Re: [PATCH v5 11/30] ARM: GICv3 ITS: introduce device mapping

[Stefano Stabellini <sstabellini@kernel.org>]

On Thu, 6 Apr 2017, Andre Przywara wrote:
> The ITS uses device IDs to map LPIs to a device. Dom0 will later use
> those IDs, which we directly pass on to the host.
> For this we have to map each device that Dom0 may request to a host
> ITS device with the same identifier.
> Allocate the respective memory and enter each device into an rbtree to
> later be able to iterate over it or to easily teardown guests.
> Because device IDs are per ITS, we need to identify a virtual ITS. We
> use the doorbell address for that purpose, as it is a nice architectural
> MSI property and spares us handling with opaque pointer or break
> the VGIC abstraction.
> 
> Signed-off-by: Andre Przywara <andre.przywara@arm.com>
> ---
>  xen/arch/arm/gic-v3-its.c        | 263 +++++++++++++++++++++++++++++++++++++++
>  xen/arch/arm/vgic-v3-its.c       |   3 +
>  xen/include/asm-arm/domain.h     |   3 +
>  xen/include/asm-arm/gic_v3_its.h |  13 ++
>  4 files changed, 282 insertions(+)
> 
> diff --git a/xen/arch/arm/gic-v3-its.c b/xen/arch/arm/gic-v3-its.c
> index eb47c9d..45bbfa7 100644
> --- a/xen/arch/arm/gic-v3-its.c
> +++ b/xen/arch/arm/gic-v3-its.c
> @@ -21,6 +21,8 @@
>  #include <xen/lib.h>
>  #include <xen/delay.h>
>  #include <xen/mm.h>
> +#include <xen/rbtree.h>
> +#include <xen/sched.h>
>  #include <xen/sizes.h>
>  #include <asm/gic.h>
>  #include <asm/gic_v3_defs.h>
> @@ -36,6 +38,26 @@
>   */
>  LIST_HEAD(host_its_list);
>  
> +/*
> + * Describes a device which is using the ITS and is used by a guest.
> + * Since device IDs are per ITS (in contrast to vLPIs, which are per
> + * guest), we have to differentiate between different virtual ITSes.
> + * We use the doorbell address here, since this is a nice architectural
> + * property of MSIs in general and we can easily get to the base address
> + * of the ITS and look that up.
> + */
> +struct its_devices {
> +    struct rb_node rbnode;
> +    struct host_its *hw_its;
> +    void *itt_addr;
> +    paddr_t guest_doorbell;             /* Identifies the virtual ITS */
> +    uint32_t host_devid;
> +    uint32_t guest_devid;
> +    uint32_t eventids;                  /* Number of event IDs (MSIs) */
> +    uint32_t *host_lpi_blocks;          /* Which LPIs are used on the host */
> +    struct pending_irq *pend_irqs;      /* One struct per event */
> +};
> +
>  bool gicv3_its_host_has_its(void)
>  {
>      return !list_empty(&host_its_list);
> @@ -185,6 +207,30 @@ static int its_send_cmd_mapc(struct host_its *its, uint32_t collection_id,
>      return its_send_command(its, cmd);
>  }
>  
> +static int its_send_cmd_mapd(struct host_its *its, uint32_t deviceid,
> +                             uint8_t size_bits, paddr_t itt_addr, bool valid)
> +{
> +    uint64_t cmd[4];
> +
> +    if ( valid )
> +    {
> +        ASSERT(size_bits <= its->evid_bits);
> +        ASSERT(size_bits > 0);
> +        ASSERT(!(itt_addr & ~GENMASK_ULL(51, 8)));
> +
> +        /* The number of events is encoded as "number of bits minus one". */
> +        size_bits--;
> +    }
> +    cmd[0] = GITS_CMD_MAPD | ((uint64_t)deviceid << 32);
> +    cmd[1] = size_bits;
> +    cmd[2] = itt_addr;
> +    if ( valid )
> +        cmd[2] |= GITS_VALID_BIT;
> +    cmd[3] = 0x00;
> +
> +    return its_send_command(its, cmd);
> +}
> +
>  static int its_send_cmd_inv(struct host_its *its,
>                              uint32_t deviceid, uint32_t eventid)
>  {
> @@ -477,6 +523,66 @@ int gicv3_its_init(void)
>      return 0;
>  }
>  
> +static int remove_mapped_guest_device(struct its_devices *dev)
