Re: [Xen-ia64-devel] [PATCH][GFW][RFC] fix EFI_SAL_SET_VECTORS

[tgingold@xxxxxxx]

Quoting Isaku Yamahata <yamahata@xxxxxxxxxxxxx>:

> On Tue, May 13, 2008 at 12:24:16PM +0200, tgingold@xxxxxxx wrote:
> > > The uncached physical addresses are hard coded, but they aren't
> > > relocated when switching to virtual address mode.
> >
> > I am not sure ConvertPointer is able to deal with uncached addresses.
> Anyway,
> > using normal addresses should be harmless.
>
> I guess that the original auther concerned about a race so that
> he used uncached addresses.

I don't catch your point.  Uncached addresses won't prevent races.

> Anyway the variable size is 16 bytes and are written/read twice
> so that the access isn't smp safe.
> Possible choice would be
> a. don't care
>    assume that such a race won't happen and pray.
> b. use explicit lock
> c. use atomic access(cmp8xchg16)
> d. explicit synchronization betweeen cpus.
>    Probably this would be difficult in gfw.
>
> My bet is a.

I don't think that SAL has to protect against concurrency.  I can't
remember if the vector must be set for every processor.  I will look.

Tristan.

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