[xen stable-4.12] x86/vPMU: don't blindly assume IA32_PERF_CAPABILITIES MSR exists

[patchbot@xxxxxxx]

commit 3c37292c844a23beffc802192600386e2ea6888c
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Thu Apr 9 09:30:14 2020 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Thu Apr 9 09:30:14 2020 +0200

    x86/vPMU: don't blindly assume IA32_PERF_CAPABILITIES MSR exists
    
    Just like VMX'es lbr_tsx_fixup_check() the respective CPUID bit should
    be consulted first.
    
    Reported-by: Farrah Chen <farrah.chen@xxxxxxxxx>
    Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
    Acked-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    master commit: 15c39c7c913f26fba40231e103ce1ffa6101e7c9
    master date: 2020-02-26 17:35:48 +0100
---
 xen/arch/x86/cpu/vpmu_intel.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/xen/arch/x86/cpu/vpmu_intel.c b/xen/arch/x86/cpu/vpmu_intel.c
index 6e27f6ec8e..75aa11c6ad 100644
--- a/xen/arch/x86/cpu/vpmu_intel.c
+++ b/xen/arch/x86/cpu/vpmu_intel.c
@@ -900,7 +900,6 @@ int vmx_vpmu_initialise(struct vcpu *v)
 
 int __init core2_vpmu_init(void)
 {
-    u64 caps;
     unsigned int version = 0;
     unsigned int i;
 
@@ -932,8 +931,14 @@ int __init core2_vpmu_init(void)
 
     arch_pmc_cnt = core2_get_arch_pmc_count();
     fixed_pmc_cnt = core2_get_fixed_pmc_count();
-    rdmsrl(MSR_IA32_PERF_CAPABILITIES, caps);
-    full_width_write = (caps >> 13) & 1;
+
+    if ( cpu_has_pdcm )
+    {
+        uint64_t caps;
+
+        rdmsrl(MSR_IA32_PERF_CAPABILITIES, caps);
+        full_width_write = (caps >> 13) & 1;
+    }
 
     fixed_ctrl_mask = ~((1ull << (fixed_pmc_cnt * FIXED_CTR_CTRL_BITS)) - 1);
     /* mask .AnyThread bits for all fixed counters */
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.12