From 32b72ecc83b651fb8633ac4bd44957c54367699d Mon Sep 17 00:00:00 2001 From: Wanpeng Li Date: Tue, 11 Jun 2019 20:23:50 +0800 Subject: KVM: X86: Expose PV_SCHED_YIELD CPUID feature bit to guest MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Expose PV_SCHED_YIELD feature bit to guest, the guest can check this feature bit before using paravirtualized sched yield. Cc: Paolo Bonzini Cc: Radim Krčmář Cc: Liran Alon Signed-off-by: Wanpeng Li Signed-off-by: Paolo Bonzini --- Documentation/virtual/kvm/cpuid.txt | 4 ++++ 1 file changed, 4 insertions(+) (limited to 'Documentation/virtual/kvm/cpuid.txt') diff --git a/Documentation/virtual/kvm/cpuid.txt b/Documentation/virtual/kvm/cpuid.txt index 97ca1940a0dc..979a77ba5377 100644 --- a/Documentation/virtual/kvm/cpuid.txt +++ b/Documentation/virtual/kvm/cpuid.txt @@ -66,6 +66,10 @@ KVM_FEATURE_PV_SEND_IPI || 11 || guest checks this feature bit || || before using paravirtualized || || send IPIs. ------------------------------------------------------------------------------ +KVM_FEATURE_PV_SCHED_YIELD || 13 || guest checks this feature bit + || || before using paravirtualized + || || sched yield. +------------------------------------------------------------------------------ KVM_FEATURE_CLOCKSOURCE_STABLE_BIT || 24 || host will warn if no guest-side || || per-cpu warps are expected in || || kvmclock. -- cgit v1.2.3 From 9824c83f92bc8351dfb5c387436cc2816616fb4a Mon Sep 17 00:00:00 2001 From: Paolo Bonzini Date: Tue, 2 Jul 2019 18:57:29 +0200 Subject: Documentation: kvm: document CPUID bit for MSR_KVM_POLL_CONTROL Cc: Marcelo Tosatti Signed-off-by: Paolo Bonzini --- Documentation/virtual/kvm/cpuid.txt | 4 ++++ 1 file changed, 4 insertions(+) (limited to 'Documentation/virtual/kvm/cpuid.txt') diff --git a/Documentation/virtual/kvm/cpuid.txt b/Documentation/virtual/kvm/cpuid.txt index 979a77ba5377..2bdac528e4a2 100644 --- a/Documentation/virtual/kvm/cpuid.txt +++ b/Documentation/virtual/kvm/cpuid.txt @@ -66,6 +66,10 @@ KVM_FEATURE_PV_SEND_IPI || 11 || guest checks this feature bit || || before using paravirtualized || || send IPIs. ------------------------------------------------------------------------------ +KVM_FEATURE_PV_POLL_CONTROL || 12 || host-side polling on HLT can + || || be disabled by writing + || || to msr 0x4b564d05. +------------------------------------------------------------------------------ KVM_FEATURE_PV_SCHED_YIELD || 13 || guest checks this feature bit || || before using paravirtualized || || sched yield. -- cgit v1.2.3 From e287d6de62f745e223d2f7d9b621c892d4b2b45a Mon Sep 17 00:00:00 2001 From: Luke Nowakowski-Krijger Date: Wed, 10 Jul 2019 08:30:53 -0700 Subject: Documentation: kvm: Convert cpuid.txt to .rst Convert cpuid.txt to .rst format to be parsable by sphinx. Change format and spacing to make function definitions and return values much more clear. Also added a table that is parsable by sphinx and makes the information much more clean. Updated Author email to their new active email address. Added license identifier with the consent of the author. Signed-off-by: Luke Nowakowski-Krijger Signed-off-by: Paolo Bonzini --- Documentation/virtual/kvm/cpuid.rst | 107 ++++++++++++++++++++++++++++++++++++ Documentation/virtual/kvm/cpuid.txt | 91 ------------------------------ 2 files changed, 107 insertions(+), 91 deletions(-) create mode 100644 Documentation/virtual/kvm/cpuid.rst delete mode 100644 Documentation/virtual/kvm/cpuid.txt (limited to 'Documentation/virtual/kvm/cpuid.txt') diff --git a/Documentation/virtual/kvm/cpuid.rst b/Documentation/virtual/kvm/cpuid.rst new file mode 100644 index 000000000000..01b081f6e7ea --- /dev/null +++ b/Documentation/virtual/kvm/cpuid.rst @@ -0,0 +1,107 @@ +.. SPDX-License-Identifier: