From: Lai Jiangshan <laijs@linux.alibaba.com>
To: Sean Christopherson <seanjc@google.com>,
Lai Jiangshan <jiangshanlai@gmail.com>
Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
Paolo Bonzini <pbonzini@redhat.com>,
Vitaly Kuznetsov <vkuznets@redhat.com>,
Wanpeng Li <wanpengli@tencent.com>,
Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
Maxim Levitsky <mlevitsk@redhat.com>
Subject: Re: [PATCH 1/12] KVM: X86: Fix when shadow_root_level=5 && guest root_level<4
Date: Fri, 10 Dec 2021 17:34:35 +0800 [thread overview]
Message-ID: <9dcd7f1d-609d-c9f4-bcb1-c5e465383722@linux.alibaba.com> (raw)
In-Reply-To: <YbFY533IT3XSIqAK@google.com>
On 2021/12/9 09:16, Sean Christopherson wrote:
> On Wed, Nov 24, 2021, Lai Jiangshan wrote:
>> From: Lai Jiangshan <laijs@linux.alibaba.com>
>>
>> If the is an L1 with nNPT in 32bit, the shadow walk starts with
>> pae_root.
>>
>> Fixes: a717a780fc4e ("KVM: x86/mmu: Support shadowing NPT when 5-level paging is enabled in host)
>
> Have you actually run with 5-level nNPT? I don't have access to hardware, at least
> not that I know of :-)
The code is just obvious incorrect for shadow_root_level=5 && guest root_level<4.
>
> I'm staring at kvm_mmu_sync_roots() and don't see how it can possibly work for
> 5-level nNPT with a 4-level NPT guest.
>
It doesn't use pml5_root for 5-level nNPT with a 4-level NPT guest, so
kvm_mmu_sync_roots() can work in a silence way with an "unexpected" root shadow
page. It has problems for 5-level nNPT with a 4-level NPT guest.
See:
https://lore.kernel.org/lkml/20211210092508.7185-1-jiangshanlai@gmail.com/
especially patch4.
Your this reply motivated me to complete the changelog of a patchset and send
it, thanks!
Although the patchset is immature, it would be better than losing it.
next prev parent reply other threads:[~2021-12-10 9:34 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-11-24 12:20 [PATCH 00/12] KVM: X86: misc fixes and cleanup Lai Jiangshan
2021-11-24 12:20 ` [PATCH 01/12] KVM: X86: Fix when shadow_root_level=5 && guest root_level<4 Lai Jiangshan
2021-12-09 1:16 ` [PATCH 1/12] " Sean Christopherson
2021-12-09 1:21 ` Sean Christopherson
2021-12-10 9:34 ` Lai Jiangshan [this message]
2021-11-24 12:20 ` [PATCH 02/12] KVM: X86: Add parameter struct kvm_mmu *mmu into mmu->gva_to_gpa() Lai Jiangshan
2021-11-24 12:20 ` [PATCH 03/12] KVM: X86: Remove mmu->translate_gpa Lai Jiangshan
2021-11-24 12:20 ` [PATCH 04/12] KVM: X86: Use vcpu->arch.walk_mmu for kvm_mmu_invlpg() Lai Jiangshan
2021-11-24 12:20 ` [PATCH 05/12] KVM: X86: Change the type of a parameter of kvm_mmu_invalidate_gva() and mmu->invlpg() to gpa_t Lai Jiangshan
2021-11-24 12:20 ` [PATCH 06/12] KVM: X86: Add huge_page_level to __reset_rsvds_bits_mask_ept() Lai Jiangshan
2021-11-24 12:20 ` [PATCH 07/12] KVM: X86: Add parameter huge_page_level to kvm_init_shadow_ept_mmu() Lai Jiangshan
2021-11-24 12:20 ` [PATCH 08/12] KVM: VMX: Use ept_caps_to_lpage_level() in hardware_setup() Lai Jiangshan
2021-11-24 12:20 ` [PATCH 09/12] KVM: X86: Rename gpte_is_8_bytes to has_4_byte_gpte and invert the direction Lai Jiangshan
2021-11-24 12:20 ` [PATCH 10/12] KVM: X86: Remove mmu parameter from load_pdptrs() Lai Jiangshan
2021-11-24 12:20 ` [PATCH 11/12] KVM: X86: Check root_level only in fast_pgd_switch() Lai Jiangshan
2021-11-26 12:56 ` Paolo Bonzini
2021-11-24 12:20 ` [PATCH 12/12] KVM: X86: Walk shadow page starting with shadow_root_level Lai Jiangshan
2021-11-26 12:58 ` Paolo Bonzini
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