From: Sean Christopherson <seanjc@google.com>
To: Ackerley Tng <ackerleytng@google.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>,
Jonathan Corbet <corbet@lwn.net>,
Shuah Khan <skhan@linuxfoundation.org>,
Tianrui Zhao <zhaotianrui@loongson.cn>,
Bibo Mao <maobibo@loongson.cn>,
Huacai Chen <chenhuacai@kernel.org>,
WANG Xuerui <kernel@xen0n.name>,
Thomas Gleixner <tglx@kernel.org>, Ingo Molnar <mingo@redhat.com>,
Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
Fuad Tabba <tabba@google.com>,
vannapurve@google.com, x86@kernel.org,
"H. Peter Anvin" <hpa@zytor.com>,
kvm@vger.kernel.org, linux-doc@vger.kernel.org,
linux-kernel@vger.kernel.org, loongarch@lists.linux.dev
Subject: Re: [PATCH RFC 10/12] KVM: guest_memfd: Clarify comment about gmem.file vs kvm->srcu
Date: Thu, 25 Jun 2026 11:19:59 -0700 [thread overview]
Message-ID: <aj1xT7XkSpkqNFAI@google.com> (raw)
In-Reply-To: <20260527-kvm-locking-docs-v1-10-4fe8b602ff47@google.com>
On Wed, May 27, 2026, Ackerley Tng wrote:
> Clarify the existing comment about synchronize_srcu() and
> kvm_gmem_get_pfn() to provide further context. Explain which
> synchronize_srcu() prevents races with how kvm_gmem_get_pfn() is used.
>
> Also point reader to documentation for better understanding.
>
> Signed-off-by: Ackerley Tng <ackerleytng@google.com>
> ---
> virt/kvm/guest_memfd.c | 9 +++++++--
> 1 file changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c
> index 69c9d6d546b28..f2218db0af980 100644
> --- a/virt/kvm/guest_memfd.c
> +++ b/virt/kvm/guest_memfd.c
> @@ -711,8 +711,13 @@ static void __kvm_gmem_unbind(struct kvm_memory_slot *slot, struct gmem_file *f)
> xa_store_range(&f->bindings, start, end - 1, NULL, GFP_KERNEL);
>
> /*
> - * synchronize_srcu(&kvm->srcu) ensured that kvm_gmem_get_pfn()
> - * cannot see this memslot.
> + * This is called when memslots are updated, after the old
> + * memslot container is no longer in
> + * use. synchronize_srcu(&kvm->srcu) was called there, so
> + * kvm_gmem_get_pfn() from KVM's guest fault handling cannot
> + * see this memslot. See Documentation/virt/kvm/locking.rst
> + * for more information about kvm->srcu and the memslots
> + * container.
If we want to add to this comment, I would much rather do so as part of an update
to kvm_gmem_release()'s comment as well.
https://lore.kernel.org/all/20251113232229.1698886-1-seanjc@google.com
next prev parent reply other threads:[~2026-06-25 18:20 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-05-27 15:33 [PATCH RFC 00/12] Document synchronization used in managing guest faults Ackerley Tng via B4 Relay
2026-05-27 15:33 ` [PATCH RFC 01/12] Documentation: KVM: Elaborate comment on kvm_usage_lock Ackerley Tng via B4 Relay
2026-06-25 18:12 ` Sean Christopherson
2026-05-27 15:33 ` [PATCH RFC 02/12] Documentation: KVM: Consolidate notes about cpu_read_lock() and kvm_lock Ackerley Tng via B4 Relay
2026-06-25 18:12 ` Sean Christopherson
2026-05-27 15:33 ` [PATCH RFC 03/12] Documentation: KVM: Consolidate notes about kvm->slots_lock and irq_lock Ackerley Tng via B4 Relay
2026-06-25 18:12 ` Sean Christopherson
2026-05-27 15:33 ` [PATCH RFC 04/12] Documentation: KVM: Turn - into bullet point Ackerley Tng via B4 Relay
2026-05-27 15:33 ` [PATCH RFC 05/12] Documentation: KVM: Explain what rule the exception section is meant for Ackerley Tng via B4 Relay
2026-05-27 15:33 ` [PATCH RFC 06/12] Documentation: KVM: Have actual headings for exceptions Ackerley Tng via B4 Relay
2026-05-27 15:33 ` [PATCH RFC 07/12] Documentation: KVM: Drop mention of kvm->lock in SRCU documentation Ackerley Tng via B4 Relay
2026-05-27 15:33 ` [PATCH RFC 08/12] Documentation: KVM: Add example for kvm->srcu in relation to mutex/lock Ackerley Tng via B4 Relay
2026-06-25 18:17 ` Sean Christopherson
2026-05-27 15:33 ` [PATCH RFC 09/12] Documentation: KVM: Document synchronization for managing guest faults Ackerley Tng via B4 Relay
2026-05-27 15:33 ` [PATCH RFC 10/12] KVM: guest_memfd: Clarify comment about gmem.file vs kvm->srcu Ackerley Tng via B4 Relay
2026-06-25 18:19 ` Sean Christopherson [this message]
2026-05-27 15:33 ` [PATCH RFC 11/12] KVM: mmu: Point users of host_pfn_mapping_level() to docs Ackerley Tng via B4 Relay
2026-05-27 15:33 ` [PATCH RFC 12/12] Documentation: KVM: Focus acquisition order section on preventing deadlocks Ackerley Tng via B4 Relay
2026-06-25 18:25 ` Sean Christopherson
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