linux-kernel - Re: [PATCH AUTOSEL 4.19 08/26] kvm: x86: Improve emulation of CPUID leaves 0BH and 1FH

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Message-ID: <20191009224129.GX1396@sasha-vm>
Date:   Wed, 9 Oct 2019 18:41:29 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Jim Mattson <jmattson@...gle.com>,
        Marc Orr <marcorr@...gle.com>, Peter Shier <pshier@...gle.com>,
        Jacob Xu <jacobhxu@...gle.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        kvm@...r.kernel.org
Subject: Re: [PATCH AUTOSEL 4.19 08/26] kvm: x86: Improve emulation of CPUID
 leaves 0BH and 1FH

On Wed, Oct 09, 2019 at 10:58:35PM +0200, Paolo Bonzini wrote:
>On 09/10/19 19:05, Sasha Levin wrote:
>> From: Jim Mattson <jmattson@...gle.com>
>>
>> [ Upstream commit 43561123ab3759eb6ff47693aec1a307af0aef83 ]
>>
>> For these CPUID leaves, the EDX output is not dependent on the ECX
>> input (i.e. the SIGNIFCANT_INDEX flag doesn't apply to
>> EDX). Furthermore, the low byte of the ECX output is always identical
>> to the low byte of the ECX input. KVM does not produce the correct ECX
>> and EDX outputs for any undefined subleaves beyond the first.
>>
>> Special-case these CPUID leaves in kvm_cpuid, so that the ECX and EDX
>> outputs are properly generated for all undefined subleaves.
>>
>> Fixes: 0771671749b59a ("KVM: Enhance guest cpuid management")
>> Fixes: a87f2d3a6eadab ("KVM: x86: Add Intel CPUID.1F cpuid emulation support")
>> Signed-off-by: Jim Mattson <jmattson@...gle.com>
>> Reviewed-by: Marc Orr <marcorr@...gle.com>
>> Reviewed-by: Peter Shier <pshier@...gle.com>
>> Reviewed-by: Jacob Xu <jacobhxu@...gle.com>
>> Cc: Sean Christopherson <sean.j.christopherson@...el.com>
>> Cc: Paolo Bonzini <pbonzini@...hat.com>
>> Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
>> Signed-off-by: Sasha Levin <sashal@...nel.org>
>> ---
>>  arch/x86/kvm/cpuid.c | 83 +++++++++++++++++++++++++-------------------
>>  1 file changed, 47 insertions(+), 36 deletions(-)
>
>This is absolutely not stable material.  Is it possible for KVM to opt
>out of this AUTOSEL nonsense?

Sure, I've opted out KVM and removed all KVM patches from this series:

c1fac4516a61d kvm: vmx: Limit guest PMCs to those supported on the host
75b118586ec81 kvm: x86, powerpc: do not allow clearing largepages debugfs entry
06cd1710feaed KVM: VMX: Set VMENTER_L1D_FLUSH_NOT_REQUIRED if !X86_BUG_L1TF
c89fc5c082aa6 KVM: x86: Expose XSAVEERPTR to the guest
1eec6b4068e2e kvm: x86: Use AMD CPUID semantics for AMD vCPUs
5c56e6ba0afc8 kvm: x86: Improve emulation of CPUID leaves 0BH and 1FH
94a3c6f010bd2 kvm: x86: Fix a spurious -E2BIG in __do_cpuid_func
79a7ad6330bc5 KVM: arm/arm64: vgic: Use the appropriate TRACE_INCLUDE_PATH

--
Thanks,
Sasha