From: Vitaly Kuznetsov <vkuznets@redhat.com>
To: Sean Christopherson <seanjc@google.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>,
kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
David Matlack <dmatlack@google.com>,
Mingwei Zhang <mizhang@google.com>,
Yan Zhao <yan.y.zhao@intel.com>, Ben Gardon <bgardon@google.com>
Subject: Re: [PATCH v4 1/9] KVM: x86/mmu: Bug the VM if KVM attempts to double count an NX huge page
Date: Wed, 21 Sep 2022 18:08:18 +0200 [thread overview]
Message-ID: <87leqcoglp.fsf@redhat.com> (raw)
In-Reply-To: <YyswlLykptcOciOS@google.com>
Sean Christopherson <seanjc@google.com> writes:
> On Wed, Sep 21, 2022, Sean Christopherson wrote:
>> On Wed, Sep 21, 2022, Vitaly Kuznetsov wrote:
>> > [ 962.257992] ept_fetch+0x504/0x5a0 [kvm]
>> > [ 962.261959] ept_page_fault+0x2d7/0x300 [kvm]
>> > [ 962.287701] kvm_mmu_page_fault+0x258/0x290 [kvm]
>> > [ 962.292451] vmx_handle_exit+0xe/0x40 [kvm_intel]
>> > [ 962.297173] vcpu_enter_guest+0x665/0xfc0 [kvm]
>> > [ 962.307580] vcpu_run+0x33/0x250 [kvm]
>> > [ 962.311367] kvm_arch_vcpu_ioctl_run+0xf7/0x460 [kvm]
>> > [ 962.316456] kvm_vcpu_ioctl+0x271/0x670 [kvm]
>> > [ 962.320843] __x64_sys_ioctl+0x87/0xc0
>> > [ 962.324602] do_syscall_64+0x38/0x90
>> > [ 962.328192] entry_SYSCALL_64_after_hwframe+0x63/0xcd
>>
>> Ugh, past me completely forgot the basics of shadow paging[*]. The shadow MMU
>> can reuse existing shadow pages, whereas the TDP MMU always links in new pages.
>>
>> I got turned around by the "doesn't exist" check, which only means "is there
>> already a _SPTE_ here", not "is there an existing SP for the target gfn+role that
>> can be used".
>>
>> I'll drop the series from the queue, send a new pull request, and spin a v5
>> targeting 6.2, which amusing will look a lot like v1...
>
> Huh. I was expecting more churn, but dropping the offending patch and then
> "reworking" the series yields a very trivial overall diff.
>
> Vitaly, can you easily re-test with the below, i.e. simply delete the
> KVM_BUG_ON()?
This seems to work! At least, I haven't noticed anything weird when
booting my beloved Win11 + WSL2 guest.
--
Vitaly
next prev parent reply other threads:[~2022-09-21 16:28 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-08-30 23:55 [PATCH v4 0/9] KVM: x86: Apply NX mitigation more precisely Sean Christopherson
2022-08-30 23:55 ` [PATCH v4 1/9] KVM: x86/mmu: Bug the VM if KVM attempts to double count an NX huge page Sean Christopherson
2022-09-21 13:17 ` Vitaly Kuznetsov
2022-09-21 14:43 ` Sean Christopherson
2022-09-21 15:41 ` Sean Christopherson
2022-09-21 16:08 ` Vitaly Kuznetsov [this message]
2022-09-30 4:33 ` Sean Christopherson
2022-08-30 23:55 ` [PATCH v4 2/9] KVM: x86/mmu: Tag disallowed NX huge pages even if they're not tracked Sean Christopherson
2022-08-30 23:55 ` [PATCH v4 3/9] KVM: x86/mmu: Rename NX huge pages fields/functions for consistency Sean Christopherson
2022-08-30 23:55 ` [PATCH v4 4/9] KVM: x86/mmu: Properly account NX huge page workaround for nonpaging MMUs Sean Christopherson
2022-08-30 23:55 ` [PATCH v4 5/9] KVM: x86/mmu: Document implicit barriers/ordering in TDP MMU shared mode Sean Christopherson
2022-08-30 23:55 ` [PATCH v4 6/9] KVM: x86/mmu: Set disallowed_nx_huge_page in TDP MMU before setting SPTE Sean Christopherson
2022-08-30 23:55 ` [PATCH v4 7/9] KVM: x86/mmu: Track the number of TDP MMU pages, but not the actual pages Sean Christopherson
2022-08-30 23:55 ` [PATCH v4 8/9] KVM: x86/mmu: Add helper to convert SPTE value to its shadow page Sean Christopherson
2022-08-30 23:55 ` [PATCH v4 9/9] KVM: x86/mmu: explicitly check nx_hugepage in disallowed_hugepage_adjust() Sean Christopherson
2022-09-06 18:38 ` [PATCH v4 0/9] KVM: x86: Apply NX mitigation more precisely Mingwei Zhang
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