> +{
> +    int ret = 0;
> +    unsigned int i;
> +
> +    if ( dev->hw_its )
> +        /* MAPD also discards all events with this device ID. */
> +        ret = its_send_cmd_mapd(dev->hw_its, dev->host_devid, 0, 0, false);
> +
> +    for ( i = 0; i < dev->eventids / LPI_BLOCK; i++ )
> +        gicv3_free_host_lpi_block(dev->host_lpi_blocks[i]);
> +
> +    /* Make sure the MAPD command above is really executed. */
> +    if ( !ret )
> +        ret = gicv3_its_wait_commands(dev->hw_its);
> +
> +    /* This should never happen, but just in case ... */
> +    if ( ret )
> +        printk(XENLOG_WARNING "Can't unmap host ITS device 0x%x\n",
> +               dev->host_devid);
> +
> +    xfree(dev->itt_addr);
> +    xfree(dev->pend_irqs);
> +    xfree(dev->host_lpi_blocks);
> +    xfree(dev);
> +
> +    return 0;
> +}
> +
> +static struct host_its *gicv3_its_find_by_doorbell(paddr_t doorbell_address)
> +{
> +    struct host_its *hw_its;
> +
> +    list_for_each_entry(hw_its, &host_its_list, entry)
> +    {
> +        if ( hw_its->addr + ITS_DOORBELL_OFFSET == doorbell_address )
> +            return hw_its;
> +    }
> +
> +    return NULL;
> +}
> +
> +static int compare_its_guest_devices(struct its_devices *dev,
> +                                     paddr_t vdoorbell, uint32_t vdevid)
> +{
> +    if ( dev->guest_doorbell < vdoorbell )
> +        return -1;
> +
> +    if ( dev->guest_doorbell > vdoorbell )
> +        return 1;
> +
> +    if ( dev->guest_devid < vdevid )
> +        return -1;
> +
> +    if ( dev->guest_devid > vdevid )
> +        return 1;
> +
> +    return 0;
> +}
> +
>  /*
>   * On the host ITS @its, map @nr_events consecutive LPIs.
>   * The mapping connects a device @devid and event @eventid pair to LPI @lpi,
> @@ -510,6 +616,163 @@ static int gicv3_its_map_host_events(struct host_its *its,
>      return gicv3_its_wait_commands(its);
>  }
>  
> +/*
> + * Map a hardware device, identified by a certain host ITS and its device ID
> + * to domain d, a guest ITS (identified by its doorbell address) and device ID.
> + * Also provide the number of events (MSIs) needed for that device.
> + * This does not check if this particular hardware device is already mapped
> + * at another domain, it is expected that this would be done by the caller.
> + */
> +int gicv3_its_map_guest_device(struct domain *d,
> +                               paddr_t host_doorbell, uint32_t host_devid,
> +                               paddr_t guest_doorbell, uint32_t guest_devid,
> +                               uint32_t nr_events, bool valid)
> +{
> +    void *itt_addr = NULL;
> +    struct host_its *hw_its;
> +    struct its_devices *dev = NULL;
> +    struct rb_node **new = &d->arch.vgic.its_devices.rb_node, *parent = NULL;
> +    unsigned int i;
> +    int ret = -ENOENT;
> +
> +    hw_its = gicv3_its_find_by_doorbell(host_doorbell);
> +    if ( !hw_its )
> +        return ret;
> +
> +    /* Sanitise the provided hardware values against the host ITS. */
> +    if ( host_devid >= BIT(hw_its->devid_bits) )
> +        return -EINVAL;
> +
> +    /* We allocate events and LPIs in chunks of LPI_BLOCK (=32). */
> +    nr_events = ROUNDUP(nr_events, LPI_BLOCK);
> +    if ( nr_events >= BIT(hw_its->evid_bits) )
> +        return -EINVAL;
> +
> +    /* check for already existing mappings */
> +    spin_lock(&d->arch.vgic.its_devices_lock);
> +    while ( *new )
> +    {
> +        struct its_devices *temp;
> +        int cmp;
> +
> +        temp = rb_entry(*new, struct its_devices, rbnode);
> +
> +        parent = *new;
