x86/vmx: Pass an MSR value into vmx_msr_add()

The main purpose of this change is to allow us to set a specific MSR value,
without needing to know whether there is already a load/save list slot for it.

Previously, callers wanting this property needed to call both vmx_add_*_msr()
and vmx_write_*_msr() to cover both cases, and there are no callers which want
the old behaviour of being a no-op if an entry already existed for the MSR.

As a result of this API improvement, the default value for guest MSRs need not
be 0, and the default for host MSRs need not be passed via hardware register.
In practice, this cleans up the VPMU allocation logic, and avoids an MSR read
as part of vcpu construction.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Acked-by: Kevin Tian <kevin.tian@intel.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
(cherry picked from commit ee7689b94ac7094b975ab4a023cfeae209da0a36)

diff --git a/xen/arch/x86/cpu/vpmu_intel.c b/xen/arch/x86/cpu/vpmu_intel.c
index fee94a889a0e5c32af6c8b0f01f40a6d05fe8776..8fb57d3ccbc316921546f1c51567ef6efd9c92b6 100644 (file)
--- a/xen/arch/x86/cpu/vpmu_intel.c
+++ b/xen/arch/x86/cpu/vpmu_intel.c
@@ -478,13 +478,11 @@ static int core2_vpmu_alloc_resource(struct vcpu *v)
 
     if ( is_hvm_vcpu(v) )
     {
-        wrmsrl(MSR_CORE_PERF_GLOBAL_CTRL, 0);
-        if ( vmx_add_host_load_msr(v, MSR_CORE_PERF_GLOBAL_CTRL) )
+        if ( vmx_add_host_load_msr(v, MSR_CORE_PERF_GLOBAL_CTRL, 0) )
             goto out_err;
 
-        if ( vmx_add_guest_msr(v, MSR_CORE_PERF_GLOBAL_CTRL) )
+        if ( vmx_add_guest_msr(v, MSR_CORE_PERF_GLOBAL_CTRL, 0) )
             goto out_err;
-        vmx_write_guest_msr(v, MSR_CORE_PERF_GLOBAL_CTRL, 0);
     }
 
     core2_vpmu_cxt = xzalloc_bytes(sizeof(*core2_vpmu_cxt) +

diff --git a/xen/arch/x86/hvm/vmx/vmcs.c b/xen/arch/x86/hvm/vmx/vmcs.c
index 4b95fc9caaebd232432258aa887373cc459340ea..bfa06aa35b33ba26a152af041b34e7e1581b164d 100644 (file)
--- a/xen/arch/x86/hvm/vmx/vmcs.c
+++ b/xen/arch/x86/hvm/vmx/vmcs.c
@@ -1364,7 +1364,8 @@ struct vmx_msr_entry *vmx_find_msr(const struct vcpu *v, uint32_t msr,
     return ((ent < end) && (ent->index == msr)) ? ent : NULL;
 }
 
-int vmx_add_msr(struct vcpu *v, uint32_t msr, enum vmx_msr_list_type type)
+int vmx_add_msr(struct vcpu *v, uint32_t msr, uint64_t val,
+                enum vmx_msr_list_type type)
 {
     struct arch_vmx_struct *vmx = &v->arch.hvm_vmx;
     struct vmx_msr_entry **ptr, *start = NULL, *ent, *end;
@@ -1423,11 +1424,9 @@ int vmx_add_msr(struct vcpu *v, uint32_t msr, enum vmx_msr_list_type type)
     ent   = locate_msr_entry(start, end, msr);
 
     if ( (ent < end) && (ent->index == msr) )
-    {
-        rc = 0;
-        goto out;
-    }
+        goto found;
 
+    /* If there isn't an existing entry for msr, insert room for one. */
     if ( total == (PAGE_SIZE / sizeof(*ent)) )
     {
         rc = -ENOSPC;
@@ -1442,17 +1441,18 @@ int vmx_add_msr(struct vcpu *v, uint32_t msr, enum vmx_msr_list_type type)
     switch ( type )
     {
     case VMX_MSR_HOST:
-        rdmsrl(msr, ent->data);
         __vmwrite(VM_EXIT_MSR_LOAD_COUNT, ++vmx->host_msr_count);
         break;
 
     case VMX_MSR_GUEST:
-        ent->data = 0;
         __vmwrite(VM_EXIT_MSR_STORE_COUNT, ++vmx->msr_count);
         __vmwrite(VM_ENTRY_MSR_LOAD_COUNT, vmx->msr_count);
         break;
     }
 
+    /* Set the msr's value. */
+ found:
+    ent->data = val;
     rc = 0;
 
  out:

diff --git a/xen/arch/x86/hvm/vmx/vmx.c b/xen/arch/x86/hvm/vmx/vmx.c
index 251e6e286fc178e39eb00f3b24f8102c3b0841c5..e98159affb6ca8f633286bae6b94598a4bc13e30 100644 (file)
--- a/xen/arch/x86/hvm/vmx/vmx.c
+++ b/xen/arch/x86/hvm/vmx/vmx.c
@@ -3173,7 +3173,7 @@ static int vmx_msr_write_intercept(unsigned int msr, uint64_t msr_content)
 
                 for ( i = 0; i < lbr->count; i++ )
                 {
-                    int rc = vmx_add_guest_msr(v, lbr->base + i);
+                    int rc = vmx_add_guest_msr(v, lbr->base + i, 0);
 
                     if ( unlikely(rc) )
                     {

diff --git a/xen/include/asm-x86/hvm/vmx/vmcs.h b/xen/include/asm-x86/hvm/vmx/vmcs.h
index 6ed111750575caff832e6070077199aef25f9e89..16030cbd9a0a9c1f1210be4c3416ae0069c9279e 100644 (file)
--- a/xen/include/asm-x86/hvm/vmx/vmcs.h
+++ b/xen/include/asm-x86/hvm/vmx/vmcs.h
@@ -531,16 +531,24 @@ enum vmx_msr_list_type {
     VMX_MSR_GUEST,          /* MSRs saved on VMExit, loaded on VMEntry. */
 };
 
-int vmx_add_msr(struct vcpu *v, uint32_t msr, enum vmx_msr_list_type type);
+/**
+ * Add an MSR to an MSR list (inserting space for the entry if necessary), and
+ * set the MSRs value.
+ *
+ * May fail if unable to allocate memory for the list, or the total number of
+ * entries exceeds the memory allocated.
+ */
+int vmx_add_msr(struct vcpu *v, uint32_t msr, uint64_t val,
+                enum vmx_msr_list_type type);
 
-static inline int vmx_add_guest_msr(struct vcpu *v, uint32_t msr)
+static inline int vmx_add_guest_msr(struct vcpu *v, uint32_t msr, uint64_t val)
 {
-    return vmx_add_msr(v, msr, VMX_MSR_GUEST);
+    return vmx_add_msr(v, msr, val, VMX_MSR_GUEST);
 }
-
-static inline int vmx_add_host_load_msr(struct vcpu *v, uint32_t msr)
+static inline int vmx_add_host_load_msr(struct vcpu *v, uint32_t msr,
+                                        uint64_t val)
 {
-    return vmx_add_msr(v, msr, VMX_MSR_HOST);
+    return vmx_add_msr(v, msr, val, VMX_MSR_HOST);
 }
 
 struct vmx_msr_entry *vmx_find_msr(const struct vcpu *v, uint32_t msr,