[Qemu-devel] Bochs BIOS writes incorrect value into MTRR MSR

[Stanislav]

Hi All,

Bochs Bios has a bug in setup_mtrr function in rombios.cc
The code:

    /* Mark 3.5-4GB as UC, anything not specified defaults to WB */
    wrmsr_smp(MTRRphysBase_MSR(0), 0xe0000000ull | 0);
    wrmsr_smp(MTRRphysMask_MSR(0), ~(0x20000000ull - 1) | 0x800);

sets reserved bits in the MTRRphysMask MSR which would cause #GP on real
hardware.
The right way is to use physical address size provided in CPUID left
0x80000008 or set up only no more than 32 bit value.
Could somebody help to fix it ?

Thanks,
Stanislav