[PATCH v3 8/9] KVM: arm-vgic: Add GICD_SPENDSGIR and GICD_CPENDSGIR handlers

[Christoffer Dall]

On Mon, Dec 09, 2013 at 04:49:45PM +0000, Marc Zyngier wrote:
> On 2013-11-17 04:30, Christoffer Dall wrote:
> >Handle MMIO accesses to the two registers which should support
> >both the
> >case where the VMs want to read/write either of these registers
> >and the
> >case where user space reads/writes these registers to do
> >save/restore of
> >the VGIC state.
> >
> >Note that the added complexity compared to simple set/clear enable
> >registers stems from the bookkeping of source cpu ids.  It may be
> >possible to change the underlying data structure to simplify the
> >complexity, but since this is not in the critical path at all,
> >this will
> >do.
> >
> >Also note that reading this register from a live guest will not be
> >accurate compared to on hardware, because some state may be living on
> >the CPU LRs and the only way to give a consistent read would be to
> >force
> >stop all the VCPUs and request them to unqueu the LR state onto the
> >distributor.  Until we have an actual user of live reading this
> >register, we can live with the difference.
> >
> >Signed-off-by: Christoffer Dall <christoffer.dall at linaro.org>
> 
> Looks pretty good to me. Small note below, but otherwise:
> 
> Acked-by: Marc Zyngier <marc.zyngier at arm.com>
> 
> >
> >Changelog[v3]:
> > - Renamed read/write SGI set/clear functions
> > - Rely on unqueuing of interrupts from LRs instead of reading LRs
> >   directly
> > - Deduplicate code
> >
> >Changelog[v2]:
> > - Use struct kvm_exit_mmio accessors for ->data field.
> >---
> > virt/kvm/arm/vgic.c |   70
> >++++++++++++++++++++++++++++++++++++++++++++++++---
> > 1 file changed, 66 insertions(+), 4 deletions(-)
> >
> >diff --git a/virt/kvm/arm/vgic.c b/virt/kvm/arm/vgic.c
> >index 44c669b..16053eb 100644
> >--- a/virt/kvm/arm/vgic.c
> >+++ b/virt/kvm/arm/vgic.c
> >@@ -655,18 +655,80 @@ static void vgic_unqueue_irqs(struct
> >kvm_vcpu *vcpu)
> > 	}
> > }
> >
> >-static bool handle_mmio_sgi_clear(struct kvm_vcpu *vcpu,
> >-				  struct kvm_exit_mmio *mmio,
> >-				  phys_addr_t offset)
> >+/* Handle reads of GICD_CPENDSGIRn and GICD_SPENDSGIRn */
> >+static bool read_set_clear_sgi_pend_reg(struct kvm_vcpu *vcpu,
> >+					struct kvm_exit_mmio *mmio,
> >+					phys_addr_t offset)
> > {
> >+	struct vgic_dist *dist = &vcpu->kvm->arch.vgic;
> >+	int sgi;
> >+	int min_sgi = (offset & ~0x3) * 4;
> >+	int max_sgi = min_sgi + 3;
> >+	int vcpu_id = vcpu->vcpu_id;
> >+	u32 reg = 0;
> >+
> >+	/* Copy source SGIs from distributor side */
> >+	for (sgi = min_sgi; sgi <= max_sgi; sgi++) {
> >+		int shift = 8 * (sgi - min_sgi);
> >+		reg |= (u32)dist->irq_sgi_sources[vcpu_id][sgi] << shift;
> >+	}
> >+
> >+	mmio_data_write(mmio, ~0, reg);
> > 	return false;
> > }
> >
> >+static bool write_set_clear_sgi_pend_reg(struct kvm_vcpu *vcpu,
> >+					 struct kvm_exit_mmio *mmio,
> >+					 phys_addr_t offset, bool set)
> >+{
> >+	struct vgic_dist *dist = &vcpu->kvm->arch.vgic;
> >+	int sgi;
> >+	int min_sgi = (offset & ~0x3) * 4;
> >+	int max_sgi = min_sgi + 3;
> >+	int vcpu_id = vcpu->vcpu_id;
> >+	u32 reg;
> >+	bool updated = false;
> >+
> >+	reg = mmio_data_read(mmio, ~0);
> >+
> >+	/* Clear pending SGIs on the distributor */
> >+	for (sgi = min_sgi; sgi <= max_sgi; sgi++) {
> >+		u8 mask = reg >> (8 * (sgi - min_sgi));
> >+		if (set) {
> >+			if ((dist->irq_sgi_sources[vcpu_id][sgi] & mask) != mask)
> >+				updated = true;
> >+			dist->irq_sgi_sources[vcpu_id][sgi] |= mask;
> >+		} else {
> >+			if (dist->irq_sgi_sources[vcpu_id][sgi] & mask)
> >+				updated = true;
> >+			dist->irq_sgi_sources[vcpu_id][sgi] &= ~mask;
> >+		}
> >+	}
> >+
> >+	if (updated)
> >+		vgic_update_state(vcpu->kvm);
> 
> So I realize we have that construct everywhere. Surely it'd be worth
> it moving the mmio calls to vgic_update_state into vgic_handle_mmio.
> Or have I missed something?
> 

I have some very vague recollection that we once discussed if we wanted
to compare some of the register writes to their original values and only
update the vgic state in that case, and therefore have the functionality
locally (whereas now, if it's a write, we call update).

That being said, it should still work with only calling update whenever
we return true from those mmio handlers, so I guess it would work.

Are you ok with us fixing this after this code is merged, I'd really
like to get these patches in as they have been floating around for quite
a while.

Thanks,
-Christoffer

> >+	return updated;
> >+}
> >+
> > static bool handle_mmio_sgi_set(struct kvm_vcpu *vcpu,
> > 				struct kvm_exit_mmio *mmio,
> > 				phys_addr_t offset)
> > {
> >-	return false;
> >+	if (!mmio->is_write)
> >+		return read_set_clear_sgi_pend_reg(vcpu, mmio, offset);
> >+	else
> >+		return write_set_clear_sgi_pend_reg(vcpu, mmio, offset, true);
> >+}
> >+
> >+static bool handle_mmio_sgi_clear(struct kvm_vcpu *vcpu,
> >+				  struct kvm_exit_mmio *mmio,
> >+				  phys_addr_t offset)
> >+{
> >+	if (!mmio->is_write)
> >+		return read_set_clear_sgi_pend_reg(vcpu, mmio, offset);
> >+	else
> >+		return write_set_clear_sgi_pend_reg(vcpu, mmio, offset, false);
> > }
> >
> > /*
> 
> -- 
> Fast, cheap, reliable. Pick two.

-- 
Christoffer