vgic-v3-nested.c

// SPDX-License-Identifier: GPL-2.0-only

#include <linux/cpu.h>
#include <linux/kvm.h>
#include <linux/kvm_host.h>
#include <linux/interrupt.h>
#include <linux/io.h>
#include <linux/uaccess.h>

#include <kvm/arm_vgic.h>

#include <asm/kvm_arm.h>
#include <asm/kvm_emulate.h>
#include <asm/kvm_nested.h>

#include "vgic.h"

#define ICH_LRN(n)	(ICH_LR0_EL2 + (n))
#define ICH_AP0RN(n)	(ICH_AP0R0_EL2 + (n))
#define ICH_AP1RN(n)	(ICH_AP1R0_EL2 + (n))

struct mi_state {
	u16	eisr;
	u16	elrsr;
	bool	pend;
};

/*
 * The shadow registers loaded to the hardware when running a L2 guest
 * with the virtual IMO/FMO bits set.
 */
struct shadow_if {
	struct vgic_v3_cpu_if	cpuif;
	unsigned long		lr_map;
};

static DEFINE_PER_CPU(struct shadow_if, shadow_if);

static int lr_map_idx_to_shadow_idx(struct shadow_if *shadow_if, int idx)
{
	return hweight16(shadow_if->lr_map & (BIT(idx) - 1));
}

/*
 * Nesting GICv3 support
 *
 * On a non-nesting VM (only running at EL0/EL1), the host hypervisor
 * completely controls the interrupts injected via the list registers.
 * Consequently, most of the state that is modified by the guest (by ACK-ing
 * and EOI-ing interrupts) is synced by KVM on each entry/exit, so that we
 * keep a semi-consistent view of the interrupts.
 *
 * This still applies for a NV guest, but only while "InHost" (either
 * running at EL2, or at EL0 with HCR_EL2.{E2H.TGE}=={1,1}.
 *
 * When running a L2 guest ("not InHost"), things are radically different,
 * as the L1 guest is in charge of provisioning the interrupts via its own
 * view of the ICH_LR*_EL2 registers, which conveniently live in the VNCR
 * page.  This means that the flow described above does work (there is no
 * state to rebuild in the L0 hypervisor), and that most things happen on L2
 * load/put:
 *
 * - on L2 load: move the in-memory L1 vGIC configuration into a shadow,
 *   per-CPU data structure that is used to populate the actual LRs. This is
 *   an extra copy that we could avoid, but life is short. In the process,
 *   we remap any interrupt that has the HW bit set to the mapped interrupt
 *   on the host, should the host consider it a HW one. This allows the HW
 *   deactivation to take its course, such as for the timer.
 *
 * - on L2 put: perform the inverse transformation, so that the result of L2
 *   running becomes visible to L1 in the VNCR-accessible registers.
 *
 * - there is nothing to do on L2 entry apart from enabling the vgic, as
 *   everything will have happened on load. However, this is the point where
 *   we detect that an interrupt targeting L1 and prepare the grand
 *   switcheroo.
 *
 * - on L2 exit: resync the LRs and VMCR, emulate the HW bit, and deactivate
 *   corresponding the L1 interrupt. The L0 active state will be cleared by
 *   the HW if the L1 interrupt was itself backed by a HW interrupt.
 *
 * Maintenance Interrupt (MI) management:
 *
 * Since the L2 guest runs the vgic in its full glory, MIs get delivered and
 * used as a handover point between L2 and L1.
 *
 * - on delivery of a MI to L0 while L2 is running: make the L1 MI pending,
 *   and let it rip. This will initiate a vcpu_put() on L2, and allow L1 to
 *   run and process the MI.
 *
 * - L1 MI is a fully virtual interrupt, not linked to the host's MI. Its
 *   state must be computed at each entry/exit of the guest, much like we do
 *   it for the PMU interrupt.
 *
 * - because most of the ICH_*_EL2 registers live in the VNCR page, the
 *   quality of emulation is poor: L1 can setup the vgic so that an MI would
 *   immediately fire, and not observe anything until the next exit.
 *   Similarly, a pending MI is not immediately disabled by clearing
 *   ICH_HCR_EL2.En. Trying to read ICH_MISR_EL2 would do the trick, for
 *   example.
 *
 * System register emulation:
 *
 * We get two classes of registers:
 *
 * - those backed by memory (LRs, APRs, HCR, VMCR): L1 can freely access
 *   them, and L0 doesn't see a thing.
 *
 * - those that always trap (ELRSR, EISR, MISR): these are status registers
 *   that are built on the fly based on the in-memory state.
 *
 * Only L1 can access the ICH_*_EL2 registers. A non-NV L2 obviously cannot,
 * and a NV L2 would either access the VNCR page provided by L1 (memory
 * based registers), or see the access redirected to L1 (registers that
 * trap) thanks to NV being set by L1.
 */

