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[PATCH v7 03/15] x86/mm: rewrite virt_to_xen_l*e



From: Wei Liu <wei.liu2@xxxxxxxxxx>

Rewrite those functions to use the new APIs. Modify its callers to unmap
the pointer returned. Since alloc_xen_pagetable_new() is almost never
useful unless accompanied by page clearing and a mapping, introduce a
helper alloc_map_clear_xen_pt() for this sequence.

Note that the change of virt_to_xen_l1e() also requires vmap_to_mfn() to
unmap the page, which requires domain_page.h header in vmap.

Signed-off-by: Wei Liu <wei.liu2@xxxxxxxxxx>
Signed-off-by: Hongyan Xia <hongyxia@xxxxxxxxxx>

---
Changed in v7:
- remove a comment.
- use l1e_get_mfn() instead of converting things back and forth.
- add alloc_map_clear_xen_pt().
- unmap before the next mapping to reduce mapcache pressure.
- use normal unmap calls instead of the macro in error paths because
  unmap can handle NULL now.
---
 xen/arch/x86/domain_page.c | 11 +++--
 xen/arch/x86/mm.c          | 96 +++++++++++++++++++++++++++-----------
 xen/common/vmap.c          |  1 +
 xen/include/asm-x86/mm.h   |  1 +
 xen/include/asm-x86/page.h |  8 +++-
 5 files changed, 86 insertions(+), 31 deletions(-)

diff --git a/xen/arch/x86/domain_page.c b/xen/arch/x86/domain_page.c
index b03728e18e..dc8627c1b5 100644
--- a/xen/arch/x86/domain_page.c
+++ b/xen/arch/x86/domain_page.c
@@ -333,21 +333,24 @@ void unmap_domain_page_global(const void *ptr)
 mfn_t domain_page_map_to_mfn(const void *ptr)
 {
     unsigned long va = (unsigned long)ptr;
-    const l1_pgentry_t *pl1e;
+    l1_pgentry_t l1e;
 
     if ( va >= DIRECTMAP_VIRT_START )
         return _mfn(virt_to_mfn(ptr));
 
     if ( va >= VMAP_VIRT_START && va < VMAP_VIRT_END )
     {
-        pl1e = virt_to_xen_l1e(va);
+        const l1_pgentry_t *pl1e = virt_to_xen_l1e(va);
+
         BUG_ON(!pl1e);
+        l1e = *pl1e;
+        unmap_domain_page(pl1e);
     }
     else
     {
         ASSERT(va >= MAPCACHE_VIRT_START && va < MAPCACHE_VIRT_END);
-        pl1e = &__linear_l1_table[l1_linear_offset(va)];
+        l1e = __linear_l1_table[l1_linear_offset(va)];
     }
 
-    return l1e_get_mfn(*pl1e);
+    return l1e_get_mfn(l1e);
 }
diff --git a/xen/arch/x86/mm.c b/xen/arch/x86/mm.c
index 462682ba70..b67ecf4107 100644
--- a/xen/arch/x86/mm.c
+++ b/xen/arch/x86/mm.c
@@ -4948,8 +4948,28 @@ void free_xen_pagetable_new(mfn_t mfn)
         free_xenheap_page(mfn_to_virt(mfn_x(mfn)));
 }
 
+void *alloc_map_clear_xen_pt(mfn_t *pmfn)
+{
+    mfn_t mfn = alloc_xen_pagetable_new();
+    void *ret;
+
+    if ( mfn_eq(mfn, INVALID_MFN) )
+        return NULL;
+
+    if ( pmfn )
+        *pmfn = mfn;
+    ret = map_domain_page(mfn);
+    clear_page(ret);
+
+    return ret;
+}
+
 static DEFINE_SPINLOCK(map_pgdir_lock);
 
+/*
+ * For virt_to_xen_lXe() functions, they take a virtual address and return a
+ * pointer to Xen's LX entry. Caller needs to unmap the pointer.
+ */
 static l3_pgentry_t *virt_to_xen_l3e(unsigned long v)
 {
     l4_pgentry_t *pl4e;
@@ -4958,33 +4978,33 @@ static l3_pgentry_t *virt_to_xen_l3e(unsigned long v)
     if ( !(l4e_get_flags(*pl4e) & _PAGE_PRESENT) )
     {
         bool locking = system_state > SYS_STATE_boot;
-        l3_pgentry_t *l3t = alloc_xen_pagetable();
+        mfn_t l3mfn;
+        l3_pgentry_t *l3t = alloc_map_clear_xen_pt(&l3mfn);
 
         if ( !l3t )
             return NULL;
-        clear_page(l3t);
+        UNMAP_DOMAIN_PAGE(l3t);
         if ( locking )
             spin_lock(&map_pgdir_lock);
         if ( !(l4e_get_flags(*pl4e) & _PAGE_PRESENT) )
         {
-            l4_pgentry_t l4e = l4e_from_paddr(__pa(l3t), __PAGE_HYPERVISOR);
+            l4_pgentry_t l4e = l4e_from_mfn(l3mfn, __PAGE_HYPERVISOR);
 
             l4e_write(pl4e, l4e);
             efi_update_l4_pgtable(l4_table_offset(v), l4e);
-            l3t = NULL;
+            l3mfn = INVALID_MFN;
         }
         if ( locking )
             spin_unlock(&map_pgdir_lock);
-        if ( l3t )
-            free_xen_pagetable(l3t);
+        free_xen_pagetable_new(l3mfn);
     }
 
