[v3,2/7] xen/riscv: add destroy_xen_mappings() to remove mappings in Xen page tables

Commit Message

Oleksii Kurochko Dec. 17, 2024, 4:32 p.m. UTC

Introduce the destroy_xen_mappings() function, which removes page
mappings in Xen's page tables between a start address s and an end
address e.
The function ensures that both s and e are page-aligned
and verifies that the start address is less than or equal to the end
address before calling pt_update() to invalidate the mappings.
The pt_update() function is called with INVALID_MFN and PTE_VALID=0
in the flags, which tell pt_update() to remove mapping. No additional
ASSERT() is required to check these arguments, as they are hardcoded in
the call to pt_update() within destroy_xen_mappings().

Signed-off-by: Oleksii Kurochko <[e-mail]>
Acked-by: Jan Beulich <[e-mail]>
---
Changes in V3:
 - Fix code style: drop blanks in condition part of ternary operation.
---
Changes in V2:
 - Drop ASSERT(s <= e).
 - Update implementation of destroy_xen_mappings() to avoid calling of
   pt_update() when start_addr >= end_addr and return -EINVAL.
 - Add Acked-by: Jan Beulich <[e-mail]>.
---
 xen/arch/riscv/mm.c | 6 ------
 xen/arch/riscv/pt.c | 8 ++++++++
 2 files changed, 8 insertions(+), 6 deletions(-)

Patch

diff --git a/xen/arch/riscv/mm.c b/xen/arch/riscv/mm.c
index 9359dc7f33..f2bf279bac 100644
--- a/xen/arch/riscv/mm.c
+++ b/xen/arch/riscv/mm.c
@@ -360,12 +360,6 @@  int xenmem_add_to_physmap_one(struct domain *d, unsigned int space,
     return 0;
 }
 
-int destroy_xen_mappings(unsigned long s, unsigned long e)
-{
-    BUG_ON("unimplemented");
-    return -1;
-}
-
 void share_xen_page_with_guest(struct page_info *page, struct domain *d,
                                enum XENSHARE_flags flags)
 {
diff --git a/xen/arch/riscv/pt.c b/xen/arch/riscv/pt.c
index d62aceb36c..2ca23206f4 100644
--- a/xen/arch/riscv/pt.c
+++ b/xen/arch/riscv/pt.c
@@ -421,6 +421,14 @@  int map_pages_to_xen(unsigned long virt,
     return pt_update(virt, mfn, nr_mfns, flags);
 }
 
+int destroy_xen_mappings(unsigned long s, unsigned long e)
+{
+    ASSERT(IS_ALIGNED(s, PAGE_SIZE));
+    ASSERT(IS_ALIGNED(e, PAGE_SIZE));
+
+    return (s < e) ? pt_update(s, INVALID_MFN, PFN_DOWN(e - s), 0) : -EINVAL;
+}
+
 int __init populate_pt_range(unsigned long virt, unsigned long nr_mfns)
 {
     return pt_update(virt, INVALID_MFN, nr_mfns, PTE_POPULATE);