Re: [Qemu-devel] [Qemu-block] Guest unresponsive after Virtqueue size exceeded error

[Natanael Copa <ncopa@alpinelinux.org>]

On Mon, 25 Feb 2019 13:06:16 +0000
Peter Maydell <peter.maydell@linaro.org> wrote:

> On Mon, 25 Feb 2019 at 12:22, Natanael Copa <ncopa@alpinelinux.org> wrote:
> >
> > On Mon, 25 Feb 2019 10:34:23 +0000
> > Peter Maydell <peter.maydell@linaro.org> wrote:  
> > > The short term fix is to fix your toolchain/compilation
> > > environment options so that it isn't trying to override
> > > the definition of memcpy().  
> >
> > The easiest workaround is to simply disable FORTIY_SOURCE, but that
> > will weaken the security for all implemented string functions, strcpy,
> > memmove etc, so I don't want to do that.
> >
> > Is it only lduw_he_p that needs to be atomic or are the other functions
> > in include/qemu/bswap.h using memcpy also required to be atomic?  
> 
> Hard to say, since we haven't done the "audit all the callers"
> step that Stefan mentioned. If you're going to replace memcpy
> with __builtin_memcpy then the safest thing is to do it for
> all those uses (this will also give you much better generated
> code for performance purposes).

I figured that and that is exactly what I did.

Fernando: Can you please test the binary from
qemu-system-x86_64-3.1.0-r3 from alpine edge? I will backport the fix
if you can confirm it fixes the problem.

Thanks!

-nc

PS. Those issues are pretty hard to track down, so big thanks to
everyone who helped find the exact issue here. You have done a great
work!