[PATCH v4 1/4] x86: stop handling MSR_IA32_BNDCFGS save/restore in implementation code

[Paul Durrant <paul.durrant@citrix.com>]

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.

NOTE: Because vmx_get/set_guest_bndcfgs() call vmx_vmcs_enter(), the
      struct vcpu pointer passed in, and hence the vcpu pointer passed to
      guest_rdmsr() cannot be const.

Signed-off-by: Paul Durrant <paul.durrant@citrix.com>
---
Cc: Kevin Tian <kevin.tian@intel.com>
Cc: Jan Beulich <jbeulich@suse.com>
Cc: Andrew Cooper <andrew.cooper3@citrix.com>
Cc: Wei Liu <wei.liu2@citrix.com>
Cc: "Roger Pau Monné" <roger.pau@citrix.com>
Cc: Jun Nakajima <jun.nakajima@intel.com>

v4:
 - Cosmetic re-arrangements and an additional ASSERT requested by Jan

v3:
 - Address further comments from Jan
 - Dropped Kevin's R-b because of change to vmx.c

v2:
 - Addressed comments from Jan by largely removing hunks
 - Keeping Kevin's R-b since remaining hunks in vmx.c are as before
---
 xen/arch/x86/hvm/hvm.c        | 14 ++------------
 xen/arch/x86/hvm/vmx/vmx.c    | 24 ++++--------------------
 xen/arch/x86/msr.c            | 20 ++++++++++++++++++++
 xen/include/asm-x86/hvm/hvm.h |  4 ++--
 4 files changed, 28 insertions(+), 34 deletions(-)

diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
index 8adbb61b57..e566d83f8b 100644
--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -1303,6 +1303,7 @@ static int hvm_load_cpu_xsave_states(struct domain *d, hvm_domain_context_t *h)
 static const uint32_t msrs_to_send[] = {
     MSR_SPEC_CTRL,
     MSR_INTEL_MISC_FEATURES_ENABLES,
+    MSR_IA32_BNDCFGS,
     MSR_AMD64_DR0_ADDRESS_MASK,
     MSR_AMD64_DR1_ADDRESS_MASK,
     MSR_AMD64_DR2_ADDRESS_MASK,
@@ -1440,6 +1441,7 @@ 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_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);
@@ -3467,12 +3469,6 @@ int hvm_msr_read_intercept(unsigned int msr, uint64_t *msr_content)
         *msr_content = v->arch.hvm.msr_xss;
         break;
 
-    case MSR_IA32_BNDCFGS:
-        if ( !d->arch.cpuid->feat.mpx ||
-             !hvm_get_guest_bndcfgs(v, msr_content) )
-            goto gp_fault;
-        break;
-
     case MSR_K8_ENABLE_C1E:
     case MSR_AMD64_NB_CFG:
          /*
@@ -3619,12 +3615,6 @@ int hvm_msr_write_intercept(unsigned int msr, uint64_t msr_content,
         v->arch.hvm.msr_xss = msr_content;
         break;
 
-    case MSR_IA32_BNDCFGS:
-        if ( !d->arch.cpuid->feat.mpx ||
-             !hvm_set_guest_bndcfgs(v, msr_content) )
-            goto gp_fault;
-        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 725dd88c13..f8481d032a 100644
--- a/xen/arch/x86/hvm/vmx/vmx.c
+++ b/xen/arch/x86/hvm/vmx/vmx.c
@@ -805,17 +805,6 @@ static unsigned int __init vmx_init_msr(void)
 