GPL-2.0 + +============== +KVM CPUID bits +============== + +:Author: Glauber Costa + +A guest running on a kvm host, can check some of its features using +cpuid. This is not always guaranteed to work, since userspace can +mask-out some, or even all KVM-related cpuid features before launching +a guest. + +KVM cpuid functions are: + +function: KVM_CPUID_SIGNATURE (0x40000000) + +returns:: + + eax = 0x40000001 + ebx = 0x4b4d564b + ecx = 0x564b4d56 + edx = 0x4d + +Note that this value in ebx, ecx and edx corresponds to the string "KVMKVMKVM". +The value in eax corresponds to the maximum cpuid function present in this leaf, +and will be updated if more functions are added in the future. +Note also that old hosts set eax value to 0x0. This should +be interpreted as if the value was 0x40000001. +This function queries the presence of KVM cpuid leafs. + +function: define KVM_CPUID_FEATURES (0x40000001) + +returns:: + + ebx, ecx + eax = an OR'ed group of (1 << flag) + +where ``flag`` is defined as below: + +================================= =========== ================================ +flag value meaning +================================= =========== ================================ +KVM_FEATURE_CLOCKSOURCE 0 kvmclock available at msrs + 0x11 and 0x12 + +KVM_FEATURE_NOP_IO_DELAY 1 not necessary to perform delays + on PIO operations + +KVM_FEATURE_MMU_OP 2 deprecated + +KVM_FEATURE_CLOCKSOURCE2 3 kvmclock available at msrs + + 0x4b564d00 and 0x4b564d01 +KVM_FEATURE_ASYNC_PF 4 async pf can be enabled by + writing to msr 0x4b564d02 + +KVM_FEATURE_STEAL_TIME 5 steal time can be enabled by + writing to msr 0x4b564d03 + +KVM_FEATURE_PV_EOI 6 paravirtualized end of interrupt + handler can be enabled by + writing to msr 0x4b564d04 + +KVM_FEATURE_PV_UNHAULT 7 guest checks this feature bit + before enabling paravirtualized + spinlock support + +KVM_FEATURE_PV_TLB_FLUSH 9 guest checks this feature bit + before enabling paravirtualized + tlb flush + +KVM_FEATURE_ASYNC_PF_VMEXIT 10 paravirtualized async PF VM EXIT + can be enabled by setting bit 2 + when writing to msr 0x4b564d02 + +KVM_FEATURE_PV_SEND_IPI 11 guest checks this feature bit + before enabling paravirtualized + sebd IPIs + +KVM_FEATURE_PV_POLL_CONTROL 12 host-side polling on HLT can + be disabled by writing + to msr 0x4b564d05. + +KVM_FEATURE_PV_SCHED_YIELD 13 guest checks this feature bit + before using paravirtualized + sched yield. + +KVM_FEATURE_CLOCSOURCE_STABLE_BIT 24 host will warn if no guest-side + per-cpu warps are expeced in + kvmclock +================================= =========== ================================ + +:: + + edx = an OR'ed group of (1 << flag) + +Where ``flag`` here is defined as below: + +================== ============ ================================= +flag value meaning +================== ============ ================================= +KVM_HINTS_REALTIME 0 guest checks this feature bit to + determine that vCPUs are never + preempted for an unlimited time + allowing optimizations +================== ============ ================================= diff --git a/Documentation/virtual/kvm/cpuid.txt b/Documentation/virtual/kvm/cpuid.txt deleted file mode 100644 index 2bdac528e4a2..000000000000 --- a/Documentation/virtual/kvm/cpuid.txt +++ /dev/null @@ -1,91 +0,0 @@ -KVM CPUID bits -Glauber Costa , Red Hat Inc, 2010 -===================================================== - -A guest running on a kvm host, can check some of its features using -cpuid. This is not always guaranteed to work, since userspace can -mask-out some, or even all KVM-related cpuid features before launching -a guest. - -KVM cpuid functions are: - -function: KVM_CPUID_SIGNATURE (0x40000000) -returns : eax = 0x40000001, - ebx = 0x4b4d564b, - ecx = 