The QEMU model for the Bochs display has no VGA memory section at offset 0x400 [1]. By writing to this register Linux can create a write to unassigned memory which depending on machine and architecture can result in a store fault. I don't see any reference to this address at OSDev [2] or in the Bochs source code. Removing this write still allows graphics to work inside QEMU with the bochs-display. 1: https://gitlab.com/qemu-project/qemu/-/blob/master/hw/display/bochs-display.c#L264 2. https://wiki.osdev.org/Bochs_VBE_Extensions Reported-by: Khem Raj <raj.khem@xxxxxxxxx> Signed-off-by: Alistair Francis <alistair.francis@xxxxxxx> --- drivers/gpu/drm/bochs/bochs_hw.c | 15 --------------- 1 file changed, 15 deletions(-) diff --git a/drivers/gpu/drm/bochs/bochs_hw.c b/drivers/gpu/drm/bochs/bochs_hw.c index b615b7dfdd9d..dfb2a5363c62 100644 --- a/drivers/gpu/drm/bochs/bochs_hw.c +++ b/drivers/gpu/drm/bochs/bochs_hw.c @@ -10,19 +10,6 @@ /* ---------------------------------------------------------------------- */ -static void bochs_vga_writeb(struct bochs_device *bochs, u16 ioport, u8 val) -{ - if (WARN_ON(ioport < 0x3c0 || ioport > 0x3df)) - return; - - if (bochs->mmio) { - int offset = ioport - 0x3c0 + 0x400; - writeb(val, bochs->mmio + offset); - } else { - outb(val, ioport); - } -} - static u16 bochs_dispi_read(struct bochs_device *bochs, u16 reg) { u16 ret = 0; @@ -217,8 +204,6 @@ void bochs_hw_setmode(struct bochs_device *bochs, bochs->xres, bochs->yres, bochs->bpp, bochs->yres_virtual); - bochs_vga_writeb(bochs, 0x3c0, 0x20); /* unblank */ - bochs_dispi_write(bochs, VBE_DISPI_INDEX_ENABLE, 0); bochs_dispi_write(bochs, VBE_DISPI_INDEX_BPP, bochs->bpp); bochs_dispi_write(bochs, VBE_DISPI_INDEX_XRES, bochs->xres); -- 2.25.0 _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
