From: Tom Lendacky <thomas.lendacky@amd.com>
Date: Thu, 20 Mar 2025 13:26:53 +0000 (-0500)
Subject: KVM: SVM: Add a mutex to dump_vmcb() to prevent concurrent output
X-Git-Tag: v6.16-rc1~78^2~4^2~10
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=468c27ae0215c14bc62c90fa7b2ce2bc9eb4564b;p=thirdparty%2Fkernel%2Flinux.git

KVM: SVM: Add a mutex to dump_vmcb() to prevent concurrent output

If multiple VMRUN instructions fail, resulting in calls to dump_vmcb(),
the output can become interleaved and it is impossible to identify which
line of output belongs to which VMCB. Add a mutex to dump_vmcb() so that
the output is serialized.

Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Acked-by: Borislav Petkov (AMD) <bp@alien8.de>
Tested-by: Kim Phillips <kim.phillips@amd.com>
Link: https://lore.kernel.org/r/a880678afd9488e1dd6017445802712f7c02cc6d.1742477213.git.thomas.lendacky@amd.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
---

diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 272ce4bdbf111..919f98479774b 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -29,6 +29,7 @@
 #include <linux/cc_platform.h>
 #include <linux/smp.h>
 #include <linux/string_choices.h>
+#include <linux/mutex.h>
 
 #include <asm/apic.h>
 #include <asm/perf_event.h>
@@ -249,6 +250,8 @@ static unsigned long iopm_base;
 
 DEFINE_PER_CPU(struct svm_cpu_data, svm_data);
 
+static DEFINE_MUTEX(vmcb_dump_mutex);
+
 /*
  * Only MSR_TSC_AUX is switched via the user return hook.  EFER is switched via
  * the VMCB, and the SYSCALL/SYSENTER MSRs are handled by VMLOAD/VMSAVE.
@@ -3404,6 +3407,8 @@ static void dump_vmcb(struct kvm_vcpu *vcpu)
 		return;
 	}
 
+	guard(mutex)(&vmcb_dump_mutex);
+
 	vm_type = sev_snp_guest(vcpu->kvm) ? "SEV-SNP" :
 		  sev_es_guest(vcpu->kvm) ? "SEV-ES" :
 		  sev_guest(vcpu->kvm) ? "SEV" : "SVM";