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Message-ID: <ZraQ3PWOY23G2zZH@ghost>
Date: Fri, 9 Aug 2024 14:57:48 -0700
From: Charlie Jenkins <charlie@...osinc.com>
To: Evan Green <evan@...osinc.com>
Cc: Palmer Dabbelt <palmer@...belt.com>, Yangyu Chen <cyy@...self.name>,
Albert Ou <aou@...s.berkeley.edu>,
Alexandre Ghiti <alexghiti@...osinc.com>,
Andrew Jones <ajones@...tanamicro.com>,
Andy Chiu <andy.chiu@...ive.com>,
Ben Dooks <ben.dooks@...ethink.co.uk>,
Björn Töpel <bjorn@...osinc.com>,
Clément Léger <cleger@...osinc.com>,
Conor Dooley <conor.dooley@...rochip.com>,
Costa Shulyupin <costa.shul@...hat.com>,
Erick Archer <erick.archer@....com>,
"Gustavo A. R. Silva" <gustavoars@...nel.org>,
Jonathan Corbet <corbet@....net>,
Paul Walmsley <paul.walmsley@...ive.com>, linux-doc@...r.kernel.org,
enh <enh@...gle.com>, linux-kernel@...r.kernel.org,
linux-riscv@...ts.infradead.org
Subject: Re: [PATCH v4 2/2] RISC-V: hwprobe: Add SCALAR to misaligned perf
defines
On Fri, Aug 09, 2024 at 02:44:44PM -0700, Evan Green wrote:
> In preparation for misaligned vector performance hwprobe keys, rename
> the hwprobe key values associated with misaligned scalar accesses to
> include the term SCALAR. Leave the old defines in place to maintain
> source compatibility.
>
> This change is intended to be a functional no-op.
>
> Signed-off-by: Evan Green <evan@...osinc.com>
> Reviewed-by: Charlie Jenkins <charlie@...osinc.com>
>
> ---
>
> Changes in v4:
> - Add the word scalar (Charlie)
>
> Changes in v3:
> - Leave the old defines in place (Conor, Palmer)
>
> Changes in v2:
> - Added patch to rename misaligned perf key values (Palmer)
>
> Documentation/arch/riscv/hwprobe.rst | 28 ++++++++++++----------
> arch/riscv/include/uapi/asm/hwprobe.h | 5 ++++
> arch/riscv/kernel/sys_hwprobe.c | 10 ++++----
> arch/riscv/kernel/traps_misaligned.c | 6 ++---
> arch/riscv/kernel/unaligned_access_speed.c | 12 +++++-----
> 5 files changed, 34 insertions(+), 27 deletions(-)
>
> diff --git a/Documentation/arch/riscv/hwprobe.rst b/Documentation/arch/riscv/hwprobe.rst
> index a994eed75bde..85b709257918 100644
> --- a/Documentation/arch/riscv/hwprobe.rst
> +++ b/Documentation/arch/riscv/hwprobe.rst
> @@ -247,23 +247,25 @@ The following keys are defined:
> the performance of misaligned scalar native word accesses on the selected set
> of processors.
>
> - * :c:macro:`RISCV_HWPROBE_MISALIGNED_UNKNOWN`: The performance of misaligned
> - accesses is unknown.
> + * :c:macro:`RISCV_HWPROBE_MISALIGNED_SCALAR_UNKNOWN`: The performance of
> + misaligned scalar accesses is unknown.
+ enh <enh@...gle.com>
Thanks for respinning this Evan! With this wording change the patch that
changes the wording but not the macro [1] is no longer needed.
- Charlie
Link:
https://lore.kernel.org/linux-riscv/CAJgzZorn5anPH8dVPqvjVWmLKqTi5bkLDR=FH-ZAcdXFnNe8Eg@mail.gmail.com/
[1]
>
> - * :c:macro:`RISCV_HWPROBE_MISALIGNED_EMULATED`: Misaligned accesses are
> - emulated via software, either in or below the kernel. These accesses are
> - always extremely slow.
> + * :c:macro:`RISCV_HWPROBE_MISALIGNED_SCALAR_EMULATED`: Misaligned scalar
> + accesses are emulated via software, either in or below the kernel. These
> + accesses are always extremely slow.
>
> - * :c:macro:`RISCV_HWPROBE_MISALIGNED_SLOW`: Misaligned native word
> - sized accesses are slower than the equivalent quantity of byte accesses.
> - Misaligned accesses may be supported directly in hardware, or trapped and
> - emulated by software.
> + * :c:macro:`RISCV_HWPROBE_MISALIGNED_SCALAR_SLOW`: Misaligned scalar native
> + word sized accesses are slower than the equivalent quantity of byte
> + accesses. Misaligned accesses may be supported directly in hardware, or
> + trapped and emulated by software.
