linux-kernel - [PATCH v1 2/3] arm64: add error synchronization barrier in kernel_entry/kernel

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Message-ID: <1509563697-6359-3-git-send-email-gengdongjiu@huawei.com>
Date:   Thu, 2 Nov 2017 03:14:56 +0800
From:   Dongjiu Geng <gengdongjiu@...wei.com>
To:     <catalin.marinas@....com>, <will.deacon@....com>,
        <marc.zyngier@....com>, <christoffer.dall@...aro.org>,
        <james.morse@....com>, <mark.rutland@....com>,
        <ard.biesheuvel@...aro.org>, <robin.murphy@....com>,
        <cov@...eaurora.org>, <Dave.Martin@....com>,
        <gengdongjiu@...wei.com>, <suzuki.poulose@....com>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <kvmarm@...ts.cs.columbia.edu>
Subject: [PATCH v1 2/3] arm64: add error synchronization barrier in kernel_entry/kernel_exit

If taking an exception from or return to user space, insert
a Error Synchronization Barrier(ESB) to isolate the error.

If a user space process is pending a SError, when enter to
kernel, the SError will be immediately synchronized in the
handler entry. Otherwise if kernel space is pending a SError,
before return to user space, the SError will be synchronized
in the handler exit.

In order to reduce impact on performance, not check the DISR_EL1
to see whether an SError is consumed by an ESB instruction.
This is because DISR_EL1 is RAZ/WI in firmware-first RAS
solution, if happen SError, it will immediately trap to EL3
firmware.

Signed-off-by: Dongjiu Geng <gengdongjiu@...wei.com>
---
 arch/arm64/kernel/entry.S | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index e147c1d..6dde644 100644
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -138,6 +138,7 @@
 	stp	x28, x29, [sp, #16 * 14]

 	.if	\el == 0
+	error_synchronize
 	mrs	x21, sp_el0
 	ldr_this_cpu	tsk, __entry_task, x20	// Ensure MDSCR_EL1.SS is clear,
 	ldr	x19, [tsk, #TSK_TI_FLAGS]	// since we can unmask debug
@@ -281,6 +282,7 @@ alternative_if ARM64_WORKAROUND_845719
 1:
 alternative_else_nop_endif
 #endif
+	error_synchronize
 	.endif

 	msr	elr_el1, x21			// set up the return data
-- 
1.9.1