The LPAE format allows to store information in an entry even with the
valid bit unset. In a follow-up patch, we will take advantage of this
feature to re-purpose the valid bit for generating a translation fault
even if an entry contains valid information.
So we need a different way to know whether an entry contains valid
information. It is possible to use the information hold in the p2m_type
to know for that purpose. Indeed all entries containing valid
information will have a valid p2m type (i.e p2m_type != p2m_invalid).
This patch introduces a new helper p2m_is_valid, which implements that
idea, and replace most of lpae_is_valid call with the new helper. The ones
remaining are for TLBs handling and entries accounting.
With the renaming there are 2 others changes required:
- Generate table entry with a valid p2m type
- Detect new mapping for proper stats accounting
Signed-off-by: Julien Grall <julien.grall@xxxxxxx>
---
xen/arch/arm/p2m.c | 34 +++++++++++++++++++++++-----------
1 file changed, 23 insertions(+), 11 deletions(-)
diff --git a/xen/arch/arm/p2m.c b/xen/arch/arm/p2m.c
index 6c76298ebc..2a1e7e9be2 100644
--- a/xen/arch/arm/p2m.c
+++ b/xen/arch/arm/p2m.c
@@ -220,17 +220,26 @@ static p2m_access_t p2m_mem_access_radix_get(struct
p2m_domain *p2m, gfn_t gfn)
}
/*
+ * In the case of the P2M, the valid bit is used for other purpose. Use
+ * the type to check whether an entry is valid.
+ */
+static inline bool p2m_is_valid(lpae_t pte)
+{
+ return pte.p2m.type != p2m_invalid;
+}
+
+/*
* lpae_is_* helpers don't check whether the valid bit is set in the
* PTE. Provide our own overlay to check the valid bit.
*/
static inline bool p2m_is_mapping(lpae_t pte, unsigned int level)
{
- return lpae_is_valid(pte) && lpae_is_mapping(pte, level);
+ return p2m_is_valid(pte) && lpae_is_mapping(pte, level);
}
static inline bool p2m_is_superpage(lpae_t pte, unsigned int level)
{
- return lpae_is_valid(pte) && lpae_is_superpage(pte, level);
+ return p2m_is_valid(pte) && lpae_is_superpage(pte, level);
}
#define GUEST_TABLE_MAP_FAILED 0
@@ -264,7 +273,7 @@ static int p2m_next_level(struct p2m_domain *p2m, bool
read_only,
entry = *table + offset;
- if ( !lpae_is_valid(*entry) )
+ if ( !p2m_is_valid(*entry) )
{
if ( read_only )
return GUEST_TABLE_MAP_FAILED;
@@ -356,7 +365,7 @@ mfn_t p2m_get_entry(struct p2m_domain *p2m, gfn_t gfn,
entry = table[offsets[level]];
- if ( lpae_is_valid(entry) )
+ if ( p2m_is_valid(entry) )
{
*t = entry.p2m.type;
@@ -544,8 +553,11 @@ static lpae_t page_to_p2m_table(struct page_info *page)
/*
* The access value does not matter because the hardware will ignore
* the permission fields for table entry.
+ *
+ * We use p2m_ram_rw so the entry has a valid type. This is important
+ * for p2m_is_valid() to return valid on table entries.
*/
- return mfn_to_p2m_entry(page_to_mfn(page), p2m_invalid, p2m_access_rwx);
+ return mfn_to_p2m_entry(page_to_mfn(page), p2m_ram_rw, p2m_access_rwx);
}
static inline void p2m_write_pte(lpae_t *p, lpae_t pte, bool clean_pte)
@@ -569,7 +581,7 @@ static int p2m_create_table(struct p2m_domain *p2m, lpae_t
*entry)
struct page_info *page;
lpae_t *p;
- ASSERT(!lpae_is_valid(*entry));
+ ASSERT(!p2m_is_valid(*entry));
page = alloc_domheap_page(NULL, 0);
if ( page == NULL )
@@ -626,7 +638,7 @@ static int p2m_mem_access_radix_set(struct p2m_domain *p2m,
gfn_t gfn,
*/
static void p2m_put_l3_page(const lpae_t pte)
{
- ASSERT(lpae_is_valid(pte));
+ ASSERT(p2m_is_valid(pte));
/*
* TODO: Handle other p2m types
@@ -654,11 +666,11 @@ static void p2m_free_entry(struct p2m_domain *p2m,
struct page_info *pg;
/* Nothing to do if the entry is invalid. */
- if ( !lpae_is_valid(entry) )
+ if ( !p2m_is_valid(entry) )
return;
/* Nothing to do but updating the stats if the entry is a super-page. */
- if ( p2m_is_superpage(entry, level) )
+ if ( level == 3 && entry.p2m.table )