 static void vmx_save_msr(struct vcpu *v, struct hvm_msr *ctxt)
 {
-    vmx_vmcs_enter(v);
-
-    if ( cpu_has_mpx && cpu_has_vmx_mpx )
-    {
-        __vmread(GUEST_BNDCFGS, &ctxt->msr[ctxt->count].val);
-        if ( ctxt->msr[ctxt->count].val )
-            ctxt->msr[ctxt->count++].index = MSR_IA32_BNDCFGS;
-    }
-
-    vmx_vmcs_exit(v);
-
     if ( cpu_has_xsaves && cpu_has_vmx_xsaves )
     {
         ctxt->msr[ctxt->count].val = v->arch.hvm.msr_xss;
@@ -835,14 +824,6 @@ static int vmx_load_msr(struct vcpu *v, struct hvm_msr *ctxt)
     {
         switch ( ctxt->msr[i].index )
         {
-        case MSR_IA32_BNDCFGS:
-            if ( cpu_has_mpx && cpu_has_vmx_mpx &&
-                 is_canonical_address(ctxt->msr[i].val) &&
-                 !(ctxt->msr[i].val & IA32_BNDCFGS_RESERVED) )
-                __vmwrite(GUEST_BNDCFGS, ctxt->msr[i].val);
-            else if ( ctxt->msr[i].val )
-                err = -ENXIO;
-            break;
         case MSR_IA32_XSS:
             if ( cpu_has_xsaves && cpu_has_vmx_xsaves )
                 v->arch.hvm.msr_xss = ctxt->msr[i].val;
@@ -1215,8 +1196,11 @@ static bool vmx_set_guest_bndcfgs(struct vcpu *v, u64 val)
     return true;
 }
 
-static bool vmx_get_guest_bndcfgs(struct vcpu *v, u64 *val)
+static bool vmx_get_guest_bndcfgs(const struct vcpu *cv, u64 *val)
 {
+    /* Get a non-const pointer for vmx_vmcs_enter() */
+    struct vcpu *v = cv->domain->vcpu[cv->vcpu_id];
+
     ASSERT(cpu_has_mpx && cpu_has_vmx_mpx);
 
     vmx_vmcs_enter(v);
diff --git a/xen/arch/x86/msr.c b/xen/arch/x86/msr.c
index 4df4a59f4d..0e901d2397 100644
--- a/xen/arch/x86/msr.c
+++ b/xen/arch/x86/msr.c
@@ -160,6 +160,16 @@ int guest_rdmsr(const struct vcpu *v, uint32_t msr, uint64_t *val)
         ret = guest_rdmsr_x2apic(v, msr, val);
         break;
 
+    case MSR_IA32_BNDCFGS:
+        if ( !cp->feat.mpx )
+            goto gp_fault;
+
+        ASSERT(is_hvm_domain(d));
+        if (!hvm_get_guest_bndcfgs(v, val) )
+            goto gp_fault;
+
+        break;
+
     case 0x40000000 ... 0x400001ff:
         if ( is_viridian_domain(d) )
         {
@@ -323,6 +333,16 @@ int guest_wrmsr(struct vcpu *v, uint32_t msr, uint64_t val)
         ret = guest_wrmsr_x2apic(v, msr, val);
         break;
 
+    case MSR_IA32_BNDCFGS:
+        if ( !cp->feat.mpx )
+            goto gp_fault;
+
+        ASSERT(is_hvm_domain(d));
+        if ( !hvm_set_guest_bndcfgs(v, val) )
+            goto gp_fault;
+
+        break;
+
     case 0x40000000 ... 0x400001ff:
         if ( is_viridian_domain(d) )
         {
diff --git a/xen/include/asm-x86/hvm/hvm.h b/xen/include/asm-x86/hvm/hvm.h
index 53ffebb2c5..d41ed63232 100644
--- a/xen/include/asm-x86/hvm/hvm.h
+++ b/xen/include/asm-x86/hvm/hvm.h
@@ -149,7 +149,7 @@ struct hvm_function_table {
     int  (*get_guest_pat)(struct vcpu *v, u64 *);
     int  (*set_guest_pat)(struct vcpu *v, u64);
 
-    bool (*get_guest_bndcfgs)(struct vcpu *v, u64 *);
+    bool (*get_guest_bndcfgs)(const struct vcpu *v, u64 *);
     bool (*set_guest_bndcfgs)(struct vcpu *v, u64);
 
     void (*set_tsc_offset)(struct vcpu *v, u64 offset, u64 at_tsc);
@@ -448,7 +448,7 @@ static inline unsigned long hvm_get_shadow_gs_base(struct vcpu *v)
     return hvm_funcs.get_shadow_gs_base(v);
 }
 
-static inline bool hvm_get_guest_bndcfgs(struct vcpu *v, u64 *val)
+static inline bool hvm_get_guest_bndcfgs(const struct vcpu *v, u64 *val)
 {
     return hvm_funcs.get_guest_bndcfgs &&
            hvm_funcs.get_guest_bndcfgs(v, val);
-- 
2.20.1


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