[Xen-devel] [PATCH v6 15/36] ARM: introduce vgic_access_guest_memory()

[Andre Przywara <andre.przywara@xxxxxxx>]

This function allows to copy a chunk of data from and to guest physical
memory. It looks up the associated page from the guest's p2m tree
and maps this page temporarily for the time of the access.
This function was originally written by Vijaya as part of an earlier series:
https://patchwork.kernel.org/patch/8177251

Signed-off-by: Vijaya Kumar K <Vijaya.Kumar@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Andre Przywara <andre.przywara@xxxxxxx>
---
 xen/arch/arm/vgic.c        | 47 ++++++++++++++++++++++++++++++++++++++++++++++
 xen/include/asm-arm/vgic.h |  3 +++
 2 files changed, 50 insertions(+)

diff --git a/xen/arch/arm/vgic.c b/xen/arch/arm/vgic.c
index e6c97b2..5c68fe7 100644
--- a/xen/arch/arm/vgic.c
+++ b/xen/arch/arm/vgic.c
@@ -20,6 +20,7 @@
 #include <xen/bitops.h>
 #include <xen/lib.h>
 #include <xen/init.h>
+#include <xen/domain_page.h>
 #include <xen/softirq.h>
 #include <xen/irq.h>
 #include <xen/sched.h>
@@ -598,6 +599,52 @@ void vgic_free_virq(struct domain *d, unsigned int virq)
 }
 
 /*
+ * Temporarily map one physical guest page and copy data to or from it.
+ * The data to be copied cannot cross a page boundary.
+ */
+int vgic_access_guest_memory(struct domain *d, paddr_t gpa, void *buf,
+                             uint32_t size, bool_t is_write)
+{
+    struct page_info *page;
+    uint64_t offset;
+    p2m_type_t p2mt;
+    void *p;
+
+    page = get_page_from_gfn(d, paddr_to_pfn(gpa), &p2mt, P2M_ALLOC);
+    if ( !page )
+    {
+        printk(XENLOG_G_ERR "d%d: vITS: Failed to get table entry\n",
+               d->domain_id);
+        return -EINVAL;
+    }
+
+    if ( !p2m_is_ram(p2mt) )
+    {
+        put_page(page);
+        printk(XENLOG_G_ERR "d%d: vITS: memory used by the ITS should be RAM.",
+               d->domain_id);
+        return -EINVAL;
+    }
+
+    p = __map_domain_page(page);
+    /* Offset within the mapped page */
+    offset = gpa & ~PAGE_MASK;
+    /* Do not cross a page boundary. */
+    if ( size > (PAGE_SIZE - offset) )
+        size = PAGE_SIZE - offset;
+
+    if ( is_write )
+        memcpy(p + offset, buf, size);
+    else
+        memcpy(buf, p + offset, size);
+
+    unmap_domain_page(p);
+    put_page(page);
+
+    return 0;
+}
+
+/*
  * Local variables:
  * mode: C
  * c-file-style: "BSD"
diff --git a/xen/include/asm-arm/vgic.h b/xen/include/asm-arm/vgic.h
index 52856ca..967c2be 100644
--- a/xen/include/asm-arm/vgic.h
+++ b/xen/include/asm-arm/vgic.h
@@ -319,6 +319,9 @@ extern void register_vgic_ops(struct domain *d, const 
struct vgic_ops *ops);
 int vgic_v2_init(struct domain *d, int *mmio_count);
 int vgic_v3_init(struct domain *d, int *mmio_count);
 
+int vgic_access_guest_memory(struct domain *d, paddr_t gpa, void *buf,
+                             uint32_t size, bool_t is_write);
+
 extern int domain_vgic_register(struct domain *d, int *mmio_count);
 extern int vcpu_vgic_free(struct vcpu *v);
 extern bool vgic_to_sgi(struct vcpu *v, register_t sgir,
-- 
2.9.0


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