Re: [PATCH v4 21/22] KVM: arm64: ITS: Device table save/restore

Marc Zyngier
2017-04-10T12:42:26Z

On 27/03/17 10:31, Eric Auger wrote:
> This patch flushes the device table entries into guest RAM.
> Both flat table and 2 stage tables are supported. DeviceId
> indexing is used.
>
> For each device listed in the device table, we also flush
> the translation table using the vgic_its_flush/restore_itt
> routines.
>
> On restore, devices are re-allocated and their itte are
> re-built.
>
> Signed-off-by: Eric Auger <eric.auger@redhat.com>
>
> ---
> v3 -> v4:
> - use the new proto for its_alloc_device
> - compute_next_devid_offset, vgic_its_flush/restore_itt
> become static in this patch
> - change in the DTE entry format with the introduction of the
> valid bit and next field width decrease; ittaddr encoded
> on its full range
> - fix handle_l1_entry entry handling
> - correct vgic_its_table_restore error handling
>
> v2 -> v3:
> - fix itt_addr bitmask in vgic_its_restore_dte
> - addition of return 0 in vgic_its_restore_ite moved to
> the ITE related patch
>
> v1 -> v2:
> - use 8 byte format for DTE and ITE
> - support 2 stage format
> - remove kvm parameter
> - ITT flush/restore moved in a separate patch
> - use deviceid indexing
> ---
> virt/kvm/arm/vgic/vgic-its.c | 161 +++++++++++++++++++++++++++++++++++++++++--
> 1 file changed, 156 insertions(+), 5 deletions(-)
>
> diff --git a/virt/kvm/arm/vgic/vgic-its.c b/virt/kvm/arm/vgic/vgic-its.c
> index 02c0694..a516bbb 100644
> --- a/virt/kvm/arm/vgic/vgic-its.c
> +++ b/virt/kvm/arm/vgic/vgic-its.c
> @@ -1693,7 +1693,8 @@ int vgic_its_attr_regs_access(struct kvm_device *dev,
> return ret;
> }
>
> -u32 compute_next_devid_offset(struct list_head *h, struct its_device *dev)
> +static u32 compute_next_devid_offset(struct list_head *h,
> + struct its_device *dev)
> {
> struct list_head *e = &dev->dev_list;
> struct its_device *next;
> @@ -1884,7 +1885,7 @@ static int vgic_its_restore_ite(struct vgic_its *its, u32 event_id,
> return 0;
> }
>
> -int vgic_its_flush_itt(struct vgic_its *its, struct its_device *device)
> +static int vgic_its_flush_itt(struct vgic_its *its, struct its_device *device)
> {
> gpa_t base = device->itt_addr;
> struct its_ite *ite;
> @@ -1900,7 +1901,7 @@ int vgic_its_flush_itt(struct vgic_its *its, struct its_device *device)
> return 0;
> }
>
> -int vgic_its_restore_itt(struct vgic_its *its, struct its_device *dev)
> +static int vgic_its_restore_itt(struct vgic_its *its, struct its_device *dev)
> {
> size_t max_size = BIT_ULL(dev->nb_eventid_bits) * VITS_ESZ;
> gpa_t base = dev->itt_addr;
> @@ -1917,12 +1918,141 @@ int vgic_its_restore_itt(struct vgic_its *its, struct its_device *dev)
> }
>
> /**
> + * vgic_its_flush_dte - Flush a device table entry at a given GPA
> + *
> + * @its: ITS handle
> + * @dev: ITS device
> + * @ptr: GPA
> + */
> +static int vgic_its_flush_dte(struct vgic_its *its,
> + struct its_device *dev, gpa_t ptr)
> +{
> + struct kvm *kvm = its->dev->kvm;
> + u64 val, itt_addr_field;
> + int ret;
> + u32 next_offset;
> +
> + itt_addr_field = dev->itt_addr >> 8;
> + next_offset = compute_next_devid_offset(&its->device_list, dev);
> + val = (1ULL << 63 | ((u64)next_offset << 49) | (itt_addr_field << 5) |
> + (dev->nb_eventid_bits - 1));
> + val = cpu_to_le64(val);
> + ret = kvm_write_guest(kvm, ptr, &val, 8);
> + return ret;
> +}
> +
> +/**
> + * vgic_its_restore_dte - restore a device table entry
> + *
> + * @its: its handle
> + * @id: device id the DTE corresponds to
> + * @ptr: kernel VA where the 8 byte DTE is located
> + * @opaque: unused
> + * @next: offset to the next valid device id
> + *
> + * Return: < 0 on error, 0 otherwise
> + */
> +static int vgic_its_restore_dte(struct vgic_its *its, u32 id,
> + void *ptr, void *opaque, u32 *next)
> +{
> + struct its_device *dev;
> + gpa_t itt_addr;
> + u8 nb_eventid_bits;
> + u64 entry = *(u64 *)ptr;
> + bool valid;
> + int ret;
> +
> + entry = le64_to_cpu(entry);
> +
> + valid = entry >> 63;
> + nb_eventid_bits = (entry & GENMASK_ULL(4, 0)) + 1;
> + itt_addr = ((entry & GENMASK_ULL(48, 5)) >> 5) << 8;
> + *next = 1;
> +
> + if (!valid)
> + return 0;
> +
> + /* dte entry is valid */
> + *next = (entry & GENMASK_ULL(62, 49)) >> 49;
> +
> + ret = vgic_its_alloc_device(its, &dev, id,
> + itt_addr, nb_eventid_bits);
> + if (ret)
> + return ret;
> + ret = vgic_its_restore_itt(its, dev);
> +
> + return ret;
> +}
> +
> +/**
> * vgic_its_flush_device_tables - flush the device table and all ITT
> * into guest RAM
> + *
> + * L1/L2 handling is hidden by vgic_its_check_id() helper which directly
> + * returns the GPA of the device entry
> */
> static int vgic_its_flush_device_tables(struct vgic_its *its)
> {
> - return -ENXIO;
> + struct its_device *dev;
> + u64 baser;
> +
> + baser = its->baser_device_table;
> +
> + list_for_each_entry(dev, &its->device_list, dev_list) {
> + int ret;
> + gpa_t eaddr;
> +
> + if (!vgic_its_check_id(its, baser,
> + dev->device_id, &eaddr))
> + return -EINVAL;
> +
> + ret = vgic_its_flush_itt(its, dev);
> + if (ret)
> + return ret;
> +
> + ret = vgic_its_flush_dte(its, dev, eaddr);
> + if (ret)
> + return ret;
> + }
> + return 0;
> +}
> +
> +/**
> + * handle_l1_entry - callback used for L1 entries (2 stage case)
> + *
> + * @its: its handle
> + * @id: id
> + * @addr: kernel VA
> + * @opaque: unused
> + * @next_offset: offset to the next L1 entry: 0 if the last element
> + * was found, 1 otherwise
> + */
> +static int handle_l1_entry(struct vgic_its *its, u32 id, void *addr,
> + void *opaque, u32 *next_offset)
> +{
> + int l2_start_id = id * (SZ_64K / GITS_LVL1_ENTRY_SIZE);
> + u64 entry = *(u64 *)addr;
> + gpa_t gpa;
> + int ret;
> +
> + entry = le64_to_cpu(entry);
> + *next_offset = 1;
> +
> + if (!(entry & BIT_ULL(63)))
> + return 0;
> +
> + gpa = entry & GENMASK_ULL(51, 16);
> +
> + ret = lookup_table(its, gpa, SZ_64K, 8,
> + l2_start_id, vgic_its_restore_dte, NULL);
> +
> + if (ret == 1) {
> + /* last entry was found in this L2 table */
> + *next_offset = 0;
> + ret = 0;
> + }

