Windows Server 2019 Essentials will unconditionally attempt to read
P5_MC_ADDR MSR at boot and throw a BSOD if injected a #GP.
Fix this by adding dummy handling that returns 0 for reads of
P5_MC_ADDR. This seems to be enough to make Windows happy.
Reported-by: Steffen Einsle <ein...@phptrix.de>
Signed-off-by: Roger Pau Monné <roger....@citrix.com>
---
I've added it for CENTAUR and SHANGHAI because the MSR is there since
Pentium, so likely to be implemented by those vendors also, but have
no way to check.
I wonder how long it will take for Windows to also start poking at
MSR_IA32_MC0_ADDR or other MCE related registers. For now this seems
to be enough.
---
xen/arch/x86/include/asm/msr-index.h | 2 ++
xen/arch/x86/msr.c | 13 +++++++++++++
2 files changed, 15 insertions(+)
diff --git a/xen/arch/x86/include/asm/msr-index.h
b/xen/arch/x86/include/asm/msr-index.h
index 3e038db618..02af9dc039 100644
--- a/xen/arch/x86/include/asm/msr-index.h
+++ b/xen/arch/x86/include/asm/msr-index.h
@@ -15,6 +15,8 @@
* abbreviated name. Exceptions will be considered on a case-by-case basis.
*/
+#define MSR_P5_MC_ADDR 0
+
#define MSR_APIC_BASE 0x0000001b
#define APIC_BASE_BSP (_AC(1, ULL) << 8)
#define APIC_BASE_EXTD (_AC(1, ULL) << 10)
diff --git a/xen/arch/x86/msr.c b/xen/arch/x86/msr.c
index a1e268eea9..e50bbf466a 100644
--- a/xen/arch/x86/msr.c
+++ b/xen/arch/x86/msr.c
@@ -216,6 +216,19 @@ int guest_rdmsr(struct vcpu *v, uint32_t msr, uint64_t
*val)
case MSR_AMD_PPIN:
goto gp_fault;
+ case MSR_P5_MC_ADDR:
+ /*
+ * Windows Server 2019 Essentials will attempt to read the MSR and
+ * throw a BSOD if a #GP is raised, so just return 0 in order to make
+ * Windows happy.
+ */
+ if ( !(cp->x86_vendor & (X86_VENDOR_INTEL | X86_VENDOR_CENTAUR |
+ X86_VENDOR_SHANGHAI)) )
+ goto gp_fault;
+
+ *val = 0;
+ break;
+
case MSR_IA32_FEATURE_CONTROL:
/*
* Architecturally, availability of this MSR is enumerated by the
--
2.35.1
