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[PATCH v2 4/6] VT-d: restrict iommu_flush_all() to cache writeback


  • To: "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>
  • From: Jan Beulich <jbeulich@xxxxxxxx>
  • Date: Wed, 3 May 2023 11:46:11 +0200
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  • Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>, Kevin Tian <kevin.tian@xxxxxxxxx>
  • Delivery-date: Wed, 03 May 2023 09:46:24 +0000
  • List-id: Xen developer discussion <xen-devel.lists.xenproject.org>

We don't need to invalidate caches here; all we're after is that earlier
writes have made it to main memory (and aiui even that just in case).

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
---
This, aiui, being an analogue to uses of iommu_sync_cache() (just not
range restricted), I wonder whether it shouldn't be conditional upon
iommu_non_coherent. Then again I'm vaguely under the impression that
we had been here before, possibly even as far as questioning the need
for this call altogether.
---
v2: FLUSH_WRITEBACK -> FLUSH_CACHE_WRITEBACK.

--- a/xen/drivers/passthrough/vtd/iommu.c
+++ b/xen/drivers/passthrough/vtd/iommu.c
@@ -693,7 +693,7 @@ static int __must_check iommu_flush_all(
     bool_t flush_dev_iotlb;
     int rc = 0;
 
-    flush_local(FLUSH_CACHE);
+    flush_local(FLUSH_CACHE_WRITEBACK);
 
     for_each_drhd_unit ( drhd )
     {




 


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