This is a note to let you know that I've just added the patch titled
s390/cmma: fix initial kernel address space page table walk
to the 5.10-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
s390-cmma-fix-initial-kernel-address-space-page-table-walk.patch
and it can be found in the queue-5.10 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 16ba44826a04834d3eeeda4b731c2ea3481062b7 Mon Sep 17 00:00:00 2001
From: Heiko Carstens <hca@xxxxxxxxxxxxx>
Date: Tue, 17 Oct 2023 21:07:03 +0200
Subject: s390/cmma: fix initial kernel address space page table walk
From: Heiko Carstens <hca@xxxxxxxxxxxxx>
commit 16ba44826a04834d3eeeda4b731c2ea3481062b7 upstream.
If the cmma no-dat feature is available the kernel page tables are walked
to identify and mark all pages which are used for address translation (all
region, segment, and page tables). In a subsequent loop all other pages are
marked as "no-dat" pages with the ESSA instruction.
This information is visible to the hypervisor, so that the hypervisor can
optimize purging of guest TLB entries. The initial loop however does not
cover the complete kernel address space. This can result in pages being
marked as not being used for dynamic address translation, even though they
are. In turn guest TLB entries incorrectly may not be purged.
Fix this by adjusting the end address of the kernel address range being
walked.
Cc: <stable@xxxxxxxxxxxxxxx>
Reviewed-by: Claudio Imbrenda <imbrenda@xxxxxxxxxxxxx>
Reviewed-by: Alexander Gordeev <agordeev@xxxxxxxxxxxxx>
Signed-off-by: Heiko Carstens <hca@xxxxxxxxxxxxx>
Signed-off-by: Vasily Gorbik <gor@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/s390/mm/page-states.c | 13 ++++++++++---
1 file changed, 10 insertions(+), 3 deletions(-)
--- a/arch/s390/mm/page-states.c
+++ b/arch/s390/mm/page-states.c
@@ -161,15 +161,22 @@ static void mark_kernel_p4d(pgd_t *pgd,
static void mark_kernel_pgd(void)
{
- unsigned long addr, next;
+ unsigned long addr, next, max_addr;
struct page *page;
pgd_t *pgd;
int i;
addr = 0;
+ /*
+ * Figure out maximum virtual address accessible with the
+ * kernel ASCE. This is required to keep the page table walker
+ * from accessing non-existent entries.
+ */
+ max_addr = (S390_lowcore.kernel_asce.val & _ASCE_TYPE_MASK) >> 2;
+ max_addr = 1UL << (max_addr * 11 + 31);
pgd = pgd_offset_k(addr);
do {
- next = pgd_addr_end(addr, MODULES_END);
+ next = pgd_addr_end(addr, max_addr);
if (pgd_none(*pgd))
continue;
if (!pgd_folded(*pgd)) {
@@ -178,7 +185,7 @@ static void mark_kernel_pgd(void)
set_bit(PG_arch_1, &page[i].flags);
}
mark_kernel_p4d(pgd, addr, next);
- } while (pgd++, addr = next, addr != MODULES_END);
+ } while (pgd++, addr = next, addr != max_addr);
}
void __init cmma_init_nodat(void)
Patches currently in stable-queue which might be from hca@xxxxxxxxxxxxx are
queue-5.10/s390-cmma-fix-initial-kernel-address-space-page-table-walk.patch
queue-5.10/s390-cmma-fix-handling-of-swapper_pg_dir-and-invalid_pg_dir.patch
