From: Reiji Watanabe <reijiw@xxxxxxxxxx>
[ 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@xxxxxxxxxx>
Reviewed-by: Robin Murphy <robin.murphy@xxxxxxx>
Link: https://lore.kernel.org/r/20211206004736.1520989-2-reijiw@xxxxxxxxxx
Signed-off-by: Catalin Marinas <catalin.marinas@xxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
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)
--
2.34.1
