| Message ID | 20241216175803.2716565-5-qperret@google.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | KVM: arm64: Non-protected guest stage-2 support for pKVM | expand |
On Mon, 16 Dec 2024 at 17:58, Quentin Perret <qperret@google.com> wrote: > > We currently store part of the page-tracking state in PTE software bits > for the host, guests and the hypervisor. This is sub-optimal when e.g. > sharing pages as this forces to break block mappings purely to support > this software tracking. This causes an unnecessarily fragmented stage-2 > page-table for the host in particular when it shares pages with Secure, > which can lead to measurable regressions. Moreover, having this state > stored in the page-table forces us to do multiple costly walks on the > page transition path, hence causing overhead. > > In order to work around these problems, move the host-side page-tracking > logic from SW bits in its stage-2 PTEs to the hypervisor's vmemmap. > > Signed-off-by: Quentin Perret <qperret@google.com> Reviewed-by: Fuad Tabba <tabba@google.com> Cheers, /fuad > --- > arch/arm64/kvm/hyp/include/nvhe/memory.h | 6 +- > arch/arm64/kvm/hyp/nvhe/mem_protect.c | 100 ++++++++++++++++------- > arch/arm64/kvm/hyp/nvhe/setup.c | 7 +- > 3 files changed, 77 insertions(+), 36 deletions(-) > > diff --git a/arch/arm64/kvm/hyp/include/nvhe/memory.h b/arch/arm64/kvm/hyp/include/nvhe/memory.h > index 45b8d1840aa4..8bd9a539f260 100644 > --- a/arch/arm64/kvm/hyp/include/nvhe/memory.h > +++ b/arch/arm64/kvm/hyp/include/nvhe/memory.h > @@ -8,7 +8,7 @@ > #include <linux/types.h> > > /* > - * SW bits 0-1 are reserved to track the memory ownership state of each page: > + * Bits 0-1 are reserved to track the memory ownership state of each page: > * 00: The page is owned exclusively by the page-table owner. > * 01: The page is owned by the page-table owner, but is shared > * with another entity. > @@ -43,7 +43,9 @@ static inline enum pkvm_page_state pkvm_getstate(enum kvm_pgtable_prot prot) > struct hyp_page { > u16 refcount; > u8 order; > - u8 reserved; > + > + /* Host (non-meta) state. Guarded by the host stage-2 lock. */ > + enum pkvm_page_state host_state : 8; > }; > > extern u64 __hyp_vmemmap; > diff --git a/arch/arm64/kvm/hyp/nvhe/mem_protect.c b/arch/arm64/kvm/hyp/nvhe/mem_protect.c > index caba3e4bd09e..12bb5445fe47 100644 > --- a/arch/arm64/kvm/hyp/nvhe/mem_protect.c > +++ b/arch/arm64/kvm/hyp/nvhe/mem_protect.c > @@ -201,8 +201,8 @@ static void *guest_s2_zalloc_page(void *mc) > > memset(addr, 0, PAGE_SIZE); > p = hyp_virt_to_page(addr); > - memset(p, 0, sizeof(*p)); > p->refcount = 1; > + p->order = 0; > > return addr; > } > @@ -268,6 +268,7 @@ int kvm_guest_prepare_stage2(struct pkvm_hyp_vm *vm, void *pgd) > > void reclaim_guest_pages(struct pkvm_hyp_vm *vm, struct kvm_hyp_memcache *mc) > { > + struct hyp_page *page; > void *addr; > > /* Dump all pgtable pages in the hyp_pool */ > @@ -279,7 +280,9 @@ void reclaim_guest_pages(struct pkvm_hyp_vm *vm, struct kvm_hyp_memcache *mc) > /* Drain the hyp_pool into the memcache */ > addr = hyp_alloc_pages(&vm->pool, 0); > while (addr) { > - memset(hyp_virt_to_page(addr), 0, sizeof(struct hyp_page)); > + page = hyp_virt_to_page(addr); > + page->refcount = 0; > + page->order = 0; > push_hyp_memcache(mc, addr, hyp_virt_to_phys); > WARN_ON(__pkvm_hyp_donate_host(hyp_virt_to_pfn(addr), 1)); > addr = hyp_alloc_pages(&vm->pool, 0); > @@ -382,19 +385,28 @@ bool addr_is_memory(phys_addr_t phys) > return !!find_mem_range(phys, &range); > } > > -static bool addr_is_allowed_memory(phys_addr_t phys) > +static bool is_in_mem_range(u64 addr, struct kvm_mem_range *range) > +{ > + return range->start <= addr && addr < range->end; > +} > + > +static int check_range_allowed_memory(u64 start, u64 end) > { > struct memblock_region *reg; > struct kvm_mem_range range; > > - reg = find_mem_range(phys, &range); > + /* > + * Callers can't check the state of a range that overlaps memory and > + * MMIO regions, so ensure [start, end[ is in the same kvm_mem_range. > + */ > + reg = find_mem_range(start, &range); > + if (!is_in_mem_range(end - 1, &range)) > + return -EINVAL; > > - return reg && !