Re: [Qemu-devel] [PATCH] Revived GUEST_BASE support for usermode emulation targets [v4]

[Riku Voipio]

On Fri, May 15, 2009 at 12:12:50PM +0200, Martin Mohring wrote:
> Riku Voipio wrote:
> > On Fri, May 15, 2009 at 03:25:31AM +0100, Paul Brook wrote:
> >> I'm pretty sure it's still broken for large offsets.

> > It is indeed broken. Since tcg_out_addi maps on x86_64 to tgen_arithi64 
> > which
> > doesn't accept 64bit values. But as Martin said, the currrent use for this
> > patch is just to add very minimal offsets.

> Since i am using guest base, what does its brokenness mean?

Well, you are not using guest_base with large offsets, so it's not broken
for you.

> Riku, will you talk with the author to fix it according to Pauls suggestions? 
> Or
> will the patch be accepted under the assumptions/constraints it was
> written. Or is the request that a generic solution fixes other
> longstanding issues?

Well.. the patch fixes a real-life issue: qemu linux-user not working
at all with recent kernel defaults. With this patch, there is still
the potential issue - someone can set GUEST_BASE too large by hand.
That of course didn't work before this patch either.

I think short term it's best to put a size cap for guest_base offset
and look later into supporting greater offsets. So at least, qemu
linux-user will be usable out of box for most users.

But, with current "Quod licet Iovi, non licet bovi" philosophy it seems
it is not enough for bovine to provide patches that make qemu better,
but perfect patches are required.