Re: [Qemu-devel] [PATCH 15/30] memory: add address_space_valid

[David Gibson]

On Tue, May 21, 2013 at 12:57:16PM +0200, Paolo Bonzini wrote:
> The old-style IOMMU lets you check whether an access is valid in a
> given DMAContext.  There is no equivalent for AddressSpace in the
> memory API, implement it with a lookup of the dispatch tree.

I don't love the name - "address_space_valid" suggests to me it tests
the validity of the whole address space, not a specific range.  But
an obviously better name doesn't quickly occur to me.

Obviously I like the functionality, since I wrote that into the
DMAContext stuff specifically to support the spapr_llan driver :).


> 
> Signed-off-by: Paolo Bonzini <address@hidden>
> ---
>  dma-helpers.c         |  5 +++++
>  exec.c                | 25 +++++++++++++++++++++++++
>  include/exec/memory.h | 14 ++++++++++++++
>  include/sysemu/dma.h  |  3 ++-
>  4 files changed, 46 insertions(+), 1 deletion(-)
> 
> diff --git a/dma-helpers.c b/dma-helpers.c
> index 272632f..2962b69 100644
> --- a/dma-helpers.c
> +++ b/dma-helpers.c
> @@ -298,6 +298,11 @@ bool iommu_dma_memory_valid(DMAContext *dma, dma_addr_t 
> addr, dma_addr_t len,
>              plen = len;
>          }
>  
> +        if (!address_space_valid(dma->as, paddr, len,
> +                                 dir == DMA_DIRECTION_FROM_DEVICE)) {
> +            return false;
> +        }
> +
>          len -= plen;
>          addr += plen;
>      }
> diff --git a/exec.c b/exec.c
> index 8d91221..8f1b507 100644
> --- a/exec.c
> +++ b/exec.c
> @@ -2079,6 +2079,31 @@ static void cpu_notify_map_clients(void)
>      }
>  }
>  
> +bool address_space_valid(AddressSpace *as, hwaddr addr, int len, bool 
> is_write)
> +{
> +    AddressSpaceDispatch *d = as->dispatch;
> +    MemoryRegionSection *section;
> +    int l;
> +    hwaddr page;
> +
> +    while (len > 0) {
> +        page = addr & TARGET_PAGE_MASK;
> +        l = (page + TARGET_PAGE_SIZE) - addr;
> +        if (l > len) {
> +            l = len;
> +        }
> +        section = phys_page_find(d, addr >> TARGET_PAGE_BITS);
> +        if (section->mr == &io_mem_unassigned ||
> +            (is_write && section->mr->readonly)) {
> +            return false;
> +        }
> +
> +        len -= l;
> +        addr += l;
> +    }
> +    return true;
> +}
> +
>  /* Map a physical memory region into a host virtual address.
>   * May map a subset of the requested range, given by and returned in *plen.
>   * May return NULL if resources needed to perform the mapping are exhausted.
> diff --git a/include/exec/memory.h b/include/exec/memory.h
> index 6ed593c..2e5fd11 100644
> --- a/include/exec/memory.h
> +++ b/include/exec/memory.h
> @@ -860,6 +860,20 @@ void address_space_write(AddressSpace *as, hwaddr addr,
>   */
>  void address_space_read(AddressSpace *as, hwaddr addr, uint8_t *buf, int 
> len);
>  
> +/* address_space_valid: check for validity of an address space range
> + *
> + * Check whether memory is assigned to the given address space range.
> + *
> + * For now, addr and len should be aligned to a page size.  This limitation
> + * will be lifted in the future.
> + *
> + * @as: #AddressSpace to be accessed
> + * @addr: address within that address space
> + * @len: length of the area to be checked
> + * @is_write: indicates the transfer direction
> + */
> +bool address_space_valid(AddressSpace *as, hwaddr addr, int len, bool 
> is_write);
> +
>  /* address_space_map: map a physical memory region into a host virtual 
> address
>   *
>   * May map a subset of the requested range, given by and returned in @plen.
> diff --git a/include/sysemu/dma.h b/include/sysemu/dma.h
> index a52c93a..2e239dc 100644
> --- a/include/sysemu/dma.h
> +++ b/include/sysemu/dma.h
> @@ -113,7 +113,8 @@ static inline bool dma_memory_valid(DMAContext *dma,
>                                      DMADirection dir)
>  {
>      if (!dma_has_iommu(dma)) {
> -        return true;
> +        return address_space_valid(dma->as, addr, len,
> +                                   dir == DMA_DIRECTION_FROM_DEVICE);
>      } else {
>          return iommu_dma_memory_valid(dma, addr, len, dir);
>      }

-- 
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

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