[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] Re: [PATCH] xen: avoid tracking the region 0xa0000 - 0xbffff
On 2011-06-14 13:50, Stefano Stabellini wrote: > On Tue, 14 Jun 2011, Jan Kiszka wrote: >> On 2011-06-14 12:54, Alexander Graf wrote: >>> >>> On 03.06.2011, at 17:56, <stefano.stabellini@xxxxxxxxxxxxx> >>> <stefano.stabellini@xxxxxxxxxxxxx> wrote: >>> >>>> From: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx> >>>> >>>> Xen can only do dirty bit tracking for one memory region, so we should >>>> explicitly avoid trying to track the legacy VGA region between 0xa0000 >>>> and 0xbffff, rather than trying and failing. >>>> >>>> Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx> >>>> --- >>>> xen-all.c | 4 ++++ >>>> 1 files changed, 4 insertions(+), 0 deletions(-) >>>> >>>> diff --git a/xen-all.c b/xen-all.c >>>> index 9a5c3ec..1fdc2e8 100644 >>>> --- a/xen-all.c >>>> +++ b/xen-all.c >>>> @@ -218,6 +218,10 @@ static int xen_add_to_physmap(XenIOState *state, >>>> if (get_physmapping(state, start_addr, size)) { >>>> return 0; >>>> } >>>> + /* do not try to map legacy VGA memory */ >>>> + if (start_addr >= 0xa0000 && start_addr + size <= 0xbffff) { >>> >>> I don't quite like the hardcoded range here. What exactly is the issue? The >>> fact that you can only map a single region? Then do a counter and fail when >>> it's > 1. If you don't want to map the VGA region as memory slot, why not >>> change the actual mapping code in the cirrus adapter? >> >> Err, please no "if (xen_enabled())" in that code. We just got rid of the >> kvm_enabled() mess. And it doesn't scale, it would be required in e1000 >> as well e.g. > > agreed [Actually, e1000 is not using dirty logging but coalesced MMIO.] > > >> BTW, if Xen is not able to track more than one dirty region, I think >> it's time to fix that limitation. At some point it may no longer be >> possible to work around it (who knows how the new memory API will look >> like in this regard). > > you are right, however it is not a simple fix and at present we don't > actually need to track more than one region... Well, you already miss dirty logged VGA/VBE memory access this way (everything that goes to legacy VGA mem, not the framebuffer BAR). Grub provides a really poor use experience in that mode. Jan -- Siemens AG, Corporate Technology, CT T DE IT 1 Corporate Competence Center Embedded Linux _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel
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