Re: [Qemu-devel] [PATCH v2 for-2.11 2/2] accel/tcg: Handle atomic accesses to notdirty memory correctly

[Richard Henderson <richard.henderson@linaro.org>]

On 11/20/2017 07:08 PM, Peter Maydell wrote:
> To do a write to memory that is marked as notdirty, we need
> to invalidate any TBs we have cached for that memory, and
> update the cpu physical memory dirty flags for VGA and migration.
> The slowpath code in notdirty_mem_write() does all this correctly,
> but the new atomic handling code in atomic_mmu_lookup() doesn't
> do anything at all, it just clears the dirty bit in the TLB.
> 
> The effect of this bug is that if the first write to a notdirty
> page for which we have cached TBs is by a guest atomic access,
> we fail to invalidate the TBs and subsequently will execute
> incorrect code. This can be seen by trying to run 'javac' on AArch64.
> 
> Use the new notdirty_call_before() and notdirty_call_after()
> functions to correctly handle the update to notdirty memory
> in the atomic codepath.
> 
> Cc: qemu-stable@nongnu.org
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> ---
>  accel/tcg/atomic_template.h | 12 ++++++++++++
>  accel/tcg/cputlb.c          | 38 +++++++++++++++++++++++++-------------
>  accel/tcg/user-exec.c       |  1 +
>  3 files changed, 38 insertions(+), 13 deletions(-)

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>


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