On Thu, Sep 22, 2022 at 7:02 PM Marc Zyngier <maz@xxxxxxxxxx> wrote:
> To make sure that all the writes to the log marking the entries
> as being in need of reset are observed in order, use a
> smp_store_release() when updating the log entry flags.
>
> Signed-off-by: Marc Zyngier <maz@xxxxxxxxxx>
You also need a load-acquire on the load of gfn->flags in
dirty_gfn_is_dirtied. Otherwise reading cur->slot or cur->offset might
see a stale value.
Paolo
> ---
> tools/testing/selftests/kvm/dirty_log_test.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/tools/testing/selftests/kvm/dirty_log_test.c b/tools/testing/selftests/kvm/dirty_log_test.c
> index 9c883c94d478..3d29f4bf4f9c 100644
> --- a/tools/testing/selftests/kvm/dirty_log_test.c
> +++ b/tools/testing/selftests/kvm/dirty_log_test.c
> @@ -17,6 +17,7 @@
> #include <linux/bitmap.h>
> #include <linux/bitops.h>
> #include <linux/atomic.h>
> +#include <asm/barrier.h>
>
> #include "kvm_util.h"
> #include "test_util.h"
> @@ -284,7 +285,7 @@ static inline bool dirty_gfn_is_dirtied(struct kvm_dirty_gfn *gfn)
>
> static inline void dirty_gfn_set_collected(struct kvm_dirty_gfn *gfn)
> {
> - gfn->flags = KVM_DIRTY_GFN_F_RESET;
> + smp_store_release(&gfn->flags, KVM_DIRTY_GFN_F_RESET);
> }
>
> static uint32_t dirty_ring_collect_one(struct kvm_dirty_gfn *dirty_gfns,
> --
> 2.34.1
>
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