[PATCH v3 19/19] KVM: arm64: ITS: Pending table save/restore
From: andre.przywara@arm.com (Andre Przywara)
Date: 2017-03-20 18:21:51
Also in:
kvm, kvmarm
Hi Eric, just fast-forwarded to the end and noticed this one: On 06/03/17 11:34, Eric Auger wrote:
quoted hunk ↗ jump to hunk
Save and restore the pending tables. Pending table restore obviously requires the pendbaser to be already set. Signed-off-by: Eric Auger <eric.auger@redhat.com> --- v1 -> v2: - do not care about the 1st KB which should be zeroed according to the spec. --- virt/kvm/arm/vgic/vgic-its.c | 71 ++++++++++++++++++++++++++++++++++++++++++-- 1 file changed, 69 insertions(+), 2 deletions(-)diff --git a/virt/kvm/arm/vgic/vgic-its.c b/virt/kvm/arm/vgic/vgic-its.c index 27ebabd..24824be 100644 --- a/virt/kvm/arm/vgic/vgic-its.c +++ b/virt/kvm/arm/vgic/vgic-its.c@@ -1736,7 +1736,48 @@ static int lookup_table(struct vgic_its *its, gpa_t base, int size, int esz, */ static int vgic_its_flush_pending_tables(struct vgic_its *its) { - return -ENXIO; + struct kvm *kvm = its->dev->kvm; + struct vgic_dist *dist = &kvm->arch.vgic; + struct vgic_irq *irq; + int ret; + + /** + * we do not take the dist->lpi_list_lock since we have a garantee + * the LPI list is not touched while the its lock is held
Can you elaborate on what gives us this guarantee? I see that we have a locking *order*, but that doesn't mean we can avoid taking the lock. So to me it looks like we need to take the lpi_list_lock spinlock here, which unfortunately breaks the kvm_read_guest() calls below. If you agree on this, you can take a look at the INVALL implementation, where I faced the same issue. The solution we came up with is vgic_copy_lpi_list(), which you can call under the lock to create a (private) copy of the LPI list, which you can later iterate without holding the lock - and thus are free to call sleeping functions. Cheers, Andre.
quoted hunk ↗ jump to hunk
+ */ + list_for_each_entry(irq, &dist->lpi_list_head, lpi_list) { + struct kvm_vcpu *vcpu; + gpa_t pendbase, ptr; + bool stored; + u8 val; + + vcpu = irq->target_vcpu; + if (!vcpu) + return -EINVAL; + + pendbase = PENDBASER_ADDRESS(vcpu->arch.vgic_cpu.pendbaser); + + ptr = pendbase + (irq->intid / BITS_PER_BYTE); + + ret = kvm_read_guest(kvm, (gpa_t)ptr, &val, 1); + if (ret) + return ret; + + stored = val & (irq->intid % BITS_PER_BYTE); + if (stored == irq->pending_latch) + continue; + + if (irq->pending_latch) + val |= 1 << (irq->intid % BITS_PER_BYTE); + else + val &= ~(1 << (irq->intid % BITS_PER_BYTE)); + + ret = kvm_write_guest(kvm, (gpa_t)ptr, &val, 1); + if (ret) + return ret; + } + + return 0; } /**@@ -1745,7 +1786,33 @@ static int vgic_its_flush_pending_tables(struct vgic_its *its) */ static int vgic_its_restore_pending_tables(struct vgic_its *its) { - return -ENXIO; + struct vgic_irq *irq; + struct kvm *kvm = its->dev->kvm; + struct vgic_dist *dist = &kvm->arch.vgic; + int ret; + + list_for_each_entry(irq, &dist->lpi_list_head, lpi_list) { + struct kvm_vcpu *vcpu; + gpa_t pendbase, ptr; + u8 val; + + vcpu = irq->target_vcpu; + if (!vcpu) + return -EINVAL; + + if (!(vcpu->arch.vgic_cpu.pendbaser & GICR_PENDBASER_PTZ)) + return 0; + + pendbase = PENDBASER_ADDRESS(vcpu->arch.vgic_cpu.pendbaser); + + ptr = pendbase + (irq->intid / BITS_PER_BYTE); + + ret = kvm_read_guest(kvm, (gpa_t)ptr, &val, 1); + if (ret) + return ret; + irq->pending_latch = val & (1 << (irq->intid % BITS_PER_BYTE)); + } + return 0; } static int vgic_its_flush_ite(struct vgic_its *its, struct its_device *dev,