Commit 4942dc66 authored Jan 17, 2020 by Andrew Murray Committed by Catalin Marinas Jan 22, 2020

KVM: arm64: Write arch.mdcr_el2 changes since last vcpu_load on VHE



On VHE systems arch.mdcr_el2 is written to mdcr_el2 at vcpu_load time to
set options for self-hosted debug and the performance monitors
extension.

Unfortunately the value of arch.mdcr_el2 is not calculated until
kvm_arm_setup_debug() in the run loop after the vcpu has been loaded.
This means that the initial brief iterations of the run loop use a zero
value of mdcr_el2 - until the vcpu is preempted. This also results in a
delay between changes to vcpu->guest_debug taking effect.

Fix this by writing to mdcr_el2 in kvm_arm_setup_debug() on VHE systems
when a change to arch.mdcr_el2 has been detected.

Fixes: d5a21bcc ("KVM: arm64: Move common VHE/non-VHE trap config in separate functions")
Cc: <stable@vger.kernel.org> # 4.17.x-
Suggested-by: James Morse <james.morse@arm.com>
Acked-by: Will Deacon <will@kernel.org>
Reviewed-by: Marc Zyngier <maz@kernel.org>
Signed-off-by: Andrew Murray <andrew.murray@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

parent def9d278

arch/arm64/kvm/debug.c

+5 −1

Original line number	Diff line number	Diff line
		@@ -101,7 +101,7 @@ void kvm_arm_reset_debug_ptr(struct kvm_vcpu *vcpu)
		void kvm_arm_setup_debug(struct kvm_vcpu *vcpu)
		{
		bool trap_debug = !(vcpu->arch.flags & KVM_ARM64_DEBUG_DIRTY);
		unsigned long mdscr;
		unsigned long mdscr, orig_mdcr_el2 = vcpu->arch.mdcr_el2;

		trace_kvm_arm_setup_debug(vcpu, vcpu->guest_debug);

		@@ -197,6 +197,10 @@ void kvm_arm_setup_debug(struct kvm_vcpu *vcpu)
		if (vcpu_read_sys_reg(vcpu, MDSCR_EL1) & (DBG_MDSCR_KDE \| DBG_MDSCR_MDE))
		vcpu->arch.flags \|= KVM_ARM64_DEBUG_DIRTY;

		/* Write mdcr_el2 changes since vcpu_load on VHE systems */
		if (has_vhe() && orig_mdcr_el2 != vcpu->arch.mdcr_el2)
		write_sysreg(vcpu->arch.mdcr_el2, mdcr_el2);

		trace_kvm_arm_set_dreg32("MDCR_EL2", vcpu->arch.mdcr_el2);
		trace_kvm_arm_set_dreg32("MDSCR_EL1", vcpu_read_sys_reg(vcpu, MDSCR_EL1));
		}

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