[Xen-devel] [PATCH v3] Intel/VPMU: Add support for full-width PMC writes

[Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>]

A recent Linux commit (069e0c3c405814778c7475d95b9fff5318f39834) added
support for full-width PMC writes to performance counter registers,
making these registers default for perf. Since current Xen VPMU does
not support these new MSRs perf will fail to initialise in guests.

Signed-off-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
Reviewed-by: Dietmar Hahn <dietmar.hahn@xxxxxxxxxxxxxx>
---
 xen/arch/x86/hvm/vmx/vpmu_core2.c | 40 +++++++++++++++++++++++++++++++++++----
 xen/include/asm-x86/msr-index.h   |  1 +
 2 files changed, 37 insertions(+), 4 deletions(-)

diff --git a/xen/arch/x86/hvm/vmx/vpmu_core2.c 
b/xen/arch/x86/hvm/vmx/vpmu_core2.c
index 15b2036..9334d02 100644
--- a/xen/arch/x86/hvm/vmx/vpmu_core2.c
+++ b/xen/arch/x86/hvm/vmx/vpmu_core2.c
@@ -64,6 +64,10 @@
 #define PMU_FIXED_WIDTH_BITS     8  /* 8 bits 5..12 */
 #define PMU_FIXED_WIDTH_MASK     (((1 << PMU_FIXED_WIDTH_BITS) -1) << 
PMU_FIXED_WIDTH_SHIFT)
 
+/* Alias registers (0x4c1) for full-width writes to PMCs */
+#define MSR_PMC_ALIAS_MASK       (~(MSR_IA32_PERFCTR0 ^ MSR_IA32_A_PERFCTR0))
+static bool_t __read_mostly full_width_write;
+
 /*
  * QUIRK to workaround an issue on various family 6 cpus.
  * The issue leads to endless PMC interrupt loops on the processor.
@@ -195,6 +199,7 @@ static int core2_get_bitwidth_fix_count(void)
 static int is_core2_vpmu_msr(u32 msr_index, int *type, int *index)
 {
     int i;
+    u32 msr_index_pmc;
 
     for ( i = 0; i < core2_fix_counters.num; i++ )
     {
@@ -224,11 +229,12 @@ static int is_core2_vpmu_msr(u32 msr_index, int *type, 
int *index)
         return 1;
     }
 
-    if ( (msr_index >= MSR_IA32_PERFCTR0) &&
-         (msr_index < (MSR_IA32_PERFCTR0 + core2_get_pmc_count())) )
+    msr_index_pmc =  msr_index & MSR_PMC_ALIAS_MASK;
+    if ( (msr_index_pmc >= MSR_IA32_PERFCTR0) &&
+         (msr_index_pmc < (MSR_IA32_PERFCTR0 + core2_get_pmc_count())) )
     {
         *type = MSR_TYPE_ARCH_COUNTER;
-        *index = msr_index - MSR_IA32_PERFCTR0;
+        *index = msr_index_pmc - MSR_IA32_PERFCTR0;
         return 1;
     }
 
@@ -259,6 +265,13 @@ static void core2_vpmu_set_msr_bitmap(unsigned long 
*msr_bitmap)
         clear_bit(msraddr_to_bitpos(MSR_IA32_PERFCTR0+i), msr_bitmap);
         clear_bit(msraddr_to_bitpos(MSR_IA32_PERFCTR0+i),
                   msr_bitmap + 0x800/BYTES_PER_LONG);
+
+        if ( full_width_write )
+        {
+            clear_bit(msraddr_to_bitpos(MSR_IA32_A_PERFCTR0 + i), msr_bitmap);
+            clear_bit(msraddr_to_bitpos(MSR_IA32_A_PERFCTR0 + i),
+                      msr_bitmap + 0x800/BYTES_PER_LONG);
+        }
     }
 
     /* Allow Read PMU Non-global Controls Directly. */
@@ -283,7 +296,15 @@ static void core2_vpmu_unset_msr_bitmap(unsigned long 
*msr_bitmap)
         set_bit(msraddr_to_bitpos(MSR_IA32_PERFCTR0+i), msr_bitmap);
         set_bit(msraddr_to_bitpos(MSR_IA32_PERFCTR0+i),
                 msr_bitmap + 0x800/BYTES_PER_LONG);
+
+        if ( full_width_write )
+        {
+            set_bit(msraddr_to_bitpos(MSR_IA32_A_PERFCTR0 + i), msr_bitmap);
+            set_bit(msraddr_to_bitpos(MSR_IA32_A_PERFCTR0 + i),
+                      msr_bitmap + 0x800/BYTES_PER_LONG);
+        }
     }
+
     for ( i = 0; i < core2_ctrls.num; i++ )
         set_bit(msraddr_to_bitpos(core2_ctrls.msr[i]), msr_bitmap);
     for ( i = 0; i < core2_get_pmc_count(); i++ )
@@ -324,11 +345,17 @@ static inline void __core2_vpmu_load(struct vcpu *v)
 {
     int i;
     struct core2_vpmu_context *core2_vpmu_cxt = vcpu_vpmu(v)->context;
+    int pmc_start;
 
     for ( i = 0; i < core2_fix_counters.num; i++ )
         wrmsrl(core2_fix_counters.msr[i], core2_vpmu_cxt->fix_counters[i]);
+
+    if ( full_width_write )
+        pmc_start = MSR_IA32_A_PERFCTR0;
+    else
+        pmc_start = MSR_IA32_PERFCTR0;
     for ( i = 0; i < core2_get_pmc_count(); i++ )
-        wrmsrl(MSR_IA32_PERFCTR0+i, core2_vpmu_cxt->arch_msr_pair[i].counter);
+        wrmsrl(pmc_start + i, core2_vpmu_cxt->arch_msr_pair[i].counter);
 
     for ( i = 0; i < core2_ctrls.num; i++ )
         wrmsrl(core2_ctrls.msr[i], core2_vpmu_cxt->ctrls[i]);
@@ -855,6 +882,11 @@ int vmx_vpmu_initialise(struct vcpu *v, unsigned int 
vpmu_flags)
 
     if ( family == 6 )
     {
+        u64 caps;
+
+        rdmsrl(MSR_IA32_PERF_CAPABILITIES, caps);
+        full_width_write = (caps >> 13) & 1;
+
         switch ( cpu_model )
         {
         /* Core2: */
diff --git a/xen/include/asm-x86/msr-index.h b/xen/include/asm-x86/msr-index.h
index f500efd..5acaee8 100644
--- a/xen/include/asm-x86/msr-index.h
+++ b/xen/include/asm-x86/msr-index.h
@@ -34,6 +34,7 @@
 /* Intel MSRs. Some also available on other CPUs */
 #define MSR_IA32_PERFCTR0              0x000000c1
 #define MSR_IA32_PERFCTR1              0x000000c2
+#define MSR_IA32_A_PERFCTR0            0x000004c1
 #define MSR_FSB_FREQ                   0x000000cd
 
 #define MSR_NHM_SNB_PKG_CST_CFG_CTL    0x000000e2
-- 
1.8.1.4


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