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Re: [Qemu-devel] [PATCH 07/15] memory: avoid ref/unref in memory_region_
From: |
Fam Zheng |
Subject: |
Re: [Qemu-devel] [PATCH 07/15] memory: avoid ref/unref in memory_region_find |
Date: |
Mon, 26 Jan 2015 14:24:48 +0800 |
User-agent: |
Mutt/1.5.23 (2014-03-12) |
On Thu, 01/22 15:47, Paolo Bonzini wrote:
> Do the entire lookup under RCU, which avoids atomic operations.
address_space_get_flatview() already is RCU protected, I don't see why this
patch is necessary. Could you explain?
And there is one question below:
>
> Signed-off-by: Paolo Bonzini <address@hidden>
> ---
> memory.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/memory.c b/memory.c
> index a844ced..577e87c 100644
> --- a/memory.c
> +++ b/memory.c
> @@ -1828,7 +1828,8 @@ MemoryRegionSection memory_region_find(MemoryRegion *mr,
> }
> range = addrrange_make(int128_make64(addr), int128_make64(size));
>
> - view = address_space_get_flatview(as);
> + rcu_read_lock();
> + view = atomic_rcu_read(&as->current_map);
> fr = flatview_lookup(view, range);
> if (!fr) {
> flatview_unref(view);
Following lines are:
return ret;
}
Which requires a rcu_read_unlock.
Fam
> @@ -1850,7 +1851,7 @@ MemoryRegionSection memory_region_find(MemoryRegion *mr,
> ret.readonly = fr->readonly;
> memory_region_ref(ret.mr);
>
> - flatview_unref(view);
> + rcu_read_unlock();
> return ret;
> }
>
> --
> 1.8.3.1
>
>
- Re: [Qemu-devel] [PATCH 03/15] rcu: allow nesting of rcu_read_lock/rcu_read_unlock, (continued)
- [Qemu-devel] [PATCH 05/15] memory: remove assertion on memory_region_destroy, Paolo Bonzini, 2015/01/22
- [Qemu-devel] [PATCH 06/15] memory: protect current_map by RCU, Paolo Bonzini, 2015/01/22
- [Qemu-devel] [PATCH 08/15] exec: introduce cpu_reload_memory_map, Paolo Bonzini, 2015/01/22
- [Qemu-devel] [PATCH 10/15] exec: RCUify AddressSpaceDispatch, Paolo Bonzini, 2015/01/22
- [Qemu-devel] [PATCH 04/15] rcu: add call_rcu, Paolo Bonzini, 2015/01/22
- [Qemu-devel] [PATCH 07/15] memory: avoid ref/unref in memory_region_find, Paolo Bonzini, 2015/01/22
- Re: [Qemu-devel] [PATCH 07/15] memory: avoid ref/unref in memory_region_find,
Fam Zheng <=
- [Qemu-devel] [PATCH 12/15] exec: protect mru_block with RCU, Paolo Bonzini, 2015/01/22
- [Qemu-devel] [PATCH 11/15] rcu: introduce RCU-enabled QLIST, Paolo Bonzini, 2015/01/22
- [Qemu-devel] [PATCH 14/15] exec: convert ram_list to QLIST, Paolo Bonzini, 2015/01/22
- [Qemu-devel] [PATCH 13/15] cosmetic changes preparing for the following patches, Paolo Bonzini, 2015/01/22
- [Qemu-devel] [PATCH 09/15] exec: make iotlb RCU-friendly, Paolo Bonzini, 2015/01/22
- [Qemu-devel] [PATCH 15/15] Convert ram_list to RCU, Paolo Bonzini, 2015/01/22