0x564b4d56, - edx = 0x4d. -Note that this value in ebx, ecx and edx corresponds to the string "KVMKVMKVM". -The value in eax corresponds to the maximum cpuid function present in this leaf, -and will be updated if more functions are added in the future. -Note also that old hosts set eax value to 0x0. This should -be interpreted as if the value was 0x40000001. -This function queries the presence of KVM cpuid leafs. - - -function: define KVM_CPUID_FEATURES (0x40000001) -returns : ebx, ecx - eax = an OR'ed group of (1 << flag), where each flags is: - - -flag || value || meaning -============================================================================= -KVM_FEATURE_CLOCKSOURCE || 0 || kvmclock available at msrs - || || 0x11 and 0x12. ------------------------------------------------------------------------------- -KVM_FEATURE_NOP_IO_DELAY || 1 || not necessary to perform delays - || || on PIO operations. ------------------------------------------------------------------------------- -KVM_FEATURE_MMU_OP || 2 || deprecated. ------------------------------------------------------------------------------- -KVM_FEATURE_CLOCKSOURCE2 || 3 || kvmclock available at msrs - || || 0x4b564d00 and 0x4b564d01 ------------------------------------------------------------------------------- -KVM_FEATURE_ASYNC_PF || 4 || async pf can be enabled by - || || writing to msr 0x4b564d02 ------------------------------------------------------------------------------- -KVM_FEATURE_STEAL_TIME || 5 || steal time can be enabled by - || || writing to msr 0x4b564d03. ------------------------------------------------------------------------------- -KVM_FEATURE_PV_EOI || 6 || paravirtualized end of interrupt - || || handler can be enabled by writing - || || to msr 0x4b564d04. ------------------------------------------------------------------------------- -KVM_FEATURE_PV_UNHALT || 7 || guest checks this feature bit - || || before enabling paravirtualized - || || spinlock support. ------------------------------------------------------------------------------- -KVM_FEATURE_PV_TLB_FLUSH || 9 || guest checks this feature bit - || || before enabling paravirtualized - || || tlb flush. ------------------------------------------------------------------------------- -KVM_FEATURE_ASYNC_PF_VMEXIT || 10 || paravirtualized async PF VM exit - || || can be enabled by setting bit 2 - || || when writing to msr 0x4b564d02 ------------------------------------------------------------------------------- -KVM_FEATURE_PV_SEND_IPI || 11 || guest checks this feature bit - || || before using paravirtualized - || || send IPIs. ------------------------------------------------------------------------------- -KVM_FEATURE_PV_POLL_CONTROL || 12 || host-side polling on HLT can - || || be disabled by writing - || || to msr 0x4b564d05. ------------------------------------------------------------------------------- -KVM_FEATURE_PV_SCHED_YIELD || 13 || guest checks this feature bit - || || before using paravirtualized - || || sched yield. ------------------------------------------------------------------------------- -KVM_FEATURE_CLOCKSOURCE_STABLE_BIT || 24 || host will warn if no guest-side - || || per-cpu warps are expected in - || || kvmclock. ------------------------------------------------------------------------------- - - edx = an OR'ed group of (1 << flag), where each flags is: - - -flag || value || meaning -================================================================================== -KVM_HINTS_REALTIME || 0 || guest checks this feature bit to - || || determine that vCPUs are never - || || preempted for an unlimited time, - || || allowing optimizations ----------------------------------------------------------------------------------- -- cgit v1.2.3