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From: Paolo Bonzini <pbonzini@redhat.com>
To: Jim Mattson <jmattson@google.com>,
	Sean Christopherson <seanjc@google.com>
Cc: Yu Zhang <yu.c.zhang@linux.intel.com>,
	Wei Huang <wei.huang2@amd.com>,
	kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
	vkuznets@redhat.com, wanpengli@tencent.com, joro@8bytes.org,
	tglx@linutronix.de, mingo@redhat.com, bp@alien8.de,
	x86@kernel.org, hpa@zytor.com
Subject: Re: [PATCH v2 1/3] KVM: x86: Allow CPU to force vendor-specific TDP level
Date: Tue, 10 Aug 2021 11:23:48 +0200	[thread overview]
Message-ID: <400f8ca7-8f82-308b-3427-b644144cfa5c@redhat.com> (raw)
In-Reply-To: <CALMp9eRfuntBFz=gnsvEuTXAXZorWJFAPq0ZdwZePxxQYGzdQA@mail.gmail.com>

On 09/08/21 23:49, Jim Mattson wrote:
> Doesn't this break legacy type 2 hypervisors that don't know anything
> about 5-level NPT and don't have any control over whether or not the
> host uses 5-level paging?

Yes, where "legacy" probably means "all released versions of all of 
them", including KVM.  Host support for LA57 was merged in 4.13, while 
KVM started supporting 5-level page tables in EPT in 4.14 and even then 
just returned PT64_ROOT_LEVEL (i.e. 4) for the maximum NPT level.

So all Linux versions up to 5.13, which has "KVM: x86: Prevent KVM SVM 
from loading on kernels with 5-level paging", will break horribly. 
Better backport that patch to stable...

Paolo


  reply	other threads:[~2021-08-10  9:24 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-08 19:26 [PATCH v2 0/3] SVM 5-level page table support Wei Huang
2021-08-08 19:26 ` [PATCH v2 1/3] KVM: x86: Allow CPU to force vendor-specific TDP level Wei Huang
2021-08-09  3:58   ` Yu Zhang
2021-08-09  4:11     ` Wei Huang
2021-08-09  4:27       ` Yu Zhang
2021-08-09  4:33         ` Wei Huang
2021-08-09  6:42           ` Yu Zhang
2021-08-09 15:30             ` Sean Christopherson
2021-08-09 21:49               ` Jim Mattson
2021-08-10  9:23                 ` Paolo Bonzini [this message]
2021-08-10  7:40               ` Yu Zhang
2021-08-10  9:25                 ` Paolo Bonzini
2021-08-10 11:00                   ` Yu Zhang
2021-08-10 12:47                     ` Paolo Bonzini
2021-08-10 14:37                       ` Yu Zhang
2021-08-08 19:26 ` [PATCH v2 2/3] KVM: x86: Handle the case of 5-level shadow page table Wei Huang
2021-08-09 15:17   ` Sean Christopherson
2021-08-09 17:03     ` Wei Huang
2021-08-08 19:26 ` [PATCH v2 3/3] KVM: SVM: Add 5-level page table support for SVM Wei Huang

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