[Qemu-devel] Re: [PATCH] Fix segfault with ram_size > 4095M without kvm

[Luiz Capitulino]

On Wed, 08 Dec 2010 12:23:12 -0600
Anthony Liguori <address@hidden> wrote:

> On 12/08/2010 12:01 PM, Luiz Capitulino wrote:
> > Currently, x86_64-softmmu qemu segfaults when trying to use>  4095M memsize.
> > This patch adds a simple check and error message (much like the 2047 limit 
> > on
> > 32-bit hosts) on ram_size in the control path after we determine we're
> > not using kvm
> >
> > Upstream qemu-kvm is affected if using the -no-kvm option; this patch 
> > address
> > the segfault there as well.
> >
> > Signed-off-by: Ryan Harper<address@hidden>
> > Signed-off-by: Aurelien Jarno<address@hidden>
> > ---
> > NOTE: this patch was applied in the v0.12.x branch, but it seems it got
> >        lost for master
> >    
> 
> No, it was intentional.  We should fix the segv, this is not a known 
> limitation but rather a bug.

A TCG bug, I presume?

> 
> Regards,
> 
> Anthony Liguori
> 
> >   vl.c |    6 ++++++
> >   1 files changed, 6 insertions(+), 0 deletions(-)
> >
> > diff --git a/vl.c b/vl.c
> > index 2dbb6db..bb9c21c 100644
> > --- a/vl.c
> > +++ b/vl.c
> > @@ -5792,6 +5792,12 @@ int main(int argc, char **argv, char **envp)
> >               fprintf(stderr, "failed to initialize KVM\n");
> >               exit(1);
> >           }
> > +    } else {
> > +        /* without kvm enabled, we can only support 4095 MB RAM */
> > +        if (ram_size>  (4095UL<<  20)) {
> > +            fprintf(stderr, "qemu: without kvm support at most 4095 MB RAM 
> > can be simulated\n");
> > +            exit(1);
> > +        }
> >       }
> >
> >       if (qemu_init_main_loop()) {
> >    
>