Re: [PATCH v5 09/22] KVM: arm64: vgic-its: Introduce migration ABI infrastructure

Christoffer Dall
2017-04-27T13:12:00Z

On Fri, Apr 14, 2017 at 12:15:21PM +0200, Eric Auger wrote:
> We plan to support different migration ABIs, ie. characterizing
> the ITS table layout format in guest RAM. Typically a new ABI will

nit: s/Typically/For example,

> be needed if vLPIs get supported for nested use case.
>
> So let's introduce an array of supported ABIs (at the moment a single
> ABI is supported though). The following characteristics are foreseen
> to vary with the ABI: size of table entries, save/restore operation.
>
> By default the MAX_ABI_REV is applied on its creation. In subsequent
> patches we will introduce a way for the userspace to change the ABI
> in use.
>
> The entry sizes now are set according to the ABI version and not
> hardcoded anymore.
>
> Signed-off-by: Eric Auger <eric.auger@redhat.com>
>
> ---
>
> v5: creation and squash KVM: arm64: ITS: Report the ITE size in
> GITS_TYPER
> ---
> include/kvm/arm_vgic.h | 3 ++
> include/linux/irqchip/arm-gic-v3.h | 4 ++
> virt/kvm/arm/vgic/vgic-its.c | 82 ++++++++++++++++++++++++++++++++++++--
> 3 files changed, 85 insertions(+), 4 deletions(-)
>
> diff --git a/include/kvm/arm_vgic.h b/include/kvm/arm_vgic.h
> index c0b3d99..285474a 100644
> --- a/include/kvm/arm_vgic.h
> +++ b/include/kvm/arm_vgic.h
> @@ -162,6 +162,9 @@ struct vgic_its {
> u32 creadr;
> u32 cwriter;
>
> + /* migration ABI revision in use */
> + u32 abi_rev;
> +
> /* Protects the device and collection lists */
> struct mutex its_lock;
> struct list_head device_list;
> diff --git a/include/linux/irqchip/arm-gic-v3.h b/include/linux/irqchip/arm-gic-v3.h
> index 97cbca1..9648bad 100644
> --- a/include/linux/irqchip/arm-gic-v3.h
> +++ b/include/linux/irqchip/arm-gic-v3.h
> @@ -132,6 +132,8 @@
> #define GIC_BASER_SHAREABILITY(reg, type) \
> (GIC_BASER_##type << reg##_SHAREABILITY_SHIFT)
>
> +#define GIC_ENCODE_SZ(n, w) (((unsigned long)(n) - 1) & GENMASK_ULL(((w) - 1), 0))
> +

This is a very generic name. Could you add a comment about what the
idea is?

> #define GICR_PROPBASER_SHAREABILITY_SHIFT (10)
> #define GICR_PROPBASER_INNER_CACHEABILITY_SHIFT (7)
> #define GICR_PROPBASER_OUTER_CACHEABILITY_SHIFT (56)
> @@ -232,6 +234,7 @@
> #define GITS_CTLR_QUIESCENT (1U << 31)
>
> #define GITS_TYPER_PLPIS (1UL << 0)
> +#define GITS_TYPER_ITT_ENTRY_SIZE_SHIFT 4
> #define GITS_TYPER_IDBITS_SHIFT 8
> #define GITS_TYPER_DEVBITS_SHIFT 13
> #define GITS_TYPER_DEVBITS(r) ((((r) >> GITS_TYPER_DEVBITS_SHIFT) & 0x1f) + 1)
> @@ -290,6 +293,7 @@
> #define GITS_BASER_TYPE(r) (((r) >> GITS_BASER_TYPE_SHIFT) & 7)
> #define GITS_BASER_ENTRY_SIZE_SHIFT (48)
> #define GITS_BASER_ENTRY_SIZE(r) ((((r) >> GITS_BASER_ENTRY_SIZE_SHIFT) & 0x1f) + 1)
> +#define GITS_BASER_ENTRY_SIZE_MASK GENMASK_ULL(52, 48)
> #define GITS_BASER_SHAREABILITY_SHIFT (10)
> #define GITS_BASER_InnerShareable \
> GIC_BASER_SHAREABILITY(GITS_BASER, InnerShareable)
> diff --git a/virt/kvm/arm/vgic/vgic-its.c b/virt/kvm/arm/vgic/vgic-its.c
> index 79ed1c2..69ecfe4 100644
> --- a/virt/kvm/arm/vgic/vgic-its.c
> +++ b/virt/kvm/arm/vgic/vgic-its.c
> @@ -33,6 +33,12 @@
> #include "vgic.h"
> #include "vgic-mmio.h"
>
> +/* Highest migration ABI revision supported by this code */
> +#define MAX_ABI_REV 0
> +
> +static int vgic_its_set_abi(struct vgic_its *its, int rev);
> +static const struct vgic_its_abi *vgic_its_get_abi(struct vgic_its *its);
> +
> /*
> * Creates a new (reference to a) struct vgic_irq for a given LPI.
> * If this LPI is already mapped on another ITS, we increase its refcount
> @@ -123,6 +129,15 @@ struct its_ite {
> u32 event_id;
> };
>
> +struct vgic_its_abi {
> + int cte_esz;
> + int dte_esz;
> + int ite_esz;
> + int (*save_tables)(struct vgic_its *its);
> + int (*restore_tables)(struct vgic_its *its);
> + int (*commit)(struct vgic_its *its);

Can you document what these functions do (especially the commit function
seems to be internal and not be related to the ABI as such).

