| Message ID | 146221113787.32310.7342723782230547207.stgit@bahia.huguette.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Tue, 03 May 2016 06:52:02 +0200 Greg Kurz <gkurz@linux.vnet.ibm.com> wrote: > The KVM_MAX_VCPUS define provides the maximum number of vCPUs per guest, and > also the upper limit for vCPU ids. This is okay for all archs except PowerPC > which can have higher ids, depending on the cpu/core/thread topology. In the > worst case (single threaded guest, host with 8 threads per core), it limits > the maximum number of vCPUS to KVM_MAX_VCPUS / 8. > > This patch separates the vCPU numbering from the total number of vCPUs, with > the introduction of KVM_MAX_VCPU_ID, as the maximal valid value for vCPU ids > plus one. > > The corresponding KVM_CAP_MAX_VCPU_ID allows userspace to validate vCPU ids > before passing them to KVM_CREATE_VCPU. > > Only PowerPC gets unlimited vCPU ids for the moment. This patch doesn't > change anything for other archs. > > Suggested-by: Radim Krcmar <rkrcmar@redhat.com> > Signed-off-by: Greg Kurz <gkurz@linux.vnet.ibm.com> > --- > Documentation/virtual/kvm/api.txt | 10 ++++++++-- > arch/powerpc/include/asm/kvm_host.h | 2 ++ > arch/powerpc/kvm/powerpc.c | 3 +++ > include/linux/kvm_host.h | 4 ++++ > include/uapi/linux/kvm.h | 1 + > virt/kvm/kvm_main.c | 2 +- > 6 files changed, 19 insertions(+), 3 deletions(-) > > diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h > index 23bfe1bd159c..3b4efa1c088c 100644 > --- a/include/linux/kvm_host.h > +++ b/include/linux/kvm_host.h > @@ -35,6 +35,10 @@ > > #include <asm/kvm_host.h> > > +#ifndef KVM_MAX_VCPU_ID > +#define KVM_MAX_VCPU_ID KVM_MAX_VCPUS As you are defining KVM_MAX_VCPU_ID in any case, would it make sense to provide the cap in generic code? power will simply override the value. > +#endif > + > /* > * The bit 16 ~ bit 31 of kvm_memory_region::flags are internally used > * in kvm, other bits are visible for userspace which are defined in -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Tue, 3 May 2016 08:49:12 +0200 Cornelia Huck <cornelia.huck@de.ibm.com> wrote: > On Tue, 03 May 2016 06:52:02 +0200 > Greg Kurz <gkurz@linux.vnet.ibm.com> wrote: > > > The KVM_MAX_VCPUS define provides the maximum number of vCPUs per guest, and > > also the upper limit for vCPU ids. This is okay for all archs except PowerPC > > which can have higher ids, depending on the cpu/core/thread topology. In the > > worst case (single threaded guest, host with 8 threads per core), it limits > > the maximum number of vCPUS to KVM_MAX_VCPUS / 8. > > > > This patch separates the vCPU numbering from the total number of vCPUs, with > > the introduction of KVM_MAX_VCPU_ID, as the maximal valid value for vCPU ids > > plus one. > > > > The corresponding KVM_CAP_MAX_VCPU_ID allows userspace to validate vCPU ids > > before passing them to KVM_CREATE_VCPU. > > > > Only PowerPC gets unlimited vCPU ids for the moment. This patch doesn't > > change anything for other archs. > > > > Suggested-by: Radim Krcmar <rkrcmar@redhat.com> > > Signed-off-by: Greg Kurz <gkurz@linux.vnet.ibm.com> > > --- > > Documentation/virtual/kvm/api.txt | 10 ++++++++-- > > arch/powerpc/include/asm/kvm_host.h | 2 ++ > > arch/powerpc/kvm/powerpc.c | 3 +++ > > include/linux/kvm_host.h | 4 ++++ > > include/uapi/linux/kvm.h | 1 + > > virt/kvm/kvm_main.c | 2 +- > > 6 files changed, 19 insertions(+), 3 deletions(-) > > > > > diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h > > index 23bfe1bd159c..3b4efa1c088c 100644 > > --- a/include/linux/kvm_host.h > > +++ b/include/linux/kvm_host.h > > @@ -35,6 +35,10 @@ > > > > #include <asm/kvm_host.h> > > > > +#ifndef KVM_MAX_VCPU_ID > > +#define KVM_MAX_VCPU_ID KVM_MAX_VCPUS > > As you are defining KVM_MAX_VCPU_ID in any case, would it make sense to > provide the cap in generic code? power will simply override the value. > I'll do that in v6. Thanks ! > > +#endif > > + > > /* > > * The bit 16 ~ bit 31 of kvm_memory_region::flags are internally used > > * in kvm, other bits are visible for userspace which are defined in -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
