From: Luke Nowakowski-Krijger <lnowakow@xxxxxxxxxxxx> 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. Signed-off-by: Luke Nowakowski-Krijger <lnowakow@xxxxxxxxxxxx> --- Documentation/virtual/kvm/cpuid.rst | 99 +++++++++++++++++++++++++++++ Documentation/virtual/kvm/cpuid.txt | 83 ------------------------ 2 files changed, 99 insertions(+), 83 deletions(-) create mode 100644 Documentation/virtual/kvm/cpuid.rst delete mode 100644 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..1a03336a500e --- /dev/null +++ b/Documentation/virtual/kvm/cpuid.rst @@ -0,0 +1,99 @@ +.. SPDX-License-Identifier: GPL-2.0 + +============== +KVM CPUID bits +============== + +:Author: Glauber Costa <glommer@xxxxxxxxxx>, 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 ``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_CLOCSOURCE_STABLE | 24 | host will warn if no guest-side | +| _BIT | | 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 97ca1940a0dc..000000000000 --- a/Documentation/virtual/kvm/cpuid.txt +++ /dev/null @@ -1,83 +0,0 @@ -KVM CPUID bits -Glauber Costa <glommer@xxxxxxxxxx>, 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_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 ----------------------------------------------------------------------------------- -- 2.20.1
