[Xen-devel] [PATCH 2/8] x86/AMD: Do not intercept access to performance counters MSRs

[Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>]

Access to performance counters and reads of event selects don't
need to always be intercepted.

Signed-off-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
---
 xen/arch/x86/hvm/svm/svm.c  |  2 +-
 xen/arch/x86/hvm/svm/vpmu.c | 43 +++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 44 insertions(+), 1 deletion(-)

diff --git a/xen/arch/x86/hvm/svm/svm.c b/xen/arch/x86/hvm/svm/svm.c
index 8ce37c9..89e47b3 100644
--- a/xen/arch/x86/hvm/svm/svm.c
+++ b/xen/arch/x86/hvm/svm/svm.c
@@ -1052,8 +1052,8 @@ static int svm_vcpu_initialise(struct vcpu *v)
 
 static void svm_vcpu_destroy(struct vcpu *v)
 {
-    svm_destroy_vmcb(v);
     vpmu_destroy(v);
+    svm_destroy_vmcb(v);
     passive_domain_destroy(v);
 }
 
diff --git a/xen/arch/x86/hvm/svm/vpmu.c b/xen/arch/x86/hvm/svm/vpmu.c
index 16170da..f194975 100644
--- a/xen/arch/x86/hvm/svm/vpmu.c
+++ b/xen/arch/x86/hvm/svm/vpmu.c
@@ -88,6 +88,7 @@ struct amd_vpmu_context {
     u64 counters[MAX_NUM_COUNTERS];
     u64 ctrls[MAX_NUM_COUNTERS];
     u32 hw_lapic_lvtpc;
+    bool_t msr_bitmap_set;
 };
 
 static inline int get_pmu_reg_type(u32 addr)
@@ -138,6 +139,36 @@ static inline u32 get_fam15h_addr(u32 addr)
     return addr;
 }
 
+static void amd_vpmu_set_msr_bitmap(struct vcpu *v)
+{
+    int i;
+    struct vpmu_struct *vpmu = vcpu_vpmu(v);
+    struct amd_vpmu_context *ctxt = vpmu->context;
+
+    for ( i = 0; i < num_counters; i++ )
+    {
+        svm_intercept_msr(v, counters[i], MSR_INTERCEPT_NONE);
+        svm_intercept_msr(v, ctrls[i], MSR_INTERCEPT_WRITE);
+    }
+
+    ctxt->msr_bitmap_set = 1;
+}
+
+static void amd_vpmu_unset_msr_bitmap(struct vcpu *v)
+{
+    int i;
+    struct vpmu_struct *vpmu = vcpu_vpmu(v);
+    struct amd_vpmu_context *ctxt = vpmu->context;
+
+    for ( i = 0; i < num_counters; i++ )
+    {
+        svm_intercept_msr(v, counters[i], MSR_INTERCEPT_RW);
+        svm_intercept_msr(v, ctrls[i], MSR_INTERCEPT_RW);
+    }
+
+    ctxt->msr_bitmap_set = 0;
+}
+
 static int amd_vpmu_do_interrupt(struct cpu_user_regs *regs)
 {
     struct vcpu *v = current;
@@ -219,6 +250,10 @@ static void amd_vpmu_save(struct vcpu *v)
         return;
 
     context_save(v);
+
+    if ( !vpmu_is_set(vpmu, VPMU_RUNNING) && ctx->msr_bitmap_set )
+        amd_vpmu_unset_msr_bitmap(v);
+
     ctx->hw_lapic_lvtpc = apic_read(APIC_LVTPC);
     apic_write(APIC_LVTPC,  ctx->hw_lapic_lvtpc | APIC_LVT_MASKED);
 }
@@ -267,6 +302,9 @@ static int amd_vpmu_do_wrmsr(unsigned int msr, uint64_t 
msr_content)
             return 1;
         vpmu_set(vpmu, VPMU_RUNNING);
         apic_write(APIC_LVTPC, PMU_APIC_VECTOR);
+
+        if ( !((struct amd_vpmu_context *)vpmu->context)->msr_bitmap_set )
+            amd_vpmu_set_msr_bitmap(v);
     }
 
     /* stop saving & restore if guest stops first counter */
@@ -275,6 +313,8 @@ static int amd_vpmu_do_wrmsr(unsigned int msr, uint64_t 
msr_content)
     {
         apic_write(APIC_LVTPC, PMU_APIC_VECTOR | APIC_LVT_MASKED);
         vpmu_reset(vpmu, VPMU_RUNNING);
+        if ( ((struct amd_vpmu_context *)vpmu->context)->msr_bitmap_set )
+            amd_vpmu_unset_msr_bitmap(v);
         release_pmu_ownship(PMU_OWNER_HVM);
     }
 
@@ -345,6 +385,9 @@ static void amd_vpmu_destroy(struct vcpu *v)
     if ( !vpmu_is_set(vpmu, VPMU_CONTEXT_ALLOCATED) )
         return;
 
+    if ( ((struct amd_vpmu_context *)vpmu->context)->msr_bitmap_set )
+        amd_vpmu_unset_msr_bitmap(v);
+
     xfree(vpmu->context);
     vpmu_reset(vpmu, VPMU_CONTEXT_ALLOCATED);
 
-- 
1.8.1.2


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