Re: [PATCH RESENT v4] dell_rbu: make firmware payload memory uncachable

From: Stuart Hayes
Date: Wed May 09 2018 - 11:17:53 EST



On 4/18/2018 12:46 AM, Takashi Iwai wrote:
> From: Stuart Hayes <stuart.w.hayes@xxxxxxxxx>
>
> The dell_rbu driver takes firmware update payloads and puts them in memory so
> the system BIOS can find them after a reboot. This sometimes fails (though
> rarely), because the memory containing the payload is in the CPU cache but
> never gets written back to main memory before the system is rebooted (CPU
> cache contents are lost on reboot).
>
> With this patch, the payload memory will be changed to uncachable to ensure
> that the payload is actually in main memory before the system is rebooted.
>
> Signed-off-by: Stuart Hayes <stuart.w.hayes@xxxxxxxxx>
> Reviewed-by: Takashi Iwai <tiwai@xxxxxxx>
> Signed-off-by: Takashi Iwai <tiwai@xxxxxxx>
> ---
> v2 Added include, removed extra parentheses
> v3 Corrected formatting and include line
> v4 Moved set_memory_uc() outside the while loop so that the memory is
> definitely allocated before it is set to uncachable
>
> Andrew, could you pick up this orphan one? Thanks!
>
> diff --git a/drivers/firmware/dell_rbu.c b/drivers/firmware/dell_rbu.c
> index 2f452f1f7c8a..53f27a6e2d76 100644
> --- a/drivers/firmware/dell_rbu.c
> +++ b/drivers/firmware/dell_rbu.c
> @@ -45,6 +45,7 @@
> #include <linux/moduleparam.h>
> #include <linux/firmware.h>
> #include <linux/dma-mapping.h>
> +#include <asm/set_memory.h>
>
> MODULE_AUTHOR("Abhay Salunke <abhay_salunke@xxxxxxxx>");
> MODULE_DESCRIPTION("Driver for updating BIOS image on DELL systems");
> @@ -181,6 +182,11 @@ static int create_packet(void *data, size_t length)
> packet_data_temp_buf = NULL;
> }
> }
> + /*
> + * set to uncachable or it may never get written back before reboot
> + */
> + set_memory_uc((unsigned long)packet_data_temp_buf, 1 << ordernum);
> +
> spin_lock(&rbu_data.lock);
>
> newpacket->data = packet_data_temp_buf;
> @@ -349,6 +355,8 @@ static void packet_empty_list(void)
> * to make sure there are no stale RBU packets left in memory
> */
> memset(newpacket->data, 0, rbu_data.packetsize);
> + set_memory_wb((unsigned long)newpacket->data,
> + 1 << newpacket->ordernum);
> free_pages((unsigned long) newpacket->data,
> newpacket->ordernum);
> kfree(newpacket);
>

Just a reminder... I don't think this has been picked up yet. Please let me know if there's anything I could do.
Thanks!
Stuart