[Xen-devel] [PATCH] x86/msr: Virtualise MSR_PLATFORM_ID properly

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

This is an Intel-only, read-only MSR related to microcode loading.  Expose it
in similar circumstances as the PATCHLEVEL MSR.

This should have been alongside c/s 013896cb8b2 "x86/msr: Fix handling of
MSR_AMD_PATCHLEVEL/MSR_IA32_UCODE_REV"

Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
CC: Jan Beulich <JBeulich@xxxxxxxx>
CC: Wei Liu <wl@xxxxxxx>
CC: Roger Pau Monné <roger.pau@xxxxxxxxxx>

Turns out I wrote this nearly a year ago and didn't send it.  It obviously got
dropped in the leadup to MDS.
---
 xen/arch/x86/msr.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/xen/arch/x86/msr.c b/xen/arch/x86/msr.c
index 785574de67..1cea777680 100644
--- a/xen/arch/x86/msr.c
+++ b/xen/arch/x86/msr.c
@@ -143,6 +143,13 @@ int guest_rdmsr(struct vcpu *v, uint32_t msr, uint64_t 
*val)
         /* Not offered to guests. */
         goto gp_fault;
 
+    case MSR_IA32_PLATFORM_ID:
+        if ( !(cp->x86_vendor & X86_VENDOR_INTEL) ||
+             !(boot_cpu_data.x86_vendor & X86_VENDOR_INTEL) )
+            goto gp_fault;
+        rdmsrl(MSR_IA32_PLATFORM_ID, *val);
+        break;
+
     case MSR_AMD_PATCHLEVEL:
         BUILD_BUG_ON(MSR_IA32_UCODE_REV != MSR_AMD_PATCHLEVEL);
         /*
@@ -275,6 +282,7 @@ int guest_wrmsr(struct vcpu *v, uint32_t msr, uint64_t val)
     {
         uint64_t rsvd;
 
+    case MSR_IA32_PLATFORM_ID:
     case MSR_INTEL_CORE_THREAD_COUNT:
     case MSR_INTEL_PLATFORM_INFO:
     case MSR_ARCH_CAPABILITIES:
-- 
2.11.0


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