[RFC PATCH 7/8] target/i386: Populate x86_ext_save_areas offsets using cpuid where possible

[David Edmondson <david.edmondson@oracle.com>]

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>
---
 target/i386/cpu.c         | 13 +------------
 target/i386/cpu.h         |  2 +-
 target/i386/hvf/hvf-cpu.c | 34 ++++++++++++++++++++++++++++++++++
 target/i386/kvm/kvm-cpu.c | 36 ++++++++++++++++++++++++++++++++++++
 target/i386/tcg/tcg-cpu.c | 20 ++++++++++++++++++++
 5 files changed, 92 insertions(+), 13 deletions(-)

diff --git a/target/i386/cpu.c b/target/i386/cpu.c
index 13caa0de50..5f595a0d7e 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 c9c0a34330..96b672f8bd 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 8fbc423888..3c7c44698f 100644
--- a/target/i386/hvf/hvf-cpu.c
+++ b/target/i386/hvf/hvf-cpu.c
@@ -30,6 +30,38 @@ static void hvf_cpu_max_instance_init(X86CPU *cpu)
         hvf_get_supported_cpuid(0xC0000000, 0, R_EAX);
 }
 
+static void hvf_cpu_xsave_init(void)
+{
+    int i;
+
+    /*
+     * The allocated storage must be large enough for all of the
+     * possible XSAVE state components.
+     */
+    assert(hvf_get_supported_cpuid(0xd, 0, R_ECX) <= 4096);
+
+    /* x87 state is in the legacy region of the XSAVE area. */
+    x86_ext_save_areas[XSTATE_FP_BIT].offset = 0;
+    /* SSE state is in the legacy region of the XSAVE area. */
+    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);
+                fprintf(stderr, "%s: state area %d: offset 0x%x, size 0x%x\n",
+                        __func__, i, esa->offset, esa->size);
+            }
+        }
+    }
+}
+
 static void hvf_cpu_instance_init(CPUState *cs)
 {
     X86CPU *cpu = X86_CPU(cs);
@@ -42,6 +74,8 @@ 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/kvm/kvm-cpu.c b/target/i386/kvm/kvm-cpu.c
index 00369c2000..f474cc5b83 100644
--- a/target/i386/kvm/kvm-cpu.c
+++ b/target/i386/kvm/kvm-cpu.c
@@ -122,6 +122,40 @@ 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)
+{
+    KVMState *s = kvm_state;
+    int i;
+
+    /*
+     * The allocated storage must be large enough for all of the
+     * possible XSAVE state components.
+     */
+    assert(sizeof(struct kvm_xsave) >=
+           kvm_arch_get_supported_cpuid(s, 0xd, 0, R_ECX));
+
+    /* x87 state is in the legacy region of the XSAVE area. */
+    x86_ext_save_areas[XSTATE_FP_BIT].offset = 0;
+    /* SSE state is in the legacy region of the XSAVE area. */
+    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);
+                fprintf(stderr, "%s: state area %d: offset 0x%x, size 0x%x\n",
+                        __func__, i, esa->offset, esa->size);
+            }
+        }
+    }
+}
+
 static void kvm_cpu_instance_init(CPUState *cs)
 {
     X86CPU *cpu = X86_CPU(cs);
@@ -141,6 +175,8 @@ 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/tcg/tcg-cpu.c b/target/i386/tcg/tcg-cpu.c
index 014ebea2f6..e96ec9bbcc 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)
-- 
2.30.2