> > > --- a/arch/x86/events/intel/pt.c
> > > +++ b/arch/x86/events/intel/pt.c
> > > @@ -76,14 +76,20 @@
> > > PT_CAP(psb_periods, 1, CPUID_EBX, 0xffff0000),
> > > };
> > >
> > > -u32 pt_cap_get(enum pt_capabilities cap)
> > > +u32 pt_cap_decode(u32 *caps, enum pt_capabilities cap)
> > > {
> > > struct pt_cap_desc *cd = &pt_caps[cap];
> > > - u32 c = pt_pmu.caps[cd->leaf * PT_CPUID_REGS_NUM + cd->reg];
> > > + u32 c = caps[cd->leaf * PT_CPUID_REGS_NUM + cd->reg];
> >
> > We are accessing offset "cd->leaf * PT_CPUID_REGS_NUM + cd->reg" of
> > array caps. But the array may not be big enough. Is it sufficient to use "struct pt_pmu *pt_pmu" and "pt_pmu->caps" instead?
> >
>
> Thanks for your review.
> Function pt_cap_get() can get the capability of native because "pt_pmu.caps[] " include native Intel PT CPUID info.
> In virtualization, the guest CPUID info is configurable. So I introduce this function pt_cap_decode() to check if guest CPUID support
> specific capability. I introduce a structure "struct pt_desc" which include a member "u32 caps[PT_CPUID_REGS_NUM *
> PT_CPUID_LEAVES]" like native "struct pt_pmu" in patch 8.
> So, I can't use "struct pt_pmu *pt_pmu" or "pt_pmu->caps" here because they are native parameter not guest.
>
What about move pt_cap_decode() to kvm and remove the static of "pt_caps[]" so that kvm can access this variable.
To avoid the array may not be big enough, change the function parameter like this:
u32 pt_cap_decode(struct pt_desc *pt_desc, enum pt_capabilities cap)
{
struct pt_cap_desc *cd = &pt_caps[cap];
u32 c = pt_desc->caps[cd->leaf * PT_CPUID_REGS_NUM + cd->reg];
... ...
}
Thanks,
Luwei Kang
>
> >
> > > unsigned int shift = __ffs(cd->mask);
> > >
> > > return (c & cd->mask) >> shift;
> > > }
> > > +EXPORT_SYMBOL_GPL(pt_cap_decode);
> > > +
> > > +u32 pt_cap_get(enum pt_capabilities cap) {
> > > + return pt_cap_decode(pt_pmu.caps, cap); }
> > > EXPORT_SYMBOL_GPL(pt_cap_get);
> > >
> > > static ssize_t pt_cap_show(struct device *cdev, diff --git
> > > a/arch/x86/include/asm/intel_pt.h b/arch/x86/include/asm/intel_pt.h
> > > index 2de4db0..9c71453 100644
> > > --- a/arch/x86/include/asm/intel_pt.h
> > > +++ b/arch/x86/include/asm/intel_pt.h
> > > @@ -27,9 +27,11 @@ enum pt_capabilities { #if
> > > defined(CONFIG_PERF_EVENTS) && defined(CONFIG_CPU_SUP_INTEL) void
> > > cpu_emergency_stop_pt(void); extern u32 pt_cap_get(enum
> > > pt_capabilities cap);
> > > +extern u32 pt_cap_decode(u32 *caps, enum pt_capabilities cap);
> > > #else
> > > static inline void cpu_emergency_stop_pt(void) {} static inline u32
> > > pt_cap_get(enum pt_capabilities cap) { return 0; }
> > > +static u32 pt_cap_decode(u32 *caps, enum pt_capabilities cap) {
> > > +return 0; }
> > > #endif
> > >
> > > #endif /* _ASM_X86_INTEL_PT_H */
> > > --
> > > 1.8.3.1
> > >
