On Fri, Jul 10, 2015 at 08:43:44PM +1000, Alexey Kardashevskiy wrote: > These started switching from TARGET_PAGE_MASK (hardcoded as 4K) to > a real host page size: > 4e51361d7 "cpu-all: complete "real" host page size API" and > f7ceed190 "vfio: cpu: Use "real" page size API" > > This finished the transition by: > - %s/TARGET_PAGE_MASK/qemu_real_host_page_mask/ > - %s/TARGET_PAGE_ALIGN/REAL_HOST_PAGE_ALIGN/ > - removing bitfield length for offsets in VFIOQuirk::data as > qemu_real_host_page_mask is not a macro
This does not make much sense to me. f7ceed190 moved to
REAL_HOST_PAGE_SIZE because it's back end stuff that really depends
only on the host page size.
Here you're applying a blanket change to vfio code, in particular to
the DMA handling code, and for DMA both the host and target page size
can be relevant, depending on the details of the IOMMU implementation.
> This keeps using TARGET_PAGE_MASK for IOMMU regions though as it is
> the minimum page size which IOMMU regions may be using and at the moment
> memory regions do not carry the actual page size.
And this exception also doesn't make much sense to me. Partly it's
confusing because the listener is doing different things depending on
whether we have a guest visible IOMMU or not.
In short, there doesn't seem to be a coherent explanation here of
where the page size / alignment restriction is coming from, and
therefore whether it needs to be a host page alignment, a guest page
alignment, or both.
> Signed-off-by: Alexey Kardashevskiy <a...@ozlabs.ru>
> ---
>
> In reality DMA windows are always a lot bigger than a single 4K page
> and aligned to 32/64MB, may be only use here
> qemu_real_host_page_mask?
I don't understand this question either.
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
pgpwNRyv0ggc3.pgp
Description: PGP signature
