On Thu, 2007-01-18 at 13:30 +0530, Vivek Goyal wrote:
> On Thu, Jan 18, 2007 at 12:10:55AM -0700, Eric W. Biederman wrote:
> > Vivek Goyal <[EMAIL PROTECTED]> writes:
> > >
> > > Or how about making physical_dest field also 8bit like logical_dest field.
> > > This will work both for 4bit and 8bit physical apic ids at the same time
> > > code becomes more intutive and it is easier to know whether IOAPIC is
> > > being
> > > put in physical or destination logical mode.
> >
> > Exactly what I was trying to suggest.
> >
> > Looking closer at the code I think it makes sense to just kill the union and
> > stop the discrimination between physical and logical modes and just have a
> > dest field in the structure. Roughly as you were suggesting at first.
> >
> > The reason we aren't bitten by this on a regular basis is the normal code
> > path uses logical.logical_dest in both logical and physical modes.
> > Which is a little confusing.
> >
> > Since there really isn't a distinction to be made we should just stop
> > trying, which will make maintenance easier :)
> >
> > Currently there are several non-common case users of physical_dest
> > that are probably bitten by this problem under the right
> > circumstances.
> >
> > So I think we should just make the structure:
> >
> > struct IO_APIC_route_entry {
> > __u32 vector : 8,
> > delivery_mode : 3, /* 000: FIXED
> > * 001: lowest prio
> > * 111: ExtINT
> > */
> > dest_mode : 1, /* 0: physical, 1: logical */
> > delivery_status : 1,
> > polarity : 1,
> > irr : 1,
> > trigger : 1, /* 0: edge, 1: level */
> > mask : 1, /* 0: enabled, 1: disabled */
> > __reserved_2 : 15;
> >
> > __u32 __reserved_3 : 24,
> > __dest : 8;
> > } __attribute__ ((packed));
> >
> > And fixup the users. This should keep us from getting bit by this bug
> > in the future. Like when people start introducing support for more
> > than 256 cores and the low 24bits start getting used.
> >
> > Or when someone new starts working on the code and thinks the fact
> > the field name says logical we are actually using the apic in logical
> > mode.
>
> This makes perfect sense to me. Ben, interested in providing a patch
> for this?
>
> Thanks
> Vivek
Sure! I'll fix it up and get a revised patch out as soon as I can. :)
-- Ben
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