(reg->flags & MEMBLOCK_NOMAP); > -} > + if (!reg || reg->flags & MEMBLOCK_NOMAP) > + return -EPERM; > > -static bool is_in_mem_range(u64 addr, struct kvm_mem_range *range) > -{ > - return range->start <= addr && addr < range->end; > + return 0; > } > > static bool range_is_memory(u64 start, u64 end) > @@ -454,8 +466,10 @@ static int host_stage2_adjust_range(u64 addr, struct kvm_mem_range *range) > if (kvm_pte_valid(pte)) > return -EAGAIN; > > - if (pte) > + if (pte) { > + WARN_ON(addr_is_memory(addr) && hyp_phys_to_page(addr)->host_state != PKVM_NOPAGE); > return -EPERM; > + } > > do { > u64 granule = kvm_granule_size(level); > @@ -477,10 +491,33 @@ int host_stage2_idmap_locked(phys_addr_t addr, u64 size, > return host_stage2_try(__host_stage2_idmap, addr, addr + size, prot); > } > > +static void __host_update_page_state(phys_addr_t addr, u64 size, enum pkvm_page_state state) > +{ > + phys_addr_t end = addr + size; > + > + for (; addr < end; addr += PAGE_SIZE) > + hyp_phys_to_page(addr)->host_state = state; > +} > + > int host_stage2_set_owner_locked(phys_addr_t addr, u64 size, u8 owner_id) > { > - return host_stage2_try(kvm_pgtable_stage2_set_owner, &host_mmu.pgt, > - addr, size, &host_s2_pool, owner_id); > + int ret; > + > + if (!addr_is_memory(addr)) > + return -EPERM; > + > + ret = host_stage2_try(kvm_pgtable_stage2_set_owner, &host_mmu.pgt, > + addr, size, &host_s2_pool, owner_id); > + if (ret) > + return ret; > + > + /* Don't forget to update the vmemmap tracking for the host */ > + if (owner_id == PKVM_ID_HOST) > + __host_update_page_state(addr, size, PKVM_PAGE_OWNED); > + else > + __host_update_page_state(addr, size, PKVM_NOPAGE); > + > + return 0; > } > > static bool host_stage2_force_pte_cb(u64 addr, u64 end, enum kvm_pgtable_prot prot) > @@ -604,35 +641,38 @@ static int check_page_state_range(struct kvm_pgtable *pgt, u64 addr, u64 size, > return kvm_pgtable_walk(pgt, addr, size, &walker); > } > > -static enum pkvm_page_state host_get_page_state(kvm_pte_t pte, u64 addr) > -{ > - if (!addr_is_allowed_memory(addr)) > - return PKVM_NOPAGE; > - > - if (!kvm_pte_valid(pte) && pte) > - return PKVM_NOPAGE; > - > - return pkvm_getstate(kvm_pgtable_stage2_pte_prot(pte)); > -} > - > static int __host_check_page_state_range(u64 addr, u64 size, > enum pkvm_page_state state) > { > - struct check_walk_data d = { > - .desired = state, > - .get_page_state = host_get_page_state, > - }; > + u64 end = addr + size; > + int ret; > + > + ret = check_range_allowed_memory(addr, end); > + if (ret) > + return ret; > > hyp_assert_lock_held(&host_mmu.lock); > - return check_page_state_range(&host_mmu.pgt, addr, size, &d); > + for (; addr < end; addr += PAGE_SIZE) { > + if (hyp_phys_to_page(addr)->host_state != state) > + return -EPERM; > + } > + > + return 0; > } > > static int __host_set_page_state_range(u64 addr, u64 size, > enum pkvm_page_state state) > { > - enum kvm_pgtable_prot prot = pkvm_mkstate(PKVM_HOST_MEM_PROT, state); > + if (hyp_phys_to_page(addr)->host_state == PKVM_NOPAGE) { > + int ret = host_stage2_idmap_locked(addr, size, PKVM_HOST_MEM_PROT); > > - return