From: Reiji Watanabe reijiw@google.com
[ Upstream commit f0616abd4e67143b45b04b565839148458857347 ]
Currently, clear_page() uses DC ZVA instruction unconditionally. But it should make sure that DCZID_EL0.DZP, which indicates whether or not use of DC ZVA instruction is prohibited, is zero when using the instruction. Use STNP instead when DCZID_EL0.DZP == 1.
Fixes: f27bb139c387 ("arm64: Miscellaneous library functions") Signed-off-by: Reiji Watanabe reijiw@google.com Reviewed-by: Robin Murphy robin.murphy@arm.com Link: https://lore.kernel.org/r/20211206004736.1520989-2-reijiw@google.com Signed-off-by: Catalin Marinas catalin.marinas@arm.com Signed-off-by: Sasha Levin sashal@kernel.org --- arch/arm64/lib/clear_page.S | 10 ++++++++++ 1 file changed, 10 insertions(+)
diff --git a/arch/arm64/lib/clear_page.S b/arch/arm64/lib/clear_page.S index b84b179edba3a..1fd5d790ab800 100644 --- a/arch/arm64/lib/clear_page.S +++ b/arch/arm64/lib/clear_page.S @@ -16,6 +16,7 @@ */ SYM_FUNC_START_PI(clear_page) mrs x1, dczid_el0 + tbnz x1, #4, 2f /* Branch if DC ZVA is prohibited */ and w1, w1, #0xf mov x2, #4 lsl x1, x2, x1 @@ -25,5 +26,14 @@ SYM_FUNC_START_PI(clear_page) tst x0, #(PAGE_SIZE - 1) b.ne 1b ret + +2: stnp xzr, xzr, [x0] + stnp xzr, xzr, [x0, #16] + stnp xzr, xzr, [x0, #32] + stnp xzr, xzr, [x0, #48] + add x0, x0, #64 + tst x0, #(PAGE_SIZE - 1) + b.ne 2b + ret SYM_FUNC_END_PI(clear_page) EXPORT_SYMBOL(clear_page)