Re: [PATCH ] Documentation/kvm: Update cpuid documentation for steal time and pv eoi
On Fri, Aug 23, 2013 at 05:34:47PM +0530, Raghavendra K T wrote: Signed-off-by: Raghavendra K T raghavendra...@linux.vnet.ibm.com --- While adding documentation for pvspinlock, I found that these two should be updated. I have based this on top of pvspinlock kvm host patchset (V12) I would change the description to merely say what the CPUID bits mean, and what they mean is exactly that an MSR is valid. Use KVM_FEATURE_ASYNC_PF as a template. Documentation/virtual/kvm/cpuid.txt | 9 + 1 file changed, 9 insertions(+) diff --git a/Documentation/virtual/kvm/cpuid.txt b/Documentation/virtual/kvm/cpuid.txt index 22ff659..15a5ac20 100644 --- a/Documentation/virtual/kvm/cpuid.txt +++ b/Documentation/virtual/kvm/cpuid.txt @@ -43,6 +43,15 @@ KVM_FEATURE_CLOCKSOURCE2 || 3 || kvmclock available at msrs KVM_FEATURE_ASYNC_PF || 4 || async pf can be enabled by || || writing to msr 0x4b564d02 -- +KVM_FEATURE_STEAL_TIME || 5 || guest accounts fine granularity + || || task steal time. I'm not sure what this phrase means. Steal time is a host feature, not a guest feature: IIUC if this bit is set, the hypervisor can pass the guest information about how much time was spent running other processes outside the VM. enabled when + || || shedstat or task delay accounting + || || is supported by the host. I think it's enabled by guest, not by host. +-- +KVM_FEATURE_PV_EOI || 6 || overrides the generic EOI + || || implementation with an optimized + || || version. More exactly with a paravirtualized version. +-- KVM_FEATURE_PV_UNHALT || 7 || guest checks this feature bit || || before enabling paravirtualized || || spinlock support. -- 1.7.11.7 -- To unsubscribe from this list: send the line unsubscribe kvm in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH ] Documentation/kvm: Update cpuid documentation for steal time and pv eoi
On 08/26/2013 12:37 PM, Michael S. Tsirkin wrote: I would change the description to merely say what the CPUID bits mean, and what they mean is exactly that an MSR is valid. Use KVM_FEATURE_ASYNC_PF as a template. Thank you for the review. Changing the doc accordingly by adding msr info. Please refer below. +KVM_FEATURE_STEAL_TIME || 5 || guest accounts fine granularity + || || task steal time. I'm not sure what this phrase means. Steal time is a host feature, not a guest feature: IIUC if this bit is set, the hypervisor can pass the guest information about how much time was spent running other processes outside the VM. Okay. I guess I need some help here. I took this from the PARAVIRT_TIME_ACCOUNTING config help. also I saw that guest is actually returning the steal time in kvm_steal_clock(). enabled when + || || shedstat or task delay accounting + || || is supported by the host. I think it's enabled by guest, not by host. true. My understanding was, Guest enables it when host has schedstat or task delay accounting on. I referred to this hunk in kvm/cpuid.c if (sched_info_on()) entry-eax |= (1 KVM_FEATURE_STEAL_TIME); and sched_info_on() is true when schedstat or task delay accounting is on. Does this look good? Enabled by writing to msr 0x4b564d03. The feature is enabled by guest when host has schedstat or task delay accounting support. +KVM_FEATURE_PV_EOI || 6 || overrides the generic EOI + || || implementation with an optimized + || || version. More exactly with a paravirtualized version. Okay. So how does this sound? overrides the generic EOI implementation with a paravirtualized version. This feature is enabled by writing to msr 0x4b564d04. -- To unsubscribe from this list: send the line unsubscribe kvm in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