bool vgic_state_is_nested(struct kvm_vcpu *vcpu)
{
	u64 xmo;

	if (is_nested_ctxt(vcpu)) {
		xmo = __vcpu_sys_reg(vcpu, HCR_EL2) & (HCR_IMO | HCR_FMO);
		WARN_ONCE(xmo && xmo != (HCR_IMO | HCR_FMO),
			  "Separate virtual IRQ/FIQ settings not supported\n");

		return !!xmo;
	}

	return false;
}

static struct shadow_if *get_shadow_if(void)
{
	return this_cpu_ptr(&shadow_if);
}

static bool lr_triggers_eoi(u64 lr)
{
	return !(lr & (ICH_LR_STATE | ICH_LR_HW)) && (lr & ICH_LR_EOI);
}

static void vgic_compute_mi_state(struct kvm_vcpu *vcpu, struct mi_state *mi_state)
{
	u16 eisr = 0, elrsr = 0;
	bool pend = false;

	for (int i = 0; i < kvm_vgic_global_state.nr_lr; i++) {
		u64 lr = __vcpu_sys_reg(vcpu, ICH_LRN(i));

		if (lr_triggers_eoi(lr))
			eisr |= BIT(i);
		if (!(lr & ICH_LR_STATE))
			elrsr |= BIT(i);
		pend |= (lr & ICH_LR_PENDING_BIT);
	}

	mi_state->eisr	= eisr;
	mi_state->elrsr	= elrsr;
	mi_state->pend	= pend;
}

u16 vgic_v3_get_eisr(struct kvm_vcpu *vcpu)
{
	struct mi_state mi_state;

	vgic_compute_mi_state(vcpu, &mi_state);
	return mi_state.eisr;
}

u16 vgic_v3_get_elrsr(struct kvm_vcpu *vcpu)
{
	struct mi_state mi_state;

	vgic_compute_mi_state(vcpu, &mi_state);
	return mi_state.elrsr;
}

u64 vgic_v3_get_misr(struct kvm_vcpu *vcpu)
{
	struct mi_state mi_state;
	u64 reg = 0, hcr, vmcr;

	hcr = __vcpu_sys_reg(vcpu, ICH_HCR_EL2);
	vmcr = __vcpu_sys_reg(vcpu, ICH_VMCR_EL2);

	vgic_compute_mi_state(vcpu, &mi_state);

	if (mi_state.eisr)
		reg |= ICH_MISR_EL2_EOI;

	if (__vcpu_sys_reg(vcpu, ICH_HCR_EL2) & ICH_HCR_EL2_UIE) {
		int used_lrs = kvm_vgic_global_state.nr_lr;

		used_lrs -= hweight16(mi_state.elrsr);
		reg |= (used_lrs <= 1) ? ICH_MISR_EL2_U : 0;
	}

	if ((hcr & ICH_HCR_EL2_LRENPIE) && FIELD_GET(ICH_HCR_EL2_EOIcount_MASK, hcr))
		reg |= ICH_MISR_EL2_LRENP;

	if ((hcr & ICH_HCR_EL2_NPIE) && !mi_state.pend)
		reg |= ICH_MISR_EL2_NP;

	if ((hcr & ICH_HCR_EL2_VGrp0EIE) && (vmcr & ICH_VMCR_EL2_VENG0_MASK))
		reg |= ICH_MISR_EL2_VGrp0E;

	if ((hcr & ICH_HCR_EL2_VGrp0DIE) && !(vmcr & ICH_VMCR_EL2_VENG0_MASK))
		reg |= ICH_MISR_EL2_VGrp0D;

	if ((hcr & ICH_HCR_EL2_VGrp1EIE) && (vmcr & ICH_VMCR_EL2_VENG1_MASK))
		reg |= ICH_MISR_EL2_VGrp1E;

	if ((hcr & ICH_HCR_EL2_VGrp1DIE) && !(vmcr & ICH_VMCR_EL2_VENG1_MASK))
		reg |= ICH_MISR_EL2_VGrp1D;

	return reg;
}

static u64 translate_lr_pintid(struct kvm_vcpu *vcpu, u64 lr)
{
	struct vgic_irq *irq;

	if (!(lr & ICH_LR_HW))
		return lr;

