linux-kernel - Re: [PATCH v2] KVM: selftest: Enhance handling WRMSR ICR register in x2APIC mode

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Date:   Thu, 23 Jun 2022 20:34:27 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Chao Gao <chao.gao@...el.com>
Cc:     Zeng Guang <guang.zeng@...el.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Shuah Khan <shuah@...nel.org>, linux-kselftest@...r.kernel.org,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        Venkatesh Srinivas <venkateshs@...omium.org>
Subject: Re: [PATCH v2] KVM: selftest: Enhance handling WRMSR ICR register in
 x2APIC mode

+Venkatesh

On Thu, Jun 23, 2022, Chao Gao wrote:
> On Thu, Jun 23, 2022 at 05:45:11PM +0800, Zeng Guang wrote:
> >Hardware would directly write x2APIC ICR register instead of software
> >emulation in some circumstances, e.g when Intel IPI virtualization is
> >enabled. This behavior requires normal reserved bits checking to ensure
> >them input as zero, otherwise it will cause #GP. So we need mask out
> >those reserved bits from the data written to vICR register.
> 
> OK. One open is:
> 
> Current KVM doesn't emulate this #GP. Is there any historical reason?
> if no, we will fix KVM and add some tests to verify this #GP is
> correctly emulated.

It's a bug.  There are patches posted[*], but they need to be refreshed to fix a
rebase goof.

Venkatesh, are you planning on sending a v3 soonish?

[*] https://lore.kernel.org/all/20220525173933.1611076-1-venkateshs@chromium.org