[Xen-devel] [PATCH v3 3/4] x86: stop handling MSR_IA32_XSS save/restore in implementation code

[Paul Durrant <paul.durrant@xxxxxxxxxx>]

Saving and restoring the value of this MSR is currently handled by
implementation-specific code despite it being architectural. This patch
moves handling of accesses to this MSR from hvm.c into the msr.c, thus
allowing the common MSR save/restore code to handle it.

This patch also adds proper checks of CPUID policy in the new get/set code.

NOTE: MSR_IA32_XSS is the last MSR to be saved and restored by
      implementation-specific code. This patch therefore removes the
      (VMX) definitions and of the init_msr(), save_msr() and
      load_msr() hvm_funcs, as they are no longer necessary. The
      declarations of and calls to those hvm_funcs will be cleaned up
      by a subsequent patch.

Signed-off-by: Paul Durrant <paul.durrant@xxxxxxxxxx>
Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
Reviewed-by: Kevin Tian <kevin.tian@xxxxxxxxx>
---
Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
Cc: Wei Liu <wei.liu2@xxxxxxxxxx>
Cc: "Roger Pau Monné" <roger.pau@xxxxxxxxxx>
Cc: Jun Nakajima <jun.nakajima@xxxxxxxxx>
---
 xen/arch/x86/hvm/hvm.c     | 15 ++----------
 xen/arch/x86/hvm/vmx/vmx.c | 49 --------------------------------------
 xen/arch/x86/msr.c         | 18 ++++++++++++++
 3 files changed, 20 insertions(+), 62 deletions(-)

diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
index dff590e658..deb7fb2adb 100644
--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -1304,6 +1304,7 @@ static const uint32_t msrs_to_send[] = {
     MSR_SPEC_CTRL,
     MSR_INTEL_MISC_FEATURES_ENABLES,
     MSR_IA32_BNDCFGS,
+    MSR_IA32_XSS,
     MSR_AMD64_DR0_ADDRESS_MASK,
     MSR_AMD64_DR1_ADDRESS_MASK,
     MSR_AMD64_DR2_ADDRESS_MASK,
@@ -1442,6 +1443,7 @@ static int hvm_load_cpu_msrs(struct domain *d, 
hvm_domain_context_t *h)
         case MSR_SPEC_CTRL:
         case MSR_INTEL_MISC_FEATURES_ENABLES:
         case MSR_IA32_BNDCFGS:
+        case MSR_IA32_XSS:
         case MSR_AMD64_DR0_ADDRESS_MASK:
         case MSR_AMD64_DR1_ADDRESS_MASK ... MSR_AMD64_DR3_ADDRESS_MASK:
             rc = guest_wrmsr(v, ctxt->msr[i].index, ctxt->msr[i].val);
@@ -3463,12 +3465,6 @@ int hvm_msr_read_intercept(unsigned int msr, uint64_t 
*msr_content)
                                                     MTRRcap_VCNT))];
         break;
 
-    case MSR_IA32_XSS:
-        if ( !d->arch.cpuid->xstate.xsaves )
-            goto gp_fault;
-        *msr_content = v->arch.msrs->xss.raw;
-        break;
-
     case MSR_K8_ENABLE_C1E:
     case MSR_AMD64_NB_CFG:
          /*
@@ -3608,13 +3604,6 @@ int hvm_msr_write_intercept(unsigned int msr, uint64_t 
msr_content,
             goto gp_fault;
         break;
 
-    case MSR_IA32_XSS:
-        /* No XSS features currently supported for guests. */
-        if ( !d->arch.cpuid->xstate.xsaves || msr_content != 0 )
-            goto gp_fault;
-        v->arch.msrs->xss.raw = msr_content;
-        break;
-
     case MSR_AMD64_NB_CFG:
         /* ignore the write */
         break;
diff --git a/xen/arch/x86/hvm/vmx/vmx.c b/xen/arch/x86/hvm/vmx/vmx.c
index 4941924cf6..043c4268a0 100644
--- a/xen/arch/x86/hvm/vmx/vmx.c
+++ b/xen/arch/x86/hvm/vmx/vmx.c
@@ -797,52 +797,6 @@ static int vmx_load_vmcs_ctxt(struct vcpu *v, struct 
hvm_hw_cpu *ctxt)
     return 0;
 }
 
