From 8f6a457d387ca9737ab60ea30fbbc90f8ef0d933 Mon Sep 17 00:00:00 2001 From: baoxfusion Date: Mon, 15 Dec 2025 11:34:44 +0800 Subject: [PATCH] backport:KVM: arm64: selftest: Perform ISB before reading PAR_EL1 reference:https://github.com/torvalds/linux/commit/06899aa5dd3d76e888b28d7e8d7304c0a7ec6262 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 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 Acked-by: Marc Zyngier Link: https://lore.kernel.org/r/20231007124043.626-2-yuzenghui@huawei.com Signed-off-by: Oliver Upton Signed-off-by: baoxfusion --- 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 47bb914ab2fa..0497c08dd7d8 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); -- Gitee