	/* We have the HW bit set, check for validity of pINTID */
	irq = vgic_get_vcpu_irq(vcpu, FIELD_GET(ICH_LR_PHYS_ID_MASK, lr));
	/* If there was no real mapping, nuke the HW bit */
	if (!irq || !irq->hw || irq->intid > VGIC_MAX_SPI)
		lr &= ~ICH_LR_HW;

	/* Translate the virtual mapping to the real one, even if invalid */
	if (irq) {
		lr &= ~ICH_LR_PHYS_ID_MASK;
		lr |= FIELD_PREP(ICH_LR_PHYS_ID_MASK, (u64)irq->hwintid);
		vgic_put_irq(vcpu->kvm, irq);
	}

	return lr;
}

/*
 * For LRs which have HW bit set such as timer interrupts, we modify them to
 * have the host hardware interrupt number instead of the virtual one programmed
 * by the guest hypervisor.
 */
static void vgic_v3_create_shadow_lr(struct kvm_vcpu *vcpu,
				     struct vgic_v3_cpu_if *s_cpu_if)
{
	struct shadow_if *shadow_if;

	shadow_if = container_of(s_cpu_if, struct shadow_if, cpuif);
	shadow_if->lr_map = 0;

	for (int i = 0; i < kvm_vgic_global_state.nr_lr; i++) {
		u64 lr = __vcpu_sys_reg(vcpu, ICH_LRN(i));

		if (!(lr & ICH_LR_STATE))
			continue;

		lr = translate_lr_pintid(vcpu, lr);

		s_cpu_if->vgic_lr[hweight16(shadow_if->lr_map)] = lr;
		shadow_if->lr_map |= BIT(i);
	}

	s_cpu_if->used_lrs = hweight16(shadow_if->lr_map);
}

void vgic_v3_flush_nested(struct kvm_vcpu *vcpu)
{
	u64 val = __vcpu_sys_reg(vcpu, ICH_HCR_EL2);

	write_sysreg_s(val | vgic_ich_hcr_trap_bits(), SYS_ICH_HCR_EL2);
}

void vgic_v3_sync_nested(struct kvm_vcpu *vcpu)
{
	struct shadow_if *shadow_if = get_shadow_if();
	int i;

	for_each_set_bit(i, &shadow_if->lr_map, kvm_vgic_global_state.nr_lr) {
		u64 val, host_lr, lr;

		host_lr = __gic_v3_get_lr(lr_map_idx_to_shadow_idx(shadow_if, i));

		/* Propagate the new LR state */
		lr = __vcpu_sys_reg(vcpu, ICH_LRN(i));
		val = lr & ~ICH_LR_STATE;
		val |= host_lr & ICH_LR_STATE;
		__vcpu_assign_sys_reg(vcpu, ICH_LRN(i), val);

		/*
		 * Deactivation of a HW interrupt: the LR must have the HW
		 * bit set, have been in a non-invalid state before the run,
		 * and now be in an invalid state. If any of that doesn't
		 * hold, we're done with this LR.
		 */
		if (!((lr & ICH_LR_HW) && (lr & ICH_LR_STATE) &&
		      !(host_lr & ICH_LR_STATE)))
			continue;

		/*
		 * If we had a HW lr programmed by the guest hypervisor, we
		 * need to emulate the HW effect between the guest hypervisor
		 * and the nested guest.
		 */
		vgic_v3_deactivate(vcpu, FIELD_GET(ICH_LR_PHYS_ID_MASK, lr));
	}

