linux-kernel - Re: [PATCH v2 00/11] KVM: Support guest MAXPHYADDR

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Message-ID: <87312ebb-e842-3b21-e216-916d54557319@redhat.com>
Date:   Fri, 19 Jun 2020 17:43:25 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Mohammed Gamal <mgamal@...hat.com>, kvm@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, vkuznets@...hat.com,
        sean.j.christopherson@...el.com, wanpengli@...cent.com,
        jmattson@...gle.com, joro@...tes.org, thomas.lendacky@....com,
        babu.moger@....com
Subject: Re: [PATCH v2 00/11] KVM: Support guest MAXPHYADDR < host MAXPHYADDR

On 19/06/20 17:39, Mohammed Gamal wrote:
> The last 3 patches (i.e. SVM bits and patch 11) are not intended for
> immediate inclusion and probably need more discussion.
> We've been noticing some unexpected behavior in handling NPF vmexits
> on AMD CPUs (see individual patches for details), and thus we are
> proposing a workaround (see last patch) that adds a capability that
> userspace can use to decide who to deal with hosts that might have
> issues supprting guest MAXPHYADDR < host MAXPHYADDR.

I think patch 11 can be committed (more or less).  You would actually
move it to the beginning of the series and have
"allow_smaller_maxphyaddr = !enable_ept;" for VMX.  It is then changed
to "allow_smaller_maxphyaddr = true;" in "KVM: VMX: Add guest physical
address check in EPT violation and misconfig".

In fact, it would be a no-brainer to commit patch 11 in that form, so
feel free to submit it separately.

Thanks,

Paolo