Re: [Qemu-devel] [PATCH v7 14/17] memory: add MemoryRegionIOMMUOps.replay() callback

[Peter Xu]

On Mon, Mar 27, 2017 at 08:35:05AM +0000, Liu, Yi L wrote:
> > -----Original Message-----
> > From: Qemu-devel [mailto:address@hidden On
> > Behalf Of Peter Xu
> > Sent: Tuesday, February 7, 2017 4:28 PM
> > To: address@hidden
> > Cc: Lan, Tianyu <address@hidden>; Tian, Kevin <address@hidden>;
> > address@hidden; address@hidden; address@hidden;
> > address@hidden; address@hidden; address@hidden; David
> > Gibson <address@hidden>
> > Subject: [Qemu-devel] [PATCH v7 14/17] memory: add
> > MemoryRegionIOMMUOps.replay() callback
> > 
> > Originally we have one memory_region_iommu_replay() function, which is the
> > default behavior to replay the translations of the whole IOMMU region. 
> > However,
> > on some platform like x86, we may want our own replay logic for IOMMU 
> > regions.
> > This patch add one more hook for IOMMUOps for the callback, and it'll 
> > override the
> > default if set.
> > 
> > Signed-off-by: Peter Xu <address@hidden>
> > ---
> >  include/exec/memory.h | 2 ++
> >  memory.c              | 6 ++++++
> >  2 files changed, 8 insertions(+)
> > 
> > diff --git a/include/exec/memory.h b/include/exec/memory.h index
> > 0767888..30b2a74 100644
> > --- a/include/exec/memory.h
> > +++ b/include/exec/memory.h
> > @@ -191,6 +191,8 @@ struct MemoryRegionIOMMUOps {
> >      void (*notify_flag_changed)(MemoryRegion *iommu,
> >                                  IOMMUNotifierFlag old_flags,
> >                                  IOMMUNotifierFlag new_flags);
> > +    /* Set this up to provide customized IOMMU replay function */
> > +    void (*replay)(MemoryRegion *iommu, IOMMUNotifier *notifier);
> >  };
> > 
> >  typedef struct CoalescedMemoryRange CoalescedMemoryRange; diff --git
> > a/memory.c b/memory.c index 7a4f2f9..9c253cc 100644
> > --- a/memory.c
> > +++ b/memory.c
> > @@ -1630,6 +1630,12 @@ void memory_region_iommu_replay(MemoryRegion
> > *mr, IOMMUNotifier *n,
> >      hwaddr addr, granularity;
> >      IOMMUTLBEntry iotlb;
> > +    /* If the IOMMU has its own replay callback, override */
> > +    if (mr->iommu_ops->replay) {
> > +        mr->iommu_ops->replay(mr, n);
> > +        return;
> > +    }
> 
> Hi Alex, Peter,
> 
> Will all the other vendors(e.g. PPC, s390, ARM) add their own replay callback
> as well? I guess it depends on whether the original replay algorithm work well
> for them? Do you have such knowledge?

I guess so. At least for VT-d we had this callback since the default
replay mechanism did not work well on x86 due to its extremely large
memory region size. Thanks,

-- peterx