riscv: Flush the instruction cache during SMP bringup

Instruction cache flush IPIs are sent only to CPUs in cpu_online_mask,
so they will not target a CPU until it calls set_cpu_online() earlier in
smp_callin(). As a result, if instruction memory is modified between the
CPU coming out of reset and that point, then its instruction cache may
contain stale data. Therefore, the instruction cache must be flushed
after the set_cpu_online() synchronization point.

Fixes: 08f051ed ("RISC-V: Flush I$ when making a dirty page executable")
Reviewed-by: Alexandre Ghiti <alexghiti@rivosinc.com>
Signed-off-by: Samuel Holland <samuel.holland@sifive.com>
Link: https://lore.kernel.org/r/20240327045035.368512-2-samuel.holland@sifive.comSigned-off-by: Palmer Dabbelt <palmer@rivosinc.com>

arch/riscv/kernel/smpboot.c

@@ -26,7 +26,7 @@
 #include <linux/sched/task_stack.h>
 #include <linux/sched/mm.h>
 
-#include <asm/cpufeature.h>
+#include <asm/cacheflush.h>
 #include <asm/cpu_ops.h>
 #include <asm/irq.h>
 #include <asm/mmu_context.h>
@@ -234,9 +234,10 @@ asmlinkage __visible void smp_callin(void)
 	riscv_user_isa_enable();
 
 	/*
-	 * Remote TLB flushes are ignored while the CPU is offline, so emit
-	 * a local TLB flush right now just in case.
+	 * Remote cache and TLB flushes are ignored while the CPU is offline,
+	 * so flush them both right now just in case.
 	 */
+	local_flush_icache_all();
 	local_flush_tlb_all();
 	complete(&cpu_running);
 	/*