On 03/11/2016 10:27, Jason Wang wrote:
> This patch introduces a helper to query the iotlb entry for a
> possible iova. This will be used by later device IOTLB API to enable
> the capability for a dataplane (e.g vhost) to query the IOTLB.
>
> Cc: Paolo Bonzini <pbonz...@redhat.com>
> Cc: Peter Crosthwaite <crosthwaite.pe...@gmail.com>
> Cc: Richard Henderson <r...@twiddle.net>
> Signed-off-by: Jason Wang <jasow...@redhat.com>
> ---
> exec.c | 33 +++++++++++++++++++++++++++++++++
> include/exec/memory.h | 6 ++++++
> 2 files changed, 39 insertions(+)
>
> diff --git a/exec.c b/exec.c
> index b1094c0..00c7a2b 100644
> --- a/exec.c
> +++ b/exec.c
> @@ -449,6 +449,39 @@ address_space_translate_internal(AddressSpaceDispatch
> *d, hwaddr addr, hwaddr *x
> }
>
> /* Called from RCU critical section */
> +IOMMUTLBEntry address_space_get_iotlb_entry(AddressSpace *as, hwaddr addr,
> + bool is_write)
> +{
> + IOMMUTLBEntry iotlb = {0};
> + MemoryRegionSection *section;
> + MemoryRegion *mr;
> + hwaddr plen;
plen must be initialized on entry to address_space_translate_internal,
since it's set to
MIN(plen, MIN(section->size,
addr - section->offset_within_address_space))
after address_space_translate_internal calls
address_space_lookup_region. But you don't really need plen, so you
should do this:
section = address_space_lookup_region(d, addr, false);
addr = addr
- section->offset_within_address_space
+ section->offset_within_region;
instead of
section = address_space_translate_internal(d, addr, &addr,
&plen, true);
and then you don't even need a plen anymore.
Also:
> + for (;;) {
> + AddressSpaceDispatch *d = atomic_rcu_read(&as->dispatch);
> + section = address_space_translate_internal(d, addr, &addr, &plen,
> true);
> + mr = section->mr;
> +
> + if (!mr->iommu_ops) {
> + break;
> + }
> +
> + iotlb = mr->iommu_ops->translate(mr, addr, is_write);
> + addr = ((iotlb.translated_addr & ~iotlb.addr_mask)
> + | (addr & iotlb.addr_mask));
This addr assignment is only needed after the iotlb.perm check, so move
it there.
Thanks,
Paolo
> + plen = MIN(plen, (addr | iotlb.addr_mask) - addr + 1);
> + if (!(iotlb.perm & (1 << is_write))) {
> + iotlb.target_as = NULL;
> + break;
> + }
> +
> + as = iotlb.target_as;
> + }
> +
> + return iotlb;
> +}
> +
> +/* Called from RCU critical section */
> MemoryRegion *address_space_translate(AddressSpace *as, hwaddr addr,
> hwaddr *xlat, hwaddr *plen,
> bool is_write)
> diff --git a/include/exec/memory.h b/include/exec/memory.h
> index 9728a2f..e605de3 100644
> --- a/include/exec/memory.h
> +++ b/include/exec/memory.h
> @@ -1404,6 +1404,12 @@ void address_space_stq_le(AddressSpace *as, hwaddr
> addr, uint64_t val,
> void address_space_stq_be(AddressSpace *as, hwaddr addr, uint64_t val,
> MemTxAttrs attrs, MemTxResult *result);
>
> +/* address_space_get_iotlb_entry: translate an address into an IOTLB
> + * entry. Should be called from an RCU critical section.
> + */
> +IOMMUTLBEntry address_space_get_iotlb_entry(AddressSpace *as, hwaddr addr,
> + bool is_write);
> +
> /* address_space_translate: translate an address range into an address space
> * into a MemoryRegion and an address range into that section. Should be
> * called from an RCU critical section, to avoid that the last reference
>
