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Re: [Qemu-devel] [SeaBIOS] [PATCH v2] fw/msr_feature_control: add suppor
Re: [Qemu-devel] [SeaBIOS] [PATCH v2] fw/msr_feature_control: add support to set MSR_IA32_FEATURE_CONTROL
Fri, 17 Jun 2016 11:26:21 -0400
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);
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.