linux-kernel - [PATCH 02/17] KVM: x86: Remove separate "bit" defines for page fault error code masks

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Message-ID: <20240507155817.3951344-3-pbonzini@redhat.com>
Date: Tue,  7 May 2024 11:58:02 -0400
From: Paolo Bonzini <pbonzini@...hat.com>
To: linux-kernel@...r.kernel.org,
	kvm@...r.kernel.org
Cc: Sean Christopherson <seanjc@...gle.com>
Subject: [PATCH 02/17] KVM: x86: Remove separate "bit" defines for page fault error code masks

From: Sean Christopherson <seanjc@...gle.com>

Open code the bit number directly in the PFERR_* masks and drop the
intermediate PFERR_*_BIT defines, as having to bounce through two macros
just to see which flag corresponds to which bit is quite annoying, as is
having to define two macros just to add recognition of a new flag.

Use ternary operator to derive the bit in permission_fault(), the one
function that actually needs the bit number as part of clever shifting
to avoid conditional branches.  Generally the compiler is able to turn
it into a conditional move, and if not it's not really a big deal.

No functional change intended.

Signed-off-by: Sean Christopherson <seanjc@...gle.com>
Reviewed-by: Paolo Bonzini <pbonzini@...hat.com>
Message-ID: <20240228024147.41573-3-seanjc@...gle.com>
Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
---
 arch/x86/include/asm/kvm_host.h | 32 ++++++++++----------------------
 arch/x86/kvm/mmu.h              |  5 ++---
 2 files changed, 12 insertions(+), 25 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 9f92bdb78504..a047480da5af 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -254,28 +254,16 @@ enum x86_intercept_stage;
 	KVM_GUESTDBG_INJECT_DB | \
 	KVM_GUESTDBG_BLOCKIRQ)
 
-
-#define PFERR_PRESENT_BIT 0
-#define PFERR_WRITE_BIT 1
-#define PFERR_USER_BIT 2
-#define PFERR_RSVD_BIT 3
-#define PFERR_FETCH_BIT 4
-#define PFERR_PK_BIT 5
-#define PFERR_SGX_BIT 15
-#define PFERR_GUEST_FINAL_BIT 32
-#define PFERR_GUEST_PAGE_BIT 33
-#define PFERR_IMPLICIT_ACCESS_BIT 48
-
-#define PFERR_PRESENT_MASK	BIT(PFERR_PRESENT_BIT)
-#define PFERR_WRITE_MASK	BIT(PFERR_WRITE_BIT)
-#define PFERR_USER_MASK		BIT(PFERR_USER_BIT)
-#define PFERR_RSVD_MASK		BIT(PFERR_RSVD_BIT)
-#define PFERR_FETCH_MASK	BIT(PFERR_FETCH_BIT)
-#define PFERR_PK_MASK		BIT(PFERR_PK_BIT)
-#define PFERR_SGX_MASK		BIT(PFERR_SGX_BIT)
-#define PFERR_GUEST_FINAL_MASK	BIT_ULL(PFERR_GUEST_FINAL_BIT)
-#define PFERR_GUEST_PAGE_MASK	BIT_ULL(PFERR_GUEST_PAGE_BIT)
-#define PFERR_IMPLICIT_ACCESS	BIT_ULL(PFERR_IMPLICIT_ACCESS_BIT)
+#define PFERR_PRESENT_MASK	BIT(0)
+#define PFERR_WRITE_MASK	BIT(1)
+#define PFERR_USER_MASK		BIT(2)
+#define PFERR_RSVD_MASK		BIT(3)
+#define PFERR_FETCH_MASK	BIT(4)
+#define PFERR_PK_MASK		BIT(5)
+#define PFERR_SGX_MASK		BIT(15)
+#define PFERR_GUEST_FINAL_MASK	BIT_ULL(32)
+#define PFERR_GUEST_PAGE_MASK	BIT_ULL(33)
+#define PFERR_IMPLICIT_ACCESS	BIT_ULL(48)
 
 #define PFERR_NESTED_GUEST_PAGE (PFERR_GUEST_PAGE_MASK |	\
 				 PFERR_WRITE_MASK |		\
diff --git a/arch/x86/kvm/mmu.h b/arch/x86/kvm/mmu.h
index 60f21bb4c27b..2343c9f00e31 100644
--- a/arch/x86/kvm/mmu.h
+++ b/arch/x86/kvm/mmu.h
@@ -213,7 +213,7 @@ static inline u8 permission_fault(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu,
 	 */
 	u64 implicit_access = access & PFERR_IMPLICIT_ACCESS;
 	bool not_smap = ((rflags & X86_EFLAGS_AC) | implicit_access) == X86_EFLAGS_AC;
-	int index = (pfec + (not_smap << PFERR_RSVD_BIT)) >> 1;
+	int index = (pfec | (not_smap ? PFERR_RSVD_MASK : 0)) >> 1;
 	u32 errcode = PFERR_PRESENT_MASK;
 	bool fault;
 
@@ -234,8 +234,7 @@ static inline u8 permission_fault(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu,
 		pkru_bits = (vcpu->arch.pkru >> (pte_pkey * 2)) & 3;
 
 		/* clear present bit, replace PFEC.RSVD with ACC_USER_MASK. */
-		offset = (pfec & ~1) +
-			((pte_access & PT_USER_MASK) << (PFERR_RSVD_BIT - PT_USER_SHIFT));
+		offset = (pfec & ~1) | ((pte_access & PT_USER_MASK) ? PFERR_RSVD_MASK : 0);
 
 		pkru_bits &= mmu->pkru_mask >> offset;
 		errcode |= -pkru_bits & PFERR_PK_MASK;
-- 
2.43.0