File xsa299-9.patch of Package xen.26348
From 4e0388af70146faaef6443a8b57807cd61e0960f Mon Sep 17 00:00:00 2001
From: George Dunlap <george.dunlap@citrix.com>
Date: Thu, 10 Oct 2019 17:57:49 +0100
Subject: [PATCH 09/12] x86/mm: Collapse PTF_partial_set and
PTF_partial_general_ref into one
...now that they are equivalent. No functional change intended.
Reported-by: George Dunlap <george.dunlap@citrix.com>
Signed-off-by: George Dunlap <george.dunlap@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
---
xen/arch/x86/mm.c | 50 +++++++++++-----------------------------
xen/include/asm-x86/mm.h | 29 +++++++++++------------
2 files changed, 26 insertions(+), 53 deletions(-)
--- a/xen/arch/x86/mm.c
+++ b/xen/arch/x86/mm.c
@@ -757,13 +757,12 @@ static int __get_page_type(struct page_i
/*
* The following flags are used to specify behavior of various get and
- * put commands. The first two are also stored in page->partial_flags
- * to indicate the state of the page pointed to by
+ * put commands. The first is also stored in page->partial_flags to
+ * indicate the state of the page pointed to by
* page->pte[page->nr_validated_entries]. See the comment in mm.h for
* more information.
*/
#define PTF_partial_set (1 << 0)
-#define PTF_partial_general_ref (1 << 1)
#define PTF_preemptible (1 << 2)
#define PTF_defer (1 << 3)
#define PTF_retain_ref_on_restart (1 << 4)
@@ -776,13 +775,10 @@ static int get_page_and_type_from_pagenr
struct page_info *page = mfn_to_page(page_nr);
int rc;
bool_t preemptible = !!(flags & PTF_preemptible),
- partial_ref = !!(flags & PTF_partial_general_ref),
partial_set = !!(flags & PTF_partial_set),
retain_ref = !!(flags & PTF_retain_ref_on_restart);
- ASSERT(partial_ref == partial_set);
-
- if ( likely(!partial_ref) &&
+ if ( likely(!partial_set) &&
unlikely(!get_page_from_pagenr(page_nr, d)) )
return -EINVAL;
@@ -792,14 +788,14 @@ static int get_page_and_type_from_pagenr
* Retain the refcount if:
* - page is fully validated (rc == 0)
* - page is not validated (rc < 0) but:
- * - We came in with a reference (partial_ref)
+ * - We came in with a reference (partial_set)
* - page is partially validated (rc == -ERESTART), and the
* caller has asked the ref to be retained in that case
* - page is partially validated but there's been an error
* (page == current->arch.old_guest_table)
*
- * The partial_ref-on-error clause is worth an explanation. There
- * are two scenarios where partial_ref might be true coming in:
+ * The partial_set-on-error clause is worth an explanation. There
+ * are two scenarios where partial_set might be true coming in:
* - mfn has been partially promoted / demoted as type `type`;
* i.e. has PGT_partial set
* - mfn has been partially demoted as L(type+1) (i.e., a linear
@@ -822,7 +818,7 @@ static int get_page_and_type_from_pagenr
* count retained unless we succeeded, or the operation was
* preemptible.
