linux-kernel - Re: [PATCH v3] ACPI, APEI, EINJ: Relax platform response timeout to 1 second.

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Date:   Tue, 26 Oct 2021 10:05:49 -0700
From:   "Luck, Tony" <tony.luck@...el.com>
To:     "Rafael J. Wysocki" <rafael@...nel.org>,
        Shuai Xue <xueshuai@...ux.alibaba.com>
Cc:     linux-kernel@...r.kernel.org, linux-acpi@...r.kernel.org,
        bp@...en8.de, james.morse@....com, lenb@...nel.org,
        rjw@...ysocki.net, zhangliguang@...ux.alibaba.com,
        zhuo.song@...ux.alibaba.com
Subject: Re: [PATCH v3] ACPI, APEI, EINJ: Relax platform response timeout to
 1 second.

On Tue, Oct 26, 2021 at 03:28:29PM +0800, Shuai Xue wrote:
> When injecting an error into the platform, the OSPM executes an
> EXECUTE_OPERATION action to instruct the platform to begin the injection
> operation. And then, the OSPM busy waits for a while by continually
> executing CHECK_BUSY_STATUS action until the platform indicates that the
> operation is complete. More specifically, the platform is limited to
> respond within 1 millisecond right now. This is too strict for some
> platforms.
> 
> For example, in Arm platform, when injecting a Processor Correctable error,
> the OSPM will warn:
>     Firmware does not respond in time.
> 
> And a message is printed on the console:
>     echo: write error: Input/output error
> 
> We observe that the waiting time for DDR error injection is about 10 ms and
> that for PCIe error injection is about 500 ms in Arm platform.
> 
> In this patch, we relax the response timeout to 1 second.
> 
> Signed-off-by: Shuai Xue <xueshuai@...ux.alibaba.com>

Reviewed-by: Tony Luck <tony.luck@...el.com>

Rafael: Do you want to take this in the acpi tree? If not, I can
apply it to the RAS tree (already at -rc7, so in next merge cycle
after 5.16-rc1 comes out).

> ---
> Changelog v2 -> v3:
> - Implemented the timeout in usleep_range instead of msleep.
> - Dropped command line interface of timeout.
> - Link to the v1 patch: https://lkml.org/lkml/2021/10/14/1402
> ---
>  drivers/acpi/apei/einj.c | 15 ++++++++-------
>  1 file changed, 8 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/acpi/apei/einj.c b/drivers/acpi/apei/einj.c
> index 133156759551..6e1ff4b62a8f 100644
> --- a/drivers/acpi/apei/einj.c
> +++ b/drivers/acpi/apei/einj.c
> @@ -28,9 +28,10 @@
>  #undef pr_fmt
>  #define pr_fmt(fmt) "EINJ: " fmt
>  
> -#define SPIN_UNIT		100			/* 100ns */
> -/* Firmware should respond within 1 milliseconds */
> -#define FIRMWARE_TIMEOUT	(1 * NSEC_PER_MSEC)
> +#define SLEEP_UNIT_MIN		1000			/* 1ms */
> +#define SLEEP_UNIT_MAX		5000			/* 5ms */
> +/* Firmware should respond within 1 seconds */
> +#define FIRMWARE_TIMEOUT	(1 * USEC_PER_SEC)
>  #define ACPI5_VENDOR_BIT	BIT(31)
>  #define MEM_ERROR_MASK		(ACPI_EINJ_MEMORY_CORRECTABLE | \
>  				ACPI_EINJ_MEMORY_UNCORRECTABLE | \
> @@ -171,13 +172,13 @@ static int einj_get_available_error_type(u32 *type)
>  
>  static int einj_timedout(u64 *t)
>  {
> -	if ((s64)*t < SPIN_UNIT) {
> +	if ((s64)*t < SLEEP_UNIT_MIN) {
>  		pr_warn(FW_WARN "Firmware does not respond in time\n");
>  		return 1;
>  	}
> -	*t -= SPIN_UNIT;
> -	ndelay(SPIN_UNIT);
> -	touch_nmi_watchdog();
> +	*t -= SLEEP_UNIT_MIN;
> +	usleep_range(SLEEP_UNIT_MIN, SLEEP_UNIT_MAX);
> +
>  	return 0;
>  }
>  
> -- 
> 2.20.1.12.g72788fdb
>