linux-kernel - [PATCH v3 09/27] KVM: VMX: Do not use MAX_POSSIBLE_PASSTHROUGH

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Message-ID: <20241001050110.3643764-10-xin@zytor.com>
Date: Mon, 30 Sep 2024 22:00:52 -0700
From: "Xin Li (Intel)" <xin@...or.com>
To: kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-doc@...r.kernel.org
Cc: seanjc@...gle.com, pbonzini@...hat.com, corbet@....net, tglx@...utronix.de,
        mingo@...hat.com, bp@...en8.de, dave.hansen@...ux.intel.com,
        x86@...nel.org, hpa@...or.com, luto@...nel.org, peterz@...radead.org,
        andrew.cooper3@...rix.com, xin@...or.com
Subject: [PATCH v3 09/27] KVM: VMX: Do not use MAX_POSSIBLE_PASSTHROUGH_MSRS in array definition

No need to use MAX_POSSIBLE_PASSTHROUGH_MSRS in the definition of array
vmx_possible_passthrough_msrs, as the macro name indicates the _possible_
maximum size of passthrough MSRs.

Use ARRAY_SIZE instead of MAX_POSSIBLE_PASSTHROUGH_MSRS when the size of
the array is needed and add a BUILD_BUG_ON to make sure the actual array
size does not exceed the possible maximum size of passthrough MSRs.

Signed-off-by: Xin Li (Intel) <xin@...or.com>
Tested-by: Shan Kang <shan.kang@...el.com>
---
 arch/x86/kvm/vmx/vmx.c | 8 +++++---
 arch/x86/kvm/vmx/vmx.h | 2 +-
 2 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 9acc9661fdb2..28cf89c97bda 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -167,7 +167,7 @@ module_param(allow_smaller_maxphyaddr, bool, S_IRUGO);
  * List of MSRs that can be directly passed to the guest.
  * In addition to these x2apic, PT and LBR MSRs are handled specially.
  */
-static u32 vmx_possible_passthrough_msrs[MAX_POSSIBLE_PASSTHROUGH_MSRS] = {
+static u32 vmx_possible_passthrough_msrs[] = {
 	MSR_IA32_SPEC_CTRL,
 	MSR_IA32_PRED_CMD,
 	MSR_IA32_FLUSH_CMD,
@@ -4182,6 +4182,8 @@ void vmx_msr_filter_changed(struct kvm_vcpu *vcpu)
 	if (!cpu_has_vmx_msr_bitmap())
 		return;
 
+	BUILD_BUG_ON(ARRAY_SIZE(vmx_possible_passthrough_msrs) > MAX_POSSIBLE_PASSTHROUGH_MSRS);
+
 	/*
 	 * Redo intercept permissions for MSRs that KVM is passing through to
 	 * the guest.  Disabling interception will check the new MSR filter and
@@ -7626,8 +7628,8 @@ int vmx_vcpu_create(struct kvm_vcpu *vcpu)
 	}
 
 	/* The MSR bitmap starts with all ones */
-	bitmap_fill(vmx->shadow_msr_intercept.read, MAX_POSSIBLE_PASSTHROUGH_MSRS);
-	bitmap_fill(vmx->shadow_msr_intercept.write, MAX_POSSIBLE_PASSTHROUGH_MSRS);
+	bitmap_fill(vmx->shadow_msr_intercept.read, ARRAY_SIZE(vmx_possible_passthrough_msrs));
+	bitmap_fill(vmx->shadow_msr_intercept.write, ARRAY_SIZE(vmx_possible_passthrough_msrs));
 
 	vmx_disable_intercept_for_msr(vcpu, MSR_IA32_TSC, MSR_TYPE_R);
 #ifdef CONFIG_X86_64
diff --git a/arch/x86/kvm/vmx/vmx.h b/arch/x86/kvm/vmx/vmx.h
index e0d76d2460ef..e7409f8f28b1 100644
--- a/arch/x86/kvm/vmx/vmx.h
+++ b/arch/x86/kvm/vmx/vmx.h
@@ -356,7 +356,7 @@ struct vcpu_vmx {
 	struct lbr_desc lbr_desc;
 
 	/* Save desired MSR intercept (read: pass-through) state */
-#define MAX_POSSIBLE_PASSTHROUGH_MSRS	16
+#define MAX_POSSIBLE_PASSTHROUGH_MSRS	64
 	struct {
 		DECLARE_BITMAP(read, MAX_POSSIBLE_PASSTHROUGH_MSRS);
 		DECLARE_BITMAP(write, MAX_POSSIBLE_PASSTHROUGH_MSRS);
-- 
2.46.2