>
> - * :c:macro:`RISCV_HWPROBE_MISALIGNED_FAST`: Misaligned native word
> - sized accesses are faster than the equivalent quantity of byte accesses.
> + * :c:macro:`RISCV_HWPROBE_MISALIGNED_SCALAR_FAST`: Misaligned scalar native
> + word sized accesses are faster than the equivalent quantity of byte
> + accesses.
>
> - * :c:macro:`RISCV_HWPROBE_MISALIGNED_UNSUPPORTED`: Misaligned accesses are
> - not supported at all and will generate a misaligned address fault.
> + * :c:macro:`RISCV_HWPROBE_MISALIGNED_SCALAR_UNSUPPORTED`: Misaligned scalar
> + accesses are not supported at all and will generate a misaligned address
> + fault.
>
> * :c:macro:`RISCV_HWPROBE_KEY_ZICBOZ_BLOCK_SIZE`: An unsigned int which
> represents the size of the Zicboz block in bytes.
> diff --git a/arch/riscv/include/uapi/asm/hwprobe.h b/arch/riscv/include/uapi/asm/hwprobe.h
> index 635753084275..1e153cda57db 100644
> --- a/arch/riscv/include/uapi/asm/hwprobe.h
> +++ b/arch/riscv/include/uapi/asm/hwprobe.h
> @@ -83,6 +83,11 @@ struct riscv_hwprobe {
> #define RISCV_HWPROBE_KEY_HIGHEST_VIRT_ADDRESS 7
> #define RISCV_HWPROBE_KEY_TIME_CSR_FREQ 8
> #define RISCV_HWPROBE_KEY_MISALIGNED_SCALAR_PERF 9
> +#define RISCV_HWPROBE_MISALIGNED_SCALAR_UNKNOWN 0
> +#define RISCV_HWPROBE_MISALIGNED_SCALAR_EMULATED 1
> +#define RISCV_HWPROBE_MISALIGNED_SCALAR_SLOW 2
> +#define RISCV_HWPROBE_MISALIGNED_SCALAR_FAST 3
> +#define RISCV_HWPROBE_MISALIGNED_SCALAR_UNSUPPORTED 4
> /* Increase RISCV_HWPROBE_MAX_KEY when adding items. */
>
> /* Flags */
> diff --git a/arch/riscv/kernel/sys_hwprobe.c b/arch/riscv/kernel/sys_hwprobe.c
> index 2d0f4f6a32c3..cea0ca2bf2a2 100644
> --- a/arch/riscv/kernel/sys_hwprobe.c
> +++ b/arch/riscv/kernel/sys_hwprobe.c
> @@ -178,13 +178,13 @@ static u64 hwprobe_misaligned(const struct cpumask *cpus)
> perf = this_perf;
>
> if (perf != this_perf) {
> - perf = RISCV_HWPROBE_MISALIGNED_UNKNOWN;
> + perf = RISCV_HWPROBE_MISALIGNED_SCALAR_UNKNOWN;
> break;
> }
> }
>
> if (perf == -1ULL)
> - return RISCV_HWPROBE_MISALIGNED_UNKNOWN;
> + return RISCV_HWPROBE_MISALIGNED_SCALAR_UNKNOWN;
>
> return perf;
> }
> @@ -192,12 +192,12 @@ static u64 hwprobe_misaligned(const struct cpumask *cpus)
> static u64 hwprobe_misaligned(const struct cpumask *cpus)
> {
> if (IS_ENABLED(CONFIG_RISCV_EFFICIENT_UNALIGNED_ACCESS))
> - return RISCV_HWPROBE_MISALIGNED_FAST;
> + return RISCV_HWPROBE_MISALIGNED_SCALAR_FAST;
>
> if (IS_ENABLED(CONFIG_RISCV_EMULATED_UNALIGNED_ACCESS) && unaligned_ctl_available())
> - return RISCV_HWPROBE_MISALIGNED_EMULATED;
> + return RISCV_HWPROBE_MISALIGNED_SCALAR_EMULATED;
>
> - return RISCV_HWPROBE_MISALIGNED_SLOW;
> + return RISCV_HWPROBE_MISALIGNED_SCALAR_SLOW;
> }
> #endif
>
> diff --git a/arch/riscv/kernel/traps_misaligned.c b/arch/riscv/kernel/traps_misaligned.c
> index b62d5a2f4541..192cd5603e95 100644
> --- a/arch/riscv/kernel/traps_misaligned.c
> +++ b/arch/riscv/kernel/traps_misaligned.c
> @@ -338,7 +338,7 @@ int handle_misaligned_load(struct pt_regs *regs)
> perf_sw_event(PERF_COUNT_SW_ALIGNMENT_FAULTS, 1, regs, addr);
>
