Re: [PATCH v4 09/13] iommu/arm-smmu-v3: Prepare for handling arm_smmu_write_ctx_desc() failure

On Tue, Jan 14, 2020 at 12:42:47PM +0000, Will Deacon wrote:

On Thu, Dec 19, 2019 at 05:30:29PM +0100, Jean-Philippe Brucker wrote:

quoted

Second-level context descriptor tables will be allocated lazily in
arm_smmu_write_ctx_desc(). Help with handling allocation failure by
moving the CD write into arm_smmu_domain_finalise_s1().

Reviewed-by: Eric Auger <eric.auger@redhat.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Jean-Philippe Brucker <redacted>
---
 drivers/iommu/arm-smmu-v3.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/drivers/iommu/arm-smmu-v3.c b/drivers/iommu/arm-smmu-v3.c
index e147087198ef..b825a5639afc 100644
--- a/drivers/iommu/arm-smmu-v3.c
+++ b/drivers/iommu/arm-smmu-v3.c

@@ -2301,8 +2301,15 @@ static int arm_smmu_domain_finalise_s1(struct arm_smmu_domain *smmu_domain,
 	cfg->cd.ttbr	= pgtbl_cfg->arm_lpae_s1_cfg.ttbr[0];
 	cfg->cd.tcr	= pgtbl_cfg->arm_lpae_s1_cfg.tcr;
 	cfg->cd.mair	= pgtbl_cfg->arm_lpae_s1_cfg.mair;
+
+	ret = arm_smmu_write_ctx_desc(smmu_domain, 0, &cfg->cd);

Hmm. This ends up calling arm_smmu_sync_cd() but I think that happens before
we've added the master to the devices list of the domain. Does that mean we
miss the new SSID during the invalidation?

Yes, the arm_smmu_sync_cd() isn't useful in this case, it's only needed
when the STE is live and arm_smmu_write_ctx_desc() is called for a
ssid!=0. On this path, the CD cache is invalidated by a CFGI_STE executed
later, when arm_smmu_attach_dev() installs the STE. I didn't want to add a
special case that avoids the sync when ssid==0 in because a spurious sync
probably doesn't impact performance here and arm_smmu_write_ctx_desc() is
quite fiddly already.

Thanks,
Jean

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