Re: [Qemu-devel] [PATCH 1/2] tcg: Ensure safe tb_jmp_cache lookup out of 'tb_lock'

[Richard Henderson <rth@twiddle.net>]

On 07/01/2016 09:16 AM, Alex Bennée wrote:
> From: Sergey Fedorov <serge.fdrv@gmail.com>
>
> First, ensure atomicity of CPU's 'tb_jmp_cache' access by:
>  * using atomic_read() to look up a TB when not holding 'tb_lock';
>  * using atomic_write() to remove a TB from each CPU's local cache on
>    TB invalidation.
>
> Second, add some memory barriers to ensure we don't put the TB being
> invalidated back to CPU's 'tb_jmp_cache'. If we fail to look up a TB in
> CPU's local cache because it is being invalidated by some other thread
> then it must not be found in the shared TB hash table. Otherwise we'd
> put it back to CPU's local cache.
>
> Note that this patch does *not* make CPU's TLB invalidation safe if it
> is done from some other thread while the CPU is in its execution loop.
>
> Signed-off-by: Sergey Fedorov <serge.fdrv@gmail.com>
> Signed-off-by: Sergey Fedorov <sergey.fedorov@linaro.org>
> [AJB: fixed missing atomic set, tweak title]
> Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
>
> ---
> AJB:
>   - tweak title
>   - fixed missing set of tb_jmp_cache
> ---
>  cpu-exec.c      | 9 +++++++--
>  translate-all.c | 7 ++++++-
>  2 files changed, 13 insertions(+), 3 deletions(-)

Reviewed-by: Richard Henderson <rth@twiddle.net>


r~