linux-kernel - [PATCH 2/2] hyperv_fb: Update screen_info after removing old framebuffer

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Message-Id: <20201014092429.1415040-3-kasong@redhat.com>
Date:   Wed, 14 Oct 2020 17:24:29 +0800
From:   Kairui Song <kasong@...hat.com>
To:     linux-kernel@...r.kernel.org
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Ard Biesheuvel <ardb@...nel.org>,
        "K. Y. Srinivasan" <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Wei Liu <wei.liu@...nel.org>, Dexuan Cui <decui@...rosoft.com>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        Dave Young <dyoung@...hat.com>, x86@...nel.org,
        linux-hyperv@...r.kernel.org, kexec@...ts.infradead.org,
        Kairui Song <kasong@...hat.com>
Subject: [PATCH 2/2] hyperv_fb: Update screen_info after removing old framebuffer

On gen2 HyperV VM, hyperv_fb will remove the old framebuffer, the
new allocated framebuffer address could be at a differnt location,
and it's no longer VGA framebuffer. Update screen_info
so that after kexec, kernel won't try to reuse the old invalid
framebuffer address as VGA.

Signed-off-by: Kairui Song <kasong@...hat.com>
---
 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 02411d89cb46..e36fb1a0ecdb 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;
-- 
2.28.0