Re: [Qemu-devel] [PATCH 0/7] memory: address_space_to_flatview needs RCU lock
On 06/03/2018 08:47, Alexey Kardashevskiy wrote:
> On 05/03/18 19:36, Paolo Bonzini wrote:
>> I noticed that the introduction of flatview_{read,write} placed
>> address_space_to_flatview outside the RCU lock. This is wrong and has
>> to be fixed, because address_space_to_flatview does an atomic_rcu_read.
>> These patches fix this one function at a time.
>
> out of curiosity - has this caused any actual bug? should be hard to
> reproduce, I suppose...
No, I just noticed it by code inspection, while looking at a
reimplementation of MemoryRegionCache (reverted in 2.9). One of the
differences between address_space_read and address_space_read_cached was
that the latter expects to be called within rcu_read_lock, so it was
surprising that address_space_read was expecting the same. :)
Paolo
Re: [Qemu-devel] [PATCH 0/7] memory: address_space_to_flatview needs RCU lock
On 05/03/18 19:36, Paolo Bonzini wrote:
> I noticed that the introduction of flatview_{read,write} placed
> address_space_to_flatview outside the RCU lock. This is wrong and has
> to be fixed, because address_space_to_flatview does an atomic_rcu_read.
> These patches fix this one function at a time.
out of curiosity - has this caused any actual bug? should be hard to
reproduce, I suppose...
>
> Paolo Bonzini (7):
> openpic_kvm: drop address_space_to_flatview call
> memory: inline some performance-sensitive accessors
> address_space_write: address_space_to_flatview needs RCU lock
> address_space_read: address_space_to_flatview needs RCU lock
> address_space_access_valid: address_space_to_flatview needs RCU lock
> address_space_map: address_space_to_flatview needs RCU lock
> address_space_rw: address_space_to_flatview needs RCU lock
>
> exec.c | 90
> +-
> hw/intc/openpic_kvm.c | 4 --
> include/exec/memory-internal.h | 13 --
> include/exec/memory.h | 47 ++
> memory.c | 30 --
> 5 files changed, 93 insertions(+), 91 deletions(-)
>
--
Alexey
