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Re: [Xen-devel] [PATCH v4 1/2] arm: read/write rank->vcpu atomically
Hi Stefano,
On 11/02/17 02:05, Stefano Stabellini wrote:
We don't need a lock in vgic_get_target_vcpu anymore, solving the
following lock inversion bug: the rank lock should be taken first, then
the vgic lock. However, gic_update_one_lr is called with the vgic lock
held, and it calls vgic_get_target_vcpu, which tries to obtain the rank
lock.
Coverity-ID: 1381855
Coverity-ID: 1381853
Signed-off-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>
---
xen/arch/arm/vgic-v2.c | 6 +++---
xen/arch/arm/vgic-v3.c | 6 +++---
xen/arch/arm/vgic.c | 27 +++++----------------------
3 files changed, 11 insertions(+), 28 deletions(-)
diff --git a/xen/arch/arm/vgic-v2.c b/xen/arch/arm/vgic-v2.c
index 3dbcfe8..b30379e 100644
--- a/xen/arch/arm/vgic-v2.c
+++ b/xen/arch/arm/vgic-v2.c
@@ -79,7 +79,7 @@ static uint32_t vgic_fetch_itargetsr(struct vgic_irq_rank
*rank,
offset &= ~(NR_TARGETS_PER_ITARGETSR - 1);
for ( i = 0; i < NR_TARGETS_PER_ITARGETSR; i++, offset++ )
- reg |= (1 << rank->vcpu[offset]) << (i * NR_BITS_PER_TARGET);
+ reg |= (1 << read_atomic(&rank->vcpu[offset])) << (i *
NR_BITS_PER_TARGET);
I was about to suggested to turn vcpu into an atomic_t to catch
potential misuse. But unfortunately atomic_t is int.
So I would probably add a comment on top of the field vcpu in
vgic_irq_rank explaining that vcpu should be read using atomic.
With that:
Reviewed-by: Julien Grall <julien.grall@xxxxxxx>
Cheers,
--
Julien Grall
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