host_stage2_idmap_locked(addr, size, prot); > + if (ret) > + return ret; > + } > + > + __host_update_page_state(addr, size, state); > + > + return 0; > } > > static int host_request_owned_transition(u64 *completer_addr, > diff --git a/arch/arm64/kvm/hyp/nvhe/setup.c b/arch/arm64/kvm/hyp/nvhe/setup.c > index cbdd18cd3f98..7e04d1c2a03d 100644 > --- a/arch/arm64/kvm/hyp/nvhe/setup.c > +++ b/arch/arm64/kvm/hyp/nvhe/setup.c > @@ -180,7 +180,6 @@ static void hpool_put_page(void *addr) > static int fix_host_ownership_walker(const struct kvm_pgtable_visit_ctx *ctx, > enum kvm_pgtable_walk_flags visit) > { > - enum kvm_pgtable_prot prot; > enum pkvm_page_state state; > phys_addr_t phys; > > @@ -203,16 +202,16 @@ static int fix_host_ownership_walker(const struct kvm_pgtable_visit_ctx *ctx, > case PKVM_PAGE_OWNED: > return host_stage2_set_owner_locked(phys, PAGE_SIZE, PKVM_ID_HYP); > case PKVM_PAGE_SHARED_OWNED: > - prot = pkvm_mkstate(PKVM_HOST_MEM_PROT, PKVM_PAGE_SHARED_BORROWED); > + hyp_phys_to_page(phys)->host_state = PKVM_PAGE_SHARED_BORROWED; > break; > case PKVM_PAGE_SHARED_BORROWED: > - prot = pkvm_mkstate(PKVM_HOST_MEM_PROT, PKVM_PAGE_SHARED_OWNED); > + hyp_phys_to_page(phys)->host_state = PKVM_PAGE_SHARED_OWNED; > break; > default: > return -EINVAL; > } > > - return host_stage2_idmap_locked(phys, PAGE_SIZE, prot); > + return 0; > } > > static int fix_hyp_pgtable_refcnt_walker(const struct kvm_pgtable_visit_ctx *ctx, > -- > 2.47.1.613.gc27f4b7a9f-goog >
On Mon, 16 Dec 2024 17:57:49 +0000, Quentin Perret <qperret@google.com> wrote: > > We currently store part of the page-tracking state in PTE software bits > for the host, guests and the hypervisor. This is sub-optimal when e.g. > sharing pages as this forces to break block mappings purely to support > this software tracking. This causes an unnecessarily fragmented stage-2 > page-table for the host in particular when it shares pages with Secure, > which can lead to measurable regressions. Moreover, having this state > stored in the page-table forces us to do multiple costly walks on the > page transition path, hence causing overhead. > > In order to work around these problems, move the host-side page-tracking > logic from SW bits in its stage-2 PTEs to the hypervisor's vmemmap. > > Signed-off-by: Quentin Perret <qperret@google.com> > --- > arch/arm64/kvm/hyp/include/nvhe/memory.h | 6 +- > arch/arm64/kvm/hyp/nvhe/mem_protect.c | 100 ++++++++++++++++------- > arch/arm64/kvm/hyp/nvhe/setup.c | 7 +- > 3 files changed, 77 insertions(+), 36 deletions(-) > > diff --git a/arch/arm64/kvm/hyp/include/nvhe/memory.h b/arch/arm64/kvm/hyp/include/nvhe/memory.h > index 45b8d1840aa4..8bd9a539f260 100644 > --- a/arch/arm64/kvm/hyp/include/nvhe/memory.h > +++ b/arch/arm64/kvm/hyp/include/nvhe/memory.h > @@ -8,7 +8,7 @@ > #include <linux/types.h> > > /* > - * SW bits 0-1 are reserved to track the memory ownership state of each page: > + * Bits 0-1 are reserved to track the memory ownership state of each page: > * 00: The page is owned exclusively by the page-table owner. > * 01: The page is owned by the page-table owner, but is shared > * with another entity. > @@ -43,7 +43,9 @@ static inline enum pkvm_page_state pkvm_getstate(enum kvm_pgtable_prot prot) > struct hyp_page { > u16 refcount; > u8 order; > - u8 reserved; > + > + /* Host (non-meta) state. Guarded by the host stage-2 lock. */ > + enum pkvm_page_state host_state : 8; An enum as a bitfield? Crazy! :) You probably want an assert somewhere that ensures that hyp_page is a 32bit quantity, just to make sure (and avoid hard to track bugs). Thanks, M.
