Messages in this thread | | | Subject | Re: [PATCH v5 20/23] KVM: arm64: GICv4.1: Plumb SGI implementation selection in the distributor | From | Zenghui Yu <> | Date | Wed, 18 Mar 2020 14:34:59 +0800 |
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Hi Marc,
On 2020/3/5 4:33, Marc Zyngier wrote: > The GICv4.1 architecture gives the hypervisor the option to let > the guest choose whether it wants the good old SGIs with an > active state, or the new, HW-based ones that do not have one. > > For this, plumb the configuration of SGIs into the GICv3 MMIO > handling, present the GICD_TYPER2.nASSGIcap to the guest, > and handle the GICD_CTLR.nASSGIreq setting. > > In order to be able to deal with the restore of a guest, also > apply the GICD_CTLR.nASSGIreq setting at first run so that we > can move the restored SGIs to the HW if that's what the guest > had selected in a previous life.
I'm okay with the restore path. But it seems that we still fail to save the pending state of vSGI - software pending_latch of HW-based vSGIs will not be updated (and always be false) because we directly inject them through ITS, so vgic_v3_uaccess_read_pending() can't tell the correct pending state to user-space (the correct one should be latched in HW).
It would be good if we can sync the hardware state into pending_latch at an appropriate time (just before save), but not sure if we can...
> > Signed-off-by: Marc Zyngier <maz@kernel.org> > --- > virt/kvm/arm/vgic/vgic-mmio-v3.c | 48 ++++++++++++++++++++++++++++++-- > virt/kvm/arm/vgic/vgic-v3.c | 2 ++ > 2 files changed, 48 insertions(+), 2 deletions(-) > > diff --git a/virt/kvm/arm/vgic/vgic-mmio-v3.c b/virt/kvm/arm/vgic/vgic-mmio-v3.c > index de89da76a379..442f3b8c2559 100644 > --- a/virt/kvm/arm/vgic/vgic-mmio-v3.c > +++ b/virt/kvm/arm/vgic/vgic-mmio-v3.c > @@ -3,6 +3,7 @@ > * VGICv3 MMIO handling functions > */ > > +#include <linux/bitfield.h> > #include <linux/irqchip/arm-gic-v3.h> > #include <linux/kvm.h> > #include <linux/kvm_host.h> > @@ -70,6 +71,8 @@ static unsigned long vgic_mmio_read_v3_misc(struct kvm_vcpu *vcpu, > if (vgic->enabled) > value |= GICD_CTLR_ENABLE_SS_G1; > value |= GICD_CTLR_ARE_NS | GICD_CTLR_DS; > + if (kvm_vgic_global_state.has_gicv4_1 && vgic->nassgireq)
Looking at how we handle the GICD_CTLR.nASSGIreq setting, I think "nassgireq==true" already indicates "has_gicv4_1==true". So this can be simplified.
But I wonder that should we use nassgireq to *only* keep track what the guest had written into the GICD_CTLR.nASSGIreq. If not, we may lose the guest-request bit after migration among hosts with different has_gicv4_1 settings.
The remaining patches all look good to me :-). I will wait for you to confirm these two concerns.
Thanks, Zenghui
> + value |= GICD_CTLR_nASSGIreq; > break; > case GICD_TYPER: > value = vgic->nr_spis + VGIC_NR_PRIVATE_IRQS; > @@ -81,6 +84,10 @@ static unsigned long vgic_mmio_read_v3_misc(struct kvm_vcpu *vcpu, > value |= (INTERRUPT_ID_BITS_SPIS - 1) << 19; > } > break; > + case GICD_TYPER2: > + if (kvm_vgic_global_state.has_gicv4_1) > + value = GICD_TYPER2_nASSGIcap; > + break; > case GICD_IIDR: > value = (PRODUCT_ID_KVM << GICD_IIDR_PRODUCT_ID_SHIFT) | > (vgic->implementation_rev << GICD_IIDR_REVISION_SHIFT) | > @@ -98,17 +105,43 @@ static void vgic_mmio_write_v3_misc(struct kvm_vcpu *vcpu, > unsigned long val) > { > struct vgic_dist *dist = &vcpu->kvm->arch.vgic; > - bool was_enabled = dist->enabled; > > switch (addr & 0x0c) { > - case GICD_CTLR: > + case GICD_CTLR: { > + bool was_enabled, is_hwsgi; > + > + mutex_lock(&vcpu->kvm->lock); > + > + was_enabled = dist->enabled; > + is_hwsgi = dist->nassgireq; > + > dist->enabled = val & GICD_CTLR_ENABLE_SS_G1; > > + /* Not a GICv4.1? No HW SGIs */ > + if (!kvm_vgic_global_state.has_gicv4_1) > + val &= ~GICD_CTLR_nASSGIreq; > + > + /* Dist stays enabled? nASSGIreq is RO */ > + if (was_enabled && dist->enabled) { > + val &= ~GICD_CTLR_nASSGIreq; > + val |= FIELD_PREP(GICD_CTLR_nASSGIreq, is_hwsgi); > + } > + > + /* Switching HW SGIs? */ > + dist->nassgireq = val & GICD_CTLR_nASSGIreq; > + if (is_hwsgi != dist->nassgireq) > + vgic_v4_configure_vsgis(vcpu->kvm); > + > if (!was_enabled && dist->enabled) > vgic_kick_vcpus(vcpu->kvm); > + > + mutex_unlock(&vcpu->kvm->lock); > break; > + } > case GICD_TYPER: > + case GICD_TYPER2: > case GICD_IIDR: > + /* This is at best for documentation purposes... */ > return; > } > } > @@ -117,10 +150,21 @@ static int vgic_mmio_uaccess_write_v3_misc(struct kvm_vcpu *vcpu, > gpa_t addr, unsigned int len, > unsigned long val) > { > + struct vgic_dist *dist = &vcpu->kvm->arch.vgic; > + > switch (addr & 0x0c) { > case GICD_IIDR: > if (val != vgic_mmio_read_v3_misc(vcpu, addr, len)) > return -EINVAL; > + return 0; > + case GICD_CTLR: > + /* Not a GICv4.1? No HW SGIs */ > + if (!kvm_vgic_global_state.has_gicv4_1) > + val &= ~GICD_CTLR_nASSGIreq; > + > + dist->enabled = val & GICD_CTLR_ENABLE_SS_G1; > + dist->nassgireq = val & GICD_CTLR_nASSGIreq; > + return 0; > } > > vgic_mmio_write_v3_misc(vcpu, addr, len, val); > diff --git a/virt/kvm/arm/vgic/vgic-v3.c b/virt/kvm/arm/vgic/vgic-v3.c > index 1bc09b523486..2c9fc13e2c59 100644 > --- a/virt/kvm/arm/vgic/vgic-v3.c > +++ b/virt/kvm/arm/vgic/vgic-v3.c > @@ -540,6 +540,8 @@ int vgic_v3_map_resources(struct kvm *kvm) > goto out; > } > > + if (kvm_vgic_global_state.has_gicv4_1) > + vgic_v4_configure_vsgis(kvm); > dist->ready = true; > > out: >
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