linux-kernel - [PATCH 4/4] KVM: arm64: Don't retrieve memory slot again in page fault handler

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Date:   Mon, 15 Mar 2021 12:18:44 +0800
From:   Gavin Shan <gshan@...hat.com>
To:     kvmarm@...ts.cs.columbia.edu
Cc:     linux-kernel@...r.kernel.org, maz@...nel.org, will@...nel.org,
        alexandru.elisei@....com, shan.gavin@...il.com
Subject: [PATCH 4/4] KVM: arm64: Don't retrieve memory slot again in page fault handler

We needn't retrieve the memory slot again in user_mem_abort() because
the corresponding memory slot has been passed from the caller. This
would save some CPU cycles. For example, the time used to write 1GB
memory, which is backed by 2MB hugetlb pages and write-protected, is
dropped by 6.8% from 928ms to 864ms.

Signed-off-by: Gavin Shan <gshan@...hat.com>
---
 arch/arm64/kvm/mmu.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
index a5a8ade9fde4..4a4abcccfafb 100644
--- a/arch/arm64/kvm/mmu.c
+++ b/arch/arm64/kvm/mmu.c
@@ -846,7 +846,8 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
 	 */
 	smp_rmb();
 
-	pfn = gfn_to_pfn_prot(kvm, gfn, write_fault, &writable);
+	pfn = __gfn_to_pfn_memslot(memslot, gfn, false, NULL,
+				   write_fault, &writable, NULL);
 	if (pfn == KVM_PFN_ERR_HWPOISON) {
 		kvm_send_hwpoison_signal(hva, vma_shift);
 		return 0;
@@ -912,7 +913,7 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
 	/* Mark the page dirty only if the fault is handled successfully */
 	if (writable && !ret) {
 		kvm_set_pfn_dirty(pfn);
-		mark_page_dirty(kvm, gfn);
+		mark_page_dirty_in_slot(kvm, memslot, gfn);
 	}
 
 out_unlock:
-- 
2.23.0