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[Bug 1752646] Re: Freezing VNC screen on some the UEFI framebuffer appli
From: |
Thomas Huth |
Subject: |
[Bug 1752646] Re: Freezing VNC screen on some the UEFI framebuffer applications |
Date: |
Tue, 24 Nov 2020 16:10:44 -0000 |
The QEMU project is currently considering to move its bug tracking to another
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If you still think this bug report here is valid, then please switch the state
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** Changed in: qemu
Status: New => Incomplete
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https://bugs.launchpad.net/bugs/1752646
Title:
Freezing VNC screen on some the UEFI framebuffer applications
Status in QEMU:
Incomplete
Bug description:
Hi folks!
I use TianCore (UEFI) formware on the qemu (master version last commit
a6e0344).
When kernel/linux is start, it using UEFI Framebuffer. Then I run UEFI
application (which writes directly to the framebuffer) my VNS screen is
freezing. Then I restart vnclient I see only one frame.
When I run application, I getting in the file hw/display/vga.c on
function 'vga_ioport_write' some commands, it change "s->ar_index"
from 0x20 -> 0x10
In the function vga_update_display:
1751 if (!(s->ar_index & 0x20)) {
1752 graphic_mode = GMODE_BLANK;
1753 } else {
And I got GMODE_BLANK mode. If I patch it:
1751 if (0) {
my VNC not freezing.
From "Hardware Level VGA and SVGA Video Programming Information Page"
I saw, what ar_index is 0x3C0 (Attribute Controller Data Write
Register), 0x20(5-bit) is PAS -- Palette Address Source
If there is a output via the UEFI framebuffer, does the difference
have a PAS or not? Why do we need to pause the output if the PAS is
exposed? Especially when the application outputs via framebuffer.
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