[Xen-devel] [PATCH v6 06/11] x86/vmce: emulate MSR_IA32_MCG_EXT_CTL

[Haozhong Zhang <haozhong.zhang@xxxxxxxxx>]

If MCG_LMCE_P is present in guest MSR_IA32_MCG_CAP, then allow guest
to read/write MSR_IA32_MCG_EXT_CTL.

Signed-off-by: Haozhong Zhang <haozhong.zhang@xxxxxxxxx>
---
Changes in v6:
 * Remove Jan's R-b.
 * Handle hvm_vmce_vcpu::mcg_ext_ctl in XEN_DOMCTL_{set,get}_ext_vcpucontext.
---
 xen/arch/x86/cpu/mcheck/vmce.c         | 34 +++++++++++++++++++++++++++++++++-
 xen/arch/x86/domctl.c                  | 19 +++++++++++++++++--
 xen/include/asm-x86/mce.h              |  1 +
 xen/include/public/arch-x86/hvm/save.h |  1 +
 4 files changed, 52 insertions(+), 3 deletions(-)

diff --git a/xen/arch/x86/cpu/mcheck/vmce.c b/xen/arch/x86/cpu/mcheck/vmce.c
index 1356f611ab..060e2d0582 100644
--- a/xen/arch/x86/cpu/mcheck/vmce.c
+++ b/xen/arch/x86/cpu/mcheck/vmce.c
@@ -91,6 +91,7 @@ int vmce_restore_vcpu(struct vcpu *v, const struct 
hvm_vmce_vcpu *ctxt)
     v->arch.vmce.mcg_cap = ctxt->caps;
     v->arch.vmce.bank[0].mci_ctl2 = ctxt->mci_ctl2_bank0;
     v->arch.vmce.bank[1].mci_ctl2 = ctxt->mci_ctl2_bank1;
+    v->arch.vmce.mcg_ext_ctl = ctxt->mcg_ext_ctl;
 
     return 0;
 }
@@ -200,6 +201,26 @@ int vmce_rdmsr(uint32_t msr, uint64_t *val)
         mce_printk(MCE_VERBOSE, "MCE: %pv: rd MCG_CTL %#"PRIx64"\n", cur, 
*val);
         break;
 
+    case MSR_IA32_MCG_EXT_CTL:
+        /*
+         * If MCG_LMCE_P is present in guest MSR_IA32_MCG_CAP, the LMCE and 
LOCK
+         * bits are always set in guest MSR_IA32_FEATURE_CONTROL by Xen, so it
+         * does not need to check them here.
+         */
+        if ( cur->arch.vmce.mcg_cap & MCG_LMCE_P )
+        {
+            *val = cur->arch.vmce.mcg_ext_ctl;
+            mce_printk(MCE_VERBOSE, "MCE: %pv: rd MCG_EXT_CTL %#"PRIx64"\n",
+                       cur, *val);
+        }
+        else
+        {
+            ret = -1;
+            mce_printk(MCE_VERBOSE, "MCE: %pv: rd MCG_EXT_CTL, not 
supported\n",
+                       cur);
+        }
+        break;
+
     default:
         ret = mce_bank_msr(cur, msr) ? bank_mce_rdmsr(cur, msr, val) : 0;
         break;
@@ -309,6 +330,16 @@ int vmce_wrmsr(uint32_t msr, uint64_t val)
         mce_printk(MCE_VERBOSE, "MCE: %pv: MCG_CAP is r/o\n", cur);
         break;
 
+    case MSR_IA32_MCG_EXT_CTL:
+        if ( (cur->arch.vmce.mcg_cap & MCG_LMCE_P) &&
+             !(val & ~MCG_EXT_CTL_LMCE_EN) )
+            cur->arch.vmce.mcg_ext_ctl = val;
+        else
+            ret = -1;
+        mce_printk(MCE_VERBOSE, "MCE: %pv: wr MCG_EXT_CTL %"PRIx64"%s\n",
+                   cur, val, (ret == -1) ? ", not supported" : "");
+        break;
+
     default:
         ret = mce_bank_msr(cur, msr) ? bank_mce_wrmsr(cur, msr, val) : 0;
         break;
@@ -327,7 +358,8 @@ static int vmce_save_vcpu_ctxt(struct domain *d, 
hvm_domain_context_t *h)
         struct hvm_vmce_vcpu ctxt = {
             .caps = v->arch.vmce.mcg_cap,
             .mci_ctl2_bank0 = v->arch.vmce.bank[0].mci_ctl2,
-            .mci_ctl2_bank1 = v->arch.vmce.bank[1].mci_ctl2
+            .mci_ctl2_bank1 = v->arch.vmce.bank[1].mci_ctl2,
+            .mcg_ext_ctl = v->arch.vmce.mcg_ext_ctl,
         };
 
