[Xen-devel] [PATCH v2 3/4] amd-iommu: disable iommu_hap_pt_share with AMD IOMMUs

[Roger Pau Monne <roger.pau@xxxxxxxxxx>]

According to the comment in p2m.h, AMD IOMMUs don't work correctly
with page types different than p2m_ram_rw when the p2m is shared
between HAP and IOMMU, so disable this sharing when using AMD IOMMUs.

Signed-off-by: Roger Pau Monnà <roger.pau@xxxxxxxxxx>
Cc: Suravee Suthikulpanit <suravee.suthikulpanit@xxxxxxx>
Cc: Xiantao Zhang <xiantao.zhang@xxxxxxxxx>
Cc: Jan Beulich <jbeulich@xxxxxxxx>
---
I have not tested this patch on AMD hardware, so I would like some
confirmation that this actually works.
---
Changes since v1:
 - Add a debug message when disabling iommu_hap_pt_share.
---
 xen/drivers/passthrough/amd/iommu_init.c |    8 ++++++++
 1 files changed, 8 insertions(+), 0 deletions(-)

diff --git a/xen/drivers/passthrough/amd/iommu_init.c 
b/xen/drivers/passthrough/amd/iommu_init.c
index 4686813..a717601 100644
--- a/xen/drivers/passthrough/amd/iommu_init.c
+++ b/xen/drivers/passthrough/amd/iommu_init.c
@@ -1255,6 +1255,14 @@ int __init amd_iommu_init(void)
     if ( iterate_ivrs_mappings(amd_iommu_setup_device_table) != 0 )
         goto error_out;
 
+    /*
+     * Disable sharing HAP page tables with AMD IOMMU,
+     * since it only supports p2m_ram_rw, and this would
+     * prevent doing IO to/from mapped grant frames.
+     */
+    iommu_hap_pt_share = 0;
+    printk(XENLOG_DEBUG "AMD-Vi: Disabled HAP memory map sharing with 
IOMMU\n");
+
     /* per iommu initialization  */
     for_each_amd_iommu ( iommu )
         if ( amd_iommu_init_one(iommu) != 0 )
-- 
1.7.7.5 (Apple Git-26)


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