Hello!
> -----Original Message-----
> From: kvm-ow...@vger.kernel.org [mailto:kvm-ow...@vger.kernel.org] On Behalf
> Of Andre Przywara
> Sent: Wednesday, October 07, 2015 5:55 PM
> To: marc.zyng...@arm.com; christoffer.d...@linaro.org
> Cc: eric.au...@linaro.org; p.fe...@samsung.com; kvm...@lists.cs.columbia.edu;
> linux-arm-
> ker...@lists.infradead.org; kvm@vger.kernel.org
> Subject: [PATCH v3 13/16] KVM: arm64: sync LPI configuration and pending
> tables
>
> The LPI configuration and pending tables of the GICv3 LPIs are held
> in tables in (guest) memory. To achieve reasonable performance, we
> cache this data in our own data structures, so we need to sync those
> two views from time to time. This behaviour is well described in the
> GICv3 spec and is also exercised by hardware, so the sync points are
> well known.
>
> Provide functions that read the guest memory and store the
> information from the configuration and pending tables in the kernel.
>
> Signed-off-by: Andre Przywara <andre.przyw...@arm.com>
> ---
> Changelog v2..v3:
> - rework functions to avoid propbaser/pendbaser accesses inside lock
>
> include/kvm/arm_vgic.h | 2 +
> virt/kvm/arm/its-emul.c | 133
> ++++++++++++++++++++++++++++++++++++++++++++++++
> virt/kvm/arm/its-emul.h | 3 ++
> 3 files changed, 138 insertions(+)
>
> diff --git a/include/kvm/arm_vgic.h b/include/kvm/arm_vgic.h
> index 035911f..4ea023c 100644
> --- a/include/kvm/arm_vgic.h
> +++ b/include/kvm/arm_vgic.h
> @@ -179,6 +179,8 @@ struct vgic_its {
> int cwriter;
> struct list_head device_list;
> struct list_head collection_list;
> + /* memory used for buffering guest's memory */
> + void *buffer_page;
> };
>
> struct vgic_dist {
> diff --git a/virt/kvm/arm/its-emul.c b/virt/kvm/arm/its-emul.c
> index 8349970..7a8c5db 100644
> --- a/virt/kvm/arm/its-emul.c
> +++ b/virt/kvm/arm/its-emul.c
> @@ -59,6 +59,7 @@ struct its_itte {
> struct its_collection *collection;
> u32 lpi;
> u32 event_id;
> + u8 priority;
> bool enabled;
> unsigned long *pending;
> };
> @@ -80,8 +81,124 @@ static struct its_itte *find_itte_by_lpi(struct kvm *kvm,
> int lpi)
> return NULL;
> }
>
> +#define LPI_PROP_ENABLE_BIT(p) ((p) & LPI_PROP_ENABLED)
> +#define LPI_PROP_PRIORITY(p) ((p) & 0xfc)
> +
> +/* stores the priority and enable bit for a given LPI */
> +static void update_lpi_config(struct kvm *kvm, struct its_itte *itte, u8
> prop)
> +{
> + itte->priority = LPI_PROP_PRIORITY(prop);
> + itte->enabled = LPI_PROP_ENABLE_BIT(prop);
> +}
> +
> +#define GIC_LPI_OFFSET 8192
> +
> +/* We scan the table in chunks the size of the smallest page size */
> +#define CHUNK_SIZE 4096U
> +
> #define BASER_BASE_ADDRESS(x) ((x) & 0xfffffffff000ULL)
>
> +static int nr_idbits_propbase(u64 propbaser)
> +{
> + int nr_idbits = (1U << (propbaser & 0x1f)) + 1;
> +
> + return max(nr_idbits, INTERRUPT_ID_BITS_ITS);
> +}
> +
> +/*
> + * Scan the whole LPI configuration table and put the LPI configuration
> + * data in our own data structures. This relies on the LPI being
> + * mapped before.
> + */
> +static bool its_update_lpis_configuration(struct kvm *kvm, u64 prop_base_reg)
> +{
> + struct vgic_dist *dist = &kvm->arch.vgic;
> + u8 *prop = dist->its.buffer_page;
> + u32 tsize;
> + gpa_t propbase;
> + int lpi = GIC_LPI_OFFSET;
> + struct its_itte *itte;
> + struct its_device *device;
> + int ret;
> +
> + propbase = BASER_BASE_ADDRESS(prop_base_reg);
> + tsize = nr_idbits_propbase(prop_base_reg);
> +
> + while (tsize > 0) {
> + int chunksize = min(tsize, CHUNK_SIZE);
> +
> + ret = kvm_read_guest(kvm, propbase, prop, chunksize);
> + if (ret)
> + return false;
I think it would be more convenient to return 'ret' here, and 0 on success. I
see that currently nobody consumes the error code,
but with live migration this may change. And the same in
its_sync_lpi_pending_table().
