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Re: [PATCH] target/i386: VMRUN and VMLOAD canonicalizations


From: Paolo Bonzini
Subject: Re: [PATCH] target/i386: VMRUN and VMLOAD canonicalizations
Date: Fri, 6 Aug 2021 16:06:02 +0200
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0

On 04/08/21 13:30, Lara Lazier wrote:
APM2 requires that VMRUN and VMLOAD canonicalize (sign extend to 63
from 48/57) all base addresses in the segment registers that have been
respectively loaded.

Signed-off-by: Lara Lazier <laramglazier@gmail.com>
---
  target/i386/cpu.c                   | 19 +++++++++++--------
  target/i386/cpu.h                   |  2 ++
  target/i386/tcg/sysemu/svm_helper.c | 27 +++++++++++++++++----------
  3 files changed, 30 insertions(+), 18 deletions(-)

diff --git a/target/i386/cpu.c b/target/i386/cpu.c
index 71d26cf1bd..de4c8316c9 100644
--- a/target/i386/cpu.c
+++ b/target/i386/cpu.c
@@ -5108,6 +5108,15 @@ static void x86_register_cpudef_types(const 
X86CPUDefinition *def)
} +uint32_t cpu_x86_virtual_addr_width(CPUX86State *env)
+{
+    if  (env->features[FEAT_7_0_ECX] & CPUID_7_0_ECX_LA57) {
+        return 57; /* 57 bits virtual */
+    } else {
+        return 48; /* 48 bits virtual */
+    }
+}
+
  void cpu_x86_cpuid(CPUX86State *env, uint32_t index, uint32_t count,
                     uint32_t *eax, uint32_t *ebx,
                     uint32_t *ecx, uint32_t *edx)
@@ -5510,16 +5519,10 @@ void cpu_x86_cpuid(CPUX86State *env, uint32_t index, 
uint32_t count,
          break;
      case 0x80000008:
          /* virtual & phys address size in low 2 bytes. */
+        *eax = cpu->phys_bits;
          if (env->features[FEAT_8000_0001_EDX] & CPUID_EXT2_LM) {
              /* 64 bit processor */
-            *eax = cpu->phys_bits; /* configurable physical bits */
-            if  (env->features[FEAT_7_0_ECX] & CPUID_7_0_ECX_LA57) {
-                *eax |= 0x00003900; /* 57 bits virtual */
-            } else {
-                *eax |= 0x00003000; /* 48 bits virtual */
-            }
-        } else {
-            *eax = cpu->phys_bits;
+             *eax |= (cpu_x86_virtual_addr_width(env) << 8);
          }
          *ebx = env->features[FEAT_8000_0008_EBX];
          if (cs->nr_cores * cs->nr_threads > 1) {
diff --git a/target/i386/cpu.h b/target/i386/cpu.h
index 6c50d3ab4f..c9c7350c76 100644
--- a/target/i386/cpu.h
+++ b/target/i386/cpu.h
@@ -1954,6 +1954,8 @@ typedef struct PropValue {
  } PropValue;
  void x86_cpu_apply_props(X86CPU *cpu, PropValue *props);
+uint32_t cpu_x86_virtual_addr_width(CPUX86State *env);
+
  /* cpu.c other functions (cpuid) */
  void cpu_x86_cpuid(CPUX86State *env, uint32_t index, uint32_t count,
                     uint32_t *eax, uint32_t *ebx,
diff --git a/target/i386/tcg/sysemu/svm_helper.c 
b/target/i386/tcg/sysemu/svm_helper.c
index 6c29a6a778..032561ef8c 100644
--- a/target/i386/tcg/sysemu/svm_helper.c
+++ b/target/i386/tcg/sysemu/svm_helper.c
@@ -41,6 +41,16 @@ static inline void svm_save_seg(CPUX86State *env, hwaddr 
addr,
               ((sc->flags >> 8) & 0xff) | ((sc->flags >> 12) & 0x0f00));
  }
+/*
+ * VMRUN and VMLOAD canonicalizes (i.e., sign-extend to bit 63) all base
+ * addresses in the segment registers that have been loaded.
