[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] RE: [Xen-devel] VT/ioemu: vga memory access?
> -----Original Message----- > From: Gerd Hoffmann [mailto:kraxel@xxxxxxx] > Sent: 16 May 2006 16:57 > To: Petersson, Mats > Cc: Xen devel list > Subject: Re: [Xen-devel] VT/ioemu: vga memory access? > > Hi, > > >> How is vga vram access handled in the device model? Is there some > >> kind of notification system, by mapping those pages > read-only, then > >> trap and forward any write access to qemu-dm? > > > > Actually, xen HVM handles all memory mapped IO in the same > way - pages > > are not present, causing a page-fault and then checking the address > > against a "memory mapped IO range" in the function > > mmio_space() [I haven't looked inside this function], and if it's a > > match it's passed to QEMU via handle_mmio(). > > I think I found the bug. It's actually in handle_mmio() ;) > The "case INSTR_MOVS" has code which deals with page > boundaries. The code allways _adds_ the count (ecx) to > figure whenever the "repz movsb" crosses a page boundary or > not. In case the direction flag is set this isn't correct, > it should subtract instead. Subsequently it mis-calculates > count, making it _larger_ than it was because the copy > wouldn't have crossed a page boundary, leading to the > negative ecx value in the register dump ... I think you're right... I'll write some simple test code to check it out, and let you know... -- Mats > > cheers, > > Gerd > > -- > Gerd Hoffmann <kraxel@xxxxxxx> > Erst mal heiraten, ein, zwei Kinder, und wenn alles läuft > geh' ich nach drei Jahren mit der Familie an die Börse. > http://www.suse.de/~kraxel/julika-dora.jpeg > > _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel
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