arm64: use alternative auto-nop

Make use of the new alternative_if and alternative_else_nop_endif and
get rid of our homebew NOP sleds, making the code simpler to read.

Note that for cpu_do_switch_mm the ret has been moved out of the
alternative sequence, and in the default case there will be three
additional NOPs executed.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: James Morse <james.morse@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>

1 files changed, 2 insertions, 8 deletions

diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index 6880dcc3b465..223d54a4d66b 100644
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -150,13 +150,7 @@
         ldr     x23, [sp, #S_SP]                // load return stack pointer
         msr     sp_el0, x23
 #ifdef CONFIG_ARM64_ERRATUM_845719
-alternative_if_not ARM64_WORKAROUND_845719
-        nop
-        nop
-#ifdef CONFIG_PID_IN_CONTEXTIDR
-        nop
-#endif
-alternative_else
+alternative_if ARM64_WORKAROUND_845719
         tbz     x22, #4, 1f
 #ifdef CONFIG_PID_IN_CONTEXTIDR
         mrs     x29, contextidr_el1
@@ -165,7 +159,7 @@ alternative_else
         msr contextidr_el1, xzr
 #endif
 1:
-alternative_endif
+alternative_else_nop_endif
 #endif
         .endif
         msr     elr_el1, x21                    // set up the return data