[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [Qemu-devel] [PATCH v5 3/3] x86: define a new MSR based feature word
From: |
Robert Hoo |
Subject: |
Re: [Qemu-devel] [PATCH v5 3/3] x86: define a new MSR based feature word -- FEATURE_WORDS_ARCH_CAPABILITIES |
Date: |
Fri, 26 Oct 2018 11:01:25 +0800 |
On Wed, 2018-10-24 at 07:06 -0300, Eduardo Habkost wrote:
> On Mon, Oct 15, 2018 at 12:47:25PM +0800, Robert Hoo wrote:
> > Note RSBA is specially treated -- no matter host support it or not,
> > qemu
> > pretends it is supported.
> >
> > Signed-off-by: Robert Hoo <address@hidden>
>
> I am now wondering what else we need to be able to remove
> CPUID_7_0_EDX_ARCH_CAPABILITIES from
> feature_word_info[FEAT_7_0_EDX].unmigratable_flags.
>
> This series is necessary for that, be I think we still can't let
> the VM be migrated if arch-capabilities is enabled and we're
> running on a host that doesn't have MSR_IA32_ARCH_CAPABILITIES on
> kvm_feature_msrs.
>
> Reviewed-by: Eduardo Habkost <address@hidden>
>
> > ---
> > target/i386/cpu.c | 31 ++++++++++++++++++++++++++++++-
> > target/i386/cpu.h | 8 ++++++++
> > target/i386/kvm.c | 11 +++++++++++
> > 3 files changed, 49 insertions(+), 1 deletion(-)
> >
[...]
> >
> > typedef struct X86RegisterInfo32 {
> > @@ -3696,7 +3717,15 @@ static uint32_t
> > x86_cpu_get_supported_feature_word(FeatureWord w,
> > wi-
> > >cpuid.reg);
> > break;
> > case MSR_FEATURE_WORD:
> > - r = kvm_arch_get_supported_msr_feature(kvm_state, wi-
> > >msr.index);
> > + /* Special case:
> > + * No matter host status, IA32_ARCH_CAPABILITIES.RSBA
> > [bit 2]
> > + * is always supported in guest.
> > + */
> > + if (wi->msr.index == MSR_IA32_ARCH_CAPABILITIES) {
> > + r = MSR_ARCH_CAP_RSBA;
> > + }
> > + r |= kvm_arch_get_supported_msr_feature(kvm_state,
> > + wi->msr.index);
> > break;
After I add the filtering out MSR feature, whose CPUID dependency fails
, in x86_cpu_filter_features(), 1 issue comes out here:
If running on an old platform that doesn't have ARCH_CAPABILITIES MSR,
but we still pretends it here, then qemu will always print out
"warning: host doesn't support requested feature: MSR(10AH).rsba [bit
2]", with -cpu 'host', which does not look comfortable.
How about remove this hunk for now? leave it to when we fully decide
how to handle ARCH_CAPABILITIES live-migration safely.
> > }
> > } else if (hvf_enabled()) {
[...]
[Qemu-devel] [PATCH v5 1/3] kvm: Add support to KVM_GET_MSR_FEATURE_INDEX_LIST and KVM_GET_MSRS system ioctl, Robert Hoo, 2018/10/15