diff mbox series

[v3,1/4] x86/shim: map and unmap page tables in replace_va_mapping

Message ID 37ad7487bc6e6f76e2082c0b42b4cf819007f513.1586951696.git.hongyxia@amazon.com (mailing list archive)
State Superseded
Headers show
Series use new API for Xen page tables | expand

Commit Message

Hongyan Xia April 15, 2020, 11:59 a.m. UTC 
From: Wei Liu <wei.liu2@citrix.com>

Also, introduce lYe_from_lXe() macros which do not rely on the direct
map when walking page tables. Unfortunately, they cannot be inline
functions due to the header dependency on domain_page.h, so keep them as
macros just like map_lYt_from_lXe().

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

---
Changed in v3:
- use unmap_domain_page() instead of the macro in several places.
- also introduce l1e_from_l2e().
- add _ prefix in macros to avoid aliasing.

Changed in v2:
- instead of map, map, map, read/write, unmap, unmap, unmap, do map,
  read PTE, unmap for each level instead.
- use lYe_from_lXe() macros and lift them from a later patch to this
  patch.
- const qualify pointers in new macros.
---
 xen/arch/x86/pv/shim.c     |  9 +++++----
 xen/include/asm-x86/page.h | 19 +++++++++++++++++++
 2 files changed, 24 insertions(+), 4 deletions(-)

Comments

Jan Beulich April 15, 2020, 2:03 p.m. UTC | #1 
On 15.04.2020 13:59, Hongyan Xia wrote:
> From: Wei Liu <wei.liu2@citrix.com>
> 
> Also, introduce lYe_from_lXe() macros which do not rely on the direct
> map when walking page tables. Unfortunately, they cannot be inline
> functions due to the header dependency on domain_page.h, so keep them as
> macros just like map_lYt_from_lXe().
> 
> Signed-off-by: Wei Liu <wei.liu2@citrix.com>
> Signed-off-by: Hongyan Xia <hongyxia@amazon.com>
> 
> ---
> Changed in v3:
> - use unmap_domain_page() instead of the macro in several places.
> - also introduce l1e_from_l2e().
> - add _ prefix in macros to avoid aliasing.

Why prefixes, violating name space rules? In my reply to v2
requesting the adjustment I specifically said "suffixes".

Jan
diff mbox series

Patch

diff --git a/xen/arch/x86/pv/shim.c b/xen/arch/x86/pv/shim.c
index ed2ece8a8a..31264582cc 100644
--- a/xen/arch/x86/pv/shim.c
+++ b/xen/arch/x86/pv/shim.c
@@ -168,16 +168,17 @@  const struct platform_bad_page *__init pv_shim_reserved_pages(unsigned int *size
 static void __init replace_va_mapping(struct domain *d, l4_pgentry_t *l4start,
                                       unsigned long va, mfn_t mfn)
 {
-    l4_pgentry_t *pl4e = l4start + l4_table_offset(va);
-    l3_pgentry_t *pl3e = l4e_to_l3e(*pl4e) + l3_table_offset(va);
-    l2_pgentry_t *pl2e = l3e_to_l2e(*pl3e) + l2_table_offset(va);
-    l1_pgentry_t *pl1e = l2e_to_l1e(*pl2e) + l1_table_offset(va);
+    l4_pgentry_t l4e = l4start[l4_table_offset(va)];
+    l3_pgentry_t l3e = l3e_from_l4e(l4e, l3_table_offset(va));
+    l2_pgentry_t l2e = l2e_from_l3e(l3e, l2_table_offset(va));
+    l1_pgentry_t *pl1e = map_l1t_from_l2e(l2e) + l1_table_offset(va);
     struct page_info *page = mfn_to_page(l1e_get_mfn(*pl1e));
 
     put_page_and_type(page);
 
     *pl1e = l1e_from_mfn(mfn, (!is_pv_32bit_domain(d) ? L1_PROT
                                                       : COMPAT_L1_PROT));
+    unmap_domain_page(pl1e);
 }
 
 static void evtchn_reserve(struct domain *d, unsigned int port)
diff --git a/xen/include/asm-x86/page.h b/xen/include/asm-x86/page.h
index eb73a0fc23..d50989a357 100644
--- a/xen/include/asm-x86/page.h
+++ b/xen/include/asm-x86/page.h
@@ -197,6 +197,25 @@  static inline l4_pgentry_t l4e_from_paddr(paddr_t pa, unsigned int flags)
 #define map_l2t_from_l3e(x)        (l2_pgentry_t *)map_domain_page(l3e_get_mfn(x))
 #define map_l3t_from_l4e(x)        (l3_pgentry_t *)map_domain_page(l4e_get_mfn(x))
 
+/* Unlike lYe_to_lXe(), lXe_from_lYe() do not rely on the direct map. */
+#define l1e_from_l2e(_l2e, _offset) ({                      \
+        const l1_pgentry_t *_l1t = map_l1t_from_l2e(_l2e);  \
+        l1_pgentry_t _l1e = _l1t[_offset];                  \
+        unmap_domain_page(_l1t);                            \
+        _l1e; })
+
+#define l2e_from_l3e(_l3e, _offset) ({                      \
+        const l2_pgentry_t *_l2t = map_l2t_from_l3e(_l3e);  \
+        l2_pgentry_t _l2e = _l2t[_offset];                  \
+        unmap_domain_page(_l2t);                            \
+        _l2e; })
+
+#define l3e_from_l4e(_l4e, _offset) ({                      \
+        const l3_pgentry_t *_l3t = map_l3t_from_l4e(_l4e);  \
+        l3_pgentry_t _l3e = _l3t[_offset];                  \
+        unmap_domain_page(_l3t);                            \
+        _l3e; })
+
 /* Given a virtual address, get an entry offset into a page table. */
 #define l1_table_offset(a)         \
     (((a) >> L1_PAGETABLE_SHIFT) & (L1_PAGETABLE_ENTRIES - 1))