGE_SHIFT, level, sev_get_asid(kvm), true); > >> + if (ret) { > >> + ret = -EFAULT; > >> + goto e_unpin; > >> + } > >> + > >> + n++; > >> + data.address = __sme_page_pa(inpages[i]); > >> + data.page_size = X86_TO_RMP_PG_LEVEL(level); > >> + data.page_type = params.page_type; > >> + data.vmpl3_perms = params.vmpl3_perms; > >> + data.vmpl2_perms = params.vmpl2_perms; > >> + data.vmpl1_perms = params.vmpl1_perms; > >> + ret = __sev_issue_cmd(argp->sev_fd, SEV_CMD_SNP_LAUNCH_UPDATE, &data, error); > >> + if (ret) { > >> + /* > >> + * If the command failed then need to reclaim the page. > >> + */ > >> + snp_page_reclaim(pfn); > >> + goto e_unpin; > >> + } > > > > Hmm if this call fails after the first iteration of this loop it will > > lead to a hard to reproduce LaunchDigest right? Say if we are > > SnpLaunchUpdating just 2 pages A and B. If we first call this ioctl > > and A is SNP_LAUNCH_UPDATED'd but B fails, we then make A shared again > > in the RMP. So we must call the ioctl with 2 pages again, after fixing > > the issue with page B. Now the Launch digest has something like > > Hash(A) then HASH(A & B) right (overly simplified) so A will be > > included twice right? I am not sure if anything better can be done > > here but might be worth documenting IIUC. > > > > I can add a comment in documentation that if a LAUNCH_UPDATE fails then > user need to destroy the existing context and start from the beginning. > I am not sure if we want to support the partial update cases. But in > case we have two choices a) decommission the context on failure or b) > add a new command to destroy the existing context. > Agreed supporting the partial update case seems very tricky. > > >> + > >> + gfn++; > >> + } > >> + > >> +e_unpin: > >> + /* Content of memory is updated, mark pages dirty */ > >> + for (i = 0; i < n; i++) { > >> + set_page_dirty_lock(inpages[i]); > >> + mark_page_accessed(inpages[i]); > >> + > >> + /* > >> + * If its an error, then update RMP entry to change page ownership > >> + * to the hypervisor. > >> + */ > >> + if (ret) > >> + host_rmp_make_shared(pfn, level, true); > >> + } > >> + > >> + /* Unlock the user pages */ > >> + sev_unpin_memory(kvm, inpages, npages); > >> + > >> + return ret; > >> +} > >> + > >> int svm_mem_enc_op(struct kvm *kvm, void __user *argp) > >> { > >> struct kvm_sev_cmd sev_cmd; > >> @@ -1712,6 +1873,9 @@ int svm_mem_enc_op(struct kvm *kvm, void __user *argp) > >> case KVM_SEV_SNP_LAUNCH_START: > >> r = snp_launch_start(kvm, &sev_cmd); > >> break; > >> + case KVM_SEV_SNP_LAUNCH_UPDATE: > >> + r = snp_launch_update(kvm, &sev_cmd); > >> + break; > >> default: > >> r = -EINVAL; > >> goto out; > >> @@ -1794,6 +1958,29 @@ find_enc_region(struct kvm *kvm, struct kvm_enc_region *range) > >> static void __unregister_enc_region_locked(struct kvm *kvm, > >> struct enc_region *region) > >> { > >> + unsigned long i, pfn; > >> + int level; > >> + > >> + /* > >> + * The guest memory pages are assigned in the RMP table. Unassign it > >> + * before releasing the memory. > >> + */ > >> + if (sev_snp_guest(kvm)) { > >> + for (i = 0; i < region->npages; i++) { > >> + pfn = page_to_pfn(region->pages[i]); > >> + > >> + if (!snp_lookup_rmpentry(pfn, &level)) > >> + continue; > >> + > >> + cond_resched(); > >> + > >> + if (level > PG_LEVEL_4K) > >> + pfn &= ~(KVM_PAGES_PER_HPAGE(PG_LEVEL_2M) - 