Commit 596b3678326d ("x86/video: Only fall back to vga_default_device()
without screen info") made video_is_primary_device() rely exclusively
on screen_info resources whenever any are available.
However, screen_info_resources() also returns legacy I/O and memory
ranges for VGA text modes. These ranges are not PCI BARs, so
pci_find_resource() does not find them and the default VGA fallback is
skipped. As a result, no device is primary in VGA text mode.
On a SeaBIOS QEMU guest with bochs and VKMS, the boot VGA (bochs) loses
its DRM boot_display attribute. VKMS registers fb0 and bochs registers
fb1. VKMS is not a PCI device, so it is not primary either. With no
primary device, fbcon keeps the console on fb0 and never remaps it to
bochs. This can be checked with:
cat /sys/class/drm/card1/boot_display
stty -F /dev/tty1 size
Without the fix, boot_display is missing and tty1 is 48 rows by 128
columns. With it, boot_display contains 1 and tty1 is 50 rows by 160
columns. VKMS only makes the console part visible. Without VKMS, tty1
has the same size with and without the fix, but boot_display is still
missing without it.
Use resource-based selection only for linear framebuffers. Fall back to
vga_default_device() for legacy display modes, while keeping EFI and
VESA framebuffer ownership authoritative.
Fixes: 596b3678326d ("x86/video: Only fall back to vga_default_device() without
screen info")
Cc: [email protected]
Reviewed-by: Mario Limonciello (AMD) <[email protected]>
Reviewed-by: Thomas Zimmermann <[email protected]>
Signed-off-by: Hengyu Liang <[email protected]>
---
Changes in v2:
- Explain in the commit message why no device is primary in text mode
and what VKMS shows (Boris, Thomas).
- Add the Reviewed-by tags. No code change.
- v1: https://lore.kernel.org/all/[email protected]/
arch/x86/video/video-common.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/x86/video/video-common.c b/arch/x86/video/video-common.c
index 8ed82fff7638..b8f83346dfe8 100644
--- a/arch/x86/video/video-common.c
+++ b/arch/x86/video/video-common.c
@@ -45,7 +45,7 @@ bool video_is_primary_device(struct device *dev)
#ifdef CONFIG_SCREEN_INFO
numres = screen_info_resources(si, res, ARRAY_SIZE(res));
- if (numres > 0) {
+ if (numres > 0 && __screen_info_has_lfb(screen_info_video_type(si))) {
for (i = 0; i < numres; ++i) {
if (!(res[i].flags & IORESOURCE_MEM))
continue;
base-commit: c339f4010dea8b0d754f84ace70cd1b089878ef8
--
2.53.0