2016-05-03 06:52+0200, Greg Kurz: > The KVM_MAX_VCPUS define provides the maximum number of vCPUs per guest, and > also the upper limit for vCPU ids. This is okay for all archs except PowerPC > which can have higher ids, depending on the cpu/core/thread topology. In the > worst case (single threaded guest, host with 8 threads per core), it limits > the maximum number of vCPUS to KVM_MAX_VCPUS / 8. > > This patch separates the vCPU numbering from the total number of vCPUs, with > the introduction of KVM_MAX_VCPU_ID, as the maximal valid value for vCPU ids > plus one. > > The corresponding KVM_CAP_MAX_VCPU_ID allows userspace to validate vCPU ids > before passing them to KVM_CREATE_VCPU. > > Only PowerPC gets unlimited vCPU ids for the moment. This patch doesn't > change anything for other archs. > > Suggested-by: Radim Krcmar <rkrcmar@redhat.com> > Signed-off-by: Greg Kurz <gkurz@linux.vnet.ibm.com> > --- > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c > @@ -2272,7 +2272,7 @@ static int kvm_vm_ioctl_create_vcpu(struct kvm *kvm, u32 id) > int r; > struct kvm_vcpu *vcpu; > > - if (id >= KVM_MAX_VCPUS) > + if (id >= KVM_MAX_VCPU_ID) > return -EINVAL; book3s_hv will currently fail with vcpu_id above threads_per_subcore * KVM_MAX_VCORES, so userspace cannot use KVM_CAP_MAX_VCPU_ID to limit vcpu_id ... I thought the check for vcpu_id would move to arch-specific code, like the previous version did, to simplify implementation of a dynamic limit. The dynamic limit was too complicated to be worth it? (This version is ok too.) -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Wed, 4 May 2016 18:45:34 +0200 Radim Kr?má? <rkrcmar@redhat.com> wrote: > 2016-05-03 06:52+0200, Greg Kurz: > > The KVM_MAX_VCPUS define provides the maximum number of vCPUs per guest, and > > also the upper limit for vCPU ids. This is okay for all archs except PowerPC > > which can have higher ids, depending on the cpu/core/thread topology. In the > > worst case (single threaded guest, host with 8 threads per core), it limits > > the maximum number of vCPUS to KVM_MAX_VCPUS / 8. > > > > This patch separates the vCPU numbering from the total number of vCPUs, with > > the introduction of KVM_MAX_VCPU_ID, as the maximal valid value for vCPU ids > > plus one. > > > > The corresponding KVM_CAP_MAX_VCPU_ID allows userspace to validate vCPU ids > > before passing them to KVM_CREATE_VCPU. > > > > Only PowerPC gets unlimited vCPU ids for the moment. This patch doesn't > > change anything for other archs. > > > > Suggested-by: Radim Krcmar <rkrcmar@redhat.com> > > Signed-off-by: Greg Kurz <gkurz@linux.vnet.ibm.com> > > --- > > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c > > @@ -2272,7 +2272,7 @@ static int kvm_vm_ioctl_create_vcpu(struct kvm *kvm, u32 id) > > int r; > > struct kvm_vcpu *vcpu; > > > > - if (id >= KVM_MAX_VCPUS) > > + if (id >= KVM_MAX_VCPU_ID) > > return -EINVAL; > > book3s_hv will currently fail with vcpu_id above threads_per_subcore * > KVM_MAX_VCORES, so userspace cannot use KVM_CAP_MAX_VCPU_ID to limit > vcpu_id ... You're right, I guess powerpc should return threads_per_subcore * KVM_MAX_VCORES instead of INT_MAX then. > I thought the check for vcpu_id would move to arch-specific > code, like the previous version did, to simplify implementation of a > dynamic limit. > > The dynamic limit was too complicated to be worth it? > (This version is ok too.) > Actually no, it can be as simple as this in arch/powerpc/include/asm/kvm_host.h: #include <asm/cputhreads.h> #define KVM_MAX_VCPU_ID (threads_per_subcore * KVM_MAX_VCORES) Thanks ! -- Greg -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt index 4d0542c5206b..2da127f21ffc 100644 --- a/Documentation/virtual/kvm/api.txt +++ b/Documentation/virtual/kvm/api.txt @@ -199,8 +199,8 @@ Type: vm ioctl Parameters: vcpu id (apic id on x86) Returns: vcpu fd on success, -1 on error -This API adds a vcpu to a virtual machine. The vcpu id is a small integer -in the range [0, max_vcpus). +This