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author | Guang Zeng <guang.zeng@intel.com> | 2022-01-05 15:35:29 +0300 |
---|---|---|
committer | Paolo Bonzini <pbonzini@redhat.com> | 2022-01-14 21:44:41 +0300 |
commit | be50b2065dfa3d88428fdfdc340d154d96bf6848 (patch) | |
tree | 5432dea5e77167c758a70ba6f0249655c241d4f8 /Documentation/virt/kvm | |
parent | c60427dd50ba9b20063ccaed0e98d62e886d7a3b (diff) | |
download | linux-be50b2065dfa3d88428fdfdc340d154d96bf6848.tar.xz |
kvm: x86: Add support for getting/setting expanded xstate buffer
With KVM_CAP_XSAVE, userspace uses a hardcoded 4KB buffer to get/set
xstate data from/to KVM. This doesn't work when dynamic xfeatures
(e.g. AMX) are exposed to the guest as they require a larger buffer
size.
Introduce a new capability (KVM_CAP_XSAVE2). Userspace VMM gets the
required xstate buffer size via KVM_CHECK_EXTENSION(KVM_CAP_XSAVE2).
KVM_SET_XSAVE is extended to work with both legacy and new capabilities
by doing properly-sized memdup_user() based on the guest fpu container.
KVM_GET_XSAVE is kept for backward-compatible reason. Instead,
KVM_GET_XSAVE2 is introduced under KVM_CAP_XSAVE2 as the preferred
interface for getting xstate buffer (4KB or larger size) from KVM
(Link: https://lkml.org/lkml/2021/12/15/510)
Also, update the api doc with the new KVM_GET_XSAVE2 ioctl.
Signed-off-by: Guang Zeng <guang.zeng@intel.com>
Signed-off-by: Wei Wang <wei.w.wang@intel.com>
Signed-off-by: Jing Liu <jing2.liu@intel.com>
Signed-off-by: Kevin Tian <kevin.tian@intel.com>
Signed-off-by: Yang Zhong <yang.zhong@intel.com>
Message-Id: <20220105123532.12586-19-yang.zhong@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'Documentation/virt/kvm')
-rw-r--r-- | Documentation/virt/kvm/api.rst | 42 |
1 files changed, 40 insertions, 2 deletions
diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst index f4ea5e41a4d0..d3791a14eb9a 100644 --- a/Documentation/virt/kvm/api.rst +++ b/Documentation/virt/kvm/api.rst @@ -1569,6 +1569,7 @@ otherwise it will return EBUSY error. struct kvm_xsave { __u32 region[1024]; + __u32 extra[0]; }; This ioctl would copy current vcpu's xsave struct to the userspace. @@ -1577,7 +1578,7 @@ This ioctl would copy current vcpu's xsave struct to the userspace. 4.43 KVM_SET_XSAVE ------------------ -:Capability: KVM_CAP_XSAVE +:Capability: KVM_CAP_XSAVE and KVM_CAP_XSAVE2 :Architectures: x86 :Type: vcpu ioctl :Parameters: struct kvm_xsave (in) @@ -1588,9 +1589,18 @@ This ioctl would copy current vcpu's xsave struct to the userspace. struct kvm_xsave { __u32 region[1024]; + __u32 extra[0]; }; -This ioctl would copy userspace's xsave struct to the kernel. +This ioctl would copy userspace's xsave struct to the kernel. It copies +as many bytes as are returned by KVM_CHECK_EXTENSION(KVM_CAP_XSAVE2), +when invoked on the vm file descriptor. The size value returned by +KVM_CHECK_EXTENSION(KVM_CAP_XSAVE2) will always be at least 4096. +Currently, it is only greater than 4096 if a dynamic feature has been +enabled with ``arch_prctl()``, but this may change in the future. + +The offsets of the state save areas in struct kvm_xsave follow the +contents of CPUID leaf 0xD on the host. 4.44 KVM_GET_XCRS @@ -5535,6 +5545,34 @@ the trailing ``'\0'``, is indicated by ``name_size`` in the header. The Stats Data block contains an array of 64-bit values in the same order as the descriptors in Descriptors block. +4.42 KVM_GET_XSAVE2 +------------------ + +:Capability: KVM_CAP_XSAVE2 +:Architectures: x86 +:Type: vcpu ioctl +:Parameters: struct kvm_xsave (out) +:Returns: 0 on success, -1 on error + + +:: + + struct kvm_xsave { + __u32 region[1024]; + __u32 extra[0]; + }; + +This ioctl would copy current vcpu's xsave struct to the userspace. It +copies as many bytes as are returned by KVM_CHECK_EXTENSION(KVM_CAP_XSAVE2) +when invoked on the vm file descriptor. The size value returned by +KVM_CHECK_EXTENSION(KVM_CAP_XSAVE2) will always be at least 4096. +Currently, it is only greater than 4096 if a dynamic feature has been +enabled with ``arch_prctl()``, but this may change in the future. + +The offsets of the state save areas in struct kvm_xsave follow the contents +of CPUID leaf 0xD on the host. + + 5. The kvm_run structure ======================== |