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    Subject[PATCH 5.9 076/133] hyperv_fb: Update screen_info after removing old framebuffer
    Date
    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;
    --
    2.27.0


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