[Qemu-devel] Re: Add target memory mapping API

[Mike Day <ncmike@ncultra.org>]

On 18/01/09 21:53 +0200, Avi Kivity wrote:
> Devices accessing large amounts of memory (as with DMA) will wish to obtain
> a pointer to guest memory rather than access it indirectly via
> cpu_physical_memory_rw().  Add a new API to convert target addresses to
> host pointers.
> 
> In case the target address does not correspond to RAM, a bounce buffer is
> allocated.  To prevent the guest from causing the host to allocate unbounded
> amounts of bounce buffer, this memory is limited (currently to one page).
> 
> Signed-off-by: Avi Kivity <avi@redhat.com>
> ---
>  cpu-all.h |    5 +++
>  exec.c    |   93 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 98 insertions(+), 0 deletions(-)
> 
> diff --git a/cpu-all.h b/cpu-all.h
> index ee0a6e3..3439999 100644
> --- a/cpu-all.h
> +++ b/cpu-all.h
> @@ -923,6 +923,11 @@ static inline void cpu_physical_memory_write(target_phys_addr_t addr,
>  {
>      cpu_physical_memory_rw(addr, (uint8_t *)buf, len, 1);
>  }
> +void *cpu_physical_memory_map(target_phys_addr_t addr,
> +                              target_phys_addr_t *plen,
> +                              int is_write);
> +void cpu_physical_memory_unmap(void *buffer, target_phys_addr_t len,
> +                               int is_write);
>  uint32_t ldub_phys(target_phys_addr_t addr);
>  uint32_t lduw_phys(target_phys_addr_t addr);
>  uint32_t ldl_phys(target_phys_addr_t addr);
> diff --git a/exec.c b/exec.c
> index faa6333..7162271 100644
> --- a/exec.c
> +++ b/exec.c
> @@ -3045,6 +3045,99 @@ void cpu_physical_memory_write_rom(target_phys_addr_t addr,
>      }
>  }
>  
> +typedef struct {
> +    void *buffer;
> +    target_phys_addr_t addr;
> +    target_phys_addr_t len;
> +} BounceBuffer;
> +
> +static BounceBuffer bounce;


Should there be one bounce buffer for each vcpu? Eventually the device
model lock will be refactored to allow more parallelism, right? 


Mike

-- 
Mike Day
http://www.ncultra.org
AIM: ncmikeday |  Yahoo IM: ultra.runner
PGP key: http://www.ncultra.org/ncmike/pubkey.asc