On Tuesday 17 Dec 2024 at 11:03:08 (+0000), Marc Zyngier wrote: > On Mon, 16 Dec 2024 17:57:49 +0000, > Quentin Perret <qperret@google.com> wrote: > > > > We currently store part of the page-tracking state in PTE software bits > > for the host, guests and the hypervisor. This is sub-optimal when e.g. > > sharing pages as this forces to break block mappings purely to support > > this software tracking. This causes an unnecessarily fragmented stage-2 > > page-table for the host in particular when it shares pages with Secure, > > which can lead to measurable regressions. Moreover, having this state > > stored in the page-table forces us to do multiple costly walks on the > > page transition path, hence causing overhead. > > > > In order to work around these problems, move the host-side page-tracking > > logic from SW bits in its stage-2 PTEs to the hypervisor's vmemmap. > > > > Signed-off-by: Quentin Perret <qperret@google.com> > > --- > > arch/arm64/kvm/hyp/include/nvhe/memory.h | 6 +- > > arch/arm64/kvm/hyp/nvhe/mem_protect.c | 100 ++++++++++++++++------- > > arch/arm64/kvm/hyp/nvhe/setup.c | 7 +- > > 3 files changed, 77 insertions(+), 36 deletions(-) > > > > diff --git a/arch/arm64/kvm/hyp/include/nvhe/memory.h b/arch/arm64/kvm/hyp/include/nvhe/memory.h > > index 45b8d1840aa4..8bd9a539f260 100644 > > --- a/arch/arm64/kvm/hyp/include/nvhe/memory.h > > +++ b/arch/arm64/kvm/hyp/include/nvhe/memory.h > > @@ -8,7 +8,7 @@ > > #include <linux/types.h> > > > > /* > > - * SW bits 0-1 are reserved to track the memory ownership state of each page: > > + * Bits 0-1 are reserved to track the memory ownership state of each page: > > * 00: The page is owned exclusively by the page-table owner. > > * 01: The page is owned by the page-table owner, but is shared > > * with another entity. > > @@ -43,7 +43,9 @@ static inline enum pkvm_page_state pkvm_getstate(enum kvm_pgtable_prot prot) > > struct hyp_page { > > u16 refcount; > > u8 order; > > - u8 reserved; > > + > > + /* Host (non-meta) state. Guarded by the host stage-2 lock. */ > > + enum pkvm_page_state host_state : 8; > > An enum as a bitfield? Crazy! :) Hehe, it works so why not :) > You probably want an assert somewhere that ensures that hyp_page is a > 32bit quantity, just to make sure (and avoid hard to track bugs). Sounds like a good idea, I'll stick a BUILD_BUG_ON() somewhere.
diff --git a/arch/arm64/kvm/hyp/include/nvhe/memory.h b/arch/arm64/kvm/hyp/include/nvhe/memory.h index 45b8d1840aa4..8bd9a539f260 100644 --- a/arch/arm64/kvm/hyp/include/nvhe/memory.h +++ b/arch/arm64/kvm/hyp/include/nvhe/memory.h @@ -8,7 +8,7 @@ #include <linux/types.h> /* - * SW bits 0-1 are reserved to track the memory ownership state of each page: + * Bits 0-1 are reserved to track the memory ownership state of each page: * 00: The page is owned exclusively by the page-table owner. * 01: The page is owned by the page-table owner, but is shared * with another entity. @@ -43,7 +43,9 @@ static inline enum pkvm_page_state pkvm_getstate(enum kvm_pgtable_prot prot) struct hyp_page { u16 refcount; u8 order; - u8 reserved; + + /* Host (non-meta) state. Guarded by the host stage-2 lock. */ + enum pkvm_page_state host_state : 8; }; extern u64 __hyp_vmemmap; diff --git a/arch/arm64/kvm/hyp/nvhe/mem_protect.c b/arch/arm64/kvm/hyp/nvhe/mem_protect.c index caba3e4bd09e..12bb5445fe47 100644 --- a/arch/arm64/kvm/hyp/nvhe/mem_protect.c +++ b/arch/arm64/kvm/hyp/nvhe/mem_protect.c @@ -201,8 +201,8 @@ static void *guest_s2_zalloc_page(void *mc) memset(addr, 0, PAGE_SIZE); p = hyp_virt_to_page(addr); - memset(p, 0, sizeof(*p)); p->refcount = 1; + p->order = 0; return addr; } @@ -268,6 +268,7 @@ int kvm_guest_prepare_stage2(struct pkvm_hyp_vm *vm, void *pgd) void reclaim_guest_pages(struct pkvm_hyp_vm *vm, struct kvm_hyp_memcache *mc) { + struct hyp_page *page; void *addr; /* Dump all pgtable pages in the hyp_pool */ @@ -279,7 +280,9 @@ void reclaim_guest_pages(struct pkvm_hyp_vm *vm, struct kvm_hyp_memcache *mc) /* Drain the hyp_pool into the memcache */ addr = hyp_alloc_pages(&vm->pool, 0); while (addr) { - memset(hyp_virt_to_page(addr), 0, sizeof(struct hyp_page)); + page = hyp_virt_to_page(addr); + page->refcount = 0; + page->order = 0; push_hyp_memcache(mc, addr, hyp_virt_to_phys); WARN_ON(__pkvm_hyp_donate_host(hyp_virt_to_pfn(addr), 1)); addr = hyp_alloc_pages(&vm->pool, 0); @@ -382,19 +385,28 @@ bool addr_is_memory(phys_addr_t phys) return !!find_mem_range(phys, &range); } -static bool addr_is_allowed_memory(phys_addr_t phys) +static bool is_in_mem_range(u64 addr, struct kvm_mem_range *range) +{ + return range->start <= addr && addr < range->end; +} + +static int check_range_allowed_memory(u64 start, u64 end) { struct memblock_region *reg; struct kvm_mem_range range; - reg = find_mem_range(phys, &range); + /* + * Callers can't check the state of a range that overlaps memory and + * MMIO regions, so ensure [start, end[ is in the same kvm_mem_range. + */ + reg = find_mem_range(start, &range); + if (!is_in_mem_range(end - 1, &range)) + return -EINVAL; - return reg && !(reg->flags & MEMBLOCK_NOMAP); -} + if (!reg || reg->flags & MEMBLOCK_NOMAP) + return -EPERM; -static bool is_in_mem_range(u64 addr, struct kvm_mem_range *range) -{ - return range->start <= addr && addr < range->end; + return 0; } static bool range_is_memory(u64 start, u64 end) @@ -454,8 +466,10 @@ static int host_stage2_adjust_range(u64 addr, struct kvm_mem_range *range) if (kvm_pte_valid(pte)) return -EAGAIN; - if (pte) + if (pte) { + WARN_ON(addr_is_memory(addr) && hyp_phys_to_page(addr)->host_state != PKVM_NOPAGE); return -EPERM; + } do { u64 granule = kvm_granule_size(level); @@ -477,10 +491,33 @@ int host_stage2_idmap_locked(phys_addr_t addr, u64 size, return host_stage2_try(__host_stage2_idmap, addr, addr + size, prot); } +static void __host_update_page_state(phys_addr_t addr, u64 size, enum pkvm_page_state state) +{ + phys_addr_t end = addr + size; + + for (; addr < end; addr += PAGE_SIZE) + hyp_phys_to_page(addr)->host_state = state; +} + int host_stage2_set_owner_locked(phys_addr_t addr, u64 size, u8 owner_id) { - return host_stage2_try(kvm_pgtable_stage2_set_owner, &host_mmu.pgt, - addr, size, &host_s2_pool, owner_id); + int ret; + + if (!addr_is_memory(addr)) + return -EPERM; + + ret = host_stage2_try(kvm_pgtable_stage2_set_owner, &host_mmu.pgt, + addr, size, &host_s2_pool, owner_id); + if (ret) + return ret; + + /* Don't forget to update the vmemmap tracking for the host */ + if (owner_id == PKVM_ID_HOST) + __host_update_page_state(addr, size, PKVM_PAGE_OWNED); + else + __host_update_page_state(addr, size, PKVM_NOPAGE); + + return 0; } static bool host_stage2_force_pte_cb(u64 addr, u64 end, enum kvm_pgtable_prot prot) @@ -604,35 +641,38 @@ static int check_page_state_range(struct kvm_pgtable *pgt, u64 addr, u64 size, return