linux-kernel - [PATCH 07/28] KVM: SVM: Clean up macros related to architectural MSRPM definitions

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Message-ID: <20250529234013.3826933-8-seanjc@google.com>
Date: Thu, 29 May 2025 16:39:52 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: Sean Christopherson <seanjc@...gle.com>, Paolo Bonzini <pbonzini@...hat.com>
Cc: kvm@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Borislav Petkov <bp@...en8.de>, Xin Li <xin@...or.com>, Chao Gao <chao.gao@...el.com>, 
	Dapeng Mi <dapeng1.mi@...ux.intel.com>
Subject: [PATCH 07/28] KVM: SVM: Clean up macros related to architectural
 MSRPM definitions

Move SVM's MSR Permissions Map macros to svm.h in antipication of adding
helpers that are available to SVM code, and opportunistically replace a
variety of open-coded literals with (hopefully) informative macros.

Opportunistically open code ARRAY_SIZE(msrpm_ranges) instead of wrapping
it as NUM_MSR_MAPS, which is an ambiguous name even if it were qualified
with "SVM_MSRPM".

No functional change intended.

Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 arch/x86/kvm/svm/svm.c | 18 +++++++++---------
 arch/x86/kvm/svm/svm.h | 17 ++++++++++++++++-
 2 files changed, 25 insertions(+), 10 deletions(-)

diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 2085259644b6..1c70293400bc 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -266,24 +266,24 @@ static DEFINE_MUTEX(vmcb_dump_mutex);
  */
 static int tsc_aux_uret_slot __read_mostly = -1;
 
-static const u32 msrpm_ranges[] = {0, 0xc0000000, 0xc0010000};
-
-#define NUM_MSR_MAPS ARRAY_SIZE(msrpm_ranges)
-#define MSRS_RANGE_SIZE 2048
-#define MSRS_IN_RANGE (MSRS_RANGE_SIZE * 8 / 2)
+static const u32 msrpm_ranges[] = {
+	SVM_MSRPM_RANGE_0_BASE_MSR,
+	SVM_MSRPM_RANGE_1_BASE_MSR,
+	SVM_MSRPM_RANGE_2_BASE_MSR
+};
 
 u32 svm_msrpm_offset(u32 msr)
 {
 	u32 offset;
 	int i;
 
-	for (i = 0; i < NUM_MSR_MAPS; i++) {
+	for (i = 0; i < ARRAY_SIZE(msrpm_ranges); i++) {
 		if (msr < msrpm_ranges[i] ||
-		    msr >= msrpm_ranges[i] + MSRS_IN_RANGE)
+		    msr >= msrpm_ranges[i] + SVM_MSRS_PER_RANGE)
 			continue;
 
-		offset  = (msr - msrpm_ranges[i]) / 4; /* 4 msrs per u8 */
-		offset += (i * MSRS_RANGE_SIZE);       /* add range offset */
+		offset  = (msr - msrpm_ranges[i]) / SVM_MSRS_PER_BYTE;
+		offset += (i * SVM_MSRPM_BYTES_PER_RANGE);  /* add range offset */
 
 		/* Now we have the u8 offset - but need the u32 offset */
 		return offset / 4;
diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h
index f1e466a10219..909b9af6b3c1 100644
--- a/arch/x86/kvm/svm/svm.h
+++ b/arch/x86/kvm/svm/svm.h
@@ -613,11 +613,26 @@ static inline void svm_vmgexit_no_action(struct vcpu_svm *svm, u64 data)
 	svm_vmgexit_set_return_code(svm, GHCB_HV_RESP_NO_ACTION, data);
 }
 
-/* svm.c */
+/*
+ * The MSRPM is 8KiB in size, divided into four 2KiB ranges (the fourth range
+ * is reserved).  Each MSR within a range is covered by two bits, one each for
+ * read (bit 0) and write (bit 1), where a bit value of '1' means intercepted.
+ */
+#define SVM_MSRPM_BYTES_PER_RANGE 2048
+#define SVM_BITS_PER_MSR 2
+#define SVM_MSRS_PER_BYTE (BITS_PER_BYTE / SVM_BITS_PER_MSR)
+#define SVM_MSRS_PER_RANGE (SVM_MSRPM_BYTES_PER_RANGE * SVM_MSRS_PER_BYTE)
+static_assert(SVM_MSRS_PER_RANGE == 8192);
+
+#define SVM_MSRPM_RANGE_0_BASE_MSR	0
+#define SVM_MSRPM_RANGE_1_BASE_MSR	0xc0000000
+#define SVM_MSRPM_RANGE_2_BASE_MSR	0xc0010000
+
 #define MSR_INVALID				0xffffffffU
 
 #define DEBUGCTL_RESERVED_BITS (~DEBUGCTLMSR_LBR)
 
+/* svm.c */
 extern bool dump_invalid_vmcb;
 
 u32 svm_msrpm_offset(u32 msr);
-- 
2.49.0.1204.g71687c7c1d-goog