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SubjectRe: [PATCH 4.19 383/422] firmware: dell_rbu: Make payload memory uncachable
Hi!

> From: Stuart Hayes <stuart.w.hayes@gmail.com>
>
> [ Upstream commit 6aecee6ad41cf97c0270f72da032c10eef025bf0 ]
>
> 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.

Flushing the cache sounds like easier way to accomplish same
goal... and perhaps with better performance too.

Best regards,
Pavel

> +++ 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@dell.com>");
> 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);
> --
> 2.20.1
>
>

--
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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