Commit cc45963c authored by Marc Zyngier's avatar Marc Zyngier
Browse files

KVM: arm64: nv: Publish emulated timer interrupt state in the in-memory state 



With FEAT_NV2, the EL0 timer state is entirely stored in memory,
meaning that the hypervisor can only provide a very poor emulation.

The only thing we can really do is to publish the interrupt state
in the guest view of CNT{P,V}_CTL_EL0, and defer everything else
to the next exit.

Only FEAT_ECV will allow us to fix it, at the cost of extra trapping.

Suggested-by: default avatarChase Conklin <chase.conklin@arm.com>
Suggested-by: default avatarGanapatrao Kulkarni <gankulkarni@os.amperecomputing.com>
Acked-by: default avatarOliver Upton <oliver.upton@linux.dev>
Link: https://lore.kernel.org/r/20241217142321.763801-4-maz@kernel.org


Signed-off-by: default avatarMarc Zyngier <maz@kernel.org>
parent 4bad3068

arch/arm64/kvm/arch_timer.c

+21 −0
Original line number Diff line number Diff line
@@ -441,11 +441,30 @@ void kvm_timer_update_run(struct kvm_vcpu *vcpu) 
		regs->device_irq_level |= KVM_ARM_DEV_EL1_PTIMER;

}



static void kvm_timer_update_status(struct arch_timer_context *ctx, bool level)

{

	/*

	 * Paper over NV2 brokenness by publishing the interrupt status

	 * bit. This still results in a poor quality of emulation (guest

	 * writes will have no effect until the next exit).

	 *

	 * But hey, it's fast, right?

	 */

	if (is_hyp_ctxt(ctx->vcpu) &&

	    (ctx == vcpu_vtimer(ctx->vcpu) || ctx == vcpu_ptimer(ctx->vcpu))) {

		unsigned long val = timer_get_ctl(ctx);

		__assign_bit(__ffs(ARCH_TIMER_CTRL_IT_STAT), &val, level);

		timer_set_ctl(ctx, val);

	}

}



static void kvm_timer_update_irq(struct kvm_vcpu *vcpu, bool new_level,

				 struct arch_timer_context *timer_ctx)

{

	int ret;



	kvm_timer_update_status(timer_ctx, new_level);



	timer_ctx->irq.level = new_level;

	trace_kvm_timer_update_irq(vcpu->vcpu_id, timer_irq(timer_ctx),

				   timer_ctx->irq.level);
@@ -471,6 +490,8 @@ static void timer_emulate(struct arch_timer_context *ctx) 
		return;

	}



	kvm_timer_update_status(ctx, should_fire);



	/*

	 * If the timer can fire now, we don't need to have a soft timer

	 * scheduled for the future.  If the timer cannot fire at all,

arch/arm64/kvm/arm.c

+1 −1
Original line number Diff line number Diff line
@@ -1228,7 +1228,7 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu) 
		if (unlikely(!irqchip_in_kernel(vcpu->kvm)))

			kvm_timer_sync_user(vcpu);



		if (vcpu_has_nv(vcpu))

		if (is_hyp_ctxt(vcpu))

			kvm_timer_sync_nested(vcpu);



		kvm_arch_vcpu_ctxsync_fp(vcpu);