target/i386: Populate x86_ext_save_areas offsets using cpuid where possible

Rather than relying on the X86XSaveArea structure definition,
determine the offset of XSAVE state areas using CPUID leaf 0xd where
possible (KVM and HVF).

Signed-off-by: David Edmondson <david.edmondson@oracle.com>
Message-Id: <20210705104632.2902400-8-david.edmondson@oracle.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

7 files changed, 94 insertions, 13 deletions

diff --git a/target/i386/cpu.c b/target/i386/cpu.c
index 13caa0d..5f595a0 100644
--- a/target/i386/cpu.c
+++ b/target/i386/cpu.c
@@ -1304,48 +1304,37 @@ static const X86RegisterInfo32 x86_reg_info_32[CPU_NB_REGS32] = {
 };
 #undef REGISTER
 
-const ExtSaveArea x86_ext_save_areas[XSAVE_STATE_AREA_COUNT] = {
+ExtSaveArea x86_ext_save_areas[XSAVE_STATE_AREA_COUNT] = {
     [XSTATE_FP_BIT] = {
         /* x87 FP state component is always enabled if XSAVE is supported */
         .feature = FEAT_1_ECX, .bits = CPUID_EXT_XSAVE,
-        /* x87 state is in the legacy region of the XSAVE area */
-        .offset = 0,
         .size = sizeof(X86LegacyXSaveArea) + sizeof(X86XSaveHeader),
     },
     [XSTATE_SSE_BIT] = {
         /* SSE state component is always enabled if XSAVE is supported */
         .feature = FEAT_1_ECX, .bits = CPUID_EXT_XSAVE,
-        /* SSE state is in the legacy region of the XSAVE area */
-        .offset = 0,
         .size = sizeof(X86LegacyXSaveArea) + sizeof(X86XSaveHeader),
     },
     [XSTATE_YMM_BIT] =
           { .feature = FEAT_1_ECX, .bits = CPUID_EXT_AVX,
-            .offset = offsetof(X86XSaveArea, avx_state),
             .size = sizeof(XSaveAVX) },
     [XSTATE_BNDREGS_BIT] =
           { .feature = FEAT_7_0_EBX, .bits = CPUID_7_0_EBX_MPX,
-            .offset = offsetof(X86XSaveArea, bndreg_state),
             .size = sizeof(XSaveBNDREG)  },
     [XSTATE_BNDCSR_BIT] =
           { .feature = FEAT_7_0_EBX, .bits = CPUID_7_0_EBX_MPX,
-            .offset = offsetof(X86XSaveArea, bndcsr_state),
             .size = sizeof(XSaveBNDCSR)  },
     [XSTATE_OPMASK_BIT] =
           { .feature = FEAT_7_0_EBX, .bits = CPUID_7_0_EBX_AVX512F,
-            .offset = offsetof(X86XSaveArea, opmask_state),
             .size = sizeof(XSaveOpmask) },
     [XSTATE_ZMM_Hi256_BIT] =
           { .feature = FEAT_7_0_EBX, .bits = CPUID_7_0_EBX_AVX512F,
-            .offset = offsetof(X86XSaveArea, zmm_hi256_state),
             .size = sizeof(XSaveZMM_Hi256) },
     [XSTATE_Hi16_ZMM_BIT] =
           { .feature = FEAT_7_0_EBX, .bits = CPUID_7_0_EBX_AVX512F,
-            .offset = offsetof(X86XSaveArea, hi16_zmm_state),
             .size = sizeof(XSaveHi16_ZMM) },
     [XSTATE_PKRU_BIT] =
           { .feature = FEAT_7_0_ECX, .bits = CPUID_7_0_ECX_PKU,
-            .offset = offsetof(X86XSaveArea, pkru_state),
             .size = sizeof(XSavePKRU) },
 };
 
diff --git a/target/i386/cpu.h b/target/i386/cpu.h
index c9c0a34..96b672f 100644
--- a/target/i386/cpu.h
+++ b/target/i386/cpu.h
@@ -1377,7 +1377,7 @@ typedef struct ExtSaveArea {
 
