linux-kernel - [PATCH v1 3/3] KVM: arm64: add ESB in exception handler entry and exit.

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Date:   Thu, 2 Nov 2017 03:14:57 +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 3/3] KVM: arm64: add ESB in exception handler entry and exit.

Some hardware platform can support RAS Extension instead
of support IESB, so software need to insert Synchronization
Barrier operations at exception handler entry and exit.

In the __guest_exit(), it added a ESB instruction, but can
not cover the path which is not guest exit. For example, if
EL1 host call HVC instruction enter to hypervisor, it will
not call __guest_exit().

In the kvm_arm_vhe_guest_enter(), it synchronised any host
RAS errors for VHE mode, but it can not handle the non-VHE
mode. For example, if EL1 host is pending a SError, the error
can be propagated to guest without error synchronization
operation.

Only add the ESB in the important exception handler path to
reduce the impact on performance.

Signed-off-by: Dongjiu Geng <gengdongjiu@...wei.com>
---
 arch/arm64/kvm/hyp/entry.S     | 2 ++
 arch/arm64/kvm/hyp/hyp-entry.S | 1 +
 2 files changed, 3 insertions(+)

diff --git a/arch/arm64/kvm/hyp/entry.S b/arch/arm64/kvm/hyp/entry.S
index 96caa53..fce6806 100644
--- a/arch/arm64/kvm/hyp/entry.S
+++ b/arch/arm64/kvm/hyp/entry.S
@@ -84,6 +84,8 @@ ENTRY(__guest_enter)
 	// Restore guest reg x18
 	ldr	x18,      [x18, #CPU_XREG_OFFSET(18)]

+	// synchronize host pending asynchronous error
+	error_synchronize
 	// Do not touch any register after this!
 	eret
 ENDPROC(__guest_enter)
diff --git a/arch/arm64/kvm/hyp/hyp-entry.S b/arch/arm64/kvm/hyp/hyp-entry.S
index 5170ce1..ac85029 100644
--- a/arch/arm64/kvm/hyp/hyp-entry.S
+++ b/arch/arm64/kvm/hyp/hyp-entry.S
@@ -54,6 +54,7 @@ ENTRY(__vhe_hyp_call)
 ENDPROC(__vhe_hyp_call)

 el1_sync:				// Guest trapped into EL2
+	error_synchronize
 	stp	x0, x1, [sp, #-16]!

 alternative_if_not ARM64_HAS_VIRT_HOST_EXTN
-- 
1.9.1