[PATCH 2/2] KVM: arm64: selftest: Perform ISB before reading PAR_EL1

[Marc Zyngier]

On Sat, 07 Oct 2023 13:40:43 +0100,
Zenghui Yu <yuzenghui at 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 at huawei.com>

Acked-by: Marc Zyngier <maz at kernel.org>

	M.

-- 
Without deviation from the norm, progress is not possible.