On 2021/3/11 16:57, Marc Zyngier wrote:

quoted

On Wed, 27 Jan 2021 12:13:34 +0000,
Shenming Lu [off-list ref] wrote:

quoted

With GICv4.1 and the vPE unmapped, which indicates the invalidation
of any VPT caches associated with the vPE, we can get the VLPI state
by peeking at the VPT. So we add a function for this.

Signed-off-by: Shenming Lu <redacted>
---
 arch/arm64/kvm/vgic/vgic-v4.c | 19 +++++++++++++++++++
 arch/arm64/kvm/vgic/vgic.h    |  1 +
 2 files changed, 20 insertions(+)

diff --git a/arch/arm64/kvm/vgic/vgic-v4.c b/arch/arm64/kvm/vgic/vgic-v4.c
index 66508b03094f..ac029ba3d337 100644
--- a/arch/arm64/kvm/vgic/vgic-v4.c
+++ b/arch/arm64/kvm/vgic/vgic-v4.c

@@ -203,6 +203,25 @@ void vgic_v4_configure_vsgis(struct kvm *kvm)
 	kvm_arm_resume_guest(kvm);
 }
 
+/*
+ * Must be called with GICv4.1 and the vPE unmapped, which
+ * indicates the invalidation of any VPT caches associated
+ * with the vPE, thus we can get the VLPI state by peeking
+ * at the VPT.
+ */
+void vgic_v4_get_vlpi_state(struct vgic_irq *irq, bool *val)
+{
+	struct its_vpe *vpe = &irq->target_vcpu->arch.vgic_cpu.vgic_v3.its_vpe;
+	int mask = BIT(irq->intid % BITS_PER_BYTE);
+	void *va;
+	u8 *ptr;
+
+	va = page_address(vpe->vpt_page);
+	ptr = va + irq->intid / BITS_PER_BYTE;
+
+	*val = !!(*ptr & mask);

What guarantees that you can actually read anything valid? Yes, the
VPT caches are clean. But that doesn't make them coherent with CPU
caches.

You need some level of cache maintenance here.

Yeah, and you have come up with some codes for this in v2:

diff --git a/drivers/irqchip/irq-gic-v3-its.c

b/drivers/irqchip/irq-gic-v3-its.c
index 7db602434ac5..2dbef127ca15 100644

--- a/drivers/irqchip/irq-gic-v3-its.c
+++ b/drivers/irqchip/irq-gic-v3-its.c

@@ -4552,6 +4552,10 @@ static void its_vpe_irq_domain_deactivate(struct

irq_domain *domain,

  		its_send_vmapp(its, vpe, false);
  	}
+
+	if (find_4_1_its() && !atomic_read(vpe->vmapp_count))
+		gic_flush_dcache_to_poc(page_address(vpe->vpt_page),
+					LPI_PENDBASE_SZ);
  }

  static const struct irq_domain_ops its_vpe_domain_ops = {

Could I add it to this series? :-)