diff options
Diffstat (limited to 'system/xen/xsa/xsa299-4.12-0006-x86-mm-Have-alloc_l-23-_table-clear-partial_flags-wh.patch')
| -rw-r--r-- | system/xen/xsa/xsa299-4.12-0006-x86-mm-Have-alloc_l-23-_table-clear-partial_flags-wh.patch | 111 |
1 files changed, 0 insertions, 111 deletions
diff --git a/system/xen/xsa/xsa299-4.12-0006-x86-mm-Have-alloc_l-23-_table-clear-partial_flags-wh.patch b/system/xen/xsa/xsa299-4.12-0006-x86-mm-Have-alloc_l-23-_table-clear-partial_flags-wh.patch deleted file mode 100644 index 72ee3eac9e..0000000000 --- a/system/xen/xsa/xsa299-4.12-0006-x86-mm-Have-alloc_l-23-_table-clear-partial_flags-wh.patch +++ /dev/null @@ -1,111 +0,0 @@ -From 4ad70553611a7a4e4494d5a3b51b5cc295a488e0 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 06/11] x86/mm: Have alloc_l[23]_table clear partial_flags when - preempting - -In order to allow recursive pagetable promotions and demotions to be -interrupted, Xen must keep track of the state of the sub-pages -promoted or demoted. This is stored in two elements in the page -struct: nr_entries_validated and partial_flags. - -The rule is that entries [0, nr_entries_validated) should always be -validated and hold a general reference count. If partial_flags is -zero, then [nr_entries_validated] is not validated and no reference -count is held. If PTF_partial_set is set, then [nr_entries_validated] -is partially validated. - -At the moment, a distinction is made between promotion and demotion -with regard to whether the entry itself "holds" a general reference -count: when entry promotion is interrupted (i.e., returns -ERESTART), -the entry is not considered to hold a reference; when entry demotion -is interrupted, the entry is still considered to hold a general -reference. - -PTF_partial_general_ref is used to distinguish between these cases. -If clear, it's a partial promotion => no general reference count held -by the entry; if set, it's partial demotion, so a general reference -count held. Because promotions and demotions can be interleaved, this -value is passed to get_page_and_type_from_mfn and put_page_from_l*e, -to be able to properly handle reference counts. - -Unfortunately, when alloc_l[23]_table check hypercall_preempt_check() -and return -ERESTART, they set nr_entries_validated, but don't clear -partial_flags. - -If we were picking up from a previously-interrupted promotion, that -means that PTF_partial_set would be set even though -[nr_entries_validated] was not partially validated. This means that -if the page in this state were de-validated, put_page_type() would -erroneously be called on that entry. - -Perhaps worse, if we were racing with a de-validation, then we might -leave both PTF_partial_set and PTF_partial_general_ref; and when -de-validation picked up again, both the type and the general ref would -be erroneously dropped from [nr_entries_validated]. - -In a sense, the real issue here is code duplication. Rather than -duplicate the interruption code, set rc to -EINTR and fall through to -the code which already handles that case correctly. - -Given the logic at this point, it should be impossible for -partial_flags to be non-zero; add an ASSERT() to catch any changes. - -This is part of XSA-299. - -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 | 25 ++++++------------------- - 1 file changed, 6 insertions(+), 19 deletions(-) - -diff --git a/xen/arch/x86/mm.c b/xen/arch/x86/mm.c -index 0a4d39a2c3..bbd29a68f4 100644 ---- a/xen/arch/x86/mm.c -+++ b/xen/arch/x86/mm.c -@@ -1554,21 +1554,13 @@ static int alloc_l2_table(struct page_info *page, unsigned long type) - for ( i = page->nr_validated_ptes; i < L2_PAGETABLE_ENTRIES; - i++, partial_flags = 0 ) - { -- l2_pgentry_t l2e; -+ l2_pgentry_t l2e = pl2e[i]; - - if ( i > page->nr_validated_ptes && hypercall_preempt_check() ) -- { -- page->nr_validated_ptes = i; -- rc = -ERESTART; -- break; -- } -- -- if ( !is_guest_l2_slot(d, type, i) ) -+ rc = -EINTR; -+ else if ( !is_guest_l2_slot(d, type, i) ) - continue; -- -- l2e = pl2e[i]; -- -- if ( !(l2e_get_flags(l2e) & _PAGE_PRESENT) ) -+ else if ( !(l2e_get_flags(l2e) & _PAGE_PRESENT) ) - { - if ( !pv_l1tf_check_l2e(d, l2e) ) - continue; -@@ -1640,13 +1632,8 @@ static int alloc_l3_table(struct page_info *page) - l3_pgentry_t l3e = pl3e[i]; - - if ( i > page->nr_validated_ptes && hypercall_preempt_check() ) -- { -- page->nr_validated_ptes = i; -- rc = -ERESTART; -- break; -- } -- -- if ( is_pv_32bit_domain(d) && (i == 3) ) -+ rc = -EINTR; -+ else if ( is_pv_32bit_domain(d) && (i == 3) ) - { - if ( !(l3e_get_flags(l3e) & _PAGE_PRESENT) || - (l3e_get_flags(l3e) & l3_disallow_mask(d)) ) --- -2.23.0 - |