Re: [Qemu-devel] [PATCH 1/4] memory: add memory_region_flush_rom_device()

[Stefan Hajnoczi]

On Tue, Jan 22, 2019 at 04:36:36PM +0000, Peter Maydell wrote:
> On Sun, 20 Jan 2019 at 14:35, Stefan Hajnoczi <address@hidden> wrote:
> >
> > ROM devices go via MemoryRegionOps->write() callbacks for write
> > operations and do not dirty/invalidate that memory.  Device emulation
> > must be able to mark memory ranges that have been modified internally
> > (e.g. using memory_region_get_ram_ptr()).
> >
> > Introduce the memory_region_flush_rom_device() API for this purpose.
> >
> > Signed-off-by: Stefan Hajnoczi <address@hidden>
> > ---
> >  include/exec/memory.h | 18 ++++++++++++++++++
> >  exec.c                | 12 ++++++++++++
> >  2 files changed, 30 insertions(+)
> >
> > diff --git a/include/exec/memory.h b/include/exec/memory.h
> > index cd2f209b64..abe9cc79c0 100644
> > --- a/include/exec/memory.h
> > +++ b/include/exec/memory.h
> > @@ -1344,6 +1344,24 @@ bool memory_region_snapshot_get_dirty(MemoryRegion 
> > *mr,
> >  void memory_region_reset_dirty(MemoryRegion *mr, hwaddr addr,
> >                                 hwaddr size, unsigned client);
> >
> > +/**
> > + * memory_region_flush_rom_device: Mark a range of pages dirty and 
> > invalidate
> > + *                                 TBs (for self-modifying code).
> > + *
> > + * The MemoryRegionOps->write() callback of a ROM device must use this 
> > function
> > + * to mark byte ranges that have been modified internally, such as by 
> > directly
> > + * accessing the memory returned by memory_region_get_ram_ptr().
> > + *
> > + * This function marks the range dirty and invalidates TBs so that TCG can
> > + * detect self-modifying code.
> > + *
> > + * @mr: the region being flushed.
> > + * @addr: the start, relative to the start of the region, of the range 
> > being
> > + *        flushed.
> > + * @size: the size, in bytes, of the range being flushed.
> > + */
> > +void memory_region_flush_rom_device(MemoryRegion *mr, hwaddr addr, hwaddr 
> > size);
> > +
> >  /**
> >   * memory_region_set_readonly: Turn a memory region read-only (or 
> > read-write)
> >   *
> > diff --git a/exec.c b/exec.c
> > index 895449f926..105ff21e74 100644
> > --- a/exec.c
> > +++ b/exec.c
> > @@ -3162,6 +3162,18 @@ static void invalidate_and_set_dirty(MemoryRegion 
> > *mr, hwaddr addr,
> >      cpu_physical_memory_set_dirty_range(addr, length, dirty_log_mask);
> >  }
> >
> > +void memory_region_flush_rom_device(MemoryRegion *mr, hwaddr addr, hwaddr 
> > size)
> > +{
> > +    /* In principle this function would work on other memory region types 
> > too,
> > +     * but the ROM device use case is the only one where this operation is
> > +     * necessary.  Other memory regions should use the
> > +     * address_space_read/write() APIs.
> > +     */
> > +    assert(memory_region_is_romd(mr));
> > +
> > +    invalidate_and_set_dirty(mr, addr, size);
> > +}
> > +
> >  static int memory_access_size(MemoryRegion *mr, unsigned l, hwaddr addr)
> >  {
> >      unsigned access_size_max = mr->ops->valid.max_access_size;
> 
> API and implementation make sense to me, but better that Paolo reviews
> this I think. I guess we should add calls to this to the pflash device
> models too...

Okay, will cover pflash in the next revision.

Stefan

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