> #ifdef CONFIG_RISCV_PROBE_UNALIGNED_ACCESS
> - *this_cpu_ptr(&misaligned_access_speed) = RISCV_HWPROBE_MISALIGNED_EMULATED;
> + *this_cpu_ptr(&misaligned_access_speed) = RISCV_HWPROBE_MISALIGNED_SCALAR_EMULATED;
> #endif
>
> if (!unaligned_enabled)
> @@ -532,13 +532,13 @@ static bool check_unaligned_access_emulated(int cpu)
> unsigned long tmp_var, tmp_val;
> bool misaligned_emu_detected;
>
> - *mas_ptr = RISCV_HWPROBE_MISALIGNED_UNKNOWN;
> + *mas_ptr = RISCV_HWPROBE_MISALIGNED_SCALAR_UNKNOWN;
>
> __asm__ __volatile__ (
> " "REG_L" %[tmp], 1(%[ptr])\n"
> : [tmp] "=r" (tmp_val) : [ptr] "r" (&tmp_var) : "memory");
>
> - misaligned_emu_detected = (*mas_ptr == RISCV_HWPROBE_MISALIGNED_EMULATED);
> + misaligned_emu_detected = (*mas_ptr == RISCV_HWPROBE_MISALIGNED_SCALAR_EMULATED);
> /*
> * If unaligned_ctl is already set, this means that we detected that all
> * CPUS uses emulated misaligned access at boot time. If that changed
> diff --git a/arch/riscv/kernel/unaligned_access_speed.c b/arch/riscv/kernel/unaligned_access_speed.c
> index a9a6bcb02acf..160628a2116d 100644
> --- a/arch/riscv/kernel/unaligned_access_speed.c
> +++ b/arch/riscv/kernel/unaligned_access_speed.c
> @@ -34,9 +34,9 @@ static int check_unaligned_access(void *param)
> struct page *page = param;
> void *dst;
> void *src;
> - long speed = RISCV_HWPROBE_MISALIGNED_SLOW;
> + long speed = RISCV_HWPROBE_MISALIGNED_SCALAR_SLOW;
>
> - if (per_cpu(misaligned_access_speed, cpu) != RISCV_HWPROBE_MISALIGNED_UNKNOWN)
> + if (per_cpu(misaligned_access_speed, cpu) != RISCV_HWPROBE_MISALIGNED_SCALAR_UNKNOWN)
> return 0;
>
> /* Make an unaligned destination buffer. */
> @@ -95,14 +95,14 @@ static int check_unaligned_access(void *param)
> }
>
> if (word_cycles < byte_cycles)
> - speed = RISCV_HWPROBE_MISALIGNED_FAST;
> + speed = RISCV_HWPROBE_MISALIGNED_SCALAR_FAST;
>
> ratio = div_u64((byte_cycles * 100), word_cycles);
> pr_info("cpu%d: Ratio of byte access time to unaligned word access is %d.%02d, unaligned accesses are %s\n",
> cpu,
> ratio / 100,
> ratio % 100,
> - (speed == RISCV_HWPROBE_MISALIGNED_FAST) ? "fast" : "slow");
> + (speed == RISCV_HWPROBE_MISALIGNED_SCALAR_FAST) ? "fast" : "slow");
>
> per_cpu(misaligned_access_speed, cpu) = speed;
>
> @@ -110,7 +110,7 @@ static int check_unaligned_access(void *param)
> * Set the value of fast_misaligned_access of a CPU. These operations
> * are atomic to avoid race conditions.
> */
> - if (speed == RISCV_HWPROBE_MISALIGNED_FAST)
> + if (speed == RISCV_HWPROBE_MISALIGNED_SCALAR_FAST)
> cpumask_set_cpu(cpu, &fast_misaligned_access);
> else
> cpumask_clear_cpu(cpu, &fast_misaligned_access);
> @@ -188,7 +188,7 @@ static int riscv_online_cpu(unsigned int cpu)
> static struct page *buf;
>
> /* We are already set since the last check */
> - if (per_cpu(misaligned_access_speed, cpu) != RISCV_HWPROBE_MISALIGNED_UNKNOWN)
> + if (per_cpu(misaligned_access_speed, cpu) != RISCV_HWPROBE_MISALIGNED_SCALAR_UNKNOWN)
> goto exit;
>
> buf = alloc_pages(GFP_KERNEL, MISALIGNED_BUFFER_ORDER);
> --
> 2.34.1
>
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