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diff --git a/Documentation/virtual/kvm/cpuid.rst b/Documentation/virtual/kvm/cpuid.rst deleted file mode 100644 index 01b081f6e7ea..000000000000 --- a/Documentation/virtual/kvm/cpuid.rst +++ /dev/null @@ -1,107 +0,0 @@ -.. SPDX-License-Identifier: GPL-2.0 - -============== -KVM CPUID bits -============== - -:Author: Glauber Costa <glommer@gmail.com> - -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 -================== ============ ================================= |