[PATCH v5 37/45] x86/shadow: use map_domain_pages() for cross-page emulated writes

[George Dunlap <gwd@xxxxxxxxxxxxxx>]

sh_emulate_map_dest() picks its mapping method purely on whether the
write straddles a page boundary: a single page goes through
map_domain_page(), two pages through vmap() -- mapping the destination
in every context for the duration, those of domains on the sparse
directmap view included, whatever the guest's own configuration.
map_domain_pages() maps it only in the page tables of the guest's own
domain; use it for the two-page case.

The NULL return handling is unchanged: the primitive can fail only for
want of a free slot, and the emulation then bails out as unhandleable
exactly as before.

This is one of the two in-tree consumers of the primitive.

Assisted-by: Claude Code:claude-fable-5, Claude Code:claude-opus-5-5
Signed-off-by: George Dunlap <gwd@xxxxxxxxxxxxxx>
---
Changes in v5:
- New in this version.
---
 xen/arch/x86/mm/shadow/hvm.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/xen/arch/x86/mm/shadow/hvm.c b/xen/arch/x86/mm/shadow/hvm.c
index 0b23326214..b1c3d5e637 100644
--- a/xen/arch/x86/mm/shadow/hvm.c
+++ b/xen/arch/x86/mm/shadow/hvm.c
@@ -506,7 +506,7 @@ static void *sh_emulate_map_dest(struct vcpu *v, unsigned 
long vaddr,
         /* Cross-page writes mean probably not a pagetable. */
         sh_remove_shadows(d, sh_ctxt->mfn[1], 0, 0 /* Slow, can fail. */ );
 
-        map = vmap(sh_ctxt->mfn, 2);
+        map = map_domain_pages(sh_ctxt->mfn, 2);
         if ( !map )
         {
             put_page(mfn_to_page(sh_ctxt->mfn[0]));
@@ -670,7 +670,7 @@ static void sh_emulate_unmap_dest(struct vcpu *v, void 
*addr,
     if ( unlikely(mfn_valid(sh_ctxt->mfn[1])) )
     {
         put_page(mfn_to_page(sh_ctxt->mfn[1]));
-        vunmap((void *)((unsigned long)addr & PAGE_MASK));
+        unmap_domain_pages(addr, 2);
     }
     else
         unmap_domain_page(addr);
-- 
2.56.0