[PATCH 3/3] x86/msr: Fix Solaris and turbostat following XSA-351

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
CC: Jan Beulich <JBeulich@xxxxxxxx>
CC: Roger Pau Monné <roger.pau@xxxxxxxxxx>
CC: Wei Liu <wl@xxxxxxx>
CC: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
CC: Ian Jackson <iwj@xxxxxxxxxxxxxx>

For 4.15 This wants backporting to all security trees, as it is a fix to a
regression introduced in XSA-351.

Also it means that users don't need msr_relaxed=1 to unbreak Solaris guests,
which is a strict useability improvement.
---
 xen/arch/x86/msr.c | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/xen/arch/x86/msr.c b/xen/arch/x86/msr.c
index 5927b6811b..a83a1d7fba 100644
--- a/xen/arch/x86/msr.c
+++ b/xen/arch/x86/msr.c
@@ -188,7 +188,6 @@ int guest_rdmsr(struct vcpu *v, uint32_t msr, uint64_t *val)
     case MSR_TSX_CTRL:
     case MSR_MCU_OPT_CTRL:
     case MSR_RTIT_OUTPUT_BASE ... MSR_RTIT_ADDR_B(7):
-    case MSR_RAPL_POWER_UNIT:
     case MSR_PKG_POWER_LIMIT  ... MSR_PKG_POWER_INFO:
     case MSR_DRAM_POWER_LIMIT ... MSR_DRAM_POWER_INFO:
     case MSR_PP0_POWER_LIMIT  ... MSR_PP0_POLICY:
@@ -284,6 +283,18 @@ int guest_rdmsr(struct vcpu *v, uint32_t msr, uint64_t 
*val)
             goto gp_fault;
         break;
 
+    case MSR_RAPL_POWER_UNIT:
+        /*
+         * This MSR is non-architectural.  However, some versions of Solaris
+         * blindly reads it without a #GP guard, and some versions of
+         * turbostat crash after expecting a read of /proc/cpu/0/msr not to
+         * fail.  Read as zero on Intel hardware.
+         */
+        if ( !(cp->x86_vendor & X86_VENDOR_INTEL) )
+            goto gp_fault;
+        *val = 0;
+        break;
+
         /*
          * These MSRs are not enumerated in CPUID.  They have been around
          * since the Pentium 4, and implemented by other vendors.
-- 
2.11.0