Re: [Qemu-devel] [6392] Add BIOS fixes from KVM tree

[Marcelo Tosatti <mtosatti@redhat.com>]

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On Thu, Jan 22, 2009 at 01:14:32AM +0100, Carl-Daniel Hailfinger wrote:
> Hi,
> 
> I'm sorry to say that, but my tests showed that
> 0004_kvm-bios-add-mtrr-support.patch is buggy. It reads MSR_MTRRcap
> unconditionally which is not allowed if the CPUID features do not have
> CPUID_MTRR set. Real hardware will #GP in that case.
> This was found by my MSR access tracing patch.
> 
> Please add a check for the CPUID_MTRR feature bit before reading
> MSR_MTRRcap. Thanks.

Attached, can you confirm it works for you, please?



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diff --git a/bios/rombios32.c b/bios/rombios32.c
index 9d2eaaa..3944d25 100755
--- a/bios/rombios32.c
+++ b/bios/rombios32.c
@@ -48,6 +48,7 @@ typedef unsigned long long uint64_t;
 #define wbinvd() asm volatile("wbinvd")
 
 #define CPUID_APIC (1 << 9)
+#define CPUID_MTRR (1 << 12)
 
 #define APIC_BASE    ((uint8_t *)0xfee00000)
 #define APIC_ICR_LOW 0x300
@@ -540,6 +541,9 @@ void setup_mtrr(void)
         uint64_t val;
     } u;
 
+    if (!(cpuid_features & CPUID_MTRR))
+       return;
+
     mtrr_cap = rdmsr(MSR_MTRRcap);
     vcnt = mtrr_cap & 0xff;
     fix = mtrr_cap & 0x100;
@@ -2201,10 +2205,10 @@ void rombios32_init(uint32_t *s3_resume_vector, uint8_t *shutdown_flag)
 
     init_smp_msrs();
 
-    ram_probe();
-
     cpu_probe();
 
+    ram_probe();
+
     smp_probe();
 
     find_bios_table_area();