linux-kernel - RE: [PATCH V2] ACPI, APEI: Fixup incorrect 16-bit access width firmware bug

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Date:   Mon, 31 Jul 2017 02:09:10 +0000
From:   "Zheng, Lv" <lv.zheng@...el.com>
To:     "Song, Liwei (Wind River)" <liwei.song@...driver.com>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        "Rafael J . Wysocki" <rjw@...ysocki.net>,
        "Len Brown" <lenb@...nel.org>
CC:     linux-acpi <linux-acpi@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        "Song, Liwei (Wind River)" <liwei.song@...driver.com>,
        "Moore, Robert" <robert.moore@...el.com>
Subject: RE: [PATCH V2] ACPI, APEI: Fixup incorrect 16-bit access width
 firmware bug

Hi,

> From: linux-acpi-owner@...r.kernel.org [mailto:linux-acpi-owner@...r.kernel.org] On Behalf Of Song
> liwei
> Subject: [PATCH V2] ACPI, APEI: Fixup incorrect 16-bit access width firmware bug
> 
> From: Liwei Song <liwei.song@...driver.com>
> 
> This is a follow up to commit f712c71f7b2b ("ACPI, APEI: Fixup common
> access width firmware bug") fix the following firmware bug:
> 
> [Firmware Bug]: APEI: Invalid bit width + offset in GAR [0xb2/16/0/1/1]
> 
> This is due to an 8-bit access width is specified for a 16-bit register,
> Rearrange the condition and add 8-bit width check.
> 
> Signed-off-by: Liwei Song <liwei.song@...driver.com>
> ---
>  drivers/acpi/apei/apei-base.c | 12 ++++++------
>  1 file changed, 6 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/acpi/apei/apei-base.c b/drivers/acpi/apei/apei-base.c
> index da370e1..eca3d7a 100644
> --- a/drivers/acpi/apei/apei-base.c
> +++ b/drivers/acpi/apei/apei-base.c
> @@ -604,12 +604,12 @@ static int apei_check_gar(struct acpi_generic_address *reg, u64 *paddr,
>  	*access_bit_width = 1UL << (access_size_code + 2);
> 
>  	/* Fixup common BIOS bug */
> -	if (bit_width == 32 && bit_offset == 0 && (*paddr & 0x03) == 0 &&
> -	    *access_bit_width < 32)
> -		*access_bit_width = 32;
> -	else if (bit_width == 64 && bit_offset == 0 && (*paddr & 0x07) == 0 &&
> -	    *access_bit_width < 64)
> -		*access_bit_width = 64;
> +	if (*access_bit_width < bit_width && bit_offset == 0) {
> +		if ((bit_width == 16 && (*paddr & 0x01) == 0) ||
> +		    (bit_width == 32 && (*paddr & 0x03) == 0) ||
> +		    (bit_width == 64 && (*paddr & 0x07) == 0))
> +			*access_bit_width = bit_width;
> +	}
> 
>  	if ((bit_width + bit_offset) > *access_bit_width) {
>  		pr_warning(FW_BUG APEI_PFX

IMO, such problem could also be fixed by this commit and a cleanup of APEI
GAR code to invoke generic ACPICA GAR API - acpi_read()/acpi_write() directly.
https://github.com/acpica/acpica/pull/209

Thanks and best regards
Lv