From 78b2eb8a1f10f366681acad8d21c974c1f66791a Mon Sep 17 00:00:00 2001
From: Venkata Ramana Nayana <venkata.ramana.nayana@intel.com>
Date: Fri, 27 Nov 2020 12:07:16 +0000
Subject: [PATCH] drm/i915/gt: Retain default context state across shrinking
Git-commit: 78b2eb8a1f10f366681acad8d21c974c1f66791a
Patch-mainline: v5.10-rc7
No-fix: a9d71f76ccfd309f3bd5f7c9b60e91a4decae792
References: git-fixes

As we use a shmemfs file to hold the context state, when not in use it
may be swapped out, such as across suspend. Since we wrote into the
shmemfs without marking the pages as dirty, the contents may be dropped
instead of being written back to swap. On re-using the shmemfs file,
such as creating a new context after resume, the contents of that file
were likely garbage and so the new context could then hang the GPU.

Simply mark the page as being written when copying into the shmemfs
file, and it the new contents will be retained across swapout.

Fixes: be1cb55a07bf ("drm/i915/gt: Keep a no-frills swappable copy of the default context state")
Cc: Sudeep Dutt <sudeep.dutt@intel.com>
Cc: Matthew Auld <matthew.auld@intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Ramalingam C <ramalingam.c@intel.com>
Signed-off-by: CQ Tang <cq.tang@intel.com>
Signed-off-by: Venkata Ramana Nayana <venkata.ramana.nayana@intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: <stable@vger.kernel.org> # v5.8+
Link: https://patchwork.freedesktop.org/patch/msgid/20201127120718.454037-161-matthew.auld@intel.com
(cherry picked from commit a9d71f76ccfd309f3bd5f7c9b60e91a4decae792)

Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 drivers/gpu/drm/i915/gt/shmem_utils.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/gt/shmem_utils.c b/drivers/gpu/drm/i915/gt/shmem_utils.c
index f011ea42487e..463af675fadd 100644
--- a/drivers/gpu/drm/i915/gt/shmem_utils.c
+++ b/drivers/gpu/drm/i915/gt/shmem_utils.c
@@ -103,10 +103,13 @@ static int __shmem_rw(struct file *file, loff_t off,
 			return PTR_ERR(page);
 
 		vaddr = kmap(page);
-		if (write)
+		if (write) {
 			memcpy(vaddr + offset_in_page(off), ptr, this);
-		else
+			set_page_dirty(page);
+		} else {
 			memcpy(ptr, vaddr + offset_in_page(off), this);
+		}
+		mark_page_accessed(page);
 		kunmap(page);
 		put_page(page);
 
-- 
2.26.2