1); > >> + > >> + host_rmp_make_shared(pfn, level, true); > >> + } > >> + } > >> + > >> sev_unpin_memory(kvm, region->pages, region->npages); > >> list_del(®ion->list); > >> kfree(region); > >> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h > >> index e6416e58cd9a..0681be4bdfdf 100644 > >> --- a/include/uapi/linux/kvm.h > >> +++ b/include/uapi/linux/kvm.h > >> @@ -1715,6 +1715,7 @@ enum sev_cmd_id { > >> /* SNP specific commands */ > >> KVM_SEV_SNP_INIT, > >> KVM_SEV_SNP_LAUNCH_START, > >> + KVM_SEV_SNP_LAUNCH_UPDATE, > >> > >> KVM_SEV_NR_MAX, > >> }; > >> @@ -1831,6 +1832,24 @@ struct kvm_sev_snp_launch_start { > >> __u8 pad[6]; > >> }; > >> > >> +#define KVM_SEV_SNP_PAGE_TYPE_NORMAL 0x1 > >> +#define KVM_SEV_SNP_PAGE_TYPE_VMSA 0x2 > >> +#define KVM_SEV_SNP_PAGE_TYPE_ZERO 0x3 > >> +#define KVM_SEV_SNP_PAGE_TYPE_UNMEASURED 0x4 > >> +#define KVM_SEV_SNP_PAGE_TYPE_SECRETS 0x5 > >> +#define KVM_SEV_SNP_PAGE_TYPE_CPUID 0x6 > >> + > >> +struct kvm_sev_snp_launch_update { > >> + __u64 start_gfn; > >> + __u64 uaddr; > >> + __u32 len; > >> + __u8 imi_page; > >> + __u8 page_type; > >> + __u8 vmpl3_perms; > >> + __u8 vmpl2_perms; > >> + __u8 vmpl1_perms; > >> +}; > >> + > >> #define KVM_DEV_ASSIGN_ENABLE_IOMMU (1 << 0) > >> #define KVM_DEV_ASSIGN_PCI_2_3 (1 << 1) > >> #define KVM_DEV_ASSIGN_MASK_INTX (1 << 2) > >> -- > >> 2.17.1 > >> > >>
diff --git a/Documentation/virt/kvm/amd-memory-encryption.rst b/Documentation/virt/kvm/amd-memory-encryption.rst index 937af3447954..ddcd94e9ffed 100644 --- a/Documentation/virt/kvm/amd-memory-encryption.rst +++ b/Documentation/virt/kvm/amd-memory-encryption.rst @@ -478,6 +478,35 @@ Returns: 0 on success, -negative on error See the SEV-SNP specification for further detail on the launch input. +20. KVM_SNP_LAUNCH_UPDATE +------------------------- + +The KVM_SNP_LAUNCH_UPDATE is used for encrypting a memory region. It also +calculates a measurement of the memory contents. The measurement is a signature +of the memory contents that can be sent to the guest owner as an attestation +that the memory was encrypted correctly by the firmware. + +Parameters (in): struct kvm_snp_launch_update + +Returns: 0 on success, -negative on error + +:: + + struct kvm_sev_snp_launch_update { + __u64 start_gfn; /* Guest page number to start from. */ + __u64 uaddr; /* userspace address need to be encrypted */ + __u32 len; /* length of memory region */ + __u8 imi_page; /* 1 if memory is part of the IMI */ + __u8 page_type; /* page type */ + __u8 vmpl3_perms; /* VMPL3 permission mask */ + __u8 vmpl2_perms; /* VMPL2 permission mask */ + __u8 vmpl1_perms; /* VMPL1 permission mask */ + }; + +See the SEV-SNP spec for further details on how to build the VMPL permission +mask and page type. + + References ========== diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c index dbf04a52b23d..4b126598b7aa 100644 --- a/arch/x86/kvm/svm/sev.c +++ b/arch/x86/kvm/svm/sev.c @@ -17,6 +17,7 @@ #include <linux/misc_cgroup.h> #include <linux/processor.h> #include <linux/trace_events.h> +#include <linux/sev.h> #include <asm/fpu/internal.h> #include <asm/pkru.h> @@ -227,6 +228,49 @@ static void sev_decommission(unsigned int handle) sev_guest_decommission(&decommission, NULL); } +static inline void snp_leak_pages(u64 pfn, enum pg_level level) +{ + unsigned int npages = page_level_size(level) >> PAGE_SHIFT; + + WARN(1, "psc