> On Jul 3, 2018, at 3:04 AM, Luwei Kang <luwei.kang@xxxxxxxxx> wrote:
>
> New function pt_cap_decode() will be invoked in KVM to check
> if a specific capability is available in KVM guest.
> Another function pt_cap_get() can only check the hardware
> capabilities but this may different with KVM guest because
> some features may not be exposed to guest.
>
> Signed-off-by: Luwei Kang <luwei.kang@xxxxxxxxx>
> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> Cc: Ingo Molnar <mingo@xxxxxxxxxx>
> Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
> Cc: "Peter Zijlstra (Intel)" <peterz@xxxxxxxxxxxxx>
> Cc: Alexander Shishkin <alexander.shishkin@xxxxxxxxxxxxxxx>
> Cc: Song Liu <songliubraving@xxxxxx>
> Cc: Kate Stewart <kstewart@xxxxxxxxxxxxxxxxxxx>
> Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
> ---
> arch/x86/events/intel/pt.c | 10 ++++++++--
> arch/x86/include/asm/intel_pt.h | 2 ++
> 2 files changed, 10 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/events/intel/pt.c b/arch/x86/events/intel/pt.c
> index 00b079e..edbc930 100644
> --- 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,
Song
> 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
>
