Re: [PATCH v2 2/6] iommu/io-pgtable: Allow a pgtable implementation to skip TLB operations

[Robin Murphy]

On 2020-06-26 21:04, Jordan Crouse wrote:
Allow a io-pgtable implementation to skip TLB operations by checking for
NULL pointers in the helper functions. It will be up to to the owner
of the io-pgtable instance to make sure that they independently handle
the TLB correctly.

I don't really understand what this is for - tricking the IOMMU driver 
into not performing its TLB maintenance at points when that maintenance 
has been deemed necessary doesn't seem like the appropriate way to 
achieve anything good :/

Robin.

Signed-off-by: Jordan Crouse <jcro...@codeaurora.org>
---

  include/linux/io-pgtable.h | 11 +++++++----
  1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/include/linux/io-pgtable.h b/include/linux/io-pgtable.h
index 53d53c6c2be9..bbed1d3925ba 100644
--- a/include/linux/io-pgtable.h
+++ b/include/linux/io-pgtable.h
@@ -210,21 +210,24 @@ struct io_pgtable {
  
  static inline void io_pgtable_tlb_flush_all(struct io_pgtable *iop)
  {
-       iop->cfg.tlb->tlb_flush_all(iop->cookie);
+       if (iop->cfg.tlb)
+               iop->cfg.tlb->tlb_flush_all(iop->cookie);
  }
  
  static inline void
  io_pgtable_tlb_flush_walk(struct io_pgtable *iop, unsigned long iova,
                          size_t size, size_t granule)
  {
-       iop->cfg.tlb->tlb_flush_walk(iova, size, granule, iop->cookie);
+       if (iop->cfg.tlb)
+               iop->cfg.tlb->tlb_flush_walk(iova, size, granule, iop->cookie);
  }
  
  static inline void
  io_pgtable_tlb_flush_leaf(struct io_pgtable *iop, unsigned long iova,
                          size_t size, size_t granule)
  {
-       iop->cfg.tlb->tlb_flush_leaf(iova, size, granule, iop->cookie);
+       if (iop->cfg.tlb)
+               iop->cfg.tlb->tlb_flush_leaf(iova, size, granule, iop->cookie);
  }
  
  static inline void
@@ -232,7 +235,7 @@ io_pgtable_tlb_add_page(struct io_pgtable *iop,
                        struct iommu_iotlb_gather * gather, unsigned long iova,
                        size_t granule)
  {
-       if (iop->cfg.tlb->tlb_add_page)
+       if (iop->cfg.tlb && iop->cfg.tlb->tlb_add_page)
                iop->cfg.tlb->tlb_add_page(gather, iova, granule, iop->cookie);
  }
  

_______________________________________________
iommu mailing list
iommu@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/iommu