failed pfn 0x%llx pages %d (leaking)\n", pfn, npages); + + while (npages) { + memory_failure(pfn, 0); + dump_rmpentry(pfn); + npages--; + pfn++; + } +} + +static int snp_page_reclaim(u64 pfn) +{ + struct sev_data_snp_page_reclaim data = {0}; + int err, rc; + + data.paddr = __sme_set(pfn << PAGE_SHIFT); + rc = snp_guest_page_reclaim(&data, &err); + if (rc) { + /* + * If the reclaim failed, then page is no longer safe + * to use. + */ + snp_leak_pages(pfn, PG_LEVEL_4K); + } + + return rc; +} + +static int host_rmp_make_shared(u64 pfn, enum pg_level level, bool leak) +{ + int rc; + + rc = rmp_make_shared(pfn, level); + if (rc && leak) + snp_leak_pages(pfn, level); + + return rc; +} + static void sev_unbind_asid(struct kvm *kvm, unsigned int handle) { struct sev_data_deactivate deactivate; @@ -1620,6 +1664,123 @@ static int snp_launch_start(struct kvm *kvm, struct kvm_sev_cmd *argp) return rc; } +static bool is_hva_registered(struct kvm *kvm, hva_t hva, size_t len) +{ + struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info; + struct list_head *head = &sev->regions_list; + struct enc_region *i; + + lockdep_assert_held(&kvm->lock); + + list_for_each_entry(i, head, list) { + u64 start = i->uaddr; + u64 end = start + i->size; + + if (start <= hva && end >= (hva + len)) + return true; + } + + return false; +} + +static int snp_launch_update(struct kvm *kvm, struct kvm_sev_cmd *argp) +{ + struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info; + struct sev_data_snp_launch_update data = {0}; + struct kvm_sev_snp_launch_update params; + unsigned long npages, pfn, n = 0; + int *error = &argp->error; + struct page **inpages; + int ret, i, level; + u64 gfn; + + if (!sev_snp_guest(kvm)) + return -ENOTTY; + + if (!sev->snp_context) + return -EINVAL; + + if (copy_from_user(¶ms, (void __user *)(uintptr_t)argp->data, sizeof(params))) + return -EFAULT; + + /* Verify that the specified address range is registered. */ + if (!is_hva_registered(kvm, params.uaddr, params.len)) + return -EINVAL; + + /* + * The userspace memory is already locked so technically we don't + * need to lock it again. Later part of the function needs to know + * pfn so call the sev_pin_memory() so that we can get the list of + * pages to iterate through. + */ + inpages = sev_pin_memory(kvm, params.uaddr, params.len, &npages, 1); + if (!inpages) + return -ENOMEM; + + /* + * Verify that all the pages are marked shared in the RMP table before + * going further. This is avoid the cases where the userspace may try + * updating the same page twice. + */ + for (i = 0; i < npages; i++) { + if (snp_lookup_rmpentry(page_to_pfn(inpages[i]), &level) != 0) { + sev_unpin_memory(kvm, inpages, npages); + return -EFAULT; + } + } + + gfn = params.start_gfn; + level = PG_LEVEL_4K; + data.gctx_paddr = __psp_pa(sev->snp_context); + + for (i = 0; i < npages; i++) { + pfn = page_to_pfn(inpages[i]); + + ret = rmp_make_private(pfn, gfn << PAGE_SHIFT, level, sev_get_asid(kvm), true); + if (ret) { + ret = -EFAULT; + goto e_unpin; + } + + n++; + data.address = __sme_page_pa(inpages[i]); + data.page_size = X86_TO_RMP_PG_LEVEL(level); + data.page_type = params.page_type; + data.vmpl3_perms = params.vmpl3_perms; + data.vmpl2_perms = params.vmpl2_perms; + data.vmpl1_perms = params.vmpl1_perms; + ret = __sev_issue_cmd(argp->sev_fd, SEV_CMD_SNP_LAUNCH_UPDATE, &data, error); + if (ret) { + /* + * If the command failed then need to reclaim the page. + */ + snp_page_reclaim(pfn); + goto e_unpin; + } + + gfn++; + } + +e_unpin: + /* Content of memory is updated, mark pages dirty */ + for (i = 0; i < n; i++) { + set_page_dirty_lock(inpages[i]); + mark_page_accessed(inpages[i]); + + /* + * If its an error, then update RMP entry to change page ownership + * to the hypervisor. + */ + if (ret) + host_rmp_make_shared(pfn, level, true); + } + + /* Unlock the user pages */ + sev_unpin_memory(kvm, inpages, npages); + + return ret; +} + int svm_mem_enc_op(struct kvm *kvm, void __user *argp) { struct kvm_sev_cmd sev_cmd; @@ -1712,6 +1873,9 @@ int svm_mem_enc_op(struct kvm *kvm, void __user *argp) case KVM_SEV_SNP_LAUNCH_START: r = snp_launch_start(kvm, &sev_cmd); break; + case KVM_SEV_SNP_LAUNCH_UPDATE: + r = snp_launch_update(kvm, &sev_cmd); + break; default: r = -EINVAL; goto out; @@ -1794,6 +1958,29 @@ find_enc_region(struct kvm *kvm, struct kvm_enc_region *range) static void __unregister_enc_region_locked(struct kvm *kvm, struct enc_region *region) { + unsigned long i, pfn; + int level; + + /* + * The guest memory pages are assigned in the RMP table. Unassign it + * before releasing the memory. + */ + if (sev_snp_guest(kvm)) { + for (i = 0; i < region->npages; i++) { + pfn = page_to_pfn(region->pages[i]); + + if (!snp_lookup_rmpentry(pfn, &level)) + continue; + + cond_resched(); + + if (level > PG_LEVEL_4K) + pfn &= ~(KVM_PAGES_PER_HPAGE(PG_LEVEL_2M) - 1); + + host_rmp_make_shared(pfn, level, true); + } + } + sev_unpin_memory(kvm, region->pages, region->npages); list_del(®ion->list); kfree(region); diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h index e6416e58cd9a..0681be4bdfdf 100644 --- a/include/uapi/linux/kvm.h +++ b/include/uapi/linux/kvm.h @@ -1715,6 +1715,7 @@ enum sev_cmd_id { /* SNP specific commands */ KVM_SEV_SNP_INIT, KVM_SEV_SNP_LAUNCH_START, + KVM_SEV_SNP_LAUNCH_UPDATE, KVM_SEV_NR_MAX, }; @@ -1831,6 +1832,24 @@ struct kvm_sev_snp_launch_start { __u8 pad[6]; }; +#define KVM_SEV_SNP_PAGE_TYPE_NORMAL 0x1 +#define KVM_SEV_SNP_PAGE_TYPE_VMSA 0x2 +#define KVM_SEV_SNP_PAGE_TYPE_ZERO 0x3 +#define KVM_SEV_SNP_PAGE_TYPE_UNMEASURED 0x4 +#define KVM_SEV_SNP_PAGE_TYPE_SECRETS 0x5 +#define KVM_SEV_SNP_PAGE_TYPE_CPUID 0x6 + +struct kvm_sev_snp_launch_update { + __u64 start_gfn; + __u64 uaddr; + __u32 len; + __u8 imi_page; + __u8 page_type; + __u8 vmpl3_perms; + __u8 vmpl2_perms; + __u8 vmpl1_perms; +}; + #define KVM_DEV_ASSIGN_ENABLE_IOMMU (1 << 0) #define KVM_DEV_ASSIGN_PCI_2_3 (1 << 1) #define KVM_DEV_ASSIGN_MASK_INTX (1 << 2)
The KVM_SEV_SNP_LAUNCH_UPDATE command can be used to insert data into the guest's memory. The data is encrypted with the cryptographic context created with the KVM_SEV_SNP_LAUNCH_START. In addition to the inserting data, it can insert a two special pages into the guests memory: the secrets page and the CPUID page. While terminating the guest, reclaim the guest pages added in the RMP table. If the reclaim fails, then the page is no longer safe to be released back to the system and leak them. For more information see the SEV-SNP specification. Signed-off-by: Brijesh Singh <brijesh.singh@amd.com> --- .../virt/kvm/amd-memory-encryption.rst | 29 +++ arch/x86/kvm/svm/sev.c | 187 ++++++++++++++++++ include/uapi/linux/kvm.h | 19 ++ 3 files changed, 235 insertions(+)