target/i386: raise #GP on reserved/unimplemented MSR access (RDMSR/WRMSR)

[PATCH] target/i386: raise #GP on reserved/unimplemented MSR access (RDMSR/WRMSR)

Anastasiy posted 1 patch 1 month, 2 weeks ago

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git fetch https://github.com/patchew-project/qemu tags/patchew/20260611083422.52858-1-molenoch@protonmail.com

Maintainers: Paolo Bonzini <pbonzini@redhat.com>, Richard Henderson <richard.henderson@linaro.org>

target/i386/tcg/system/misc_helper.c | 10 +++-------
1 file changed, 3 insertions(+), 7 deletions(-)

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[PATCH] target/i386: raise #GP on reserved/unimplemented MSR access (RDMSR/WRMSR)

Posted by Anastasiy 1 month, 2 weeks ago

Three locations in helper_{rd,wr}msr() had '/* XXX: exception? */' placeholders
that silently ignored accesses to reserved or unimplemented MSRs instead of
raising #GP(0) as required by the Intel SDM (Vol. 2D, order 334569):

- helper_wrmsr() default case after MCE bank range check
- helper_rdmsr() MSR_MTRRcap when CPUID_MTRR not set
- helper_rdmsr() default case after MCE bank range check

Replace the silent fallthroughs with raise_exception_err_ra(env, EXCP0D_GPF, 0, GETPC()).

Signed-off-by: Anastasiy <molenoch@protonmail.com>
---
 target/i386/tcg/system/misc_helper.c | 10 +++-------
 1 file changed, 3 insertions(+), 7 deletions(-)

diff --git a/target/i386/tcg/system/misc_helper.c b/target/i386/tcg/system/misc_helper.c
index bb79d4e..e559d8f 100644
--- a/target/i386/tcg/system/misc_helper.c
+++ b/target/i386/tcg/system/misc_helper.c
@@ -318,8 +318,7 @@ void helper_wrmsr(CPUX86State *env)
             }
             break;
         }
-        /* XXX: exception? */
-        break;
+        goto error;
     }
     return;
 error:
@@ -442,8 +441,7 @@ void helper_rdmsr(CPUX86State *env)
             val = MSR_MTRRcap_VCNT | MSR_MTRRcap_FIXRANGE_SUPPORT |
                 MSR_MTRRcap_WC_SUPPORTED;
         } else {
-            /* XXX: exception? */
-            val = 0;
+            raise_exception_err_ra(env, EXCP0D_GPF, 0, GETPC());
         }
         break;
     case MSR_MCG_CAP:
@@ -493,9 +491,7 @@ void helper_rdmsr(CPUX86State *env)
             val = env->mce_banks[offset];
             break;
         }
-        /* XXX: exception? */
-        val = 0;
-        break;
+        raise_exception_err_ra(env, EXCP0D_GPF, 0, GETPC());
     }
     env->regs[R_EAX] = (uint32_t)(val);
     env->regs[R_EDX] = (uint32_t)(val >> 32);
-- 
2.53.0