From: Lai Jiangshan <laijs@linux.alibaba.com>
To: Lai Jiangshan <jiangshanlai@gmail.com>,
linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
Paolo Bonzini <pbonzini@redhat.com>,
Junaid Shahid <junaids@google.com>
Cc: Sean Christopherson <seanjc@google.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>,
x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>
Subject: Re: [PATCH 3/4] KVM: X86: Use smp_rmb() to pair with smp_wmb() in mmu_try_to_unsync_pages()
Date: Thu, 21 Oct 2021 10:32:30 +0800 [thread overview]
Message-ID: <4192556d-8890-d94b-d03d-23922ff1674c@linux.alibaba.com> (raw)
In-Reply-To: <20211019110154.4091-4-jiangshanlai@gmail.com>
Hello Junaid Shahid
Any comments on the patch? I may have been misunderstanding many things and I
have been often.
thanks
Lai
On 2021/10/19 19:01, Lai Jiangshan wrote:
> From: Lai Jiangshan <laijs@linux.alibaba.com>
>
> The commit 578e1c4db2213 ("kvm: x86: Avoid taking MMU lock in
> kvm_mmu_sync_roots if no sync is needed") added smp_wmb() in
> mmu_try_to_unsync_pages(), but the corresponding smp_load_acquire()
> isn't used on the load of SPTE.W which is impossible since the load of
> SPTE.W is performed in the CPU's pagetable walking.
>
> This patch changes to use smp_rmb() instead. This patch fixes nothing
> but just comments since smp_rmb() is NOP and compiler barrier() is not
> required since the load of SPTE.W is before VMEXIT.
>
> Cc: Junaid Shahid <junaids@google.com>
> Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com>
next prev parent reply other threads:[~2021-10-21 2:32 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-19 11:01 [PATCH 0/4] KVM: X86: Improve guest TLB flushing Lai Jiangshan
2021-10-19 11:01 ` [PATCH 1/4] KVM: X86: Fix tlb flush for tdp in kvm_invalidate_pcid() Lai Jiangshan
2021-10-19 15:25 ` Sean Christopherson
2021-10-20 9:54 ` Lai Jiangshan
2021-10-20 18:26 ` Sean Christopherson
2021-10-21 1:27 ` Lai Jiangshan
2021-10-21 14:52 ` Sean Christopherson
2021-10-21 17:13 ` Paolo Bonzini
2021-10-21 17:32 ` Jim Mattson
2021-10-22 0:22 ` Lai Jiangshan
2021-10-19 11:01 ` [PATCH 2/4] KVM: X86: Cache CR3 in prev_roots when PCID is disabled Lai Jiangshan
2021-10-21 17:43 ` Paolo Bonzini
2021-10-22 2:11 ` Lai Jiangshan
2021-10-19 11:01 ` [PATCH 3/4] KVM: X86: Use smp_rmb() to pair with smp_wmb() in mmu_try_to_unsync_pages() Lai Jiangshan
2021-10-21 2:32 ` Lai Jiangshan [this message]
2021-10-21 17:44 ` Paolo Bonzini
2021-10-19 11:01 ` [PATCH 4/4] KVM: X86: Don't unload MMU in kvm_vcpu_flush_tlb_guest() Lai Jiangshan
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