-    return l4e_to_l3e(*pl4e) + l3_table_offset(v);
+    return map_l3t_from_l4e(*pl4e) + l3_table_offset(v);
 }
 
 static l2_pgentry_t *virt_to_xen_l2e(unsigned long v)
 {
-    l3_pgentry_t *pl3e;
+    l3_pgentry_t *pl3e, l3e;
 
     pl3e = virt_to_xen_l3e(v);
     if ( !pl3e )
@@ -4993,31 +5013,37 @@ static l2_pgentry_t *virt_to_xen_l2e(unsigned long v)
     if ( !(l3e_get_flags(*pl3e) & _PAGE_PRESENT) )
     {
         bool locking = system_state > SYS_STATE_boot;
-        l2_pgentry_t *l2t = alloc_xen_pagetable();
+        mfn_t l2mfn;
+        l2_pgentry_t *l2t = alloc_map_clear_xen_pt(&l2mfn);
 
         if ( !l2t )
+        {
+            unmap_domain_page(pl3e);
             return NULL;
-        clear_page(l2t);
+        }
+        UNMAP_DOMAIN_PAGE(l2t);
         if ( locking )
             spin_lock(&map_pgdir_lock);
         if ( !(l3e_get_flags(*pl3e) & _PAGE_PRESENT) )
         {
-            l3e_write(pl3e, l3e_from_paddr(__pa(l2t), __PAGE_HYPERVISOR));
-            l2t = NULL;
+            l3e_write(pl3e, l3e_from_mfn(l2mfn, __PAGE_HYPERVISOR));
+            l2mfn = INVALID_MFN;
         }
         if ( locking )
             spin_unlock(&map_pgdir_lock);
-        if ( l2t )
-            free_xen_pagetable(l2t);
+        free_xen_pagetable_new(l2mfn);
     }
 
     BUG_ON(l3e_get_flags(*pl3e) & _PAGE_PSE);
-    return l3e_to_l2e(*pl3e) + l2_table_offset(v);
+    l3e = *pl3e;
+    unmap_domain_page(pl3e);
+
+    return map_l2t_from_l3e(l3e) + l2_table_offset(v);
 }
 
 l1_pgentry_t *virt_to_xen_l1e(unsigned long v)
 {
-    l2_pgentry_t *pl2e;
+    l2_pgentry_t *pl2e, l2e;
 
     pl2e = virt_to_xen_l2e(v);
     if ( !pl2e )
@@ -5026,26 +5052,32 @@ l1_pgentry_t *virt_to_xen_l1e(unsigned long v)
     if ( !(l2e_get_flags(*pl2e) & _PAGE_PRESENT) )
     {
         bool locking = system_state > SYS_STATE_boot;
-        l1_pgentry_t *l1t = alloc_xen_pagetable();
+        mfn_t l1mfn;
+        l1_pgentry_t *l1t = alloc_map_clear_xen_pt(&l1mfn);
 
         if ( !l1t )
+        {
+            unmap_domain_page(pl2e);
             return NULL;
-        clear_page(l1t);
+        }
+        UNMAP_DOMAIN_PAGE(l1t);
         if ( locking )
             spin_lock(&map_pgdir_lock);
         if ( !(l2e_get_flags(*pl2e) & _PAGE_PRESENT) )
         {
-            l2e_write(pl2e, l2e_from_paddr(__pa(l1t), __PAGE_HYPERVISOR));
-            l1t = NULL;
+            l2e_write(pl2e, l2e_from_mfn(l1mfn, __PAGE_HYPERVISOR));
+            l1mfn = INVALID_MFN;
         }
         if ( locking )
             spin_unlock(&map_pgdir_lock);
-        if ( l1t )
-            free_xen_pagetable(l1t);
+        free_xen_pagetable_new(l1mfn);
     }
 
     BUG_ON(l2e_get_flags(*pl2e) & _PAGE_PSE);
-    return l2e_to_l1e(*pl2e) + l1_table_offset(v);
+    l2e = *pl2e;
+    unmap_domain_page(pl2e);
+
+    return map_l1t_from_l2e(l2e) + l1_table_offset(v);
 }
 
