KVM: SVM: Store MSRPM pointer as "void *" instead of "u32 *"

Store KVM's MSRPM pointers as "void *" instead of "u32 *" to guard against
directly accessing the bitmaps outside of code that is explicitly written
to access the bitmaps with a specific type.

Opportunistically use svm_vcpu_free_msrpm() in svm_vcpu_free() instead of
open coding an equivalent.

Link: https://lore.kernel.org/r/20250610225737.156318-27-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

Author: sean-jc

arch/x86/kvm/svm/nested.c

@@ -277,6 +277,8 @@ int __init nested_svm_init_msrpm_merge_offsets(void)
 static bool nested_svm_merge_msrpm(struct kvm_vcpu *vcpu)
 {
 	struct vcpu_svm *svm = to_svm(vcpu);
+	u32 *msrpm02 = svm->nested.msrpm;
+	u32 *msrpm01 = svm->msrpm;
 	int i;
 
 	/*
@@ -311,7 +313,7 @@ static bool nested_svm_merge_msrpm(struct kvm_vcpu *vcpu)
 		if (kvm_vcpu_read_guest(vcpu, offset, &value, 4))
 			return false;
 
-		svm->nested.msrpm[p] = svm->msrpm[p] | value;
+		msrpm02[p] = msrpm01[p] | value;
 	}
 
 	svm->nested.force_msr_bitmap_recalc = false;

arch/x86/kvm/svm/svm.c

@@ -722,11 +722,11 @@ void svm_enable_intercept_for_msr(struct kvm_vcpu *vcpu, u32 msr, int type)
 	svm->nested.force_msr_bitmap_recalc = true;
 }
 
-u32 *svm_vcpu_alloc_msrpm(void)
+void *svm_vcpu_alloc_msrpm(void)
 {
 	unsigned int order = get_order(MSRPM_SIZE);
 	struct page *pages = alloc_pages(GFP_KERNEL_ACCOUNT, order);
-	u32 *msrpm;
+	void *msrpm;
 
 	if (!pages)
 		return NULL;
@@ -799,7 +799,7 @@ void svm_set_x2apic_msr_interception(struct vcpu_svm *svm, bool intercept)
 	svm->x2avic_msrs_intercepted = intercept;
 }
 
-void svm_vcpu_free_msrpm(u32 *msrpm)
+void svm_vcpu_free_msrpm(void *msrpm)
 {
 	__free_pages(virt_to_page(msrpm), get_order(MSRPM_SIZE));
 }
@@ -1347,7 +1347,7 @@ static void svm_vcpu_free(struct kvm_vcpu *vcpu)
 	sev_free_vcpu(vcpu);
 
 	__free_page(__sme_pa_to_page(svm->vmcb01.pa));
-	__free_pages(virt_to_page(svm->msrpm), get_order(MSRPM_SIZE));
+	svm_vcpu_free_msrpm(svm->msrpm);
 }
 
 #ifdef CONFIG_CPU_MITIGATIONS

arch/x86/kvm/svm/svm.h

@@ -186,8 +186,11 @@ struct svm_nested_state {
 	u64 vmcb12_gpa;
 	u64 last_vmcb12_gpa;
 
-	/* These are the merged vectors */
-	u32 *msrpm;
+	/*
+	 * The MSR permissions map used for vmcb02, which is the merge result
+	 * of vmcb01 and vmcb12
+	 */
+	void *msrpm;
 
 	/* A VMRUN has started but has not yet been performed, so
 	 * we cannot inject a nested vmexit yet.  */
@@ -268,7 +271,7 @@ struct vcpu_svm {
 	 */
 	u64 virt_spec_ctrl;
 
-	u32 *msrpm;
+	void *msrpm;
 
 	ulong nmi_iret_rip;
 
@@ -666,8 +669,8 @@ BUILD_SVM_MSR_BITMAP_HELPERS(void, set, __set)
 /* svm.c */
 extern bool dump_invalid_vmcb;
 
-u32 *svm_vcpu_alloc_msrpm(void);
-void svm_vcpu_free_msrpm(u32 *msrpm);
+void *svm_vcpu_alloc_msrpm(void);
+void svm_vcpu_free_msrpm(void *msrpm);
 void svm_copy_lbrs(struct vmcb *to_vmcb, struct vmcb *from_vmcb);
 void svm_enable_lbrv(struct kvm_vcpu *vcpu);
 void svm_update_lbrv(struct kvm_vcpu *vcpu);