 #define XSAVE_STATE_AREA_COUNT (XSTATE_PKRU_BIT + 1)
 
-extern const ExtSaveArea x86_ext_save_areas[XSAVE_STATE_AREA_COUNT];
+extern ExtSaveArea x86_ext_save_areas[XSAVE_STATE_AREA_COUNT];
 
 typedef enum TPRAccess {
     TPR_ACCESS_READ,
diff --git a/target/i386/hvf/hvf-cpu.c b/target/i386/hvf/hvf-cpu.c
index 8fbc423..333db59 100644
--- a/target/i386/hvf/hvf-cpu.c
+++ b/target/i386/hvf/hvf-cpu.c
@@ -30,6 +30,33 @@ static void hvf_cpu_max_instance_init(X86CPU *cpu)
         hvf_get_supported_cpuid(0xC0000000, 0, R_EAX);
 }
 
+static void hvf_cpu_xsave_init(void)
+{
+    static bool first = true;
+    int i;
+
+    if (!first) {
+        return;
+    }
+    first = false;
+
+    /* x87 and SSE states are in the legacy region of the XSAVE area. */
+    x86_ext_save_areas[XSTATE_FP_BIT].offset = 0;
+    x86_ext_save_areas[XSTATE_SSE_BIT].offset = 0;
+
+    for (i = XSTATE_SSE_BIT + 1; i < XSAVE_STATE_AREA_COUNT; i++) {
+        ExtSaveArea *esa = &x86_ext_save_areas[i];
+
+        if (esa->size) {
+            int sz = hvf_get_supported_cpuid(0xd, i, R_EAX);
+            if (sz != 0) {
+                assert(esa->size == sz);
+                esa->offset = hvf_get_supported_cpuid(0xd, i, R_EBX);
+            }
+        }
+    }
+}
+
 static void hvf_cpu_instance_init(CPUState *cs)
 {
     X86CPU *cpu = X86_CPU(cs);
@@ -42,6 +69,8 @@ static void hvf_cpu_instance_init(CPUState *cs)
     if (cpu->max_features) {
         hvf_cpu_max_instance_init(cpu);
     }
+
+    hvf_cpu_xsave_init();
 }
 
 static void hvf_cpu_accel_class_init(ObjectClass *oc, void *data)
diff --git a/target/i386/hvf/hvf.c b/target/i386/hvf/hvf.c
index e62e8df..79ba4ed 100644
--- a/target/i386/hvf/hvf.c
+++ b/target/i386/hvf/hvf.c
@@ -270,6 +270,12 @@ int hvf_arch_init_vcpu(CPUState *cpu)
     x86cpu->env.xsave_buf_len = 4096;
     x86cpu->env.xsave_buf = qemu_memalign(4096, x86cpu->env.xsave_buf_len);
 
+    /*
+     * The allocated storage must be large enough for all of the
+     * possible XSAVE state components.
+     */
+    assert(hvf_get_supported_cpuid(0xd, 0, R_ECX) <= x86cpu->env.xsave_buf_len);
+
     hv_vcpu_enable_native_msr(cpu->hvf->fd, MSR_STAR, 1);
     hv_vcpu_enable_native_msr(cpu->hvf->fd, MSR_LSTAR, 1);
     hv_vcpu_enable_native_msr(cpu->hvf->fd, MSR_CSTAR, 1);
diff --git a/target/i386/kvm/kvm-cpu.c b/target/i386/kvm/kvm-cpu.c
index 00369c2..bbe8177 100644
--- a/target/i386/kvm/kvm-cpu.c
+++ b/target/i386/kvm/kvm-cpu.c
@@ -122,6 +122,34 @@ static void kvm_cpu_max_instance_init(X86CPU *cpu)
         kvm_arch_get_supported_cpuid(s, 0xC0000000, 0, R_EAX);
 }
 
