From: Sean Christopherson <seanjc@google.com>
To: Fred Griffoul <griffoul@gmail.com>
Cc: kvm@vger.kernel.org, pbonzini@redhat.com, vkuznets@redhat.com,
shuah@kernel.org, dwmw@amazon.co.uk,
linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org,
Fred Griffoul <fgriffo@amazon.co.uk>
Subject: Re: [PATCH v4 00/10] KVM: nVMX: Improve performance for unmanaged guest memory
Date: Mon, 11 May 2026 16:56:16 -0700 [thread overview]
Message-ID: <agJsoCzokGcG5xwo@google.com> (raw)
In-Reply-To: <20260102142429.896101-1-griffoul@gmail.com>
On Fri, Jan 02, 2026, Fred Griffoul wrote:
> First, the current approach is missing proper invalidation handling in
> critical scenarios. Enlightened VMCS (eVMCS) pages can become stale when
> memslots are modified, as there is no mechanism to invalidate the cached
> mappings.
This is a non-issue. Modifying memslots while vCPUs are active will cause problems,
period. There is no magic on earth that will prevent that.
> Similarly, APIC access and virtual APIC pages can be migrated
> by the host, but without proper notification through mmu_notifier
> callbacks, the mappings become invalid and can lead to incorrect
> behavior.
No, they can't, at least not for unmanaged memory. For kernel-managed memory,
KVM obtains a long-term pin, which prevents the host from migrating the page.
prev parent reply other threads:[~2026-05-11 23:56 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-01-02 14:24 [PATCH v4 00/10] KVM: nVMX: Improve performance for unmanaged guest memory Fred Griffoul
2026-01-02 14:24 ` [PATCH v4 01/10] KVM: nVMX: Implement cache for L1 MSR bitmap Fred Griffoul
2026-05-11 23:08 ` Sean Christopherson
2026-01-02 14:24 ` [PATCH v4 02/10] KVM: pfncache: Restore guest-uses-pfn support Fred Griffoul
2026-01-02 14:24 ` [PATCH v4 03/10] KVM: x86: Add nested state validation for pfncache support Fred Griffoul
2026-01-02 14:24 ` [PATCH v4 04/10] KVM: nVMX: Implement cache for L1 APIC pages Fred Griffoul
2026-05-11 23:35 ` Sean Christopherson
2026-01-02 14:24 ` [PATCH v4 05/10] KVM: selftests: Add nested VMX APIC cache invalidation test Fred Griffoul
2026-01-02 14:24 ` [PATCH v4 06/10] KVM: nVMX: Cache evmcs fields to ensure consistency during VM-entry Fred Griffoul
2026-01-02 15:40 ` Vitaly Kuznetsov
2026-01-02 14:24 ` [PATCH v4 07/10] KVM: nVMX: Replace evmcs kvm_host_map with pfncache Fred Griffoul
2026-01-02 14:24 ` [PATCH v4 08/10] KVM: x86: Add nested context management Fred Griffoul
2026-05-12 0:13 ` Sean Christopherson
2026-01-02 14:24 ` [PATCH v4 09/10] KVM: nVMX: Use nested context for pfncache persistence Fred Griffoul
2026-01-02 14:24 ` [PATCH v4 10/10] KVM: selftests: Add L2 vcpu context switch test Fred Griffoul
2026-05-11 23:56 ` Sean Christopherson [this message]
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