Re: [PATCH 1/6] exec/memory: Introduce the translate_size function within the IOMMU class

[Ethan Chen via <qemu-devel@nongnu.org>]

On Wed, Oct 25, 2023 at 04:56:22PM +0200, David Hildenbrand wrote:
> On 25.10.23 07:14, Ethan Chen wrote:
> > IOMMU have size information during translation.
> > 
> 
> Can you add some more information why we would want this and how the backend
> can do "better" things with the size at hand?
>
With size information, IOMMU can reject a memory access which is patially in 
valid region.

Currently translation function limit memory access size with a mask, so the 
valid part of access will success. My target is to detect partially hit and 
reject whole access. Translation function cannot detect partially hit because 
it lacks size information.
> Note that I was not CCed on the cover letter.
> 
> > Signed-off-by: Ethan Chen <ethan84@andestech.com>
> > ---
> >   include/exec/memory.h | 19 +++++++++++++++++++
> >   1 file changed, 19 insertions(+)
> > 
> > diff --git a/include/exec/memory.h b/include/exec/memory.h
> > index 9087d02769..5520b7c8c0 100644
> > --- a/include/exec/memory.h
> > +++ b/include/exec/memory.h
> > @@ -396,6 +396,25 @@ struct IOMMUMemoryRegionClass {
> >        */
> >       IOMMUTLBEntry (*translate)(IOMMUMemoryRegion *iommu, hwaddr addr,
> >                                  IOMMUAccessFlags flag, int iommu_idx);
> > +    /**
> > +     * @translate_size:
> > +     *
> > +     * Return a TLB entry that contains a given address and size.
> > +     *
> > +     * @iommu: the IOMMUMemoryRegion
> > +     *
> > +     * @hwaddr: address to be translated within the memory region
> > +     *
> > +     * @size: size to indicate the scope of the entire transaction
> > +     *
> > +     * @flag: requested access permission
> > +     *
> > +     * @iommu_idx: IOMMU index for the translation
> > +     */
> > +    IOMMUTLBEntry (*translate_size)(IOMMUMemoryRegion *iommu, hwaddr addr,
> > +                                    hwaddr size, IOMMUAccessFlags flag,
> > +                                    int iommu_idx);
> > +
> >       /**
> >        * @get_min_page_size:
> >        *
> 
> -- 
> Cheers,
> 
> David / dhildenb
> 
Thanks,
Ethan Chen