[Xen-devel] [PATCH for-next 03/16] xen/arm: Extend copy_to_guest to support copying from guest VA and use it

[Julien Grall <julien.grall@xxxxxxxxxx>]

The only differences between copy_to_guest (formerly called
raw_copy_to_guest_helper) and raw_copy_from_guest is:
    - The direction of the memcpy
    - The permission use for translating the address

Extend copy_to_guest to support copying from guest VA by adding using a
bit in the flags to tell the direction of the copy.

Lastly, reimplement raw_copy_from_guest using copy_to_guest.

Signed-off-by: Julien Grall <julien.grall@xxxxxxxxxx>
---
 xen/arch/arm/guestcopy.c | 46 +++++++++++++---------------------------------
 1 file changed, 13 insertions(+), 33 deletions(-)

diff --git a/xen/arch/arm/guestcopy.c b/xen/arch/arm/guestcopy.c
index d1cfbe922c..1ffa717ca6 100644
--- a/xen/arch/arm/guestcopy.c
+++ b/xen/arch/arm/guestcopy.c
@@ -6,6 +6,8 @@
 #include <asm/guest_access.h>
 
 #define COPY_flush_dcache   (1U << 0)
+#define COPY_from_guest     (0U << 1)
+#define COPY_to_guest       (1U << 1)
 
 static unsigned long copy_guest(void *buf, paddr_t addr, unsigned int len,
                                 unsigned int flags)
@@ -19,13 +21,18 @@ static unsigned long copy_guest(void *buf, paddr_t addr, 
unsigned int len,
         unsigned size = min(len, (unsigned)PAGE_SIZE - offset);
         struct page_info *page;
 
-        page = get_page_from_gva(current, addr, GV2M_WRITE);
+        page = get_page_from_gva(current, addr,
+                                 (flags & COPY_to_guest) ? GV2M_WRITE : 
GV2M_READ);
         if ( page == NULL )
             return len;
 
         p = __map_domain_page(page);
         p += offset;
-        memcpy(p, buf, size);
+        if ( flags & COPY_to_guest )
+            memcpy(p, buf, size);
+        else
+            memcpy(buf, p, size);
+
         if ( flags & COPY_flush_dcache )
             clean_dcache_va_range(p, size);
 
@@ -46,13 +53,14 @@ static unsigned long copy_guest(void *buf, paddr_t addr, 
unsigned int len,
 
 unsigned long raw_copy_to_guest(void *to, const void *from, unsigned len)
 {
-    return copy_guest((void *)from, (unsigned long)to, len, 0);
+    return copy_guest((void *)from, (unsigned long)to, len, COPY_to_guest);
 }
 
 unsigned long raw_copy_to_guest_flush_dcache(void *to, const void *from,
                                              unsigned len)
 {
-    return copy_guest((void *)from, (unsigned long)to, len, COPY_flush_dcache);
+    return copy_guest((void *)from, (unsigned long)to, len,
+                      COPY_to_guest | COPY_flush_dcache);
 }
 
 unsigned long raw_clear_guest(void *to, unsigned len)
@@ -90,35 +98,7 @@ unsigned long raw_clear_guest(void *to, unsigned len)
 
 unsigned long raw_copy_from_guest(void *to, const void __user *from, unsigned 
len)
 {
-    unsigned offset = (vaddr_t)from & ~PAGE_MASK;
-
-    while ( len )
-    {
-        void *p;
-        unsigned size = min(len, (unsigned)(PAGE_SIZE - offset));
-        struct page_info *page;
-
-        page = get_page_from_gva(current, (vaddr_t) from, GV2M_READ);
-        if ( page == NULL )
-            return len;
-
-        p = __map_domain_page(page);
-        p += ((vaddr_t)from & (~PAGE_MASK));
-
-        memcpy(to, p, size);
-
-        unmap_domain_page(p);
-        put_page(page);
-        len -= size;
-        from += size;
-        to += size;
-        /*
-         * After the first iteration, guest virtual address is correctly
-         * aligned to PAGE_SIZE.
-         */
-        offset = 0;
-    }
-    return 0;
+    return copy_guest(to, (unsigned long)from, len, COPY_from_guest);
 }
 
 /*
-- 
2.11.0


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