[Xen-devel] [RFC 3/3] xen/common: memory: Move steal_page in common code

[Julien Grall <julien.grall@xxxxxxxxxx>]

The implementation of steal_page for ARM and x86 would be the same.
Rather than duplicating the x86 function, move it in common code.

Also introduce missing define PRtype_info for ARM in order to compile
the code.

Signed-off-by: Julien Grall <julien.grall@xxxxxxxxxx>

---
Cc: Ian Campbell <ian.campbell@xxxxxxxxxx>
Cc: Stefano Stabellini <stefano.stabellini@xxxxxxxxxx>
Cc: Keir Fraser <keir@xxxxxxx>
Cc: Jan Beulich <jbeulich@xxxxxxxx>
Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>

    Note that this patch *shouldn't* be applied before the rest of the
    series. This is because the callers of this function are not fully fixed
    for ARM and could possibly introduce security issue. steal_page was
    always returning an error which lead the rest of the code to not be
    executed for ARM.

    TODO:
        - Check that all the callers of steal_page are properly working
        for ARM.
---
 xen/arch/arm/mm.c        |  6 ------
 xen/arch/x86/mm.c        | 51 ------------------------------------------------
 xen/common/page_alloc.c  | 51 ++++++++++++++++++++++++++++++++++++++++++++++++
 xen/include/asm-arm/mm.h |  4 ++--
 xen/include/asm-x86/mm.h |  2 --
 xen/include/xen/mm.h     |  3 +++
 6 files changed, 56 insertions(+), 61 deletions(-)

diff --git a/xen/arch/arm/mm.c b/xen/arch/arm/mm.c
index 47bfb27..b2e6682 100644
--- a/xen/arch/arm/mm.c
+++ b/xen/arch/arm/mm.c
@@ -989,12 +989,6 @@ int donate_page(struct domain *d, struct page_info *page, 
unsigned int memflags)
     return -ENOSYS;
 }
 
-int steal_page(
-    struct domain *d, struct page_info *page, unsigned int memflags)
-{
-    return -1;
-}
-
 int page_is_ram_type(unsigned long mfn, unsigned long mem_type)
 {
     ASSERT(0);
diff --git a/xen/arch/x86/mm.c b/xen/arch/x86/mm.c
index 92df36f..8508d9e 100644
--- a/xen/arch/x86/mm.c
+++ b/xen/arch/x86/mm.c
@@ -4253,57 +4253,6 @@ int donate_page(
     return -1;
 }
 
-int steal_page(
-    struct domain *d, struct page_info *page, unsigned int memflags)
-{
-    unsigned long x, y;
-    bool_t drop_dom_ref = 0;
-    const struct domain *owner = dom_xen;
-
-    spin_lock(&d->page_alloc_lock);
-
-    if ( is_xen_heap_page(page) || ((owner = page_get_owner(page)) != d) )
-        goto fail;
-
-    /*
-     * We require there is just one reference (PGC_allocated). We temporarily
-     * drop this reference now so that we can safely swizzle the owner.
-     */
-    y = page->count_info;
-    do {
-        x = y;
-        if ( (x & (PGC_count_mask|PGC_allocated)) != (1 | PGC_allocated) )
-            goto fail;
-        y = cmpxchg(&page->count_info, x, x & ~PGC_count_mask);
-    } while ( y != x );
-
-    /* Swizzle the owner then reinstate the PGC_allocated reference. */
-    page_set_owner(page, NULL);
-    y = page->count_info;
-    do {
-        x = y;
-        BUG_ON((x & (PGC_count_mask|PGC_allocated)) != PGC_allocated);
-    } while ( (y = cmpxchg(&page->count_info, x, x | 1)) != x );
-
-    /* Unlink from original owner. */
-    if ( !(memflags & MEMF_no_refcount) && !domain_adjust_tot_pages(d, -1) )
-        drop_dom_ref = 1;
-    page_list_del(page, &d->page_list);
-
-    spin_unlock(&d->page_alloc_lock);
-    if ( unlikely(drop_dom_ref) )
-        put_domain(d);
-    return 0;
-
- fail:
-    spin_unlock(&d->page_alloc_lock);
-    MEM_LOG("Bad page %lx: ed=%d sd=%d caf=%08lx taf=%" PRtype_info,
-            page_to_mfn(page), d->domain_id,
-            owner ? owner->domain_id : DOMID_INVALID,
-            page->count_info, page->u.inuse.type_info);
-    return -1;
-}
-
 static int __do_update_va_mapping(
     unsigned long va, u64 val64, unsigned long flags, struct domain *pg_owner)
 {
diff --git a/xen/common/page_alloc.c b/xen/common/page_alloc.c
index 624a266..7c9d66e 100644
--- a/xen/common/page_alloc.c
+++ b/xen/common/page_alloc.c
@@ -1786,6 +1786,57 @@ int assign_pages(
     return -1;
 }
 
