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RE: [PATCH] qemu: define and use VIRTIO_PFN_SHIFT

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Hollis Blanchard wrote:
> On Thu, 2008-11-06 at 08:01 -0600, Anthony Liguori wrote:
>> Hollis Blanchard wrote:
>>> # HG changeset patch
>>> # User Hollis Blanchard <hollisb@xxxxxxxxxx>
>>> # Date 1225946837 21600
>>> # Node ID 43a111ea61b542d3823e2a11d017e7b06b7ec254
>>> # Parent  b63967268af119e0faa4adc3086cdef857815548
>>> qemu: define and use VIRTIO_PFN_SHIFT
>>> 
>>> The virtio front and back ends must agree about how big a pfn
>>> really is. Since qemu has no idea what "page size" the guest may be
>>> using, it must be independent of TARGET_PAGE_BITS.
>>> 
>>> This patch should have no functional effect on x86 or ia64, but I'd
>>> like an ack from the ia64 guys. 
>>> 
>> 
>> Would be better to add a new header in target-XXX instead of using
>> cpu.h.  Virtio is not part of the CPU ISA.
> 
> OK.
> 
>>> Signed-off-by: Hollis Blanchard <hollisb@xxxxxxxxxx>
>>> 
>>> diff --git a/qemu/hw/virtio.c b/qemu/hw/virtio.c
>>> --- a/qemu/hw/virtio.c
>>> +++ b/qemu/hw/virtio.c
>>> @@ -56,6 +56,10 @@
>>>   */
>>>  #define wmb() do { } while (0)
>>> 
>>> +#define VRING_PAGE_SIZE (1<<12)
>>> +
>>> +#define ALIGN(x, a)  (((x)+(a)-1) & ~((a)-1))
>>> +
>>>  /* virt queue functions */
>> 
>> Why is VRING_PAGE_SIZE not architecture specific?
> 
> I wanted to make sure people on non-x86 architectures couldn't run
> into vring-size related problems that didn't also appear on x86.

Hi, Hollis
	Currenlty, kvm-qemu only supports the only case which is host page_size = qemu's target page size for ia64. Does your patch meets the requirement ? For ia64, current linux support 4K, 16K and 64k page size, and 1M 16M 64M or bigger page will be supported in future, so if your patch consider the case, it should work for ia64.  Thanks! 
Thanks
Xiantao

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