target/i386: Added vVMLOAD and vVMSAVE feature

The feature allows the VMSAVE and VMLOAD instructions to execute in guest mode without
causing a VMEXIT. (APM2 15.33.1)

Signed-off-by: Lara Lazier <laramglazier@gmail.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

target/i386/cpu.h

@@ -2261,6 +2261,8 @@ static inline bool ctl_has_irq(CPUX86State *env)
     return (env->int_ctl & V_IRQ_MASK) && (int_prio >= tpr);
 }
 
+hwaddr get_hphys(CPUState *cs, hwaddr gphys, MMUAccessType access_type,
+                        int *prot);
 #if defined(TARGET_X86_64) && \
     defined(CONFIG_USER_ONLY) && \
     defined(CONFIG_LINUX)

target/i386/svm.h

@@ -24,6 +24,8 @@
 #define V_INTR_MASKING_SHIFT 24
 #define V_INTR_MASKING_MASK (1 << V_INTR_MASKING_SHIFT)
 
+#define V_VMLOAD_VMSAVE_ENABLED_MASK (1 << 1)
+
 #define SVM_INTERRUPT_SHADOW_MASK 1
 
 #define SVM_IOIO_STR_SHIFT 2

target/i386/tcg/sysemu/excp_helper.c

@@ -358,7 +358,7 @@ do_check_protect_pse36:
     return error_code;
 }
 
-static hwaddr get_hphys(CPUState *cs, hwaddr gphys, MMUAccessType access_type,
+hwaddr get_hphys(CPUState *cs, hwaddr gphys, MMUAccessType access_type,
                         int *prot)
 {
     CPUX86State *env = &X86_CPU(cs)->env;

target/i386/tcg/sysemu/svm_helper.c

@@ -120,6 +120,25 @@ static inline bool virtual_gif_enabled(CPUX86State *env)
     return false;
 }
 
+static inline bool virtual_vm_load_save_enabled(CPUX86State *env, uint32_t exit_code, uintptr_t retaddr)
+{
+    uint64_t lbr_ctl;
+
+    if (likely(env->hflags & HF_GUEST_MASK)) {
+        if (likely(!(env->hflags2 & HF2_NPT_MASK)) || !(env->efer & MSR_EFER_LMA)) {
+            cpu_vmexit(env, exit_code, 0, retaddr);
+        }
+
+        lbr_ctl = x86_ldl_phys(env_cpu(env), env->vm_vmcb + offsetof(struct vmcb,
+                                                  control.lbr_ctl));
+        return (env->features[FEAT_SVM] & CPUID_SVM_V_VMSAVE_VMLOAD)
+                && (lbr_ctl & V_VMLOAD_VMSAVE_ENABLED_MASK);
+
+    }
+
+    return false;
+}
+
 static inline bool virtual_gif_set(CPUX86State *env)
 {
     return !virtual_gif_enabled(env) || (env->int_ctl & V_GIF_MASK);
@@ -431,6 +450,7 @@ void helper_vmload(CPUX86State *env, int aflag)
 {
     CPUState *cs = env_cpu(env);
     target_ulong addr;
+    int prot;
 
     cpu_svm_check_intercept_param(env, SVM_EXIT_VMLOAD, 0, GETPC());
 
@@ -440,6 +460,10 @@ void helper_vmload(CPUX86State *env, int aflag)
         addr = (uint32_t)env->regs[R_EAX];
     }
 
+    if (virtual_vm_load_save_enabled(env, SVM_EXIT_VMLOAD, GETPC())) {
+        addr = get_hphys(cs, addr, MMU_DATA_LOAD, &prot);
+    }
+
     qemu_log_mask(CPU_LOG_TB_IN_ASM, "vmload! " TARGET_FMT_lx
                   "\nFS: %016" PRIx64 " | " TARGET_FMT_lx "\n",
                   addr, x86_ldq_phys(cs, addr + offsetof(struct vmcb,
@@ -473,6 +497,7 @@ void helper_vmsave(CPUX86State *env, int aflag)
 {
     CPUState *cs = env_cpu(env);
     target_ulong addr;
+    int prot;
 
     cpu_svm_check_intercept_param(env, SVM_EXIT_VMSAVE, 0, GETPC());
 
@@ -482,6 +507,10 @@ void helper_vmsave(CPUX86State *env, int aflag)
         addr = (uint32_t)env->regs[R_EAX];
     }
 
+    if (virtual_vm_load_save_enabled(env, SVM_EXIT_VMSAVE, GETPC())) {
+        addr = get_hphys(cs, addr, MMU_DATA_STORE, &prot);
+    }
+
     qemu_log_mask(CPU_LOG_TB_IN_ASM, "vmsave! " TARGET_FMT_lx
                   "\nFS: %016" PRIx64 " | " TARGET_FMT_lx "\n",
                   addr, x86_ldq_phys(cs,