Re: [PATCH V4 3/4] kvm: fix zero length mmio searching

From	Cornelia Huck <cornelia.huck@de.ibm.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH V4 3/4] kvm: fix zero length mmio searching
Date	2015-09-11 10:40 +0200
Message-ID	<q7s2e-4Hu-25@gated-at.bofh.it> (permalink)
References	<q7n2x-645-3@gated-at.bofh.it> <q7n2y-645-11@gated-at.bofh.it> <q7rSy-4w9-19@gated-at.bofh.it>
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On Fri, 11 Sep 2015 10:26:41 +0200
Paolo Bonzini <pbonzini@redhat.com> wrote:

> On 11/09/2015 05:17, Jason Wang wrote:
> > +	int len = r2->len ? r1->len : 0;
> > +
> >  	if (r1->addr < r2->addr)
> >  		return -1;
> > -	if (r1->addr + r1->len > r2->addr + r2->len)
> > +	if (r1->addr + len > r2->addr + r2->len)
> >  		return 1;
> 
> Perhaps better:
> 
> 	gpa_t addr1 = r1->addr;
> 	gpa_t addr2 = r2->addr;
> 
> 	if (addr1 < addr2)
> 		return -1;
> 
> 	/* If r2->len == 0, match the exact address.  If r2->len != 0,
> 	 * accept any overlapping write.  Any order is acceptable for
> 	 * overlapping ranges, because kvm_io_bus_get_first_dev ensures
> 	 * we process all of them.
> 	 */
> 	if (r2->len) {
> 		addr1 += r1->len;
> 		addr2 += r2->len;
> 	}
> 
> 	if (addr1 > addr2)
> 		return 1;
> 
> 	return 0;
> 

+1 to documenting what the semantics are :)

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Thread

[PATCH V4 0/4] Fast MMIO eventfd fixes Jason Wang <jasowang@redhat.com> - 2015-09-11 05:20 +0200
  [PATCH V4 3/4] kvm: fix zero length mmio searching Jason Wang <jasowang@redhat.com> - 2015-09-11 05:20 +0200
    Re: [PATCH V4 3/4] kvm: fix zero length mmio searching Paolo Bonzini <pbonzini@redhat.com> - 2015-09-11 10:30 +0200
      Re: [PATCH V4 3/4] kvm: fix zero length mmio searching Cornelia Huck <cornelia.huck@de.ibm.com> - 2015-09-11 10:40 +0200
        Re: [PATCH V4 3/4] kvm: fix zero length mmio searching Jason Wang <jasowang@redhat.com> - 2015-09-11 11:30 +0200
  Re: [PATCH V4 0/4] Fast MMIO eventfd fixes "Michael S. Tsirkin" <mst@redhat.com> - 2015-09-11 10:20 +0200
    Re: [PATCH V4 0/4] Fast MMIO eventfd fixes Paolo Bonzini <pbonzini@redhat.com> - 2015-09-11 10:40 +0200
      Re: [PATCH V4 0/4] Fast MMIO eventfd fixes Jason Wang <jasowang@redhat.com> - 2015-09-11 11:30 +0200
        Re: [PATCH V4 0/4] Fast MMIO eventfd fixes "Michael S. Tsirkin" <mst@redhat.com> - 2015-09-13 11:00 +0200
      Re: [PATCH V4 0/4] Fast MMIO eventfd fixes "Michael S. Tsirkin" <mst@redhat.com> - 2015-09-13 11:00 +0200

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