linux-kernel - [PATCH v3 06/21] KVM: X86: Don't take srcu lock in init_rmode_identity

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Message-Id: <20200109145729.32898-7-peterx@redhat.com>
Date:   Thu,  9 Jan 2020 09:57:14 -0500
From:   Peter Xu <peterx@...hat.com>
To:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     Christophe de Dinechin <dinechin@...hat.com>,
        "Michael S . Tsirkin" <mst@...hat.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Yan Zhao <yan.y.zhao@...el.com>,
        Alex Williamson <alex.williamson@...hat.com>,
        Jason Wang <jasowang@...hat.com>,
        Kevin Kevin <kevin.tian@...el.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>, peterx@...hat.com,
        "Dr . David Alan Gilbert" <dgilbert@...hat.com>
Subject: [PATCH v3 06/21] KVM: X86: Don't take srcu lock in init_rmode_identity_map()

We've already got the slots_lock, so we should be safe.

Signed-off-by: Peter Xu <peterx@...hat.com>
---
 arch/x86/kvm/vmx/vmx.c | 10 +++-------
 1 file changed, 3 insertions(+), 7 deletions(-)

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index b5a0c2e05825..7add2fc8d8e9 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -3475,7 +3475,7 @@ static int init_rmode_tss(struct kvm *kvm)
 static int init_rmode_identity_map(struct kvm *kvm)
 {
 	struct kvm_vmx *kvm_vmx = to_kvm_vmx(kvm);
-	int i, idx, r = 0;
+	int i, r = 0;
 	kvm_pfn_t identity_map_pfn;
 	u32 tmp;
 
@@ -3483,7 +3483,7 @@ static int init_rmode_identity_map(struct kvm *kvm)
 	mutex_lock(&kvm->slots_lock);
 
 	if (likely(kvm_vmx->ept_identity_pagetable_done))
-		goto out2;
+		goto out;
 
 	if (!kvm_vmx->ept_identity_map_addr)
 		kvm_vmx->ept_identity_map_addr = VMX_EPT_IDENTITY_PAGETABLE_ADDR;
@@ -3492,9 +3492,8 @@ static int init_rmode_identity_map(struct kvm *kvm)
 	r = __x86_set_memory_region(kvm, IDENTITY_PAGETABLE_PRIVATE_MEMSLOT,
 				    kvm_vmx->ept_identity_map_addr, PAGE_SIZE);
 	if (r < 0)
-		goto out2;
+		goto out;
 
-	idx = srcu_read_lock(&kvm->srcu);
 	r = kvm_clear_guest_page(kvm, identity_map_pfn, 0, PAGE_SIZE);
 	if (r < 0)
 		goto out;
@@ -3510,9 +3509,6 @@ static int init_rmode_identity_map(struct kvm *kvm)
 	kvm_vmx->ept_identity_pagetable_done = true;
 
 out:
-	srcu_read_unlock(&kvm->srcu, idx);
-
-out2:
 	mutex_unlock(&kvm->slots_lock);
 	return r;
 }
-- 
2.24.1