linux-kernel - [PATCH 2/2] KVM: x86: MMU: Move handle_mmio_page_fault() call to kvm_mmu_page

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Date:	Mon, 22 Feb 2016 17:23:41 +0900
From:	Takuya Yoshikawa <yoshikawa_takuya_b1@....ntt.co.jp>
To:	pbonzini@...hat.com
Cc:	kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
	Takuya Yoshikawa <yoshikawa_takuya_b1@....ntt.co.jp>
Subject: [PATCH 2/2] KVM: x86: MMU: Move handle_mmio_page_fault() call to kvm_mmu_page_fault()

Rather than placing a handle_mmio_page_fault() call in each
vcpu->arch.mmu.page_fault() handler, moving it up to
kvm_mmu_page_fault() makes the code better:

 - avoids code duplication
 - for kvm_arch_async_page_ready(), which is the other caller of
   vcpu->arch.mmu.page_fault(), removes an extra error_code check
 - avoids returning both RET_MMIO_PF_* values and raw integer values
   from vcpu->arch.mmu.page_fault()

Signed-off-by: Takuya Yoshikawa <yoshikawa_takuya_b1@....ntt.co.jp>
---
 arch/x86/kvm/mmu.c         | 39 ++++++++++++++++-----------------------
 arch/x86/kvm/paging_tmpl.h | 19 ++++++-------------
 2 files changed, 22 insertions(+), 36 deletions(-)

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index a28b734..2ce3892 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -3370,13 +3370,6 @@ static int nonpaging_page_fault(struct kvm_vcpu *vcpu, gva_t gva,
 
 	pgprintk("%s: gva %lx error %x\n", __func__, gva, error_code);
 
-	if (unlikely(error_code & PFERR_RSVD_MASK)) {
-		r = handle_mmio_page_fault(vcpu, gva, true);
-
-		if (likely(r != RET_MMIO_PF_INVALID))
-			return r;
-	}
-
 	r = mmu_topup_memory_caches(vcpu);
 	if (r)
 		return r;
@@ -3460,13 +3453,6 @@ static int tdp_page_fault(struct kvm_vcpu *vcpu, gva_t gpa, u32 error_code,
 
 	MMU_WARN_ON(!VALID_PAGE(vcpu->arch.mmu.root_hpa));
 
-	if (unlikely(error_code & PFERR_RSVD_MASK)) {
-		r = handle_mmio_page_fault(vcpu, gpa, true);
-
-		if (likely(r != RET_MMIO_PF_INVALID))
-			return r;
-	}
-
 	r = mmu_topup_memory_caches(vcpu);
 	if (r)
 		return r;
@@ -4361,18 +4347,27 @@ int kvm_mmu_page_fault(struct kvm_vcpu *vcpu, gva_t cr2, u32 error_code,
 	enum emulation_result er;
 	bool direct = vcpu->arch.mmu.direct_map || mmu_is_nested(vcpu);
 
+	if (unlikely(error_code & PFERR_RSVD_MASK)) {
+		r = handle_mmio_page_fault(vcpu, cr2, direct);
+		if (r == RET_MMIO_PF_EMULATE) {
+			emulation_type = 0;
+			goto emulate;
+		}
+		if (r == RET_MMIO_PF_RETRY)
+			return 1;
+		if (r < 0)
+			return r;
+	}
+
 	r = vcpu->arch.mmu.page_fault(vcpu, cr2, error_code, false);
 	if (r < 0)
-		goto out;
-
-	if (!r) {
-		r = 1;
-		goto out;
-	}
+		return r;
+	if (!r)
+		return 1;
 
 	if (mmio_info_in_cache(vcpu, cr2, direct))
 		emulation_type = 0;
-
+emulate:
 	er = x86_emulate_instruction(vcpu, cr2, emulation_type, insn, insn_len);
 
 	switch (er) {
@@ -4386,8 +4381,6 @@ int kvm_mmu_page_fault(struct kvm_vcpu *vcpu, gva_t cr2, u32 error_code,
 	default:
 		BUG();
 	}
-out:
-	return r;
 }
 EXPORT_SYMBOL_GPL(kvm_mmu_page_fault);
 
diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h
index 6c9fed9..05827ff 100644
--- a/arch/x86/kvm/paging_tmpl.h
+++ b/arch/x86/kvm/paging_tmpl.h
@@ -702,24 +702,17 @@ static int FNAME(page_fault)(struct kvm_vcpu *vcpu, gva_t addr, u32 error_code,
 
 	pgprintk("%s: addr %lx err %x\n", __func__, addr, error_code);
 
-	if (unlikely(error_code & PFERR_RSVD_MASK)) {
-		r = handle_mmio_page_fault(vcpu, addr, mmu_is_nested(vcpu));
-		if (likely(r != RET_MMIO_PF_INVALID))
-			return r;
-
-		/*
-		 * page fault with PFEC.RSVD  = 1 is caused by shadow
-		 * page fault, should not be used to walk guest page
-		 * table.
-		 */
-		error_code &= ~PFERR_RSVD_MASK;
-	};
-
 	r = mmu_topup_memory_caches(vcpu);
 	if (r)
 		return r;
 
 	/*
+	 * If PFEC.RSVD is set, this is a shadow page fault.
+	 * The bit needs to be cleared before walking guest page tables.
+	 */
+	error_code &= ~PFERR_RSVD_MASK;
+
+	/*
 	 * Look up the guest pte for the faulting address.
 	 */
 	r = FNAME(walk_addr)(&walker, vcpu, addr, error_code);
-- 
2.1.0