*/
- if ( likely(!rc) || partial_ref )
+ if ( likely(!rc) || partial_set )
/* nothing */;
else if ( page == current->arch.old_guest_table ||
(retain_ref && rc == -ERESTART) )
@@ -1513,13 +1509,7 @@ static int put_page_from_l2e(l2_pgentry_
struct page_info *pg = l2e_get_page(l2e);
struct page_info *ptpg = mfn_to_page(pfn);
- if ( (flags & (PTF_partial_set | PTF_partial_general_ref)) ==
- PTF_partial_set )
- {
- /* partial_set should always imply partial_ref */
- BUG();
- }
- else if ( flags & PTF_defer )
+ if ( flags & PTF_defer )
{
current->arch.old_guest_ptpg = ptpg;
current->arch.old_guest_table = pg;
@@ -1559,13 +1549,6 @@ static int put_page_from_l3e(l3_pgentry_
pg = l3e_get_page(l3e);
- if ( (flags & (PTF_partial_set | PTF_partial_general_ref)) ==
- PTF_partial_set )
- {
- /* partial_set should always imply partial_ref */
- BUG();
- }
-
if ( flags & PTF_defer )
{
current->arch.old_guest_ptpg = mfn_to_page(pfn);
@@ -1590,13 +1573,6 @@ static int put_page_from_l4e(l4_pgentry_
{
struct page_info *pg = l4e_get_page(l4e);
- if ( (flags & (PTF_partial_set | PTF_partial_general_ref)) ==
- PTF_partial_set )
- {
- /* partial_set should always imply partial_ref */
- BUG();
- }
-
if ( flags & PTF_defer )
{
current->arch.old_guest_ptpg = mfn_to_page(pfn);
@@ -1825,7 +1801,7 @@ static int alloc_l3_table(struct page_in
{
page->nr_validated_ptes = i;
/* Set 'set', leave 'general ref' set if this entry was set */
- page->partial_flags = PTF_partial_set | PTF_partial_general_ref;
+ page->partial_flags = PTF_partial_set;
}
else if ( rc == -EINTR && i )
{
@@ -1928,7 +1904,7 @@ static int alloc_l4_table(struct page_in
{
page->nr_validated_ptes = i;
/* Set 'set', leave 'general ref' set if this entry was set */
- page->partial_flags = PTF_partial_set | PTF_partial_general_ref;
+ page->partial_flags = PTF_partial_set;
}
else if ( rc < 0 )
{
@@ -2026,7 +2002,7 @@ static int free_l2_table(struct page_inf
else if ( rc == -ERESTART )
{
page->nr_validated_ptes = i;
- page->partial_flags = PTF_partial_set | PTF_partial_general_ref;
+ page->partial_flags = PTF_partial_set;
}
else if ( rc == -EINTR && i < L2_PAGETABLE_ENTRIES - 1 )
{
@@ -2077,7 +2053,7 @@ static int free_l3_table(struct page_inf
if ( rc == -ERESTART )
{
page->nr_validated_ptes = i;
- page->partial_flags = PTF_partial_set | PTF_partial_general_ref;
+ page->partial_flags = PTF_partial_set;
}
else if ( rc == -EINTR && i < L3_PAGETABLE_ENTRIES - 1 )
{
@@ -2108,7 +2084,7 @@ static int free_l4_table(struct page_inf
if ( rc == -ERESTART )
{
page->nr_validated_ptes = i;
- page->partial_flags = PTF_partial_set | PTF_partial_general_ref;
+ page->partial_flags = PTF_partial_set;
}
else if ( rc == -EINTR && i < L4_PAGETABLE_ENTRIES - 1 )
{
--- a/xen/include/asm-x86/mm.h
+++ b/xen/include/asm-x86/mm.h
@@ -146,7 +146,7 @@ struct page_info
* operation on the current page. (That page may or may not
* still have PGT_partial set.)
*
- * If PTF_partial_general_ref is set, then the PTE at
+ * Additionally, if PTF_partial_set is set, then the PTE at
* @nr_validated_ptef holds a general reference count for the
* page.
*
@@ -155,23 +155,20 @@ struct page_info
* interrupted
* - During validation, if an invalid entry is encountered and
* validation is preemptible
- * - During validation, if PTF_partial_general_ref was set on
- * this entry to begin with (perhaps because it picked up a
+ * - During validation, if PTF_partial_set was set on this
+ * entry to begin with (perhaps because it picked up a
* previous operation)
*
- * When resuming validation, if PTF_partial_general_ref is
- * clear, then a general reference must be re-acquired; if it
- * is set, no reference should be acquired.
- *
- * When resuming de-validation, if PTF_partial_general_ref is
- * clear, no reference should be dropped; if it is set, a
- * reference should be dropped.
+ * When resuming validation, if PTF_partial_set is clear, then
+ * a general reference must be re-acquired; if it is set, no
+ * reference should be acquired.
+ *
+ * When resuming de-validation, if PTF_partial_set is clear,
+ * no reference should be dropped; if it is set, a reference
+ * should be dropped.
*
- * NB at the moment, PTF_partial_set should be set if and only if
- * PTF_partial_general_ref is set.
- *
- * NB that PTF_partial_set and PTF_partial_general_ref are
- * defined in mm.c, the only place where they are used.
+ * NB that PTF_partial_set is defined in mm.c, the only place
+ * where it is used.
*
* The 3rd field, @linear_pt_count, indicates
* - by a positive value, how many same-level page table entries a page
@@ -181,8 +178,8 @@ struct page_info
*/
struct {
u16 nr_validated_ptes:PAGETABLE_ORDER + 1;
- u16 :16 - PAGETABLE_ORDER - 1 - 2;
- u16 partial_flags:2;
+ u16 :16 - PAGETABLE_ORDER - 1 - 1;
+ u16 partial_flags:1;
s16 linear_pt_count;
};