+int steal_page(
+    struct domain *d, struct page_info *page, unsigned int memflags)
+{
+    unsigned long x, y;
+    bool_t drop_dom_ref = 0;
+    const struct domain *owner = dom_xen;
+
+    spin_lock(&d->page_alloc_lock);
+
+    if ( is_xen_heap_page(page) || ((owner = page_get_owner(page)) != d) )
+        goto fail;
+
+    /*
+     * We require there is just one reference (PGC_allocated). We temporarily
+     * drop this reference now so that we can safely swizzle the owner.
+     */
+    y = page->count_info;
+    do {
+        x = y;
+        if ( (x & (PGC_count_mask|PGC_allocated)) != (1 | PGC_allocated) )
+            goto fail;
+        y = cmpxchg(&page->count_info, x, x & ~PGC_count_mask);
+    } while ( y != x );
+
+    /* Swizzle the owner then reinstate the PGC_allocated reference. */
+    page_set_owner(page, NULL);
+    y = page->count_info;
+    do {
+        x = y;
+        BUG_ON((x & (PGC_count_mask|PGC_allocated)) != PGC_allocated);
+    } while ( (y = cmpxchg(&page->count_info, x, x | 1)) != x );
+
+    /* Unlink from original owner. */
+    if ( !(memflags & MEMF_no_refcount) && !domain_adjust_tot_pages(d, -1) )
+        drop_dom_ref = 1;
+    page_list_del(page, &d->page_list);
+
+    spin_unlock(&d->page_alloc_lock);
+    if ( unlikely(drop_dom_ref) )
+        put_domain(d);
+    return 0;
+
+ fail:
+    spin_unlock(&d->page_alloc_lock);
+    gdprintk(XENLOG_WARNING,
+             "Bad page %lx: ed=%d sd=%d caf=%08lx taf=%" PRtype_info,
+             page_to_mfn(page), d->domain_id,
+             owner ? owner->domain_id : DOMID_INVALID,
+             page->count_info, page->u.inuse.type_info);
+    return -1;
+}
 
 struct page_info *alloc_domheap_pages(
     struct domain *d, unsigned int order, unsigned int memflags)
diff --git a/xen/include/asm-arm/mm.h b/xen/include/asm-arm/mm.h
index 2e9d0b2..d212d39 100644
--- a/xen/include/asm-arm/mm.h
+++ b/xen/include/asm-arm/mm.h
@@ -73,6 +73,8 @@ struct page_info
     u64 pad;
 };
 
+#define PRtype_info "016lx"/* should only be used for printk's */
+
 #define PG_shift(idx)   (BITS_PER_LONG - (idx))
 #define PG_mask(x, idx) (x ## UL << PG_shift(idx))
 
@@ -319,8 +321,6 @@ static inline int relinquish_shared_pages(struct domain *d)
 /* Arch-specific portion of memory_op hypercall. */
 long arch_memory_op(int op, XEN_GUEST_HANDLE_PARAM(void) arg);
 
-int steal_page(
-    struct domain *d, struct page_info *page, unsigned int memflags);
 int donate_page(
     struct domain *d, struct page_info *page, unsigned int memflags);
 
diff --git a/xen/include/asm-x86/mm.h b/xen/include/asm-x86/mm.h
index 67b34c6..769552e 100644
--- a/xen/include/asm-x86/mm.h
+++ b/xen/include/asm-x86/mm.h
@@ -531,8 +531,6 @@ long subarch_memory_op(unsigned long cmd, 
XEN_GUEST_HANDLE_PARAM(void) arg);
 int compat_arch_memory_op(unsigned long cmd, XEN_GUEST_HANDLE_PARAM(void));
 int compat_subarch_memory_op(int op, XEN_GUEST_HANDLE_PARAM(void));
 
-int steal_page(
-    struct domain *d, struct page_info *page, unsigned int memflags);
 int donate_page(
     struct domain *d, struct page_info *page, unsigned int memflags);
 
diff --git a/xen/include/xen/mm.h b/xen/include/xen/mm.h
index 5d4b64b..4fafd88 100644
--- a/xen/include/xen/mm.h
+++ b/xen/include/xen/mm.h
@@ -139,6 +139,9 @@ int assign_pages(
     unsigned int order,
     unsigned int memflags);
 
+int steal_page(
+    struct domain *d, struct page_info *page, unsigned int memflags);
+
 /* Dump info to serial console */
 void arch_dump_shared_mem_info(void);
 
-- 
2.1.4


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