-static unsigned int __init vmx_init_msr(void)
-{
-    return (cpu_has_mpx && cpu_has_vmx_mpx) +
-           (cpu_has_xsaves && cpu_has_vmx_xsaves);
-}
-
-static void vmx_save_msr(struct vcpu *v, struct hvm_msr *ctxt)
-{
-    if ( cpu_has_xsaves && cpu_has_vmx_xsaves )
-    {
-        ctxt->msr[ctxt->count].val = v->arch.msrs->xss.raw;
-        if ( ctxt->msr[ctxt->count].val )
-            ctxt->msr[ctxt->count++].index = MSR_IA32_XSS;
-    }
-}
-
-static int vmx_load_msr(struct vcpu *v, struct hvm_msr *ctxt)
-{
-    unsigned int i;
-    int err = 0;
-
-    vmx_vmcs_enter(v);
-
-    for ( i = 0; i < ctxt->count; ++i )
-    {
-        switch ( ctxt->msr[i].index )
-        {
-        case MSR_IA32_XSS:
-            if ( cpu_has_xsaves && cpu_has_vmx_xsaves )
-                v->arch.msrs->xss.raw = ctxt->msr[i].val;
-            else
-                err = -ENXIO;
-            break;
-        default:
-            continue;
-        }
-        if ( err )
-            break;
-        ctxt->msr[i]._rsvd = 1;
-    }
-
-    vmx_vmcs_exit(v);
-
-    return err;
-}
-
 static void vmx_fpu_enter(struct vcpu *v)
 {
     vcpu_restore_fpu_lazy(v);
@@ -2284,9 +2238,6 @@ static struct hvm_function_table __initdata 
vmx_function_table = {
     .vcpu_destroy         = vmx_vcpu_destroy,
     .save_cpu_ctxt        = vmx_save_vmcs_ctxt,
     .load_cpu_ctxt        = vmx_load_vmcs_ctxt,
-    .init_msr             = vmx_init_msr,
-    .save_msr             = vmx_save_msr,
-    .load_msr             = vmx_load_msr,
     .get_interrupt_shadow = vmx_get_interrupt_shadow,
     .set_interrupt_shadow = vmx_set_interrupt_shadow,
     .guest_x86_mode       = vmx_guest_x86_mode,
diff --git a/xen/arch/x86/msr.c b/xen/arch/x86/msr.c
index 363fd63096..cfa49d7a63 100644
--- a/xen/arch/x86/msr.c
+++ b/xen/arch/x86/msr.c
@@ -166,6 +166,13 @@ int guest_rdmsr(const struct vcpu *v, uint32_t msr, 
uint64_t *val)
 
         break;
 
+    case MSR_IA32_XSS:
+        if ( !cp->xstate.xsaves )
+            goto gp_fault;
+
+        *val = msrs->xss.raw;
+        break;
+
     case 0x40000000 ... 0x400001ff:
         if ( is_viridian_domain(d) )
         {
@@ -335,6 +342,17 @@ int guest_wrmsr(struct vcpu *v, uint32_t msr, uint64_t val)
 
         break;
 
+    case MSR_IA32_XSS:
+        if ( !cp->xstate.xsaves )
+            goto gp_fault;
+
+        /* No XSS features currently supported for guests */
+        if ( val != 0 )
+            goto gp_fault;
+
+        msrs->xss.raw = val;
+        break;
+
     case 0x40000000 ... 0x400001ff:
         if ( is_viridian_domain(d) )
         {
-- 
2.20.1


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