 /* Convert to from superpage-mapping flags for map_pages_to_xen(). */
@@ -5068,8 +5100,8 @@ int map_pages_to_xen(
     unsigned int flags)
 {
     bool locking = system_state > SYS_STATE_boot;
-    l3_pgentry_t *pl3e, ol3e;
-    l2_pgentry_t *pl2e, ol2e;
+    l3_pgentry_t *pl3e = NULL, ol3e;
+    l2_pgentry_t *pl2e = NULL, ol2e;
     l1_pgentry_t *pl1e, ol1e;
     unsigned int  i;
     int rc = -ENOMEM;
@@ -5090,6 +5122,10 @@ int map_pages_to_xen(
 
     while ( nr_mfns != 0 )
     {
+        /* Clean up mappings mapped in the previous iteration. */
+        UNMAP_DOMAIN_PAGE(pl3e);
+        UNMAP_DOMAIN_PAGE(pl2e);
+
         pl3e = virt_to_xen_l3e(virt);
 
         if ( !pl3e )
@@ -5258,6 +5294,8 @@ int map_pages_to_xen(
                 pl1e = virt_to_xen_l1e(virt);
                 if ( pl1e == NULL )
                     goto out;
+
+                UNMAP_DOMAIN_PAGE(pl1e);
             }
             else if ( l2e_get_flags(*pl2e) & _PAGE_PSE )
             {
@@ -5434,6 +5472,8 @@ int map_pages_to_xen(
     rc = 0;
 
  out:
+    unmap_domain_page(pl2e);
+    unmap_domain_page(pl3e);
     return rc;
 }
 
@@ -5457,7 +5497,7 @@ int populate_pt_range(unsigned long virt, unsigned long 
nr_mfns)
 int modify_xen_mappings(unsigned long s, unsigned long e, unsigned int nf)
 {
     bool locking = system_state > SYS_STATE_boot;
-    l3_pgentry_t *pl3e;
+    l3_pgentry_t *pl3e = NULL;
     l2_pgentry_t *pl2e;
     l1_pgentry_t *pl1e;
     unsigned int  i;
@@ -5473,6 +5513,9 @@ int modify_xen_mappings(unsigned long s, unsigned long e, 
unsigned int nf)
 
     while ( v < e )
     {
+        /* Clean up mappings mapped in the previous iteration. */
+        UNMAP_DOMAIN_PAGE(pl3e);
+
         pl3e = virt_to_xen_l3e(v);
 
         if ( !pl3e || !(l3e_get_flags(*pl3e) & _PAGE_PRESENT) )
@@ -5701,6 +5744,7 @@ int modify_xen_mappings(unsigned long s, unsigned long e, 
unsigned int nf)
     rc = 0;
 
  out:
+    unmap_domain_page(pl3e);
     return rc;
 }
 
diff --git a/xen/common/vmap.c b/xen/common/vmap.c
index faebc1ddf1..9964ab2096 100644
--- a/xen/common/vmap.c
+++ b/xen/common/vmap.c
@@ -1,6 +1,7 @@
 #ifdef VMAP_VIRT_START
 #include <xen/bitmap.h>
 #include <xen/cache.h>
+#include <xen/domain_page.h>
 #include <xen/init.h>
 #include <xen/mm.h>
 #include <xen/pfn.h>
diff --git a/xen/include/asm-x86/mm.h b/xen/include/asm-x86/mm.h
index 3d3f9d49ac..42d1a78731 100644
--- a/xen/include/asm-x86/mm.h
+++ b/xen/include/asm-x86/mm.h
@@ -587,6 +587,7 @@ void *alloc_xen_pagetable(void);
 void free_xen_pagetable(void *v);
 mfn_t alloc_xen_pagetable_new(void);
 void free_xen_pagetable_new(mfn_t mfn);
+void *alloc_map_clear_xen_pt(mfn_t *pmfn);
 
 l1_pgentry_t *virt_to_xen_l1e(unsigned long v);
 
diff --git a/xen/include/asm-x86/page.h b/xen/include/asm-x86/page.h
index 5acf3d3d5a..3854feb3ea 100644
--- a/xen/include/asm-x86/page.h
+++ b/xen/include/asm-x86/page.h
@@ -291,7 +291,13 @@ void copy_page_sse2(void *, const void *);
 #define pfn_to_paddr(pfn)   __pfn_to_paddr(pfn)
 #define paddr_to_pfn(pa)    __paddr_to_pfn(pa)
 #define paddr_to_pdx(pa)    pfn_to_pdx(paddr_to_pfn(pa))
-#define vmap_to_mfn(va)     _mfn(l1e_get_pfn(*virt_to_xen_l1e((unsigned 
long)(va))))
+
+#define vmap_to_mfn(va) ({                                                  \
+        const l1_pgentry_t *pl1e_ = virt_to_xen_l1e((unsigned long)(va));   \
+        mfn_t mfn_ = l1e_get_mfn(*pl1e_);                                   \
+        unmap_domain_page(pl1e_);                                           \
+        mfn_; })
+
 #define vmap_to_page(va)    mfn_to_page(vmap_to_mfn(va))
 
 #endif /* !defined(__ASSEMBLY__) */
-- 
2.24.1.AMZN




 


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