Re: [PATCH] KVM: x86: Fix the condition of #PF interception caused by MKTME

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On 4/9/2024 10:01 AM, Sean Christopherson wrote:
On Tue, 19 Mar 2024 11:11:11 +0800, Tao Su wrote:
Intel MKTME repurposes several high bits of physical address as 'keyID',
so boot_cpu_data.x86_phys_bits doesn't hold physical address bits reported
by CPUID anymore.

If guest.MAXPHYADDR < host.MAXPHYADDR, the bit field of ‘keyID’ belongs
to reserved bits in guest’s view, so intercepting #PF to fix error code
is necessary, just replace boot_cpu_data.x86_phys_bits with
kvm_get_shadow_phys_bits() to fix.


Applied to kvm-x86 fixes, with a massaged shortlog/changelog.

Note, I don't love using kvm_get_shadow_phys_bits(),

cannot agree more.

but only because doing
CPUID every time is so pointlessly suboptimal.  I have a series to clean up all
of the related code, which I'll hopefully post later this week.

Look forward to it.

But I didn't see any reason to hold up this fix, as I really hope no one is
using allow_smaller_maxphyaddr in a nested VM with EPT enabled, which is the
only case where CPUID is likely to have a meaningful impact (due to causing a

[1/1] KVM: x86: Fix the condition of #PF interception caused by MKTME


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