+static void kvm_cpu_xsave_init(void)
+{
+    static bool first = true;
+    KVMState *s = kvm_state;
+    int i;
+
+    if (!first) {
+        return;
+    }
+    first = false;
+
+    /* x87 and SSE states are in the legacy region of the XSAVE area. */
+    x86_ext_save_areas[XSTATE_FP_BIT].offset = 0;
+    x86_ext_save_areas[XSTATE_SSE_BIT].offset = 0;
+
+    for (i = XSTATE_SSE_BIT + 1; i < XSAVE_STATE_AREA_COUNT; i++) {
+        ExtSaveArea *esa = &x86_ext_save_areas[i];
+
+        if (esa->size) {
+            int sz = kvm_arch_get_supported_cpuid(s, 0xd, i, R_EAX);
+            if (sz != 0) {
+                assert(esa->size == sz);
+                esa->offset = kvm_arch_get_supported_cpuid(s, 0xd, i, R_EBX);
+            }
+        }
+    }
+}
+
 static void kvm_cpu_instance_init(CPUState *cs)
 {
     X86CPU *cpu = X86_CPU(cs);
@@ -141,6 +169,8 @@ static void kvm_cpu_instance_init(CPUState *cs)
     if (cpu->max_features) {
         kvm_cpu_max_instance_init(cpu);
     }
+
+    kvm_cpu_xsave_init();
 }
 
 static void kvm_cpu_accel_class_init(ObjectClass *oc, void *data)
diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c
index 41b0764..a850354 100644
--- a/target/i386/kvm/kvm.c
+++ b/target/i386/kvm/kvm.c
@@ -1891,6 +1891,13 @@ int kvm_arch_init_vcpu(CPUState *cs)
         env->xsave_buf_len = sizeof(struct kvm_xsave);
         env->xsave_buf = qemu_memalign(4096, env->xsave_buf_len);
         memset(env->xsave_buf, 0, env->xsave_buf_len);
+
+        /*
+         * The allocated storage must be large enough for all of the
+         * possible XSAVE state components.
+         */
+        assert(kvm_arch_get_supported_cpuid(kvm_state, 0xd, 0, R_ECX)
+               <= env->xsave_buf_len);
     }
 
     max_nested_state_len = kvm_max_nested_state_length();
diff --git a/target/i386/tcg/tcg-cpu.c b/target/i386/tcg/tcg-cpu.c
index 014ebea..e96ec9b 100644
--- a/target/i386/tcg/tcg-cpu.c
+++ b/target/i386/tcg/tcg-cpu.c
@@ -80,6 +80,24 @@ static void tcg_cpu_class_init(CPUClass *cc)
     cc->init_accel_cpu = tcg_cpu_init_ops;
 }
 
+static void tcg_cpu_xsave_init(void)
+{
+#define XO(bit, field) \
+    x86_ext_save_areas[bit].offset = offsetof(X86XSaveArea, field);
+
+    XO(XSTATE_FP_BIT, legacy);
+    XO(XSTATE_SSE_BIT, legacy);
+    XO(XSTATE_YMM_BIT, avx_state);
+    XO(XSTATE_BNDREGS_BIT, bndreg_state);
+    XO(XSTATE_BNDCSR_BIT, bndcsr_state);
+    XO(XSTATE_OPMASK_BIT, opmask_state);
+    XO(XSTATE_ZMM_Hi256_BIT, zmm_hi256_state);
+    XO(XSTATE_Hi16_ZMM_BIT, hi16_zmm_state);
+    XO(XSTATE_PKRU_BIT, pkru_state);
+
+#undef XO
+}
+
 /*
  * TCG-specific defaults that override all CPU models when using TCG
  */
@@ -93,6 +111,8 @@ static void tcg_cpu_instance_init(CPUState *cs)
     X86CPU *cpu = X86_CPU(cs);
     /* Special cases not set in the X86CPUDefinition structs: */
     x86_cpu_apply_props(cpu, tcg_default_props);
+
+    tcg_cpu_xsave_init();
 }
 
 static void tcg_cpu_accel_class_init(ObjectClass *oc, void *data)