[PATCH v2 08/14] x86/mm: purge unneeded destroy_perdomain_mapping()

[George Dunlap <dunlapg@umich.edu>]

From: Roger Pau Monné <roger.pau@citrix.com>

We want to change per-domain mappings to be per-vCPU mappings.  In
preparation for that, we want to arrange that
destroy_perdomain_mapping() work either with a single perdomain area,
or with a per-vCPU perdomain area.

There are two calls made from domain-scoped contexts; both calls turn
out to be unnecessary:

- destroy_perdomain_mapping() is not logically the undo of
  create_perdomain_mapping(), as the name and its use in
  hvm_domain_initialise() suggest.  create_ allocates a per-domain L3,
  but destroy_ tears down mappings without freeing it; and since the
  call here passes nr == 0, it tears down nothing at all.  The
  per-domain L3 page is actually freed by free_perdomain_mappings(),
  which hvm_domain_initialise()'s caller, arch_domain_create(),
  already invokes on its failure path.

- The call in pv_domain_destroy() is redundant: arch_domain_destroy()
  unconditionally calls free_perdomain_mappings(), which tears down
  the same entries and additionally frees the page-table structures.

Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Reviewed-by: Alejandro Vallejo <alejandro.vallejo@cloud.com>
Assisted-by: Claude Code:claude-fable-5
Signed-off-by: George Dunlap <gwd@xenproject.org>
---
Changes in v2:
- Added to the series

Changes since the previously posted version:
- Reworked the commit message to make it more clear how it fits in
  with the larger series.  No functional change.
---
 xen/arch/x86/hvm/hvm.c   | 1 -
 xen/arch/x86/pv/domain.c | 3 ---
 2 files changed, 4 deletions(-)

diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
index a6e0818468..cd425c3342 100644
--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -730,7 +730,6 @@ int hvm_domain_initialise(struct domain *d,
     XFREE(d->arch.hvm.irq);
  fail0:
     hvm_destroy_cacheattr_region_list(d);
-    destroy_perdomain_mapping(d, PERDOMAIN_VIRT_START, 0);
  fail:
     hvm_domain_relinquish_resources(d);
     XFREE(d->arch.hvm.io_handler);
diff --git a/xen/arch/x86/pv/domain.c b/xen/arch/x86/pv/domain.c
index 15a8238aff..b936ca9b26 100644
--- a/xen/arch/x86/pv/domain.c
+++ b/xen/arch/x86/pv/domain.c
@@ -383,9 +383,6 @@ void pv_domain_destroy(struct domain *d)
 {
     pv_l1tf_domain_destroy(d);
 
-    destroy_perdomain_mapping(d, GDT_LDT_VIRT_START,
-                              GDT_LDT_MBYTES << (20 - PAGE_SHIFT));
-
     XFREE(d->arch.pv.cpuidmasks);
 }
 
-- 
2.55.0