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Date: Sun, 27 Sep 2009 16:24:22 +0200
From: "Michael S. Tsirkin" <mst@redhat.com>
Subject: Re: [Qemu-devel] Re: [PATCHv2] qemu: target library, use it in msix
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To: Avi Kivity <avi@redhat.com>
Cc: Blue Swirl <blauwirbel@gmail.com>, qemu-devel@nongnu.org

On Sun, Sep 27, 2009 at 04:21:29PM +0200, Michael S. Tsirkin wrote:
> On Sun, Sep 27, 2009 at 04:14:49PM +0200, Avi Kivity wrote:
> > On 09/27/2009 04:08 PM, Michael S. Tsirkin wrote:
> >>
> >>    
> >>>> In practice, the only user is now msix and it does not.  It has 0x1000
> >>>> as a constant parameter.  For target_phys_addr_t users if we ever have
> >>>> them, we'll just add target_phys_page_align. Generally it's unusual for
> >>>> devices to care about size of target physical page.
> >>>>
> >>>>        
> >>> I'd fill better with uint64_t, at least that won't truncate.
> >>>      
> >> Doesn't naming it target_page_align32 address this concern?
> >>    
> >
> > How can the caller (except in your special case) know if it has a  
> > quantity that will fit in 32 bits?
> 
> It's actually not unusual for devices to limit addressing to 32 bit, whatever
> the bus supports.

I would say that devices normally have a specific addressing, and should
not be using target specific types at all.  This alignment to target
page size is actually an unusual thing.

>  For example, the value might come from a 32 bit pci
> bar, even on a 64 bit system this will get values 0 to 4G.
> 
> >
> > -- 
> > Do not meddle in the internals of kernels, for they are subtle and quick to panic.