linux-kernel - [PATCH v2] dell_rbu: make firmware payload memory uncachable

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Message-ID: <8c18af18-17cf-57c5-5d57-ed3878d8a004@gmail.com>
Date:   Mon, 26 Mar 2018 10:39:57 -0500
From:   Stuart Hayes <stuart.w.hayes@...il.com>
To:     linux-kernel@...r.kernel.org
Subject: [PATCH v2] dell_rbu: make firmware payload memory uncachable

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@...il.com>
---
v2 Added include, removed extra parentheses
This patch has no maintainer.


diff --git a/drivers/firmware/dell_rbu.c b/drivers/firmware/dell_rbu.c
index 2f452f1f7c8a..640a88c3418d 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@...l.com>");
 MODULE_DESCRIPTION("Driver for updating BIOS image on DELL systems");
@@ -180,6 +181,11 @@ static int create_packet(void *data, size_t length)
 			invalid_addr_packet_array[idx++] = packet_data_temp_buf;
 			packet_data_temp_buf = NULL;
 		}
+		/*
+		 * set to uncachable or it may never get written back before
+		 * reboot
+		 */
+		set_memory_uc(packet_data_temp_buf, 1 << ordernum);
 	}
 	spin_lock(&rbu_data.lock);
 
@@ -349,6 +355,7 @@ 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(newpacket->data, 1 << newpacket->ordernum);
 		free_pages((unsigned long) newpacket->data,
 			newpacket->ordernum);
 		kfree(newpacket);