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| author | Wanpeng Li <wanpengli@tencent.com> | 2018-03-12 14:53:02 +0300 |
|---|---|---|
| committer | Paolo Bonzini <pbonzini@redhat.com> | 2018-03-17 00:03:51 +0300 |
| commit | 4d5422cea3b61f158d58924cbb43feada456ba5c (patch) | |
| tree | 0657ac655c54892dd6498d8e20b89380255d592a /Documentation/virtual | |
| parent | 4956aa3b8b59e336b77f1df0ac7ce1a94c0265f2 (diff) | |
| download | linux-4d5422cea3b61f158d58924cbb43feada456ba5c.tar.xz | |
KVM: X86: Provide a capability to disable MWAIT intercepts
Allowing a guest to execute MWAIT without interception enables a guest
to put a (physical) CPU into a power saving state, where it takes
longer to return from than what may be desired by the host.
Don't give a guest that power over a host by default. (Especially,
since nothing prevents a guest from using MWAIT even when it is not
advertised via CPUID.)
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: Jan H. Schönherr <jschoenh@amazon.de>
Signed-off-by: Wanpeng Li <wanpengli@tencent.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'Documentation/virtual')
| -rw-r--r-- | Documentation/virtual/kvm/api.txt | 27 |
1 files changed, 18 insertions, 9 deletions
diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt index 786c1b4ecb59..744a202cca31 100644 --- a/Documentation/virtual/kvm/api.txt +++ b/Documentation/virtual/kvm/api.txt @@ -4358,6 +4358,24 @@ enables QEMU to build error log and branch to guest kernel registered machine check handling routine. Without this capability KVM will branch to guests' 0x200 interrupt vector. +7.13 KVM_CAP_X86_DISABLE_EXITS + +Architectures: x86 +Parameters: args[0] defines which exits are disabled +Returns: 0 on success, -EINVAL when args[0] contains invalid exits + +Valid bits in args[0] are + +#define KVM_X86_DISABLE_EXITS_MWAIT (1 << 0) + +Enabling this capability on a VM provides userspace with a way to no +longer intercept some instructions for improved latency in some +workloads, and is suggested when vCPUs are associated to dedicated +physical CPUs. More bits can be added in the future; userspace can +just pass the KVM_CHECK_EXTENSION result to KVM_ENABLE_CAP to disable +all such vmexits. + + 8. Other capabilities. ---------------------- @@ -4470,15 +4488,6 @@ reserved. Both registers and addresses are 64-bits wide. It will be possible to run 64-bit or 32-bit guest code. -8.8 KVM_CAP_X86_GUEST_MWAIT - -Architectures: x86 - -This capability indicates that guest using memory monotoring instructions -(MWAIT/MWAITX) to stop the virtual CPU will not cause a VM exit. As such time -spent while virtual CPU is halted in this way will then be accounted for as -guest running time on the host (as opposed to e.g. HLT). - 8.9 KVM_CAP_ARM_USER_IRQ Architectures: arm, arm64 |