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Re: [Qemu-devel] [PATCH] extend limit of physical sections number


From: Amos Kong
Subject: Re: [Qemu-devel] [PATCH] extend limit of physical sections number
Date: Tue, 5 Nov 2013 08:21:36 +0800
User-agent: Mutt/1.5.21 (2010-09-15)

On Fri, Sep 27, 2013 at 06:52:50PM +0200, Paolo Bonzini wrote:
> Il 27/09/2013 18:49, Amos Kong ha scritto:
> >  # qemu -drive file=/disk0,if=none,id=v0,format=qcow2 \
> >  -device virtio-blk-pci,drive=v0,id=v00,multifunction=on,addr=0x04.0
> >  ....
> > 
> > Launching guest with more than 32 virtio-blk disks,
> > qemu will crash, because there are too many BARs.
> > 
> > This patch brings the limit of non-tcg up by a factor
> > of 8 (32767 / 4096), i.e. 32*8 = 256.
> > 
> > Signed-off-by: Paolo Bonzini <address@hidden>
> > Signed-off-by: Amos Kong <address@hidden>

Hi Anthony, others


Can you help to review this patch?


Thanks, Amos

> > ---
> >  exec.c | 17 ++++++++++++-----
> >  1 file changed, 12 insertions(+), 5 deletions(-)
> > 
> > diff --git a/exec.c b/exec.c
> > index 5aef833..f639c01 100644
> > --- a/exec.c
> > +++ b/exec.c
> > @@ -763,11 +763,18 @@ void phys_mem_set_alloc(void *(*alloc)(ram_addr_t))
> >  
> >  static uint16_t phys_section_add(MemoryRegionSection *section)
> >  {
> > -    /* The physical section number is ORed with a page-aligned
> > -     * pointer to produce the iotlb entries.  Thus it should
> > -     * never overflow into the page-aligned value.
> > -     */
> > -    assert(next_map.sections_nb < TARGET_PAGE_SIZE);
> > +    if (tcg_enabled()) {
> > +        /* The physical section number is ORed with a page-aligned
> > +         * pointer to produce the iotlb entries.  Thus it should
> > +         * never overflow into the page-aligned value.
> > +         */
> > +        assert(next_map.sections_nb < TARGET_PAGE_SIZE);
> > +    } else {
> > +        /* For KVM or Xen we can use the full range of the ptr field
> > +         * in PhysPageEntry.
> > +         */
> > +        assert(next_map.sections_nb < SHRT_MAX);
> > +    }
> >  
> >      if (next_map.sections_nb == next_map.sections_nb_alloc) {
> >          next_map.sections_nb_alloc = MAX(next_map.sections_nb_alloc * 2,
> > 
> 
> Thanks for testing this patch Amos!
> 
> Paolo



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