Ah, that's why you have this complicated return convention.

> +
> + return ret;
> }
>
> /**
> @@ -1931,7 +2061,28 @@ static int vgic_its_flush_device_tables(struct vgic_its *its)
> */
> static int vgic_its_restore_device_tables(struct vgic_its *its)
> {
> - return -ENXIO;
> + u64 baser = its->baser_device_table;
> + int l1_tbl_size = GITS_BASER_NR_PAGES(baser) * SZ_64K;
> + int l1_esz = GITS_BASER_ENTRY_SIZE(baser);
> + gpa_t l1_gpa;
> + int ret;
> +
> + l1_gpa = BASER_ADDRESS(baser);
> + if (!l1_gpa)
> + return 0;
> +
> + if (baser & GITS_BASER_INDIRECT)
> + ret = lookup_table(its, l1_gpa, l1_tbl_size, 8, 0,
> + handle_l1_entry, NULL);

I wonder if you shouldn't make this a different function (maybe using
the same core helper) to parse L1 tables.

> + else
> + ret = lookup_table(its, l1_gpa, l1_tbl_size, l1_esz,
> + 0, vgic_its_restore_dte, NULL);
> +
> + if (ret < 0)
> + return ret;
> +
> + /* if last element was not found we have an issue here */
> + return ret ? 0 : -EINVAL;
> }
>
> static int vgic_its_flush_cte(struct vgic_its *its,
>

The previous comments about the the encoding still apply... ;-)

Thanks,

M.
--
Jazz is not dead. It just smells funny...