Re: [SeaBIOS] [PATCH v2] fw/msr_feature_control: add support to set MSR_IA32_FEATURE_CONTROL

[Haozhong Zhang]

On 06/17/16 11:26, Kevin O'Connor wrote:
> On Fri, Jun 17, 2016 at 03:20:10PM +0800, Haozhong Zhang wrote:
> > OS usually expects BIOS to set certain bits in MSR_IA32_FEATURE_CONTROL
> > for some features (e.g. VMX and LMCE). QEMU provides a fw_cfg file
> > "etc/msr_feature_control" to advise bits that should be set in
> > MSR_IA32_FEATURE_CONTROL. If this file exists, SeaBIOS will set the
> > advised bits in that MSR.
>
> Thanks - see my comments below.
> > --- /dev/null
> > +++ b/src/fw/msr_feature_control.c
> > @@ -0,0 +1,16 @@
> > +#include "util.h" // msr_feature_control_setup, wrmsr_smp
> > +#include "romfile.h" // romfile_find
> >
> > +#define MSR_IA32_FEATURE_CONTROL 0x0000003a
> >
> > +void msr_feature_control_setup(void)
> > +{
> > struct romfile_s *f = romfile_find("etc/msr_feature_control");
> > if (!f)
> >    return;
> > u64 feature_control_bits;
> > f->copy(f, &feature_control_bits, sizeof(feature_control_bits));
> > if (feature_control_bits)
> >    wrmsr_smp(MSR_IA32_FEATURE_CONTROL, feature_control_bits);
> >
> > +}
>
> Can you use romfile_loadint() instead?  Something like:
> u64 feature_control_bits = romfile_loadint("etc/msr_feature_control", 0);
> if (feature_control_bits)
>     wrmsr_smp(MSR_IA32_FEATURE_CONTROL, feature_control_bits);
>
> That should avoid the need for the separate romfile_find() call and it
> has the added benefit of additional sanity checks.
>
> Also, I think this code is small enough it can be placed directly in
> paravirt.c and does not need its own c file.

I'll use romfile_loadint and place the code in paravirt.c in the next version.

Thanks,
Haozhong