[Xen-devel] [PATCH v2 2/2] x86/VPMU: Don't allow any non-zero writes to MSR_IA32_PEBS_ENABLE

[Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>]

Calculation reserved bits for MSR_IA32_PEBS_ENABLE is model-dependent
and since we don't support PEBS anyway we shouldn't allow any writes to
it (but let's still permit guests wishing to disable PEBS).

We should also report PEBS as unsupported to HVM, just like we do on PV.

Signed-off-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
---
 xen/arch/x86/cpu/vpmu_intel.c |   13 ++++++-------
 1 files changed, 6 insertions(+), 7 deletions(-)

diff --git a/xen/arch/x86/cpu/vpmu_intel.c b/xen/arch/x86/cpu/vpmu_intel.c
index 03cfe50..a179717 100644
--- a/xen/arch/x86/cpu/vpmu_intel.c
+++ b/xen/arch/x86/cpu/vpmu_intel.c
@@ -264,7 +264,6 @@ static void core2_vpmu_set_msr_bitmap(unsigned long 
*msr_bitmap)
          clear_bit(msraddr_to_bitpos(MSR_P6_EVNTSEL(i)), msr_bitmap);
 
     clear_bit(msraddr_to_bitpos(MSR_CORE_PERF_FIXED_CTR_CTRL), msr_bitmap);
-    clear_bit(msraddr_to_bitpos(MSR_IA32_PEBS_ENABLE), msr_bitmap);
     clear_bit(msraddr_to_bitpos(MSR_IA32_DS_AREA), msr_bitmap);
 }
 
@@ -296,7 +295,6 @@ static void core2_vpmu_unset_msr_bitmap(unsigned long 
*msr_bitmap)
         set_bit(msraddr_to_bitpos(MSR_P6_EVNTSEL(i)), msr_bitmap);
 
     set_bit(msraddr_to_bitpos(MSR_CORE_PERF_FIXED_CTR_CTRL), msr_bitmap);
-    set_bit(msraddr_to_bitpos(MSR_IA32_PEBS_ENABLE), msr_bitmap);
     set_bit(msraddr_to_bitpos(MSR_IA32_DS_AREA), msr_bitmap);
 }
 
@@ -368,7 +366,6 @@ static inline void __core2_vpmu_load(struct vcpu *v)
     wrmsrl(MSR_CORE_PERF_FIXED_CTR_CTRL, core2_vpmu_cxt->fixed_ctrl);
     if ( vpmu_is_set(vcpu_vpmu(v), VPMU_CPU_HAS_DS) )
         wrmsrl(MSR_IA32_DS_AREA, core2_vpmu_cxt->ds_area);
-    wrmsrl(MSR_IA32_PEBS_ENABLE, core2_vpmu_cxt->pebs_enable);
 
     if ( !has_hvm_container_vcpu(v) )
     {
@@ -394,6 +391,8 @@ static int core2_vpmu_verify(struct vcpu *v)
         return -EINVAL;
     if ( core2_vpmu_cxt->global_ctrl & global_ctrl_mask )
         return -EINVAL;
+    if ( core2_vpmu_cxt->pebs_enable )
+        return -EINVAL;
 
     fixed_ctrl = core2_vpmu_cxt->fixed_ctrl;
     if ( fixed_ctrl & fixed_ctrl_mask )
@@ -606,10 +605,9 @@ static int core2_vpmu_do_wrmsr(unsigned int msr, uint64_t 
msr_content,
                  "MSR_PERF_GLOBAL_STATUS(0x38E)!\n");
         return -EINVAL;
     case MSR_IA32_PEBS_ENABLE:
-        if ( msr_content & 1 )
-            gdprintk(XENLOG_WARNING, "Guest is trying to enable PEBS, "
-                     "which is not supported.\n");
-        core2_vpmu_cxt->pebs_enable = msr_content;
+        if ( msr_content )
+            /* PEBS is reported as unavailable in MSR_IA32_MISC_ENABLE */
+            return -EINVAL;
         return 0;
     case MSR_IA32_DS_AREA:
         if ( vpmu_is_set(vpmu, VPMU_CPU_HAS_DS) )
@@ -733,6 +731,7 @@ static int core2_vpmu_do_rdmsr(unsigned int msr, uint64_t 
*msr_content)
         /* Extension for BTS */
         if ( vpmu_is_set(vpmu, VPMU_CPU_HAS_BTS) )
             *msr_content &= ~MSR_IA32_MISC_ENABLE_BTS_UNAVAIL;
+        *msr_content |= MSR_IA32_MISC_ENABLE_PEBS_UNAVAIL;
     }
 
     return 0;
-- 
1.7.1


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