> +};
> +
> /*
> * Find and returns a device in the device table for an ITS.
> * Must be called with the its_lock mutex held.
> @@ -364,6 +379,7 @@ static unsigned long vgic_mmio_read_its_typer(struct kvm *kvm,
> struct vgic_its *its,
> gpa_t addr, unsigned int len)
> {
> + const struct vgic_its_abi *abi = vgic_its_get_abi(its);
> u64 reg = GITS_TYPER_PLPIS;
>
> /*
> @@ -376,6 +392,7 @@ static unsigned long vgic_mmio_read_its_typer(struct kvm *kvm,
> */
> reg |= 0x0f << GITS_TYPER_DEVBITS_SHIFT;
> reg |= 0x0f << GITS_TYPER_IDBITS_SHIFT;
> + reg |= GIC_ENCODE_SZ(abi->ite_esz, 4) << GITS_TYPER_ITT_ENTRY_SIZE_SHIFT;
>
> return extract_bytes(reg, addr & 7, len);
> }
> @@ -1268,6 +1285,7 @@ static void vgic_mmio_write_its_baser(struct kvm *kvm,
> gpa_t addr, unsigned int len,
> unsigned long val)
> {
> + const struct vgic_its_abi *abi = vgic_its_get_abi(its);
> u64 entry_size, device_type;
> u64 reg, *regptr, clearbits = 0;
>
> @@ -1278,12 +1296,12 @@ static void vgic_mmio_write_its_baser(struct kvm *kvm,
> switch (BASER_INDEX(addr)) {
> case 0:
> regptr = &its->baser_device_table;
> - entry_size = 8;
> + entry_size = abi->dte_esz;
> device_type = GITS_BASER_TYPE_DEVICE;
> break;
> case 1:
> regptr = &its->baser_coll_table;
> - entry_size = 8;
> + entry_size = abi->cte_esz;
> device_type = GITS_BASER_TYPE_COLLECTION;
> clearbits = GITS_BASER_INDIRECT;
> break;
> @@ -1425,7 +1443,6 @@ static int vgic_register_its_iodev(struct kvm *kvm, struct vgic_its *its)
> (GIC_BASER_CACHEABILITY(GITS_BASER, INNER, RaWb) | \
> GIC_BASER_CACHEABILITY(GITS_BASER, OUTER, SameAsInner) | \
> GIC_BASER_SHAREABILITY(GITS_BASER, InnerShareable) | \
> - ((8ULL - 1) << GITS_BASER_ENTRY_SIZE_SHIFT) | \
> GITS_BASER_PAGE_SIZE_64K)
>
> #define INITIAL_PROPBASER_VALUE \
> @@ -1465,7 +1482,7 @@ static int vgic_its_create(struct kvm_device *dev, u32 type)
>
> dev->private = its;
>
> - return 0;
> + return vgic_its_set_abi(its, MAX_ABI_REV);
> }
>
> static void vgic_its_destroy(struct kvm_device *kvm_dev)
> @@ -1592,6 +1609,63 @@ int vgic_its_attr_regs_access(struct kvm_device *dev,
> return ret;
> }
>
> +/**
> + * vgic_its_save_tables_v0 - Save the ITS tables into guest ARM
> + * according to v0 ABI
> + */
> +static int vgic_its_save_tables_v0(struct vgic_its *its)
> +{
> + return -ENXIO;
> +}
> +
> +/**
> + * vgic_its_restore_tables_v0 - Restore the ITS tables from guest RAM
> + * to internal data structs according to V0 ABI
> + *
> + */
> +static int vgic_its_restore_tables_v0(struct vgic_its *its)
> +{
> + return -ENXIO;
> +}
> +
> +static int vgic_its_commit_v0(struct vgic_its *its)
> +{
> + const struct vgic_its_abi *abi;
> +
> + abi = vgic_its_get_abi(its);
> + its->baser_coll_table &= ~GITS_BASER_ENTRY_SIZE_MASK;
> + its->baser_device_table &= ~GITS_BASER_ENTRY_SIZE_MASK;
> +
> + its->baser_coll_table |= (GIC_ENCODE_SZ(abi->cte_esz, 5)
> + << GITS_BASER_ENTRY_SIZE_SHIFT);
> +
> + its->baser_device_table |= (GIC_ENCODE_SZ(abi->dte_esz, 5)
> + << GITS_BASER_ENTRY_SIZE_SHIFT);
> + return 0;
> +}
> +
> +static const struct vgic_its_abi abi[MAX_ABI_REV + 1] = {

nit: can we name this its_table_abi_versions or something like that
which is slightly more descriptive?

> + {.cte_esz = 8, .dte_esz = 8, .ite_esz = 8,
> + .save_tables = vgic_its_save_tables_v0,
> + .restore_tables = vgic_its_restore_tables_v0,
> + . commit = vgic_its_commit_v0,

stray whitespace

> + },
> +};
> +
> +inline const struct vgic_its_abi *vgic_its_get_abi(struct vgic_its *its)
> +{
> + return &abi[its->abi_rev];
> +}
> +
> +int vgic_its_set_abi(struct vgic_its *its, int rev)
> +{
> + const struct vgic_its_abi *abi;
> +
> + its->abi_rev = rev;
> + abi = vgic_its_get_abi(its);
> + return abi->commit(its);
> +}
> +
> static int vgic_its_has_attr(struct kvm_device *dev,
> struct kvm_device_attr *attr)
> {
> --
> 2.5.5
>

Thanks,
-Christoffer