kvm_pgtable_walk(pgt, addr, size, &walker); } -static enum pkvm_page_state host_get_page_state(kvm_pte_t pte, u64 addr) -{ - if (!addr_is_allowed_memory(addr)) - return PKVM_NOPAGE; - - if (!kvm_pte_valid(pte) && pte) - return PKVM_NOPAGE; - - return pkvm_getstate(kvm_pgtable_stage2_pte_prot(pte)); -} - static int __host_check_page_state_range(u64 addr, u64 size, enum pkvm_page_state state) { - struct check_walk_data d = { - .desired = state, - .get_page_state = host_get_page_state, - }; + u64 end = addr + size; + int ret; + + ret = check_range_allowed_memory(addr, end); + if (ret) + return ret; hyp_assert_lock_held(&host_mmu.lock); - return check_page_state_range(&host_mmu.pgt, addr, size, &d); + for (; addr < end; addr += PAGE_SIZE) { + if (hyp_phys_to_page(addr)->host_state != state) + return -EPERM; + } + + return 0; } static int __host_set_page_state_range(u64 addr, u64 size, enum pkvm_page_state state) { - enum kvm_pgtable_prot prot = pkvm_mkstate(PKVM_HOST_MEM_PROT, state); + if (hyp_phys_to_page(addr)->host_state == PKVM_NOPAGE) { + int ret = host_stage2_idmap_locked(addr, size, PKVM_HOST_MEM_PROT); - return host_stage2_idmap_locked(addr, size, prot); + if (ret) + return ret; + } + + __host_update_page_state(addr, size, state); + + return 0; } static int host_request_owned_transition(u64 *completer_addr, diff --git a/arch/arm64/kvm/hyp/nvhe/setup.c b/arch/arm64/kvm/hyp/nvhe/setup.c index cbdd18cd3f98..7e04d1c2a03d 100644 --- a/arch/arm64/kvm/hyp/nvhe/setup.c +++ b/arch/arm64/kvm/hyp/nvhe/setup.c @@ -180,7 +180,6 @@ static void hpool_put_page(void *addr) static int fix_host_ownership_walker(const struct kvm_pgtable_visit_ctx *ctx, enum kvm_pgtable_walk_flags visit) { - enum kvm_pgtable_prot prot; enum pkvm_page_state state; phys_addr_t phys; @@ -203,16 +202,16 @@ static int fix_host_ownership_walker(const struct kvm_pgtable_visit_ctx *ctx, case PKVM_PAGE_OWNED: return host_stage2_set_owner_locked(phys, PAGE_SIZE, PKVM_ID_HYP); case PKVM_PAGE_SHARED_OWNED: - prot = pkvm_mkstate(PKVM_HOST_MEM_PROT, PKVM_PAGE_SHARED_BORROWED); + hyp_phys_to_page(phys)->host_state = PKVM_PAGE_SHARED_BORROWED; break; case PKVM_PAGE_SHARED_BORROWED: - prot = pkvm_mkstate(PKVM_HOST_MEM_PROT, PKVM_PAGE_SHARED_OWNED); + hyp_phys_to_page(phys)->host_state = PKVM_PAGE_SHARED_OWNED; break; default: return -EINVAL; } - return host_stage2_idmap_locked(phys, PAGE_SIZE, prot); + return 0; } static int fix_hyp_pgtable_refcnt_walker(const struct kvm_pgtable_visit_ctx *ctx,
We currently store part of the page-tracking state in PTE software bits for the host, guests and the hypervisor. This is sub-optimal when e.g. sharing pages as this forces to break block mappings purely to support this software tracking. This causes an unnecessarily fragmented stage-2 page-table for the host in particular when it shares pages with Secure, which can lead to measurable regressions. Moreover, having this state stored in the page-table forces us to do multiple costly walks on the page transition path, hence causing overhead. In order to work around these problems, move the host-side page-tracking logic from SW bits in its stage-2 PTEs to the hypervisor's vmemmap. Signed-off-by: Quentin Perret <qperret@google.com> --- arch/arm64/kvm/hyp/include/nvhe/memory.h | 6 +- arch/arm64/kvm/hyp/nvhe/mem_protect.c | 100 ++++++++++++++++------- arch/arm64/kvm/hyp/nvhe/setup.c | 7 +- 3 files changed, 77 insertions(+), 36 deletions(-)