Re: [Qemu-stable] [Qemu-devel] [PATCH] memory: fix limiting of translation at a page boundary

[Mark Cave-Ayland]

On 06/02/14 23:40, Paolo Bonzini wrote:

> Commit 360e607 (address_space_translate: do not cross page boundaries,
> 2014-01-30) broke MMIO accesses in cases where the section is shorter
> than the full register width.  This can happen for example with the
> Bochs DISPI registers, which are 16 bits wide but have only a 1-byte
> long MemoryRegion (if you write to the "second byte" of the register
> your access is discarded; it doesn't write only to half of the register).
>
> Restrict the action of commit 360e607 to direct RAM accesses.  This
> is enough for Xen, since MMIO will not go through the mapcache.
>
> Reported-by: Mark Cave-Ayland<address@hidden>
> Tested-by: Anthony Perard<address@hidden>
> Cc: address@hidden
> Signed-off-by: Paolo Bonzini<address@hidden>

Hi Paolo,

Unfortunately I've just tested this patch on qemu-system-ppc and it 
still doesn't fix the issue for me :(  This is with current git master 
bc1c7 plus your patch applied.

The symptoms haven't changed in that the VGA output stays black and 
doesn't resize, again implying that the VGA VBE calls aren't working. If 
it helps, the OpenBIOS VGA driver vga.fs can be found at 
http://git.qemu.org/?p=openbios.git;a=blob;f=drivers/vga.fs;h=ec4c6c5f10ea2c4c784c3c6888c3805ec3b14496;hb=888126272f92294b0da45158393f1b862742cf6b. 



ATB,

Mark.