Introduce helper functions for safely querying the P2M (physical-to-machine)
mapping:
- add p2m_read_lock(), p2m_read_unlock(), and p2m_is_locked() for managing
P2M lock state.
- Implement p2m_get_entry() to retrieve mapping details for a given GFN,
including MFN, page order, and validity.
- Add p2m_lookup() to encapsulate read-locked MFN retrieval.
- Introduce p2m_get_page_from_gfn() to convert a GFN into a page_info
pointer, acquiring a reference to the page if valid.
- Introduce get_page().
Implementations are based on Arm's functions with some minor modifications:
- p2m_get_entry():
- Reverse traversal of page tables, as RISC-V uses the opposite level
numbering compared to Arm.
- Removed the return of p2m_access_t from p2m_get_entry() since
mem_access_settings is not introduced for RISC-V.
- Updated BUILD_BUG_ON() to check using the level 0 mask, which corresponds
to Arm's THIRD_MASK.
- Replaced open-coded bit shifts with the BIT() macro.
- Other minor changes, such as using RISC-V-specific functions to validate
P2M PTEs, and replacing Arm-specific GUEST_* macros with their RISC-V
equivalents.
Signed-off-by: Oleksii Kurochko <oleksii.kuroc...@gmail.com>
---
Changes in V3:
- Add is_p2m_foreign() macro and connected stuff.
- Change struct domain *d argument of p2m_get_page_from_gfn() to
struct p2m_domain.
- Update the comment above p2m_get_entry().
- s/_t/p2mt for local variable in p2m_get_entry().
- Drop local variable addr in p2m_get_entry() and use gfn_to_gaddr(gfn)
to define offsets array.
- Code style fixes.
- Update a check of rc code from p2m_next_level() in p2m_get_entry()
and drop "else" case.
- Do not call p2m_get_type() if p2m_get_entry()'s t argument is NULL.
- Use struct p2m_domain instead of struct domain for p2m_lookup() and
p2m_get_page_from_gfn().
- Move defintion of get_page() from "xen/riscv: implement mfn_valid() and page
reference, ownership handling helpers"
---
Changes in V2:
- New patch.
---
xen/arch/riscv/include/asm/p2m.h | 18 ++++
xen/arch/riscv/mm.c | 13 +++
xen/arch/riscv/p2m.c | 136 +++++++++++++++++++++++++++++++
3 files changed, 167 insertions(+)
diff --git a/xen/arch/riscv/include/asm/p2m.h b/xen/arch/riscv/include/asm/p2m.h
index fbc73448a7..dc3a77cc15 100644
--- a/xen/arch/riscv/include/asm/p2m.h
+++ b/xen/arch/riscv/include/asm/p2m.h
@@ -202,6 +202,24 @@ static inline int p2m_is_write_locked(struct p2m_domain
*p2m)
unsigned long construct_hgatp(struct p2m_domain *p2m, uint16_t vmid);
+static inline void p2m_read_lock(struct p2m_domain *p2m)
+{
+ read_lock(&p2m->lock);
+}
+
+static inline void p2m_read_unlock(struct p2m_domain *p2m)
+{
+ read_unlock(&p2m->lock);
+}
+
+static inline int p2m_is_locked(struct p2m_domain *p2m)
+{
+ return rw_is_locked(&p2m->lock);
+}
+
+struct page_info *p2m_get_page_from_gfn(struct p2m_domain *p2m, gfn_t gfn,
+ p2m_type_t *t);
+
#endif /* ASM__RISCV__P2M_H */
/*
diff --git a/xen/arch/riscv/mm.c b/xen/arch/riscv/mm.c
index 3ad2b9cf93..5e09d46a75 100644
--- a/xen/arch/riscv/mm.c
+++ b/xen/arch/riscv/mm.c
@@ -677,3 +677,16 @@ struct domain *page_get_owner_and_reference(struct
page_info *page)
return owner;
}
+
+bool get_page(struct page_info *page, const struct domain *domain)
+{
+ const struct domain *owner = page_get_owner_and_reference(page);
+
+ if ( likely(owner == domain) )
+ return true;
+
+ if ( owner != NULL )
+ put_page(page);
+
+ return false;
+}
diff --git a/xen/arch/riscv/p2m.c b/xen/arch/riscv/p2m.c
index e9e6818da2..24a09d4537 100644
--- a/xen/arch/riscv/p2m.c
+++ b/xen/arch/riscv/p2m.c
@@ -852,3 +852,139 @@ int map_regions_p2mt(struct domain *d,
{
return p2m_insert_mapping(p2m_get_hostp2m(d), gfn, nr, mfn, p2mt);
}
+
+/*
+ * Get the details of a given gfn.
