From: Vitaly Kuznetsov <vkuznets@redhat.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: Jim Mattson <jmattson@google.com>,
Aaron Lewis <aaronlewis@google.com>,
Babu Moger <Babu.Moger@amd.com>,
Yang Weijiang <weijiang.yang@intel.com>,
Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
kvm@vger.kernel.org
Subject: Re: [Patch 2/6] KVM: VMX: Use wrmsr for switching between guest and host IA32_XSS
Date: Wed, 09 Oct 2019 14:34:19 +0200 [thread overview]
Message-ID: <871rvmyu5w.fsf@vitty.brq.redhat.com> (raw)
In-Reply-To: <fcec86ca-a9d2-2204-d92d-8f1e21c4a226@redhat.com>
Paolo Bonzini <pbonzini@redhat.com> writes:
> On 09/10/19 02:41, Aaron Lewis wrote:
>> Set IA32_XSS for the guest and host during VM Enter and VM Exit
>> transitions rather than by using the MSR-load areas.
>>
>> Reviewed-by: Jim Mattson <jmattson@google.com>
>> Signed-off-by: Aaron Lewis <aaronlewis@google.com>
>
> This commit message is missing an explanation of why this is a good thing.
>
> Also, the series is missing a cover letter that explains a bit more of
> the overall picture. I have no problem with no cover letter for
> two-patch series, but at six it is definitely a requirement.
>
> So I'm replying to this patch as a proxy for the whole series, and
> asking: why is it useful to enable XSAVES (on AMD or anywhere) if anyway
> IA32_XSS is limited to zero?
I know at least one good reason to do so: Hyper-V 2016 Gen1 (but not
Gen2!) doesn't seem to be able to boot without XSAVES (don't ask me
why). I'm not particularly sure if Aaron is aiming at fixing this one
though.
--
Vitaly
next prev parent reply other threads:[~2019-10-09 12:34 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-09 0:41 [Patch 1/6] KVM: VMX: Remove unneeded check for X86_FEATURE_XSAVE Aaron Lewis
2019-10-09 0:41 ` [Patch 2/6] KVM: VMX: Use wrmsr for switching between guest and host IA32_XSS Aaron Lewis
2019-10-09 4:49 ` Yang Weijiang
2019-10-09 6:30 ` Paolo Bonzini
2019-10-09 12:34 ` Vitaly Kuznetsov [this message]
2019-10-09 6:31 ` Sebastian Andrzej Siewior
2019-10-09 0:41 ` [Patch 3/6] kvm: svm: Add support for XSAVES on AMD Aaron Lewis
2019-10-09 6:44 ` Sebastian Andrzej Siewior
2019-10-10 14:42 ` Aaron Lewis
2019-10-10 16:04 ` Paolo Bonzini
2019-10-09 7:01 ` Paolo Bonzini
2019-10-09 21:29 ` Jim Mattson
2019-10-09 21:40 ` Paolo Bonzini
2019-10-09 21:58 ` Jim Mattson
2019-10-09 22:49 ` Paolo Bonzini
2019-10-10 0:42 ` Kang, Luwei
2019-10-09 0:41 ` [Patch 4/6] kvm: svm: Enumerate XSAVES in guest CPUID when it is available to the guest Aaron Lewis
2019-10-09 1:42 ` Yang Weijiang
2019-10-09 6:32 ` Paolo Bonzini
2019-10-09 23:35 ` Jim Mattson
2019-10-09 0:41 ` [Patch 5/6] kvm: x86: Add IA32_XSS to the emulated_msrs list Aaron Lewis
2019-10-09 0:41 ` [Patch 6/6] kvm: tests: Add test to verify MSR_IA32_XSS Aaron Lewis
2019-10-09 6:30 ` Paolo Bonzini
2019-10-09 23:44 ` Jim Mattson
2019-10-10 16:01 ` Paolo Bonzini
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