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Date: Tue, 19 Mar 2019 14:00:04 +0100
From: Peter Zijlstra <peterz@...radead.org>
To: kan.liang@...ux.intel.com
Cc: acme@...nel.org, mingo@...hat.com, linux-kernel@...r.kernel.org,
tglx@...utronix.de, jolsa@...nel.org, eranian@...gle.com,
alexander.shishkin@...ux.intel.com, ak@...ux.intel.com
Subject: Re: [PATCH 01/22] perf/core: Support outputting registers from a
separate array
On Mon, Mar 18, 2019 at 02:41:23PM -0700, kan.liang@...ux.intel.com wrote:
> From: Andi Kleen <ak@...ux.intel.com>
>
> Add support to the perf core for outputting registers from a separate
> array and add support for outputting XMM registers for x86.
What separate array and why?
> This requires changing all the perf_reg_value functions for the
> different architectures to pass the additional argument.
What additional argument? (basically a dangling reference here)
> Except for x86, they just ignore it.
>
> XMM registers are 128 bit. To simplify the code, they are handled like
> two different registers, which means setting two bits in the register
> bitmap. This also allows only sampling the lower 64bit bits in XMM.
So that is at least 2 changes in one patch; I though there was a rule
about that.
> Signed-off-by: Andi Kleen <ak@...ux.intel.com>
> Signed-off-by: Kan Liang <kan.liang@...ux.intel.com>
> ---
> diff --git a/arch/x86/include/uapi/asm/perf_regs.h b/arch/x86/include/uapi/asm/perf_regs.h
> index f3329cabce5c..1ff0df1c97ae 100644
> --- a/arch/x86/include/uapi/asm/perf_regs.h
> +++ b/arch/x86/include/uapi/asm/perf_regs.h
> @@ -28,7 +28,28 @@ enum perf_event_x86_regs {
> PERF_REG_X86_R14,
> PERF_REG_X86_R15,
>
> - PERF_REG_X86_32_MAX = PERF_REG_X86_GS + 1,
> - PERF_REG_X86_64_MAX = PERF_REG_X86_R15 + 1,
> + /* These all need two bits set because they are 128bit */
> + PERF_REG_X86_XMM0 = 32,
> + PERF_REG_X86_XMM1 = 34,
> + PERF_REG_X86_XMM2 = 36,
> + PERF_REG_X86_XMM3 = 38,
> + PERF_REG_X86_XMM4 = 40,
> + PERF_REG_X86_XMM5 = 42,
> + PERF_REG_X86_XMM6 = 44,
> + PERF_REG_X86_XMM7 = 46,
> + PERF_REG_X86_XMM8 = 48,
> + PERF_REG_X86_XMM9 = 50,
> + PERF_REG_X86_XMM10 = 52,
> + PERF_REG_X86_XMM11 = 54,
> + PERF_REG_X86_XMM12 = 56,
> + PERF_REG_X86_XMM13 = 58,
> + PERF_REG_X86_XMM14 = 60,
> + PERF_REG_X86_XMM15 = 62,
> +
> + /* This does not include the XMMX registers */
> + PERF_REG_GPR_X86_32_MAX = PERF_REG_X86_GS + 1,
> + PERF_REG_GPR_X86_64_MAX = PERF_REG_X86_R15 + 1,
> +
> + PERF_REG_X86_MAX = PERF_REG_X86_XMM15 + 2,
This needs explaining in both the Changelog and a comment.