+ *
+ * If the entry is present, the associated MFN will be returned type filled up.
+ * The page_order will correspond to the order of the mapping in the page
+ * table (i.e it could be a superpage).
+ *
+ * If the entry is not present, INVALID_MFN will be returned and the
+ * page_order will be set according to the order of the invalid range.
+ *
+ * valid will contain the value of bit[0] (e.g valid bit) of the
+ * entry.
+ */
+static mfn_t p2m_get_entry(struct p2m_domain *p2m, gfn_t gfn,
+ p2m_type_t *t,
+ unsigned int *page_order,
+ bool *valid)
+{
+ unsigned int level = 0;
+ pte_t entry, *table;
+ int rc;
+ mfn_t mfn = INVALID_MFN;
+ DECLARE_OFFSETS(offsets, gfn_to_gaddr(gfn));
+
+ ASSERT(p2m_is_locked(p2m));
+ BUILD_BUG_ON(XEN_PT_LEVEL_MAP_MASK(0) != PAGE_MASK);
+
+ if ( valid )
+ *valid = false;
+
+ /* XXX: Check if the mapping is lower than the mapped gfn */
+
+ /* This gfn is higher than the highest the p2m map currently holds */
+ if ( gfn_x(gfn) > gfn_x(p2m->max_mapped_gfn) )
+ {
+ for ( level = P2M_ROOT_LEVEL; level; level-- )
+ if ( (gfn_x(gfn) & (XEN_PT_LEVEL_MASK(level) >> PAGE_SHIFT)) >
+ gfn_x(p2m->max_mapped_gfn) )
+ break;
+
+ goto out;
+ }
+
+ table = p2m_get_root_pointer(p2m, gfn);
+
+ /*
+ * the table should always be non-NULL because the gfn is below
+ * p2m->max_mapped_gfn and the root table pages are always present.
+ */
+ if ( !table )
+ {
+ ASSERT_UNREACHABLE();
+ level = P2M_ROOT_LEVEL;
+ goto out;
+ }
+
+ for ( level = P2M_ROOT_LEVEL; level; level-- )
+ {
+ rc = p2m_next_level(p2m, true, level, &table, offsets[level]);
+ if ( (rc == P2M_TABLE_MAP_NONE) || (rc == P2M_TABLE_MAP_NOMEM) )
+ goto out_unmap;
+
+ if ( rc != P2M_TABLE_NORMAL )
+ break;
+ }
+
+ entry = table[offsets[level]];
+
+ if ( pte_is_valid(entry) )
+ {
+ if ( t )
+ *t = p2m_get_type(entry);
+
+ mfn = pte_get_mfn(entry);
+ /*
+ * The entry may point to a superpage. Find the MFN associated
+ * to the GFN.
+ */
+ mfn = mfn_add(mfn,
+ gfn_x(gfn) & (BIT(XEN_PT_LEVEL_ORDER(level), UL) - 1));
+
+ if ( valid )
+ *valid = pte_is_valid(entry);
+ }
+
+ out_unmap:
+ unmap_domain_page(table);
+
+ out:
+ if ( page_order )
+ *page_order = XEN_PT_LEVEL_ORDER(level);
+
+ return mfn;
+}
+
+static mfn_t p2m_lookup(struct p2m_domain *p2m, gfn_t gfn, p2m_type_t *t)
+{
+ mfn_t mfn;
+
+ p2m_read_lock(p2m);
+ mfn = p2m_get_entry(p2m, gfn, t, NULL, NULL);
+ p2m_read_unlock(p2m);
+
+ return mfn;
+}
+
+struct page_info *p2m_get_page_from_gfn(struct p2m_domain *p2m, gfn_t gfn,
+ p2m_type_t *t)
+{
+ struct page_info *page;
+ p2m_type_t p2mt = p2m_invalid;
+ mfn_t mfn = p2m_lookup(p2m, gfn, t);
+
+ if ( !mfn_valid(mfn) )
+ return NULL;
+
+ if ( t )
+ p2mt = *t;
+
+ page = mfn_to_page(mfn);
+
+ /*
+ * get_page won't work on foreign mapping because the page doesn't
+ * belong to the current domain.
+ */
+ if ( p2m_is_foreign(p2mt) )
+ {
+ struct domain *fdom = page_get_owner_and_reference(page);
+ ASSERT(fdom != NULL);
+ ASSERT(fdom != p2m->domain);
+ return page;
+ }
+
+ return get_page(page, p2m->domain) ? page : NULL;
+}
--
2.50.1
