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Subject: Re: [PATCH v2 07/14] perf arm-spe: Refactor address packet handling
To:     Leo Yan <leo.yan@linaro.org>,
        Arnaldo Carvalho de Melo <acme@kernel.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@redhat.com>,
        Mark Rutland <mark.rutland@arm.com>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        Jiri Olsa <jolsa@redhat.com>,
        Namhyung Kim <namhyung@kernel.org>,
        Wei Li <liwei391@huawei.com>,
        James Clark <james.clark@arm.com>,
        Dave Martin <Dave.Martin@arm.com>,
        linux-kernel@vger.kernel.org, Al Grant <Al.Grant@arm.com>
References: <20200929133917.9224-1-leo.yan@linaro.org>
 <20200929133917.9224-8-leo.yan@linaro.org>
From:   =?UTF-8?Q?Andr=c3=a9_Przywara?= <andre.przywara@arm.com>
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Organization: ARM Ltd.
Message-ID: <2e9a9499-4596-2a07-4d44-30e319206c12@arm.com>
Date:   Mon, 19 Oct 2020 10:01:28 +0100
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On 29/09/2020 14:39, Leo Yan wrote:

Hi Leo,

> This patch is to refactor address packet handling, it defines macros for
> address packet's header and payload, these macros are used by decoder
> and the dump flow.

So I was thinking about these next few patches a bit. I understand that
it's common ground to not use numbers in code directly, but put names to
them (and there is good rationale for that).

However those long and complicated names don't make it really easier to
read, I think.

See below for an idea:

> Signed-off-by: Leo Yan <leo.yan@linaro.org>
> ---
>  .../util/arm-spe-decoder/arm-spe-decoder.c    | 33 ++++++++++---------
>  .../arm-spe-decoder/arm-spe-pkt-decoder.c     | 25 +++++++-------
>  .../arm-spe-decoder/arm-spe-pkt-decoder.h     | 27 ++++++++++-----
>  3 files changed, 49 insertions(+), 36 deletions(-)
> 
> diff --git a/tools/perf/util/arm-spe-decoder/arm-spe-decoder.c b/tools/perf/util/arm-spe-decoder/arm-spe-decoder.c
> index cc18a1e8c212..9d3de163d47c 100644
> --- a/tools/perf/util/arm-spe-decoder/arm-spe-decoder.c
> +++ b/tools/perf/util/arm-spe-decoder/arm-spe-decoder.c
> @@ -24,36 +24,37 @@
>  
>  static u64 arm_spe_calc_ip(int index, u64 payload)
>  {
> -	u8 *addr = (u8 *)&payload;
> -	int ns, el;
> +	u64 ns, el;

This (and the "u64 vs. u8[]" changes below) looks like a nice cleanup.
>  	/* Instruction virtual address or Branch target address */
>  	if (index == SPE_ADDR_PKT_HDR_INDEX_INS ||
>  	    index == SPE_ADDR_PKT_HDR_INDEX_BRANCH) {
> -		ns = addr[7] & SPE_ADDR_PKT_NS;
> -		el = (addr[7] & SPE_ADDR_PKT_EL_MASK) >> SPE_ADDR_PKT_EL_OFFSET;
> +		ns = payload & SPE_ADDR_PKT_INST_VA_NS;
> +		el = (payload & SPE_ADDR_PKT_INST_VA_EL_MASK)
> +			>> SPE_ADDR_PKT_INST_VA_EL_SHIFT;

So if I see this correctly, this _EL_SHIFT and _EL_MASK are only used
together, and only to read values, not to construct them.
So can you fuse them together in the header file below, like:
	el = SPE_ADDR_PKT_INST_VA_GET_EL(payload);

That should help readablity, I guess, while still keeping the actual
numbers in one place. _SHIFT and _MASK are useful when we use them to
both extract *and construct* values, but here we only parse the buffer.

Similar for other places where you just extract bits from a bitfield or
integer.