+ */
+static inline void svm_canonicalization(CPUX86State *env, target_ulong 
*seg_base)
+{
+    uint16_t shift_amt = 64 - cpu_x86_virtual_addr_width(env);
+    *seg_base = ((((long) *seg_base) << shift_amt) >> shift_amt);
+}
+
  static inline void svm_load_seg(CPUX86State *env, hwaddr addr,
                                  SegmentCache *sc)
  {
@@ -53,6 +63,7 @@ static inline void svm_load_seg(CPUX86State *env, hwaddr addr,
      sc->limit = x86_ldl_phys(cs, addr + offsetof(struct vmcb_seg, limit));
      flags = x86_lduw_phys(cs, addr + offsetof(struct vmcb_seg, attrib));
      sc->flags = ((flags & 0xff) << 8) | ((flags & 0x0f00) << 12);
+    svm_canonicalization(env, &sc->base);
  }
static inline void svm_load_seg_cache(CPUX86State *env, hwaddr addr,
@@ -256,16 +267,6 @@ void helper_vmrun(CPUX86State *env, int aflag, int 
next_eip_addend)
      env->tsc_offset = x86_ldq_phys(cs, env->vm_vmcb +
                                 offsetof(struct vmcb, control.tsc_offset));
- env->gdt.base = x86_ldq_phys(cs, env->vm_vmcb + offsetof(struct vmcb,
-                                                      save.gdtr.base));
-    env->gdt.limit = x86_ldl_phys(cs, env->vm_vmcb + offsetof(struct vmcb,
-                                                      save.gdtr.limit));
-
-    env->idt.base  = x86_ldq_phys(cs, env->vm_vmcb + offsetof(struct vmcb,
-                                                      save.idtr.base));
-    env->idt.limit = x86_ldl_phys(cs, env->vm_vmcb + offsetof(struct vmcb,
-                                                      save.idtr.limit));
-
      new_cr0 = x86_ldq_phys(cs, env->vm_vmcb + offsetof(struct vmcb, 
save.cr0));
      if (new_cr0 & SVM_CR0_RESERVED_MASK) {
          cpu_vmexit(env, SVM_EXIT_ERR, 0, GETPC());
@@ -319,6 +320,10 @@ void helper_vmrun(CPUX86State *env, int aflag, int 
next_eip_addend)
                         R_SS);
      svm_load_seg_cache(env, env->vm_vmcb + offsetof(struct vmcb, save.ds),
                         R_DS);
+    svm_load_seg(env, env->vm_vmcb + offsetof(struct vmcb, save.idtr),
+                       &env->idt);
+    svm_load_seg(env, env->vm_vmcb + offsetof(struct vmcb, save.gdtr),
+                       &env->gdt);
env->eip = x86_ldq_phys(cs,
                          env->vm_vmcb + offsetof(struct vmcb, save.rip));
@@ -456,6 +461,7 @@ void helper_vmload(CPUX86State *env, int aflag)
      env->lstar = x86_ldq_phys(cs, addr + offsetof(struct vmcb, save.lstar));
      env->cstar = x86_ldq_phys(cs, addr + offsetof(struct vmcb, save.cstar));
      env->fmask = x86_ldq_phys(cs, addr + offsetof(struct vmcb, save.sfmask));
+    svm_canonicalization(env, &env->kernelgsbase);
  #endif
      env->star = x86_ldq_phys(cs, addr + offsetof(struct vmcb, save.star));
      env->sysenter_cs = x86_ldq_phys(cs,
@@ -464,6 +470,7 @@ void helper_vmload(CPUX86State *env, int aflag)
                                                   save.sysenter_esp));
      env->sysenter_eip = x86_ldq_phys(cs, addr + offsetof(struct vmcb,
                                                   save.sysenter_eip));
+
  }
void helper_vmsave(CPUX86State *env, int aflag)


Queued, thanks.

Paolo




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