Re: [PATCH v4 0/2] kvm/cpuid: set proper GuestPhysBits in CPUID.0x80000008

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On Wed, 13 Mar 2024 13:58:41 +0100, Gerd Hoffmann wrote:
> Use the GuestPhysBits field (EAX[23:16]) to communicate the max
> addressable GPA to the guest.  Typically this is identical to the max
> effective GPA, except in case the CPU supports MAXPHYADDR > 48 but does
> not support 5-level TDP.
> See commit messages and source code comments for details.
> [...]

Applied to kvm-x86 misc, with massaged changelogs to be more verbose when
describing the impact of each change, e.g. to call out that patch 2 isn't an
urgent fix because guest firmware can simply limit itself to using GPAs that
can be addressed with 4-level paging.

I also tagged patch 1 for stable@, as KVM-on-KVM will do the wrong thing when
patch 2 lands, i.e. KVM will incorrectly advertise the addressable MAXPHYADDR
as the raw/real MAXPHYADDR.

Please holler if you (or anyone) disagrees with the changes or my analysis on
the KVM-on-KVM issue.


[1/2] KVM: x86: Don't advertise guest.MAXPHYADDR as host.MAXPHYADDR in CPUID
[2/2] KVM: x86: Advertise max mappable GPA in CPUID.0x80000008.GuestPhysBits


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