[Xen-changelog] [xen staging] AMD/IOMMU: restrict feature logging

[patchbot@xxxxxxx]

commit 93ef224d63f9f04a0897d64981c619eb4816c0d3
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Tue Jul 2 13:27:39 2019 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Tue Jul 2 13:27:39 2019 +0200

    AMD/IOMMU: restrict feature logging
    
    The common case is all IOMMUs having the same features. Log them only
    for the first IOMMU, or for any that have a differing feature set.
    
    Requested-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
    Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    Acked-by: Brian Woods <brian.woods@xxxxxxx>
---
 xen/drivers/passthrough/amd/iommu_detect.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/xen/drivers/passthrough/amd/iommu_detect.c 
b/xen/drivers/passthrough/amd/iommu_detect.c
index 3c5d4de1a3..28282e47ac 100644
--- a/xen/drivers/passthrough/amd/iommu_detect.c
+++ b/xen/drivers/passthrough/amd/iommu_detect.c
@@ -62,6 +62,7 @@ void __init get_iommu_features(struct amd_iommu *iommu)
 {
     u32 low, high;
     int i = 0 ;
+    const struct amd_iommu *first;
     static const char *__initdata feature_str[] = {
         "- Prefetch Pages Command", 
         "- Peripheral Page Service Request", 
@@ -89,6 +90,11 @@ void __init get_iommu_features(struct amd_iommu *iommu)
 
     iommu->features = ((u64)high << 32) | low;
 
+    /* Don't log the same set of features over and over. */
+    first = list_first_entry(&amd_iommu_head, struct amd_iommu, list);
+    if ( iommu != first && iommu->features == first->features )
+        return;
+
     printk("AMD-Vi: IOMMU Extended Features:\n");
 
     while ( feature_str[i] )
--
generated by git-patchbot for /home/xen/git/xen.git#staging

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