linux-kernel - [PATCH 4.9 056/310] KVM: arm64: Restore host physical timer access on hyp

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Date:   Wed, 11 Apr 2018 20:33:15 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, James Morse <james.morse@....com>,
        Marc Zyngier <marc.zyngier@....com>,
        Christoffer Dall <cdall@...aro.org>,
        Sasha Levin <alexander.levin@...rosoft.com>
Subject: [PATCH 4.9 056/310] KVM: arm64: Restore host physical timer access on hyp_panic()

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: James Morse <james.morse@....com>


[ Upstream commit e8ec032b182cd4841605de4fc297a8edffe55972 ]

When KVM panics, it hurridly restores the host context and parachutes
into the host's panic() code. At some point panic() touches the physical
timer/counter. Unless we are an arm64 system with VHE, this traps back
to EL2. If we're lucky, we panic again.

Add a __timer_save_state() call to KVMs hyp_panic() path, this saves the
guest registers and disables the traps for the host.

Fixes: 53fd5b6487e4 ("arm64: KVM: Add panic handling")
Signed-off-by: James Morse <james.morse@....com>
Reviewed-by: Marc Zyngier <marc.zyngier@....com>
Reviewed-by: Christoffer Dall <cdall@...aro.org>
Signed-off-by: Christoffer Dall <cdall@...aro.org>
Signed-off-by: Sasha Levin <alexander.levin@...rosoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 arch/arm64/kvm/hyp/switch.c |    1 +
 1 file changed, 1 insertion(+)

--- a/arch/arm64/kvm/hyp/switch.c
+++ b/arch/arm64/kvm/hyp/switch.c
@@ -404,6 +404,7 @@ void __hyp_text __noreturn __hyp_panic(v
 
 		vcpu = (struct kvm_vcpu *)read_sysreg(tpidr_el2);
 		host_ctxt = kern_hyp_va(vcpu->arch.host_cpu_context);
+		__timer_save_state(vcpu);
 		__deactivate_traps(vcpu);
 		__deactivate_vm(vcpu);
 		__sysreg_restore_host_state(host_ctxt);