| Message ID | 20231007124043.626-2-yuzenghui@huawei.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [1/2] KVM: arm64: selftest: Add the missing .guest_prepare() | expand |
On Sat, 07 Oct 2023 13:40:43 +0100, Zenghui Yu <yuzenghui@huawei.com> wrote: > > 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> M.
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);
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> --- tools/testing/selftests/kvm/aarch64/page_fault_test.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)