Cheers,
Andre


> +
> +		/* Clean highest byte */
> +		payload &= SPE_ADDR_PKT_ADDR_MASK;
>  
>  		/* Fill highest byte for EL1 or EL2 (VHE) mode */
> -		if (ns && (el == SPE_ADDR_PKT_EL1 || el == SPE_ADDR_PKT_EL2))
> -			addr[7] = 0xff;
> -		/* Clean highest byte for other cases */
> -		else
> -			addr[7] = 0x0;
> +		if (ns && (el == SPE_ADDR_PKT_INST_VA_EL1 ||
> +			   el == SPE_ADDR_PKT_INST_VA_EL2))
> +			payload |= 0xffULL << SPE_ADDR_PKT_ADDR_BYTE7_SHIFT;
>  
>  	/* Data access virtual address */
>  	} else if (index == SPE_ADDR_PKT_HDR_INDEX_DATA_VIRT) {
>  
> +		/* Clean tags */
> +		payload &= SPE_ADDR_PKT_ADDR_MASK;
> +
>  		/* Fill highest byte if bits [48..55] is 0xff */
> -		if (addr[6] == 0xff)
> -			addr[7] = 0xff;
> -		/* Otherwise, cleanup tags */
> -		else
> -			addr[7] = 0x0;
> +		if ((payload >> 48) == 0xffULL)
> +			payload |= 0xffULL << SPE_ADDR_PKT_ADDR_BYTE7_SHIFT;
>  
>  	/* Data access physical address */
>  	} else if (index == SPE_ADDR_PKT_HDR_INDEX_DATA_PHYS) {
> -		/* Cleanup byte 7 */
> -		addr[7] = 0x0;
> +		/* Clean highest byte */
> +		payload &= SPE_ADDR_PKT_ADDR_MASK;
>  	} else {
>  		pr_err("unsupported address packet index: 0x%x\n", index);
>  	}
> diff --git a/tools/perf/util/arm-spe-decoder/arm-spe-pkt-decoder.c b/tools/perf/util/arm-spe-decoder/arm-spe-pkt-decoder.c
> index e738bd04f209..b51a2207e4a0 100644
> --- a/tools/perf/util/arm-spe-decoder/arm-spe-pkt-decoder.c
> +++ b/tools/perf/util/arm-spe-decoder/arm-spe-pkt-decoder.c
> @@ -13,9 +13,6 @@
>  
>  #include "arm-spe-pkt-decoder.h"
>  
> -#define NS_FLAG		BIT(63)
> -#define EL_FLAG		(BIT(62) | BIT(61))
> -
>  #if __BYTE_ORDER == __BIG_ENDIAN
>  #define le16_to_cpu bswap_16
>  #define le32_to_cpu bswap_32
> @@ -166,9 +163,10 @@ static int arm_spe_get_addr(const unsigned char *buf, size_t len,
>  {
>  	packet->type = ARM_SPE_ADDRESS;
>  	if (ext_hdr)
> -		packet->index = ((buf[0] & 0x3) << 3) | (buf[1] & 0x7);
> +		packet->index = (((buf[0] & SPE_ADDR_PKT_HDR_EXT_INDEX_MASK) << 3) |
> +				  (buf[1] & SPE_ADDR_PKT_HDR_INDEX_MASK));
>  	else
> -		packet->index = buf[0] & 0x7;
> +		packet->index = buf[0] & SPE_ADDR_PKT_HDR_INDEX_MASK;
>  
>  	return arm_spe_get_payload(buf, len, ext_hdr, packet);
>  }
> @@ -403,18 +401,21 @@ int arm_spe_pkt_desc(const struct arm_spe_pkt *packet, char *buf,
>  		return arm_spe_pkt_snprintf(&buf, &blen, "%s %lld", name, payload);
>  	case ARM_SPE_ADDRESS:
>  		switch (idx) {
> -		case 0:
> -		case 1: ns = !!(packet->payload & NS_FLAG);
> -			el = (packet->payload & EL_FLAG) >> 61;
> -			payload &= ~(0xffULL << 56);
> +		case SPE_ADDR_PKT_HDR_INDEX_INS:
> +		case SPE_ADDR_PKT_HDR_INDEX_BRANCH:
> +			ns = !!(packet->payload & SPE_ADDR_PKT_INST_VA_NS);
> +			el = (packet->payload & SPE_ADDR_PKT_INST_VA_EL_MASK)
> +				>> SPE_ADDR_PKT_INST_VA_EL_SHIFT;
> +			payload &= SPE_ADDR_PKT_ADDR_MASK;
>  			return arm_spe_pkt_snprintf(&buf, &blen,
>  					"%s 0x%llx el%d ns=%d",
>  				        (idx == 1) ? "TGT" : "PC", payload, el, ns);
> -		case 2:
> +		case SPE_ADDR_PKT_HDR_INDEX_DATA_VIRT:
>  			return arm_spe_pkt_snprintf(&buf, &blen,
>  						    "VA 0x%llx", payload);
> -		case 3:	ns = !!(packet->payload & NS_FLAG);
> -			payload &= ~(0xffULL << 56);
> +		case SPE_ADDR_PKT_HDR_INDEX_DATA_PHYS:
> +			ns = !!(packet->payload & SPE_ADDR_PKT_INST_VA_NS);
> +			payload &= SPE_ADDR_PKT_ADDR_MASK;
>  			return arm_spe_pkt_snprintf(&buf, &blen,
>  						    "PA 0x%llx ns=%d", payload, ns);
>  		default:
> diff --git a/tools/perf/util/arm-spe-decoder/arm-spe-pkt-decoder.h b/tools/perf/util/arm-spe-decoder/arm-spe-pkt-decoder.h
> index a30fe3c5ab67..88d2231c76da 100644
> --- a/tools/perf/util/arm-spe-decoder/arm-spe-pkt-decoder.h
> +++ b/tools/perf/util/arm-spe-decoder/arm-spe-pkt-decoder.h
> @@ -61,19 +61,30 @@ struct arm_spe_pkt {
>  #define SPE_HEADER_SZ_SHIFT		(4)
>  #define SPE_HEADER_SZ_MASK		GENMASK_ULL(5, 4)
>  
> +/* Address packet header */
> +#define SPE_ADDR_PKT_HDR_INDEX_MASK		GENMASK_ULL(2, 0)
>  #define SPE_ADDR_PKT_HDR_INDEX_INS		(0x0)
>  #define SPE_ADDR_PKT_HDR_INDEX_BRANCH		(0x1)
>  #define SPE_ADDR_PKT_HDR_INDEX_DATA_VIRT	(0x2)
>  #define SPE_ADDR_PKT_HDR_INDEX_DATA_PHYS	(0x3)
>  
> -#define SPE_ADDR_PKT_NS				BIT(7)
> -#define SPE_ADDR_PKT_CH				BIT(6)
> -#define SPE_ADDR_PKT_EL_OFFSET			(5)
> -#define SPE_ADDR_PKT_EL_MASK			(0x3 << SPE_ADDR_PKT_EL_OFFSET)
> -#define SPE_ADDR_PKT_EL0			(0)
> -#define SPE_ADDR_PKT_EL1			(1)
> -#define SPE_ADDR_PKT_EL2			(2)
> -#define SPE_ADDR_PKT_EL3			(3)
> +#define SPE_ADDR_PKT_HDR_EXT_INDEX_MASK		GENMASK_ULL(1, 0)
> +
> +/* Address packet payload for data access physical address */
> +#define SPE_ADDR_PKT_ADDR_BYTE7_SHIFT		(56)
> +#define SPE_ADDR_PKT_ADDR_MASK			GENMASK_ULL(55, 0)
> +
> +#define SPE_ADDR_PKT_DATA_PA_NS			BIT(63)
> +#define SPE_ADDR_PKT_DATA_PA_CH			BIT(62)
> +
> +/* Address packet payload for instrcution virtual address */
> +#define SPE_ADDR_PKT_INST_VA_NS			BIT(63)
> +#define SPE_ADDR_PKT_INST_VA_EL_SHIFT		(61)
> +#define SPE_ADDR_PKT_INST_VA_EL_MASK		GENMASK_ULL(62, 61)
> +#define SPE_ADDR_PKT_INST_VA_EL0		(0)
> +#define SPE_ADDR_PKT_INST_VA_EL1		(1)
> +#define SPE_ADDR_PKT_INST_VA_EL2		(2)
> +#define SPE_ADDR_PKT_INST_VA_EL3		(3)
>  
>  const char *arm_spe_pkt_name(enum arm_spe_pkt_type);
>  
>