From: Paolo Bonzini <pbonzini@redhat.com>
To: Sean Christopherson <seanjc@google.com>
Cc: Vitaly Kuznetsov <vkuznets@redhat.com>,
Wanpeng Li <wanpengli@tencent.com>,
Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
Ben Gardon <bgardon@google.com>
Subject: Re: [PATCH 1/2] KVM: x86/mmu: Protect marking SPs unsync when using TDP MMU with spinlock
Date: Wed, 11 Aug 2021 13:47:39 +0200 [thread overview]
Message-ID: <74bb6910-4a0c-4d2f-e6b5-714a3181638e@redhat.com> (raw)
In-Reply-To: <20210810224554.2978735-2-seanjc@google.com>
On 11/08/21 00:45, Sean Christopherson wrote:
> Use an entirely new spinlock even though piggybacking tdp_mmu_pages_lock
> would functionally be ok. Usurping the lock could degrade performance when
> building upper level page tables on different vCPUs, especially since the
> unsync flow could hold the lock for a comparatively long time depending on
> the number of indirect shadow pages and the depth of the paging tree.
If we are to introduce a new spinlock, do we need to make it conditional
and pass it around like this? It would be simpler to just take it
everywhere (just like, in patch 2, passing "shared == true" to
tdp_mmu_link_page is always safe anyway).
Paolo
next prev parent reply other threads:[~2021-08-11 11:47 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-10 22:45 [PATCH 0/2] KVM: x86/mmu: Fix unsync races within TDP MMU Sean Christopherson
2021-08-10 22:45 ` [PATCH 1/2] KVM: x86/mmu: Protect marking SPs unsync when using TDP MMU with spinlock Sean Christopherson
2021-08-11 11:47 ` Paolo Bonzini [this message]
2021-08-11 15:52 ` Sean Christopherson
2021-08-12 15:37 ` Paolo Bonzini
2021-08-12 16:06 ` Sean Christopherson
2021-08-10 22:45 ` [PATCH 2/2] KVM: x86/mmu: Drop 'shared' param from tdp_mmu_link_page() Sean Christopherson
2021-08-11 16:33 ` Ben Gardon
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