From: Kairui Song kasong@redhat.com

[ Upstream commit 3cb73bc3fa2a3cb80b88aa63b48409939e0d996b ]

On gen2 HyperV VM, hyperv_fb will remove the old framebuffer, and the new allocated framebuffer address could be at a differnt location, and it might be no longer a VGA framebuffer.

Update screen_info so that after kexec the kernel won't try to reuse the old invalid/stale framebuffer address as VGA, corrupting memory.

[ mingo: Tidied up the changelog. ]

Signed-off-by: Kairui Song kasong@redhat.com Signed-off-by: Ingo Molnar mingo@kernel.org Cc: Dexuan Cui decui@microsoft.com Cc: Jake Oshins jakeo@microsoft.com Cc: Wei Hu weh@microsoft.com Cc: "K. Y. Srinivasan" kys@microsoft.com Cc: Haiyang Zhang haiyangz@microsoft.com Cc: Stephen Hemminger sthemmin@microsoft.com Link: https://lore.kernel.org/r/20201014092429.1415040-3-kasong@redhat.com Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/video/fbdev/hyperv_fb.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/video/fbdev/hyperv_fb.c b/drivers/video/fbdev/hyperv_fb.c index 02411d89cb462..e36fb1a0ecdbd 100644 --- a/drivers/video/fbdev/hyperv_fb.c +++ b/drivers/video/fbdev/hyperv_fb.c @@ -1114,8 +1114,15 @@ static int hvfb_getmem(struct hv_device *hdev, struct fb_info *info) getmem_done: remove_conflicting_framebuffers(info->apertures, KBUILD_MODNAME, false); - if (!gen2vm) + + if (gen2vm) { + /* framebuffer is reallocated, clear screen_info to avoid misuse from kexec */ + screen_info.lfb_size = 0; + screen_info.lfb_base = 0; + screen_info.orig_video_isVGA = 0; + } else { pci_dev_put(pdev); + } kfree(info->apertures);

return 0;