Commit 8182d4cf authored by Will Deacon's avatar Will Deacon Committed by Greg Kroah-Hartman

arm64: mm: ensure that the zero page is visible to the page table walker

commit 32d63978 upstream.

In paging_init, we allocate the zero page, memset it to zero and then
point TTBR0 to it in order to avoid speculative fetches through the
identity mapping.

In order to guarantee that the freshly zeroed page is indeed visible to
the page table walker, we need to execute a dsb instruction prior to
writing the TTBR.
Signed-off-by: default avatarWill Deacon <will.deacon@arm.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent c01afb92
......@@ -456,6 +456,9 @@ void __init paging_init(void)
empty_zero_page = virt_to_page(zero_page);
/* Ensure the zero page is visible to the page table walker */
dsb(ishst);
/*
* TTBR0 is only used for the identity mapping at this stage. Make it
* point to zero page to avoid speculatively fetching new entries.
......
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