[PATCH 2/4] KVM: arm/arm64: vgic-v3: Add core support for Group0 SGIs

STALE2992d SUPERSEDED

From: Christoffer Dall <hidden>
Date: 2018-08-09 07:40:34
Also in: kvm, kvmarm

Revision v1 of 5 in this series.

Revisions (5)

2018-08-08 v1
2018-08-09 v1 current
2018-08-09 v1
2018-08-10 v2 [diff vs current]
2018-08-11 v2 [diff vs current]

On Wed, Aug 08, 2018 at 02:14:59PM +0100, Marc Zyngier wrote:

Although vgic-v3 now supports Group0 interrupts, it still doesn't
deal with Group0 SGIs. As usually with the GIC, nothing is simple:

- ICC_SGI1R can signal SGIs of both groups, since GICD_CTLR.DS==1
  with KVM (as per 8.1.10, Non-secure EL1 access)

- ICC_SGI0R can only generate Group0 SGIs

- ICC_ASGI1R sees its scope refocussed to generate only Group0
  SGIs (as per the note at the bottom of Table 8-14)

One way to look at this is that an SGI can be generated if the
group implied by the CPU interface is lower or equal to the
group specified by the interrupt.

This sentence hurts my brain. Another way to look at it is that with
DS=1, only SGI1R allows signaling group1 interrupts.  See below.

quoted hunk ↗ jump to hunk

We only support Group1 SGIs so far, so no material change.

Signed-off-by: Marc Zyngier <redacted>
---
 arch/arm/kvm/coproc.c            |  2 +-
 arch/arm64/kvm/sys_regs.c        |  2 +-
 include/kvm/arm_vgic.h           |  2 +-
 virt/kvm/arm/vgic/vgic-mmio-v3.c | 16 +++++++++++++---
 4 files changed, 16 insertions(+), 6 deletions(-)

diff --git a/arch/arm/kvm/coproc.c b/arch/arm/kvm/coproc.c
index 3a02e76699a6..ec517992c12d 100644
--- a/arch/arm/kvm/coproc.c
+++ b/arch/arm/kvm/coproc.c

@@ -253,7 +253,7 @@ static bool access_gic_sgi(struct kvm_vcpu *vcpu,
 	reg = (u64)*vcpu_reg(vcpu, p->Rt2) << 32;
 	reg |= *vcpu_reg(vcpu, p->Rt1) ;
 
-	vgic_v3_dispatch_sgi(vcpu, reg);
+	vgic_v3_dispatch_sgi(vcpu, reg, 1);
 
 	return true;
 }

diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index e04aacb2a24c..a09139b97e81 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c

@@ -255,7 +255,7 @@ static bool access_gic_sgi(struct kvm_vcpu *vcpu,
 	if (!p->is_write)
 		return read_from_write_only(vcpu, p, r);
 
-	vgic_v3_dispatch_sgi(vcpu, p->regval);
+	vgic_v3_dispatch_sgi(vcpu, p->regval, 1);
 
 	return true;
 }

diff --git a/include/kvm/arm_vgic.h b/include/kvm/arm_vgic.h
index c134790be32c..06a25b11efa7 100644
--- a/include/kvm/arm_vgic.h
+++ b/include/kvm/arm_vgic.h

@@ -373,7 +373,7 @@ void kvm_vgic_sync_hwstate(struct kvm_vcpu *vcpu);
 void kvm_vgic_flush_hwstate(struct kvm_vcpu *vcpu);
 void kvm_vgic_reset_mapped_irq(struct kvm_vcpu *vcpu, u32 vintid);
 
-void vgic_v3_dispatch_sgi(struct kvm_vcpu *vcpu, u64 reg);
+void vgic_v3_dispatch_sgi(struct kvm_vcpu *vcpu, u64 reg, int group);
 
 /**
  * kvm_vgic_get_max_vcpus - Get the maximum number of VCPUs allowed by HW

diff --git a/virt/kvm/arm/vgic/vgic-mmio-v3.c b/virt/kvm/arm/vgic/vgic-mmio-v3.c
index 88e78b582139..11d321f7ad71 100644
--- a/virt/kvm/arm/vgic/vgic-mmio-v3.c
+++ b/virt/kvm/arm/vgic/vgic-mmio-v3.c

@@ -901,6 +901,7 @@ static int match_mpidr(u64 sgi_aff, u16 sgi_cpu_mask, struct kvm_vcpu *vcpu)
  * vgic_v3_dispatch_sgi - handle SGI requests from VCPUs
  * @vcpu: The VCPU requesting a SGI
  * @reg: The value written into the ICC_SGI1R_EL1 register by that VCPU
+ * @group: Interrupt group requested by the sender
  *
  * With GICv3 (and ARE=1) CPUs trigger SGIs by writing to a system register.
  * This will trap in sys_regs.c and call this function.

@@ -910,7 +911,7 @@ static int match_mpidr(u64 sgi_aff, u16 sgi_cpu_mask, struct kvm_vcpu *vcpu)
  * check for matching ones. If this bit is set, we signal all, but not the
  * calling VCPU.
  */
-void vgic_v3_dispatch_sgi(struct kvm_vcpu *vcpu, u64 reg)
+void vgic_v3_dispatch_sgi(struct kvm_vcpu *vcpu, u64 reg, int group)
 {
 	struct kvm *kvm = vcpu->kvm;
 	struct kvm_vcpu *c_vcpu;

@@ -959,9 +960,18 @@ void vgic_v3_dispatch_sgi(struct kvm_vcpu *vcpu, u64 reg)
 		irq = vgic_get_irq(vcpu->kvm, c_vcpu, sgi);
 
 		spin_lock_irqsave(&irq->irq_lock, flags);
-		irq->pending_latch = true;
 
-		vgic_queue_irq_unlock(vcpu->kvm, irq, flags);
+		/*
+		 * A Group0 access can only generate a Group0 SGI,
+		 * while a Group1 access can generate either group.
+		 */

nit: "Is a Group 0 access" a well-defined term?

I think it may be clearer if the parameter was: bool allow_group1

and the condition was:

if (irq->group && allow_group1) {
	...

At least that would match the comment.

+		if (irq->group <= group) {
+			irq->pending_latch = true;
+			vgic_queue_irq_unlock(vcpu->kvm, irq, flags);
+		} else {
+			spin_unlock_irqrestore(&irq->irq_lock, flags);
+		}
+
 		vgic_put_irq(vcpu->kvm, irq);
 	}
 }
-- 
2.18.0

Thanks,
-Christoffer

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