[Xen-devel] [PATCH RFC 3/4] x86/vtd: introduce a PVH implementation of iommu_inclusive_mapping

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

On certain Intel systems, as far as I can tell almost all pre-Haswell ones,
trying to boot a PVH Dom0 will freeze the box completely, up to the point that
not even the watchdog works. The freeze happens exactly when enabling the DMA
remapping in the IOMMU, the last line seen is:

(XEN) [VT-D]iommu_enable_translation: iommu->reg = ffff82c00021b000

In order to workaround this (which seems to be a lack of proper RMRR entries,
plus the IOMMU being unable to generate faults and freezing the entire system)
add a PVH specific implementation of iommu_inclusive_mapping, that maps
non-RAM, non-unusable regions into Dom0 p2m. Note that care is taken to not map
device MMIO regions that Xen is emulating, like the local APIC or the IO APIC.

Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
---
Cc: Kevin Tian <kevin.tian@xxxxxxxxx>
---
 xen/drivers/passthrough/vtd/extern.h  |  1 +
 xen/drivers/passthrough/vtd/iommu.c   |  2 ++
 xen/drivers/passthrough/vtd/x86/vtd.c | 39 +++++++++++++++++++++++++++++++++++
 3 files changed, 42 insertions(+)

diff --git a/xen/drivers/passthrough/vtd/extern.h 
b/xen/drivers/passthrough/vtd/extern.h
index fb7edfaef9..0eaf8956ff 100644
--- a/xen/drivers/passthrough/vtd/extern.h
+++ b/xen/drivers/passthrough/vtd/extern.h
@@ -100,5 +100,6 @@ bool_t platform_supports_intremap(void);
 bool_t platform_supports_x2apic(void);
 
 void vtd_set_hwdom_mapping(struct domain *d);
+void vtd_set_pvh_hwdom_mapping(struct domain *d);
 
 #endif // _VTD_EXTERN_H_
diff --git a/xen/drivers/passthrough/vtd/iommu.c 
b/xen/drivers/passthrough/vtd/iommu.c
index a5c61c6e21..6bbf319100 100644
--- a/xen/drivers/passthrough/vtd/iommu.c
+++ b/xen/drivers/passthrough/vtd/iommu.c
@@ -1293,6 +1293,8 @@ static void __hwdom_init intel_iommu_hwdom_init(struct 
domain *d)
         /* Set up 1:1 page table for hardware domain. */
         vtd_set_hwdom_mapping(d);
     }
+    else if ( is_hvm_domain(d) )
+        vtd_set_pvh_hwdom_mapping(d);
 
     setup_hwdom_pci_devices(d, setup_hwdom_device);
     setup_hwdom_rmrr(d);
diff --git a/xen/drivers/passthrough/vtd/x86/vtd.c 
b/xen/drivers/passthrough/vtd/x86/vtd.c
index 88a60b3307..79c9b0526f 100644
--- a/xen/drivers/passthrough/vtd/x86/vtd.c
+++ b/xen/drivers/passthrough/vtd/x86/vtd.c
@@ -21,10 +21,12 @@
 #include <xen/softirq.h>
 #include <xen/domain_page.h>
 #include <asm/paging.h>
+#include <xen/iocap.h>
 #include <xen/iommu.h>
 #include <xen/irq.h>
 #include <xen/numa.h>
 #include <asm/fixmap.h>
+#include <asm/p2m.h>
 #include <asm/setup.h>
 #include "../iommu.h"
 #include "../dmar.h"
@@ -159,3 +161,40 @@ void __hwdom_init vtd_set_hwdom_mapping(struct domain *d)
     }
 }
 
+void __hwdom_init vtd_set_pvh_hwdom_mapping(struct domain *d)
+{
+    unsigned long pfn;
+
+    BUG_ON(!is_hardware_domain(d));
+
+    if ( !iommu_inclusive_mapping )
+        return;
+
+    /* NB: the low 1MB is already mapped in pvh_setup_p2m. */
+    for ( pfn = PFN_DOWN(MB(1)); pfn < PFN_DOWN(GB(4)); pfn++ )
+    {
+        p2m_access_t a;
+        int rc;
+
+        if ( !(pfn & 0xfff) )
+            process_pending_softirqs();
+
+        /* Skip RAM, ACPI and unusable regions. */
+        if ( page_is_ram_type(pfn, RAM_TYPE_CONVENTIONAL) ||
+             page_is_ram_type(pfn, RAM_TYPE_UNUSABLE) ||
+             page_is_ram_type(pfn, RAM_TYPE_ACPI) ||
+             !iomem_access_permitted(d, pfn, pfn) )
+            continue;
+
+        ASSERT(!xen_in_range(pfn));
+
+        a = rangeset_contains_range(mmio_ro_ranges, pfn, pfn) ? p2m_access_r
+                                                              : p2m_access_rw;
+        rc = set_identity_p2m_entry(d, pfn, a, 0);
+        if ( rc )
+           printk(XENLOG_WARNING VTDPREFIX
+                  " d%d: IOMMU mapping failed pfn %#lx: %d\n",
+                  d->domain_id, pfn, rc);
+    }
+}
+
-- 
2.11.0 (Apple Git-81)


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