> };
> #endif /* _ASM_X86_PERF_REGS_H */
> diff --git a/arch/x86/kernel/perf_regs.c b/arch/x86/kernel/perf_regs.c
> index c06c4c16c6b6..8b44a4c5a161 100644
> --- a/arch/x86/kernel/perf_regs.c
> +++ b/arch/x86/kernel/perf_regs.c
> @@ -10,14 +10,14 @@
> #include <asm/ptrace.h>
>
> #ifdef CONFIG_X86_32
> -#define PERF_REG_X86_MAX PERF_REG_X86_32_MAX
> +#define PERF_REG_GPR_X86_MAX PERF_REG_GPR_X86_32_MAX
> #else
> -#define PERF_REG_X86_MAX PERF_REG_X86_64_MAX
> +#define PERF_REG_GPR_X86_MAX PERF_REG_GPR_X86_64_MAX
> #endif
>
> #define PT_REGS_OFFSET(id, r) [id] = offsetof(struct pt_regs, r)
>
> -static unsigned int pt_regs_offset[PERF_REG_X86_MAX] = {
> +static unsigned int pt_regs_offset[PERF_REG_GPR_X86_MAX] = {
> PT_REGS_OFFSET(PERF_REG_X86_AX, ax),
> PT_REGS_OFFSET(PERF_REG_X86_BX, bx),
> PT_REGS_OFFSET(PERF_REG_X86_CX, cx),
> @@ -57,15 +57,22 @@ static unsigned int pt_regs_offset[PERF_REG_X86_MAX] = {
> #endif
> };
>
> -u64 perf_reg_value(struct pt_regs *regs, int idx)
> +u64 perf_reg_value(struct pt_regs *regs, u64 *extra_regs, int idx)
> {
> + if (idx >= 32 && idx < 64) {
> + if (!extra_regs)
> + return 0;
> + return extra_regs[idx - 32];
> + }
> +
> if (WARN_ON_ONCE(idx >= ARRAY_SIZE(pt_regs_offset)))
> return 0;
>
> return regs_get_register(regs, pt_regs_offset[idx]);
> }
>
> -#define REG_RESERVED (~((1ULL << PERF_REG_X86_MAX) - 1ULL))
> +#define REG_RESERVED \
> + (PERF_REG_X86_MAX == 64 ? 0 : ~((1ULL << PERF_REG_X86_MAX)) - 1ULL)
>
> #ifdef CONFIG_X86_32
> int perf_reg_validate(u64 mask)
> diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
> index e47ef764f613..bd3d6a89ccd4 100644
> --- a/include/linux/perf_event.h
> +++ b/include/linux/perf_event.h
> @@ -948,6 +948,7 @@ struct perf_sample_data {
> u64 stack_user_size;
>
> u64 phys_addr;
> + u64 *extra_regs;
> } ____cacheline_aligned;
>
> /* default value for data source */
> @@ -968,6 +969,7 @@ static inline void perf_sample_data_init(struct perf_sample_data *data,
> data->weight = 0;
> data->data_src.val = PERF_MEM_NA;
> data->txn = 0;
> + data->extra_regs = NULL;
> }
NAK, why do I have to keep explaining this?
> diff --git a/kernel/events/core.c b/kernel/events/core.c
> index 5f59d848171e..560ac237b8be 100644
> --- a/kernel/events/core.c
> +++ b/kernel/events/core.c
> @@ -5858,7 +5858,8 @@ EXPORT_SYMBOL_GPL(perf_unregister_guest_info_callbacks);
>
> static void
> perf_output_sample_regs(struct perf_output_handle *handle,
> - struct pt_regs *regs, u64 mask)
> + struct pt_regs *regs,
> + u64 *extra_regs, u64 mask)
> {
> int bit;
> DECLARE_BITMAP(_mask, 64);
> @@ -5867,7 +5868,7 @@ perf_output_sample_regs(struct perf_output_handle *handle,
> for_each_set_bit(bit, _mask, sizeof(mask) * BITS_PER_BYTE) {
> u64 val;
>
> - val = perf_reg_value(regs, bit);
> + val = perf_reg_value(regs, extra_regs, bit);
> perf_output_put(handle, val);
> }
> }
> @@ -6274,6 +6275,7 @@ void perf_output_sample(struct perf_output_handle *handle,
> u64 mask = event->attr.sample_regs_user;
> perf_output_sample_regs(handle,
> data->regs_user.regs,
> + NULL,
> mask);
> }
> }
> @@ -6306,6 +6308,7 @@ void perf_output_sample(struct perf_output_handle *handle,
>
> perf_output_sample_regs(handle,
> data->regs_intr.regs,
> + data->extra_regs,
> mask);
> }
> }
See, I think most of this is completely unnessecary. Both sites pass:
&perf_regs::regs to perf_output_sample_regs()<-perf_reg_value().
So all you need to do is add the XMM crud to perf_regs, and use
container_of() on the pt_regs pointer in perf_reg_value() to get back to
perf_regs and voila, XMM registers.
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