Re: [Xen-devel] [for-4.8][PATCH v2 22/23] xen/arm: p2m: Do not handle shattering in p2m_create_table

[Julien Grall]

Hi,

On 15/09/2016 12:28, Julien Grall wrote:

The helper p2m_create_table is only called to create a brand new table.

Signed-off-by: Julien Grall 
Reviewd-by: Stefano Stabellini 


I made 2 typoes here. It should be:

Reviewed-by: Stefano Stabellini 

Regards,

--
Julien Grall

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[Xen-devel] [for-4.8][PATCH v2 22/23] xen/arm: p2m: Do not handle shattering in p2m_create_table

[Julien Grall]

The helper p2m_create_table is only called to create a brand new table.

Signed-off-by: Julien Grall 
Reviewd-by: Stefano Stabellini 

---
Changes in v2:
- Add Stefano's reviewed-by
---
 xen/arch/arm/p2m.c | 56 ++
 1 file changed, 6 insertions(+), 50 deletions(-)

diff --git a/xen/arch/arm/p2m.c b/xen/arch/arm/p2m.c
index aa740c2..c1dac09 100644
--- a/xen/arch/arm/p2m.c
+++ b/xen/arch/arm/p2m.c
@@ -278,8 +278,7 @@ static p2m_access_t p2m_mem_access_radix_get(struct 
p2m_domain *p2m, gfn_t gfn)
 #define GUEST_TABLE_SUPER_PAGE 1
 #define GUEST_TABLE_NORMAL_PAGE 2
 
-static int p2m_create_table(struct p2m_domain *p2m, lpae_t *entry,
-int level_shift);
+static int p2m_create_table(struct p2m_domain *p2m, lpae_t *entry);
 
 /*
  * Take the currently mapped table, find the corresponding GFN entry,
@@ -310,7 +309,7 @@ static int p2m_next_level(struct p2m_domain *p2m, bool 
read_only,
 if ( read_only )
 return GUEST_TABLE_MAP_FAILED;
 
-ret = p2m_create_table(p2m, entry, /* not used */ ~0);
+ret = p2m_create_table(p2m, entry);
 if ( ret )
 return GUEST_TABLE_MAP_FAILED;
 }
@@ -575,25 +574,14 @@ static inline void p2m_remove_pte(lpae_t *p, bool 
clean_pte)
 p2m_write_pte(p, pte, clean_pte);
 }
 
-/*
- * Allocate a new page table page and hook it in via the given entry.
- * apply_one_level relies on this returning 0 on success
- * and -ve on failure.
- *
- * If the existing entry is present then it must be a mapping and not
- * a table and it will be shattered into the next level down.
- *
- * level_shift is the number of bits at the level we want to create.
- */
-static int p2m_create_table(struct p2m_domain *p2m, lpae_t *entry,
-int level_shift)
+/* Allocate a new page table page and hook it in via the given entry. */
+static int p2m_create_table(struct p2m_domain *p2m, lpae_t *entry)
 {
 struct page_info *page;
 lpae_t *p;
 lpae_t pte;
-int splitting = p2m_valid(*entry);
 
-BUG_ON(p2m_table(*entry));
+ASSERT(!p2m_valid(*entry));
 
 page = alloc_domheap_page(NULL, 0);
 if ( page == NULL )
@@ -602,39 +590,7 @@ static int p2m_create_table(struct p2m_domain *p2m, lpae_t 
*entry,
 page_list_add(page, >pages);
 
 p = __map_domain_page(page);
-if ( splitting )
-{
-mfn_t mfn = _mfn(entry->p2m.base);
-int i;
-
-/*
- * We are either splitting a first level 1G page into 512 second level
- * 2M pages, or a second level 2M page into 512 third level 4K pages.
- */
- for ( i=0 ; i < LPAE_ENTRIES; i++ )
- {
- /*
-  * Use the content of the superpage entry and override
-  * the necessary fields. So the correct permissions are
-  * kept.
-  */
- pte = *entry;
- pte.p2m.base = mfn_x(mfn_add(mfn,
-  i << (level_shift - LPAE_SHIFT)));
-
- /*
-  * First and second level super pages set p2m.table = 0, but
-  * third level entries set table = 1.
-  */
- pte.p2m.table = !(level_shift - LPAE_SHIFT);
-
- write_pte([i], pte);
- }
-
- page->u.inuse.p2m_refcount = LPAE_ENTRIES;
-}
-else
-clear_page(p);
+clear_page(p);
 
 if ( p2m->clean_pte )
 clean_dcache_va_range(p, PAGE_SIZE);
-- 
1.9.1


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