From: Sean Christopherson <seanjc@google.com>
To: Rick Edgecombe <rick.p.edgecombe@intel.com>
Cc: pbonzini@redhat.com, vkuznets@redhat.com, wanpengli@tencent.com,
jmattson@google.com, joro@8bytes.org, bgardon@google.com,
kvm@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] kvm: x86/mmu: Use cpuid to determine max gfn
Date: Thu, 3 Dec 2020 16:43:54 -0800 [thread overview]
Message-ID: <X8mGSoB6KCiFsJdC@google.com> (raw)
In-Reply-To: <20201203231120.27307-1-rick.p.edgecombe@intel.com>
On Thu, Dec 03, 2020, Rick Edgecombe wrote:
> In the TDP MMU, use shadow_phys_bits to dermine the maximum possible GFN
> mapped in the guest for zapping operations. boot_cpu_data.x86_phys_bits
> may be reduced in the case of HW features that steal HPA bits for other
> purposes. However, this doesn't necessarily reduce GPA space that can be
> accessed via TDP. So zap based on a maximum gfn calculated with MAXPHYADDR
> retrieved from CPUID. This is already stored in shadow_phys_bits, so use
> it instead of x86_phys_bits.
>
> Fixes: faaf05b00aec ("kvm: x86/mmu: Support zapping SPTEs in the TDP MMU")
> Signed-off-by: Rick Edgecombe <rick.p.edgecombe@intel.com>
Dang, in hindsight it'd be nice if KVM_CAP_SMALLER_MAXPHYADDR allowed explicitly
setting the max MAXPHYADDR for an entire VM instead of being a simple toggle.
E.g. TDX and SEV-ES likely could also make use of "what's this VM's max GPA?".
Reviewed-by: Sean Christopherson <seanjc@google.com>
next prev parent reply other threads:[~2020-12-04 0:44 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-03 23:11 [PATCH] kvm: x86/mmu: Use cpuid to determine max gfn Rick Edgecombe
2020-12-04 0:43 ` Sean Christopherson [this message]
2020-12-04 8:48 ` Paolo Bonzini
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