[PATCH v4 4/4] xen: expose that grant table mappings update the IOMMU

[Roger Pau Monne <roger.pau@citrix.com>]

Add a new CPUID flag for leaf 4 that indicates that grant/foreign
mappings update the IOMMU accordingly.

Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Cc: Tim Deegan <tim@xen.org>
Cc: Jan Beulich <jbeulich@suse.com>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
---
 xen/arch/x86/hvm/hvm.c              |   10 ++++++++++
 xen/include/public/arch-x86/cpuid.h |    2 ++
 2 files changed, 12 insertions(+), 0 deletions(-)

diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
index 4f993f4..f4de00d 100644
--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -67,6 +67,7 @@
 #include <asm/mem_access.h>
 #include <public/mem_event.h>
 #include <xen/rangeset.h>
+#include <public/arch-x86/cpuid.h>
 
 bool_t __read_mostly hvm_enabled;
 
@@ -4074,6 +4075,15 @@ void hvm_hypervisor_cpuid_leaf(uint32_t sub_idx,
     *eax = *ebx = *ecx = *edx = 0;
     if ( hvm_funcs.hypervisor_cpuid_leaf )
         hvm_funcs.hypervisor_cpuid_leaf(sub_idx, eax, ebx, ecx, edx);
+
+    if ( sub_idx == 0 )
+    {
+        /*
+         * Indicate that memory mapped from other domains (either grants or
+         * foreign pages) has valid IOMMU entries.
+         */
+        *eax |= XEN_HVM_CPUID_IOMMU_MAPPINGS;
+    }
 }
 
 void hvm_cpuid(unsigned int input, unsigned int *eax, unsigned int *ebx,
diff --git a/xen/include/public/arch-x86/cpuid.h b/xen/include/public/arch-x86/cpuid.h
index 7135d54..e57a457 100644
--- a/xen/include/public/arch-x86/cpuid.h
+++ b/xen/include/public/arch-x86/cpuid.h
@@ -73,6 +73,8 @@
 /* EAX Features */
 #define XEN_HVM_CPUID_APIC_ACCESS_VIRT (1u << 0) /* Virtualized APIC registers */
 #define XEN_HVM_CPUID_X2APIC_VIRT      (1u << 1) /* Virtualized x2APIC accesses */
+/* Memory mapped from other domains has valid IOMMU entries */
+#define XEN_HVM_CPUID_IOMMU_MAPPINGS   (1u << 2)
 
 #define XEN_CPUID_MAX_NUM_LEAVES 4
 
-- 
1.7.7.5 (Apple Git-26)


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