[PATCH 6.12 233/269] KVM: x86: Snapshot the hosts DEBUGCTL in common x86

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6.12-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Sean Christopherson <seanjc@xxxxxxxxxx>

commit fb71c795935652fa20eaf9517ca9547f5af99a76 upstream.

Move KVM's snapshot of DEBUGCTL to kvm_vcpu_arch and take the snapshot in
common x86, so that SVM can also use the snapshot.

Opportunistically change the field to a u64.  While bits 63:32 are reserved
on AMD, not mentioned at all in Intel's SDM, and managed as an "unsigned
long" by the kernel, DEBUGCTL is an MSR and therefore a 64-bit value.

Reviewed-by: Xiaoyao Li <xiaoyao.li@xxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Reviewed-and-tested-by: Ravi Bangoria <ravi.bangoria@xxxxxxx>
Link: https://lore.kernel.org/r/20250227222411.3490595-4-seanjc@xxxxxxxxxx
Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 arch/x86/include/asm/kvm_host.h |    1 +
 arch/x86/kvm/vmx/vmx.c          |    8 ++------
 arch/x86/kvm/vmx/vmx.h          |    2 --
 arch/x86/kvm/x86.c              |    1 +
 4 files changed, 4 insertions(+), 8 deletions(-)

--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -761,6 +761,7 @@ struct kvm_vcpu_arch {
 	u32 pkru;
 	u32 hflags;
 	u64 efer;
+	u64 host_debugctl;
 	u64 apic_base;
 	struct kvm_lapic *apic;    /* kernel irqchip context */
 	bool load_eoi_exitmap_pending;
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -1515,16 +1515,12 @@ void vmx_vcpu_load_vmcs(struct kvm_vcpu
  */
 void vmx_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
 {
-	struct vcpu_vmx *vmx = to_vmx(vcpu);
-
 	if (vcpu->scheduled_out && !kvm_pause_in_guest(vcpu->kvm))
 		shrink_ple_window(vcpu);
 
 	vmx_vcpu_load_vmcs(vcpu, cpu, NULL);
 
 	vmx_vcpu_pi_load(vcpu, cpu);
-
-	vmx->host_debugctlmsr = get_debugctlmsr();
 }
 
 void vmx_vcpu_put(struct kvm_vcpu *vcpu)
@@ -7454,8 +7450,8 @@ fastpath_t vmx_vcpu_run(struct kvm_vcpu
 	}
 
 	/* MSR_IA32_DEBUGCTLMSR is zeroed on vmexit. Restore it if needed */
-	if (vmx->host_debugctlmsr)
-		update_debugctlmsr(vmx->host_debugctlmsr);
+	if (vcpu->arch.host_debugctl)
+		update_debugctlmsr(vcpu->arch.host_debugctl);
 
 #ifndef CONFIG_X86_64
 	/*
--- a/arch/x86/kvm/vmx/vmx.h
+++ b/arch/x86/kvm/vmx/vmx.h
@@ -339,8 +339,6 @@ struct vcpu_vmx {
 	/* apic deadline value in host tsc */
 	u64 hv_deadline_tsc;
 
-	unsigned long host_debugctlmsr;
-
 	/*
 	 * Only bits masked by msr_ia32_feature_control_valid_bits can be set in
 	 * msr_ia32_feature_control. FEAT_CTL_LOCKED is always included
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -4993,6 +4993,7 @@ void kvm_arch_vcpu_load(struct kvm_vcpu
 
 	/* Save host pkru register if supported */
 	vcpu->arch.host_pkru = read_pkru();
+	vcpu->arch.host_debugctl = get_debugctlmsr();
 
 	/* Apply any externally detected TSC adjustments (due to suspend) */
 	if (unlikely(vcpu->arch.tsc_offset_adjustment)) {






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