	/* We need these to be synchronised to generate the MI */
	__vcpu_assign_sys_reg(vcpu, ICH_VMCR_EL2, read_sysreg_s(SYS_ICH_VMCR_EL2));
	__vcpu_rmw_sys_reg(vcpu, ICH_HCR_EL2, &=, ~ICH_HCR_EL2_EOIcount);
	__vcpu_rmw_sys_reg(vcpu, ICH_HCR_EL2, |=, read_sysreg_s(SYS_ICH_HCR_EL2) & ICH_HCR_EL2_EOIcount);

	write_sysreg_s(0, SYS_ICH_HCR_EL2);
	isb();

	vgic_v3_nested_update_mi(vcpu);
}

static void vgic_v3_create_shadow_state(struct kvm_vcpu *vcpu,
					struct vgic_v3_cpu_if *s_cpu_if)
{
	struct vgic_v3_cpu_if *host_if = &vcpu->arch.vgic_cpu.vgic_v3;
	int i;

	s_cpu_if->vgic_hcr = __vcpu_sys_reg(vcpu, ICH_HCR_EL2);
	s_cpu_if->vgic_vmcr = __vcpu_sys_reg(vcpu, ICH_VMCR_EL2);
	s_cpu_if->vgic_sre = host_if->vgic_sre;

	for (i = 0; i < 4; i++) {
		s_cpu_if->vgic_ap0r[i] = __vcpu_sys_reg(vcpu, ICH_AP0RN(i));
		s_cpu_if->vgic_ap1r[i] = __vcpu_sys_reg(vcpu, ICH_AP1RN(i));
	}

	vgic_v3_create_shadow_lr(vcpu, s_cpu_if);
}

void vgic_v3_load_nested(struct kvm_vcpu *vcpu)
{
	struct shadow_if *shadow_if = get_shadow_if();
	struct vgic_v3_cpu_if *cpu_if = &shadow_if->cpuif;

	BUG_ON(!vgic_state_is_nested(vcpu));

	vgic_v3_create_shadow_state(vcpu, cpu_if);

	__vgic_v3_restore_vmcr_aprs(cpu_if);
	__vgic_v3_activate_traps(cpu_if);

	for (int i = 0; i < cpu_if->used_lrs; i++)
		__gic_v3_set_lr(cpu_if->vgic_lr[i], i);

	/*
	 * Propagate the number of used LRs for the benefit of the HYP
	 * GICv3 emulation code. Yes, this is a pretty sorry hack.
	 */
	vcpu->arch.vgic_cpu.vgic_v3.used_lrs = cpu_if->used_lrs;
}

void vgic_v3_put_nested(struct kvm_vcpu *vcpu)
{
	struct shadow_if *shadow_if = get_shadow_if();
	struct vgic_v3_cpu_if *s_cpu_if = &shadow_if->cpuif;
	int i;

	__vgic_v3_save_aprs(s_cpu_if);

	for (i = 0; i < 4; i++) {
		__vcpu_assign_sys_reg(vcpu, ICH_AP0RN(i), s_cpu_if->vgic_ap0r[i]);
		__vcpu_assign_sys_reg(vcpu, ICH_AP1RN(i), s_cpu_if->vgic_ap1r[i]);
	}

	for (i = 0; i < s_cpu_if->used_lrs; i++)
		__gic_v3_set_lr(0, i);

	__vgic_v3_deactivate_traps(s_cpu_if);

	vcpu->arch.vgic_cpu.vgic_v3.used_lrs = 0;
}

/*
 * If we exit a L2 VM with a pending maintenance interrupt from the GIC,
 * then we need to forward this to L1 so that it can re-sync the appropriate
 * LRs and sample level triggered interrupts again.
 */
void vgic_v3_handle_nested_maint_irq(struct kvm_vcpu *vcpu)
{
	bool state = read_sysreg_s(SYS_ICH_MISR_EL2);

	/* This will force a switch back to L1 if the level is high */
	kvm_vgic_inject_irq(vcpu->kvm, vcpu,
			    vcpu->kvm->arch.vgic.mi_intid, state, vcpu);

	sysreg_clear_set_s(SYS_ICH_HCR_EL2, ICH_HCR_EL2_En, 0);
}

void vgic_v3_nested_update_mi(struct kvm_vcpu *vcpu)
{
	bool level;

	level = (__vcpu_sys_reg(vcpu, ICH_HCR_EL2) & ICH_HCR_EL2_En) && vgic_v3_get_misr(vcpu);
	kvm_vgic_inject_irq(vcpu->kvm, vcpu,
			    vcpu->kvm->arch.vgic.mi_intid, level, vcpu);
}