From: Marc Zyngier <maz@kernel.org>
To: Zenghui Yu <yuzenghui@huawei.com>
Cc: <kvmarm@lists.linux.dev>, <linux-arm-kernel@lists.infradead.org>,
<oliver.upton@linux.dev>, <james.morse@arm.com>,
<suzuki.poulose@arm.com>, <ricarkol@google.com>,
<wanghaibin.wang@huawei.com>
Subject: Re: [PATCH 2/2] KVM: arm64: selftest: Perform ISB before reading PAR_EL1
Date: Sat, 07 Oct 2023 17:06:37 +0100 [thread overview]
Message-ID: <875y3imn76.wl-maz@kernel.org> (raw)
In-Reply-To: <20231007124043.626-2-yuzenghui@huawei.com>
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.
--
Without deviation from the norm, progress is not possible.
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next prev parent reply other threads:[~2023-10-07 16:07 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-10-07 12:40 [PATCH 1/2] KVM: arm64: selftest: Add the missing .guest_prepare() Zenghui Yu
2023-10-07 12:40 ` [PATCH 2/2] KVM: arm64: selftest: Perform ISB before reading PAR_EL1 Zenghui Yu
2023-10-07 16:06 ` Marc Zyngier [this message]
2023-10-07 16:05 ` [PATCH 1/2] KVM: arm64: selftest: Add the missing .guest_prepare() Marc Zyngier
2023-10-07 16:50 ` Oliver Upton
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