         err = hvm_save_entry(VMCE_VCPU, v->vcpu_id, h, &ctxt);
diff --git a/xen/arch/x86/domctl.c b/xen/arch/x86/domctl.c
index f40e989fd8..4ae9fc6451 100644
--- a/xen/arch/x86/domctl.c
+++ b/xen/arch/x86/domctl.c
@@ -871,6 +871,7 @@ long arch_do_domctl(
             evc->vmce.caps = v->arch.vmce.mcg_cap;
             evc->vmce.mci_ctl2_bank0 = v->arch.vmce.bank[0].mci_ctl2;
             evc->vmce.mci_ctl2_bank1 = v->arch.vmce.bank[1].mci_ctl2;
+            evc->vmce.mcg_ext_ctl = v->arch.vmce.mcg_ext_ctl;
 
             ret = 0;
             vcpu_unpause(v);
@@ -878,6 +879,8 @@ long arch_do_domctl(
         }
         else
         {
+            static const unsigned long vmce_off = offsetof(typeof(*evc), vmce);
+
             if ( d == currd ) /* no domain_pause() */
                 break;
             ret = -EINVAL;
@@ -917,9 +920,21 @@ long arch_do_domctl(
                          offsetof(struct xen_domctl_ext_vcpucontext,
                                   vmce.caps));
             BUILD_BUG_ON(sizeof(evc->mcg_cap) != sizeof(evc->vmce.caps));
-            if ( evc->size >= offsetof(typeof(*evc), vmce) +
-                              sizeof(evc->vmce) )
+            if ( evc->size >= vmce_off + sizeof(evc->vmce) )
                 ret = vmce_restore_vcpu(v, &evc->vmce);
+            else if ( evc->size >= vmce_off +
+                                   offsetof(typeof(evc->vmce), mcg_ext_ctl) )
+            {
+                /*
+                 * If migrating from old Xen that uses a smaller 'struct
+                 * hvm_vmce_vcpu', only restore the components in the
+                 * old version.
+                 */
+                struct hvm_vmce_vcpu vmce = { 0 };
+
+                memcpy(&vmce, &evc->vmce, evc->size - vmce_off);
+                ret = vmce_restore_vcpu(v, &vmce);
+            }
             else if ( evc->size >= offsetof(typeof(*evc), mcg_cap) +
                                    sizeof(evc->mcg_cap) )
             {
diff --git a/xen/include/asm-x86/mce.h b/xen/include/asm-x86/mce.h
index 56ad1f92dd..35f9962638 100644
--- a/xen/include/asm-x86/mce.h
+++ b/xen/include/asm-x86/mce.h
@@ -27,6 +27,7 @@ struct vmce_bank {
 struct vmce {
     uint64_t mcg_cap;
     uint64_t mcg_status;
+    uint64_t mcg_ext_ctl;
     spinlock_t lock;
     struct vmce_bank bank[GUEST_MC_BANK_NUM];
 };
diff --git a/xen/include/public/arch-x86/hvm/save.h 
b/xen/include/public/arch-x86/hvm/save.h
index 816973b9c2..fd7bf3fb38 100644
--- a/xen/include/public/arch-x86/hvm/save.h
+++ b/xen/include/public/arch-x86/hvm/save.h
@@ -610,6 +610,7 @@ struct hvm_vmce_vcpu {
     uint64_t caps;
     uint64_t mci_ctl2_bank0;
     uint64_t mci_ctl2_bank1;
+    uint64_t mcg_ext_ctl;
 };
 
 DECLARE_HVM_SAVE_TYPE(VMCE_VCPU, 18, struct hvm_vmce_vcpu);
-- 
2.11.0


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