API adds a vcpu to a virtual machine. No more than max_vcpus may be added. +The vcpu id is an integer in the range [0, max_vcpu_id). The recommended max_vcpus value can be retrieved using the KVM_CAP_NR_VCPUS of the KVM_CHECK_EXTENSION ioctl() at run-time. @@ -212,6 +212,12 @@ cpus max. If the KVM_CAP_MAX_VCPUS does not exist, you should assume that max_vcpus is same as the value returned from KVM_CAP_NR_VCPUS. +The maximum possible value for max_vcpu_id can be retrieved using the +KVM_CAP_MAX_VCPU_ID of the KVM_CHECK_EXTENSION ioctl() at run-time. + +If the KVM_CAP_MAX_VCPU_ID does not exist, you should assume that max_vcpu_id +is the same as the value returned from KVM_CAP_MAX_VCPUS. + On powerpc using book3s_hv mode, the vcpus are mapped onto virtual threads in one or more virtual CPU cores. (This is because the hardware requires all the hardware threads in a CPU core to be in the diff --git a/arch/powerpc/include/asm/kvm_host.h b/arch/powerpc/include/asm/kvm_host.h index d7b343170453..6b4b78d6131b 100644 --- a/arch/powerpc/include/asm/kvm_host.h +++ b/arch/powerpc/include/asm/kvm_host.h @@ -39,6 +39,8 @@ #define KVM_MAX_VCPUS NR_CPUS #define KVM_MAX_VCORES NR_CPUS #define KVM_USER_MEM_SLOTS 512 +#define KVM_MAX_VCPU_ID INT_MAX + #ifdef CONFIG_KVM_MMIO #define KVM_COALESCED_MMIO_PAGE_OFFSET 1 diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c index 6a68730774ee..bef0e6e5e8d0 100644 --- a/arch/powerpc/kvm/powerpc.c +++ b/arch/powerpc/kvm/powerpc.c @@ -580,6 +580,9 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext) case KVM_CAP_MAX_VCPUS: r = KVM_MAX_VCPUS; break; + case KVM_CAP_MAX_VCPU_ID: + r = KVM_MAX_VCPU_ID; + break; #ifdef CONFIG_PPC_BOOK3S_64 case KVM_CAP_PPC_GET_SMMU_INFO: r = 1; diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h index 23bfe1bd159c..3b4efa1c088c 100644 --- a/include/linux/kvm_host.h +++ b/include/linux/kvm_host.h @@ -35,6 +35,10 @@ #include <asm/kvm_host.h> +#ifndef KVM_MAX_VCPU_ID +#define KVM_MAX_VCPU_ID KVM_MAX_VCPUS +#endif + /* * The bit 16 ~ bit 31 of kvm_memory_region::flags are internally used * in kvm, other bits are visible for userspace which are defined in diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h index a7f1f8032ec1..05ebf475104c 100644 --- a/include/uapi/linux/kvm.h +++ b/include/uapi/linux/kvm.h @@ -865,6 +865,7 @@ struct kvm_ppc_smmu_info { #define KVM_CAP_SPAPR_TCE_64 125 #define KVM_CAP_ARM_PMU_V3 126 #define KVM_CAP_VCPU_ATTRIBUTES 127 +#define KVM_CAP_MAX_VCPU_ID 128 #ifdef KVM_CAP_IRQ_ROUTING diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index 4fd482fb9260..210ab88466fd 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -2272,7 +2272,7 @@ static int kvm_vm_ioctl_create_vcpu(struct kvm *kvm, u32 id) int r; struct kvm_vcpu *vcpu; - if (id >= KVM_MAX_VCPUS) + if (id >= KVM_MAX_VCPU_ID) return -EINVAL; vcpu = kvm_arch_vcpu_create(kvm, id);
The KVM_MAX_VCPUS define provides the maximum number of vCPUs per guest, and also the upper limit for vCPU ids. This is okay for all archs except PowerPC which can have higher ids, depending on the cpu/core/thread topology. In the worst case (single threaded guest, host with 8 threads per core), it limits the maximum number of vCPUS to KVM_MAX_VCPUS / 8. This patch separates the vCPU numbering from the total number of vCPUs, with the introduction of KVM_MAX_VCPU_ID, as the maximal valid value for vCPU ids plus one. The corresponding KVM_CAP_MAX_VCPU_ID allows userspace to validate vCPU ids before passing them to KVM_CREATE_VCPU. Only PowerPC gets unlimited vCPU ids for the moment. This patch doesn't change anything for other archs. Suggested-by: Radim Krcmar <rkrcmar@redhat.com> Signed-off-by: Greg Kurz <gkurz@linux.vnet.ibm.com> --- Documentation/virtual/kvm/api.txt | 10 ++++++++-- arch/powerpc/include/asm/kvm_host.h | 2 ++ arch/powerpc/kvm/powerpc.c | 3 +++ include/linux/kvm_host.h | 4 ++++ include/uapi/linux/kvm.h | 1 + virt/kvm/kvm_main.c | 2 +- 6 files changed, 19 insertions(+), 3 deletions(-) -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html