Re: [Xen-devel] [PATCH] libxl_set_memory_target: retain the same maxmem offset on top of the current target

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Mon, 1 Dec 2014, Don Slutz wrote:
> On 11/25/14 12:54, Stefano Stabellini wrote:
> > In libxl_set_memory_target when setting the new maxmem, retain the same
> > offset on top of the current target. The offset includes memory
> > allocated by QEMU for rom files.
> > 
> > Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
> > 
> > diff --git a/tools/libxl/libxl.c b/tools/libxl/libxl.c
> > index de23fec..8381c3e 100644
> > --- a/tools/libxl/libxl.c
> > +++ b/tools/libxl/libxl.c
> > @@ -4767,10 +4767,12 @@ retry_transaction:
> >                   "%s/memory/videoram", dompath));
> >       videoram = videoram_s ? atoi(videoram_s) : 0;
> >   -    if (enforce) {
> > -        memorykb = new_target_memkb;
> > -        rc = xc_domain_setmaxmem(ctx->xch, domid, memorykb +
> > -                LIBXL_MAXMEM_CONSTANT);
> > +    libxl_dominfo_init(&ptr);
> > +    xcinfo2xlinfo(ctx, &info, &ptr);
> 
> This fills ptr with uninitialized data.  You need to call
> 
> xc_domain_getinfolist()
> 
> before this.  However calling xc_domain_getinfolist() here and retry
> of the xenstore transaction, you will adjust this more then one time.
> 
> So I think that xc_domain_getinfolist() needs to be called before
> the label retry_transaction.  However rc is a mess in this routine.
> 
> rc = 1 is the normal return (since rc = xc_domain_getinfolist() is
> the last setting of rc).  So all the rest of "rc =" needs to be adjusted
> someway.

Instead of calling xc_domain_getinfolist, I think it's best to call
libxl_domain_info. You are right that I need to call it before
retry_transaction.

Thanks for the review!



>    -Don Slutz
> 
> 
> > +
> > +    if (enforce && new_target_memkb > 0) {
> > +        memorykb = ptr.max_memkb - current_target_memkb + new_target_memkb;
> > +        rc = xc_domain_setmaxmem(ctx->xch, domid, memorykb);
> >           if (rc != 0) {
> >               LIBXL__LOG_ERRNO(ctx, LIBXL__LOG_ERROR,
> >                       "xc_domain_setmaxmem domid=%d memkb=%d failed "
> > @@ -4800,8 +4802,6 @@ retry_transaction:
> >           goto out;
> >       }
> >   -    libxl_dominfo_init(&ptr);
> > -    xcinfo2xlinfo(ctx, &info, &ptr);
> >       uuid = libxl__uuid2string(gc, ptr.uuid);
> >       libxl__xs_write(gc, t, libxl__sprintf(gc, "/vm/%s/memory", uuid),
> >               "%"PRIu32, new_target_memkb / 1024);
> > 
> > _______________________________________________
> > Xen-devel mailing list
> > Xen-devel@xxxxxxxxxxxxx
> > http://lists.xen.org/xen-devel
> 

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