[Xen-devel] [PATCH v24 10/15] x86/VPMU: Use pre-computed masks when checking validity of MSRs

[Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>]

No need to compute those masks on every MSR access.

Also, when checking MSR_P6_EVNTSELx registers make sure that bit 21
(which is a reserved bit) is not set.

Signed-off-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
---
Changes in v24:
* Mentioned in the commit message that newly-checked bit 21 is reserved

 xen/arch/x86/hvm/vmx/vpmu_core2.c | 28 ++++++++++++++++++----------
 1 file changed, 18 insertions(+), 10 deletions(-)

diff --git a/xen/arch/x86/hvm/vmx/vpmu_core2.c 
b/xen/arch/x86/hvm/vmx/vpmu_core2.c
index 089154e..166277a 100644
--- a/xen/arch/x86/hvm/vmx/vpmu_core2.c
+++ b/xen/arch/x86/hvm/vmx/vpmu_core2.c
@@ -80,9 +80,16 @@ static bool_t __read_mostly full_width_write;
 #define FIXED_CTR_CTRL_BITS 4
 #define FIXED_CTR_CTRL_MASK ((1 << FIXED_CTR_CTRL_BITS) - 1)
 
+#define ARCH_CNTR_ENABLED   (1ULL << 22)
+
 /* Number of general-purpose and fixed performance counters */
 static unsigned int __read_mostly arch_pmc_cnt, fixed_pmc_cnt;
 
+/* Masks used for testing whether and MSR is valid */
+#define ARCH_CTRL_MASK  (~((1ull << 32) - 1) | (1ull << 21))
+static uint64_t __read_mostly fixed_ctrl_mask, fixed_counters_mask;
+static uint64_t __read_mostly global_ovf_ctrl_mask;
+
 /*
  * QUIRK to workaround an issue on various family 6 cpus.
  * The issue leads to endless PMC interrupt loops on the processor.
@@ -479,9 +486,7 @@ static int core2_vpmu_do_wrmsr(unsigned int msr, uint64_t 
msr_content,
 
     ASSERT(!supported);
 
-    if ( type == MSR_TYPE_COUNTER &&
-         (msr_content &
-          ~((1ull << core2_get_bitwidth_fix_count()) - 1)) )
+    if ( (type == MSR_TYPE_COUNTER) && (msr_content & fixed_counters_mask) )
         /* Writing unsupported bits to a fixed counter */
         return -EINVAL;
 
@@ -490,9 +495,7 @@ static int core2_vpmu_do_wrmsr(unsigned int msr, uint64_t 
msr_content,
     switch ( msr )
     {
     case MSR_CORE_PERF_GLOBAL_OVF_CTRL:
-        if ( msr_content & ~(0xC000000000000000 |
-                             (((1ULL << fixed_pmc_cnt) - 1) << 32) |
-                             ((1ULL << arch_pmc_cnt) - 1)) )
+        if ( msr_content & global_ovf_ctrl_mask )
             return -EINVAL;
         core2_vpmu_cxt->global_status &= ~msr_content;
         wrmsrl(MSR_CORE_PERF_GLOBAL_OVF_CTRL, msr_content);
@@ -526,8 +529,7 @@ static int core2_vpmu_do_wrmsr(unsigned int msr, uint64_t 
msr_content,
         core2_vpmu_cxt->global_ctrl = msr_content;
         break;
     case MSR_CORE_PERF_FIXED_CTR_CTRL:
-        if ( msr_content &
-             ( ~((1ull << (fixed_pmc_cnt * FIXED_CTR_CTRL_BITS)) - 1)) )
+        if ( msr_content & fixed_ctrl_mask )
             return -EINVAL;
 
         if ( has_hvm_container_vcpu(v) )
@@ -556,7 +558,7 @@ static int core2_vpmu_do_wrmsr(unsigned int msr, uint64_t 
msr_content,
             struct xen_pmu_cntr_pair *xen_pmu_cntr_pair =
                 vpmu_reg_pointer(core2_vpmu_cxt, arch_counters);
 
-            if ( msr_content & (~((1ull << 32) - 1)) )
+            if ( msr_content & ARCH_CTRL_MASK )
                 return -EINVAL;
 
             if ( has_hvm_container_vcpu(v) )
@@ -565,7 +567,7 @@ static int core2_vpmu_do_wrmsr(unsigned int msr, uint64_t 
msr_content,
             else
                 rdmsrl(MSR_CORE_PERF_GLOBAL_CTRL, core2_vpmu_cxt->global_ctrl);
 
-            if ( msr_content & (1ULL << 22) )
+            if ( msr_content & ARCH_CNTR_ENABLED )
                 *enabled_cntrs |= 1ULL << tmp;
             else
                 *enabled_cntrs &= ~(1ULL << tmp);
@@ -915,6 +917,12 @@ int __init core2_vpmu_init(void)
     rdmsrl(MSR_IA32_PERF_CAPABILITIES, caps);
     full_width_write = (caps >> 13) & 1;
 
+    fixed_ctrl_mask = ~((1ull << (fixed_pmc_cnt * FIXED_CTR_CTRL_BITS)) - 1);
+    fixed_counters_mask = ~((1ull << core2_get_bitwidth_fix_count()) - 1);
+    global_ovf_ctrl_mask = ~(0xC000000000000000 |
+                             (((1ULL << fixed_pmc_cnt) - 1) << 32) |
+                             ((1ULL << arch_pmc_cnt) - 1));
+
     check_pmc_quirk();
 
     if ( sizeof(struct xen_pmu_data) + sizeof(uint64_t) * fixed_pmc_cnt +
-- 
1.8.1.4


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