Re: [PATCH] KVM: SEV-ES: Don't intercept MSR_IA32_DEBUGCTLMSR for SEV-ES guests

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On 3/26/24 03:11, Ravi Bangoria wrote:
Currently, LBR Virtualization is dynamically enabled and disabled for
a vcpu by intercepting writes to MSR_IA32_DEBUGCTLMSR. This helps by
avoiding unnecessary save/restore of LBR MSRs when nobody is using it
in the guest. However, SEV-ES guest mandates LBR Virtualization to be
_always_ ON[1] and thus this dynamic toggling doesn't work for SEV-ES
guest, in fact it results into fatal error:

SEV-ES guest on Zen3, kvm-amd.ko loaded with lbrv=1

   [guest ~]# wrmsr 0x1d9 0x4
   KVM: entry failed, hardware error 0xffffffff
   EAX=00000004 EBX=00000000 ECX=000001d9 EDX=00000000
   ...

Fix this by never intercepting MSR_IA32_DEBUGCTLMSR for SEV-ES guests.

Adding something to the commit message that this MSR is fully virtualized (swap type A) would be good to have. Aside from that.

Reviewed-by: Tom Lendacky <thomas.lendacky@xxxxxxx>


[1]: AMD64 Architecture Programmer's Manual Pub. 40332, Rev. 4.07 - June
      2023, Vol 2, 15.35.2 Enabling SEV-ES.
      https://bugzilla.kernel.org/attachment.cgi?id=304653

Fixes: 376c6d285017 ("KVM: SVM: Provide support for SEV-ES vCPU creation/loading")
Signed-off-by: Ravi Bangoria <ravi.bangoria@xxxxxxx>
---
  arch/x86/kvm/svm/sev.c | 1 +
  arch/x86/kvm/svm/svm.c | 1 +
  arch/x86/kvm/svm/svm.h | 2 +-
  3 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index a8ce5226b3b5..ef932a7ff9bd 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -3073,6 +3073,7 @@ static void sev_es_init_vmcb(struct vcpu_svm *svm)
  	/* Clear intercepts on selected MSRs */
  	set_msr_interception(vcpu, svm->msrpm, MSR_EFER, 1, 1);
  	set_msr_interception(vcpu, svm->msrpm, MSR_IA32_CR_PAT, 1, 1);
+	set_msr_interception(vcpu, svm->msrpm, MSR_IA32_DEBUGCTLMSR, 1, 1);
  	set_msr_interception(vcpu, svm->msrpm, MSR_IA32_LASTBRANCHFROMIP, 1, 1);
  	set_msr_interception(vcpu, svm->msrpm, MSR_IA32_LASTBRANCHTOIP, 1, 1);
  	set_msr_interception(vcpu, svm->msrpm, MSR_IA32_LASTINTFROMIP, 1, 1);
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index e90b429c84f1..5a82135ae84e 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -99,6 +99,7 @@ static const struct svm_direct_access_msrs {
  	{ .index = MSR_IA32_SPEC_CTRL,			.always = false },
  	{ .index = MSR_IA32_PRED_CMD,			.always = false },
  	{ .index = MSR_IA32_FLUSH_CMD,			.always = false },
+	{ .index = MSR_IA32_DEBUGCTLMSR,		.always = false },
  	{ .index = MSR_IA32_LASTBRANCHFROMIP,		.always = false },
  	{ .index = MSR_IA32_LASTBRANCHTOIP,		.always = false },
  	{ .index = MSR_IA32_LASTINTFROMIP,		.always = false },
diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h
index 8ef95139cd24..7a1b60bcebff 100644
--- a/arch/x86/kvm/svm/svm.h
+++ b/arch/x86/kvm/svm/svm.h
@@ -30,7 +30,7 @@
  #define	IOPM_SIZE PAGE_SIZE * 3
  #define	MSRPM_SIZE PAGE_SIZE * 2
-#define MAX_DIRECT_ACCESS_MSRS 47
+#define MAX_DIRECT_ACCESS_MSRS	48
  #define MSRPM_OFFSETS	32
  extern u32 msrpm_offsets[MSRPM_OFFSETS] __read_mostly;
  extern bool npt_enabled;




[Index of Archives]     [KVM ARM]     [KVM ia64]     [KVM ppc]     [Virtualization Tools]     [Spice Development]     [Libvirt]     [Libvirt Users]     [Linux USB Devel]     [Linux Audio Users]     [Yosemite Questions]     [Linux Kernel]     [Linux SCSI]     [XFree86]

  Powered by Linux