Reply-To: Sean Christopherson <seanjc@google.com>
Date:   Thu, 23 Dec 2021 22:23:10 +0000
In-Reply-To: <20211223222318.1039223-1-seanjc@google.com>
Message-Id: <20211223222318.1039223-23-seanjc@google.com>
Mime-Version: 1.0
References: <20211223222318.1039223-1-seanjc@google.com>
Subject: [PATCH v2 22/30] KVM: x86/mmu: Do remote TLB flush before dropping
 RCU in TDP MMU resched
From:   Sean Christopherson <seanjc@google.com>
To:     Paolo Bonzini <pbonzini@redhat.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>, kvm@vger.kernel.org,
        linux-kernel@vger.kernel.org, Ben Gardon <bgardon@google.com>,
        David Matlack <dmatlack@google.com>,
        Mingwei Zhang <mizhang@google.com>
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

When yielding in the TDP MMU iterator, service any pending TLB flush
before dropping RCU protections in anticipation of using the callers RCU
"lock" as a proxy for vCPUs in the guest.

Signed-off-by: Sean Christopherson <seanjc@google.com>
Reviewed-by: Ben Gardon <bgardon@google.com>
---
 arch/x86/kvm/mmu/tdp_mmu.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c
index 21d015b38ac1..e7086eb35599 100644
--- a/arch/x86/kvm/mmu/tdp_mmu.c
+++ b/arch/x86/kvm/mmu/tdp_mmu.c
@@ -728,11 +728,11 @@ static inline bool __must_check tdp_mmu_iter_cond_resched(struct kvm *kvm,
 		return false;
 
 	if (need_resched() || rwlock_needbreak(&kvm->mmu_lock)) {
-		rcu_read_unlock();
-
 		if (flush)
 			kvm_flush_remote_tlbs(kvm);
 
+		rcu_read_unlock();
+
 		if (shared)
 			cond_resched_rwlock_read(&kvm->mmu_lock);
 		else
-- 
2.34.1.448.ga2b2bfdf31-goog