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KVM: arm64: vgic-its: Read initial LPI pending table

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The LPI pending status for a GICv3 redistributor is held in a table
in (guest) memory. To achieve reasonable performance, we cache the
pending bit in our struct vgic_irq. The initial pending state must be
read from guest memory upon enabling LPIs for this redistributor.
As we can't access the guest memory while we hold the lpi_list spinlock,
we create a snapshot of the LPI list and iterate over that.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Reviewed-by: Marc Zyngier <marc.zyngier@arm.com>
Tested-by: Eric Auger <eric.auger@redhat.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
This commit is contained in:
Andre Przywara 2016-07-15 12:43:34 +01:00 committed by Marc Zyngier
parent 3802411d01
commit 33d3bc9556
2 changed files with 100 additions and 0 deletions
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95
virt/kvm/arm/vgic/vgic-its.c
View File

@ -67,6 +67,94 @@ struct its_itte {
* supports more. Let's be restrictive here.
*/
#define CBASER_ADDRESS(x) ((x) & GENMASK_ULL(47, 12))
#define PENDBASER_ADDRESS(x) ((x) & GENMASK_ULL(47, 16))
/*
* Create a snapshot of the current LPI list, so that we can enumerate all
* LPIs without holding any lock.
* Returns the array length and puts the kmalloc'ed array into intid_ptr.
*/
static int vgic_copy_lpi_list(struct kvm *kvm, u32 **intid_ptr)
{
struct vgic_dist *dist = &kvm->arch.vgic;
struct vgic_irq *irq;
u32 *intids;
int irq_count = dist->lpi_list_count, i = 0;
/*
* We use the current value of the list length, which may change
* after the kmalloc. We don't care, because the guest shouldn't
* change anything while the command handling is still running,
* and in the worst case we would miss a new IRQ, which one wouldn't
* expect to be covered by this command anyway.
*/
intids = kmalloc_array(irq_count, sizeof(intids[0]), GFP_KERNEL);
if (!intids)
return -ENOMEM;
spin_lock(&dist->lpi_list_lock);
list_for_each_entry(irq, &dist->lpi_list_head, lpi_list) {
/* We don't need to "get" the IRQ, as we hold the list lock. */
intids[i] = irq->intid;
if (++i == irq_count)
break;
}
spin_unlock(&dist->lpi_list_lock);
*intid_ptr = intids;
return irq_count;
}
/*
* Scan the whole LPI pending table and sync the pending bit in there
* with our own data structures. This relies on the LPI being
* mapped before.
*/
static int its_sync_lpi_pending_table(struct kvm_vcpu *vcpu)
{
gpa_t pendbase = PENDBASER_ADDRESS(vcpu->arch.vgic_cpu.pendbaser);
struct vgic_irq *irq;
int last_byte_offset = -1;
int ret = 0;
u32 *intids;
int nr_irqs, i;
nr_irqs = vgic_copy_lpi_list(vcpu->kvm, &intids);
if (nr_irqs < 0)
return nr_irqs;
for (i = 0; i < nr_irqs; i++) {
int byte_offset, bit_nr;
u8 pendmask;
byte_offset = intids[i] / BITS_PER_BYTE;
bit_nr = intids[i] % BITS_PER_BYTE;
/*
* For contiguously allocated LPIs chances are we just read
* this very same byte in the last iteration. Reuse that.
*/
if (byte_offset != last_byte_offset) {
ret = kvm_read_guest(vcpu->kvm, pendbase + byte_offset,
&pendmask, 1);
if (ret) {
kfree(intids);
return ret;
}
last_byte_offset = byte_offset;
}
irq = vgic_get_irq(vcpu->kvm, NULL, intids[i]);
spin_lock(&irq->irq_lock);
irq->pending = pendmask & (1U << bit_nr);
vgic_queue_irq_unlock(vcpu->kvm, irq);
vgic_put_irq(vcpu->kvm, irq);
}
kfree(intids);
return ret;
}
static unsigned long vgic_mmio_read_its_ctlr(struct kvm *vcpu,
struct vgic_its *its,
@ -403,6 +491,13 @@ static struct vgic_register_region its_registers[] = {
VGIC_ACCESS_32bit),
};
/* This is called on setting the LPI enable bit in the redistributor. */
void vgic_enable_lpis(struct kvm_vcpu *vcpu)
{
if (!(vcpu->arch.vgic_cpu.pendbaser & GICR_PENDBASER_PTZ))
its_sync_lpi_pending_table(vcpu);
}
static int vgic_its_init_its(struct kvm *kvm, struct vgic_its *its)
{
struct vgic_io_device *iodev = &its->iodev;

5
virt/kvm/arm/vgic/vgic.h
View File

@ -25,6 +25,7 @@
#define IS_VGIC_ADDR_UNDEF(_x) ((_x) == VGIC_ADDR_UNDEF)
#define INTERRUPT_ID_BITS_SPIS 10
#define INTERRUPT_ID_BITS_ITS 16
#define VGIC_PRI_BITS 5
#define vgic_irq_is_sgi(intid) ((intid) < VGIC_NR_SGIS)
@ -76,6 +77,7 @@ int vgic_v3_probe(const struct gic_kvm_info *info);
int vgic_v3_map_resources(struct kvm *kvm);
int vgic_register_redist_iodevs(struct kvm *kvm, gpa_t dist_base_address);
bool vgic_has_its(struct kvm *kvm);
void vgic_enable_lpis(struct kvm_vcpu *vcpu);
#else
static inline void vgic_v3_process_maintenance(struct kvm_vcpu *vcpu)
{
@ -133,6 +135,9 @@ static inline bool vgic_has_its(struct kvm *kvm)
return false;
}
static inline void vgic_enable_lpis(struct kvm_vcpu *vcpu)
{
}
#endif
int kvm_register_vgic_device(unsigned long type);