> +
> + spin_lock(&dist->its.lock);
> + /*
> + * Updating the status for all allocated LPIs. We catch
> + * those LPIs that get disabled. We really don't care
> + * about unmapped LPIs, as they need to be updated
> + * later manually anyway once they get mapped.
> + */
> + for_each_lpi(device, itte, kvm) {
> + if (itte->lpi < lpi || itte->lpi >= lpi + chunksize)
> + continue;
> +
> + update_lpi_config(kvm, itte, prop[itte->lpi - lpi]);
> + }
> + spin_unlock(&dist->its.lock);
> + tsize -= chunksize;
> + lpi += chunksize;
> + propbase += chunksize;
> + }
> +
> + return true;
> +}
> +
> +/*
> + * 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 bool its_sync_lpi_pending_table(struct kvm_vcpu *vcpu, u64
> base_addr_reg)
> +{
> + struct vgic_dist *dist = &vcpu->kvm->arch.vgic;
> + unsigned long *pendmask = dist->its.buffer_page;
> + u32 nr_lpis = VITS_NR_LPIS;
> + gpa_t pendbase;
> + int lpi = 0;
> + struct its_itte *itte;
> + struct its_device *device;
> + int ret;
> + int lpi_bit, nr_bits;
> +
> + pendbase = BASER_BASE_ADDRESS(base_addr_reg);
> +
> + while (nr_lpis > 0) {
> + nr_bits = min(nr_lpis, CHUNK_SIZE * 8);
> +
> + ret = kvm_read_guest(vcpu->kvm, pendbase, pendmask,
> + nr_bits / 8);
> + if (ret)
> + return false;
> +
> + spin_lock(&dist->its.lock);
> + for_each_lpi(device, itte, vcpu->kvm) {
> + lpi_bit = itte->lpi - lpi;
> + if (lpi_bit < 0 || lpi_bit >= nr_bits)
> + continue;
> + if (test_bit(lpi_bit, pendmask))
> + __set_bit(vcpu->vcpu_id, itte->pending);
> + else
> + __clear_bit(vcpu->vcpu_id, itte->pending);
> + }
> + spin_unlock(&dist->its.lock);
> + nr_lpis -= nr_bits;
> + lpi += nr_bits;
> + pendbase += nr_bits / 8;
> + }
> +
> + return true;
> +}
> +
> /* The distributor lock is held by the VGIC MMIO handler. */
> static bool handle_mmio_misc_gits(struct kvm_vcpu *vcpu,
> struct kvm_exit_mmio *mmio,
> @@ -418,6 +535,17 @@ static const struct vgic_io_range vgicv3_its_ranges[] = {
> /* This is called on setting the LPI enable bit in the redistributor. */
> void vgic_enable_lpis(struct kvm_vcpu *vcpu)
> {
> + struct vgic_dist *dist = &vcpu->kvm->arch.vgic;
> + u64 prop_base_reg, pend_base_reg;
> +
> + pend_base_reg = dist->pendbaser[vcpu->vcpu_id];
> + prop_base_reg = dist->propbaser;
> + spin_unlock(&dist->lock);
> +
> + its_update_lpis_configuration(vcpu->kvm, prop_base_reg);
> + its_sync_lpi_pending_table(vcpu, pend_base_reg);
> +
> + spin_lock(&dist->lock);
> }
>
> int vits_init(struct kvm *kvm)
> @@ -429,6 +557,10 @@ int vits_init(struct kvm *kvm)
> if (!dist->pendbaser)
> return -ENOMEM;
>
> + its->buffer_page = kmalloc(CHUNK_SIZE, GFP_KERNEL);
> + if (!its->buffer_page)
> + return -ENOMEM;
> +
> spin_lock_init(&its->lock);
>
> INIT_LIST_HEAD(&its->device_list);
> @@ -474,6 +606,7 @@ void vits_destroy(struct kvm *kvm)
> kfree(container_of(cur, struct its_collection, coll_list));
> }
>
> + kfree(its->buffer_page);
> kfree(dist->pendbaser);
>
> its->enabled = false;
> diff --git a/virt/kvm/arm/its-emul.h b/virt/kvm/arm/its-emul.h
> index cc5d5ff..cbc3877 100644
> --- a/virt/kvm/arm/its-emul.h
> +++ b/virt/kvm/arm/its-emul.h
> @@ -29,6 +29,9 @@
>
> #include "vgic.h"
>
> +#define INTERRUPT_ID_BITS_ITS 16
> +#define VITS_NR_LPIS (1U << INTERRUPT_ID_BITS_ITS)
> +
> void vgic_enable_lpis(struct kvm_vcpu *vcpu);
> int vits_init(struct kvm *kvm);
> void vits_destroy(struct kvm *kvm);
> --
> 2.5.1
Kind regards,
Pavel Fedin
Expert Engineer
Samsung Electronics Research center Russia
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