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Re: [Qemu-devel] [PULL 1/7] exec: Limit translation limiting in address_
From: |
Stefano Stabellini |
Subject: |
Re: [Qemu-devel] [PULL 1/7] exec: Limit translation limiting in address_space_translate to xen |
Date: |
Wed, 7 May 2014 16:30:36 +0100 |
User-agent: |
Alpine 2.02 (DEB 1266 2009-07-14) |
On Wed, 7 May 2014, Paolo Bonzini wrote:
> Il 07/05/2014 17:12, Peter Maydell ha scritto:
> > > > - if (memory_access_is_direct(mr, is_write)) {
> > > > + if (xen_enabled() && memory_access_is_direct(mr, is_write)) {
> > > > hwaddr page = ((addr & TARGET_PAGE_MASK) + TARGET_PAGE_SIZE) -
> > > addr;
> > > > len = MIN(page, len);
> > > > }
> > We should put this patch in (both as an efficiency thing and an
> > expedient fix) but we really need to either track down which
> > callers of this API are relying on the returned plen not being
> > truncated, or we need to fix Xen to not truncate either. This
> > is just a bandaid IMHO.
>
> Fixing Xen to not truncate is not possible because of the Xen mapcache, unless
> of course QEMU is changed to avoid the mapcache completely on 64-bit hosts.
> I'm not sure if that makes sense from the Xen point of view.
Right, it makes sense, however we would still need to keep the 32-bit
mapcache code path working.
> Regarding fixing callers, a known one is virtio-scsi which is a bug and on my
> todo list. But another is VFIO, which cannot accept truncation if the IOMMU
> page size is greater than TARGET_PAGE_SIZE.
[Qemu-devel] [PULL 3/7] xen: move Xen PV machine files to hw/xenpv, Stefano Stabellini, 2014/05/07
[Qemu-devel] [PULL 4/7] xen: move Xen HVM files under hw/i386/xen, Stefano Stabellini, 2014/05/07
[Qemu-devel] [PULL 7/7] xen_disk: add discard support, Stefano Stabellini, 2014/05/07
[Qemu-devel] [PULL 5/7] xen: factor out common functions, Stefano Stabellini, 2014/05/07
Re: [Qemu-devel] [PULL 0/7] xen-140507, Peter Maydell, 2014/05/07