[Xen-devel] Re: [PATCH] xen: avoid tracking the region 0xa0000 - 0xbffff

[Alexander Graf <agraf@xxxxxxx>]

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?


Alex


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