From 06899aa5dd3d76e888b28d7e8d7304c0a7ec6262 Mon Sep 17 00:00:00 2001
From: Zenghui Yu <yuzenghui@huawei.com>
Date: Sat, 7 Oct 2023 20:40:43 +0800
Subject: [PATCH] KVM: arm64: selftest: Perform ISB before reading PAR_EL1
It looks like a mistake to issue ISB *after* reading PAR_EL1, we should
instead perform it between the AT instruction and the reads of PAR_EL1.
As according to DDI0487J.a IJTYVP,
"When an address translation instruction is executed, explicit
synchronization is required to guarantee the result is visible to
subsequent direct reads of PAR_EL1."
Otherwise all guest_at testcases fail on my box with
==== Test Assertion Failure ====
aarch64/page_fault_test.c:142: par & 1 == 0
pid=1355864 tid=1355864 errno=4 - Interrupted system call
1 0x0000000000402853: vcpu_run_loop at page_fault_test.c:681
2 0x0000000000402cdb: run_test at page_fault_test.c:730
3 0x0000000000403897: for_each_guest_mode at guest_modes.c:100
4 0x00000000004019f3: for_each_test_and_guest_mode at page_fault_test.c:1105
5 (inlined by) main at page_fault_test.c:1131
6 0x0000ffffb153c03b: ?? ??:0
7 0x0000ffffb153c113: ?? ??:0
8 0x0000000000401aaf: _start at ??:?
0x1 != 0x0 (par & 1 != 0)
Signed-off-by: Zenghui Yu <yuzenghui@huawei.com>
Acked-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20231007124043.626-2-yuzenghui@huawei.com
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
---
tools/testing/selftests/kvm/aarch64/page_fault_test.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/tools/testing/selftests/kvm/aarch64/page_fault_test.c b/tools/testing/selftests/kvm/aarch64/page_fault_test.c
index eb5ead50c0b1..9a3be80e8bc9 100644
--- a/tools/testing/selftests/kvm/aarch64/page_fault_test.c
+++ b/tools/testing/selftests/kvm/aarch64/page_fault_test.c
@@ -135,8 +135,8 @@ static void guest_at(void)
uint64_t par;
asm volatile("at s1e1r, %0" :: "r" (guest_test_memory));
- par = read_sysreg(par_el1);
isb();
+ par = read_sysreg(par_el1);
/* Bit 1 indicates whether the AT was successful */
GUEST_ASSERT_EQ(par & 1, 0);
--
2.30.9