> +        cmp = compare_its_guest_devices(temp, guest_doorbell, guest_devid);
> +        if ( !cmp )
> +        {
> +            if ( !valid )
> +                rb_erase(&temp->rbnode, &d->arch.vgic.its_devices);
> +
> +            spin_unlock(&d->arch.vgic.its_devices_lock);
> +
> +            if ( valid )
> +            {
> +                printk(XENLOG_G_WARNING "d%d tried to remap guest ITS device 0x%x to host device 0x%x\n",
> +                        d->domain_id, guest_devid, host_devid);
> +                return -EBUSY;
> +            }
> +
> +            return remove_mapped_guest_device(temp);
> +        }
> +
> +        if ( cmp > 0 )
> +            new = &((*new)->rb_left);
> +        else
> +            new = &((*new)->rb_right);
> +    }
> +
> +    if ( !valid )
> +        goto out_unlock;
> +
> +    ret = -ENOMEM;
> +
> +    /* An Interrupt Translation Table needs to be 256-byte aligned. */
> +    itt_addr = _xzalloc(nr_events * hw_its->itte_size, 256);
> +    if ( !itt_addr )
> +        goto out_unlock;
> +
> +    dev = xzalloc(struct its_devices);
> +    if ( !dev )
> +        goto out_unlock;
> +
> +    /*
> +     * Allocate the pending_irqs for each virtual LPI. They will be put
> +     * into the domain's radix tree upon the guest's MAPTI command.
> +     */

Please expand the comment with a link to the xen-devel conversation
about allocation strategy and a TODO saying that we shouldn't need to
preallocate all pending_irq struct, but we do it for simplicity at the
moment.


> +    dev->pend_irqs = xzalloc_array(struct pending_irq, nr_events);
> +    if ( !dev->pend_irqs )
> +        goto out_unlock;
> +
> +    dev->host_lpi_blocks = xzalloc_array(uint32_t, nr_events);
> +    if ( !dev->host_lpi_blocks )
> +        goto out_unlock;
> +
> +    ret = its_send_cmd_mapd(hw_its, host_devid, fls(nr_events - 1),
> +                            virt_to_maddr(itt_addr), true);
> +    if ( ret )
> +        goto out_unlock;
> +
> +    dev->itt_addr = itt_addr;
> +    dev->hw_its = hw_its;
> +    dev->guest_doorbell = guest_doorbell;
> +    dev->guest_devid = guest_devid;
> +    dev->host_devid = host_devid;
> +    dev->eventids = nr_events;
> +
> +    rb_link_node(&dev->rbnode, parent, new);
> +    rb_insert_color(&dev->rbnode, &d->arch.vgic.its_devices);
> +
> +    spin_unlock(&d->arch.vgic.its_devices_lock);
> +
> +    /*
> +     * Map all host LPIs within this device already. We can't afford to queue
> +     * any host ITS commands later on during the guest's runtime.
> +     */
> +    for ( i = 0; i < nr_events / LPI_BLOCK; i++ )
> +    {
> +        ret = gicv3_allocate_host_lpi_block(d, &dev->host_lpi_blocks[i]);
> +        if ( ret < 0 )
> +            break;
> +
> +        ret = gicv3_its_map_host_events(hw_its, host_devid, i * LPI_BLOCK,
> +                                        dev->host_lpi_blocks[i], LPI_BLOCK);
> +        if ( ret < 0 )
> +            break;
> +    }
> +
> +    if ( ret )
> +    {
> +        do {
> +            i--;
> +            gicv3_free_host_lpi_block(dev->host_lpi_blocks[i]);
> +            if ( i == 0 )
> +                break;
> +        } while (1);
> +
> +        /* Unmapping the device will discard all LPIs mapped so far. */
> +        its_send_cmd_mapd(hw_its, host_devid, 1, 0, false);
> +
> +        goto out;
> +    }
> +
> +    return 0;
> +
> +out_unlock:
> +    spin_unlock(&d->arch.vgic.its_devices_lock);
> +
> +out:
> +    if ( dev )
> +    {
> +        xfree(dev->pend_irqs);
> +        xfree(dev->host_lpi_blocks);
> +    }
> +    xfree(itt_addr);
> +    xfree(dev);
> +
> +    return ret;
> +}
> +
>  /* Scan the DT for any ITS nodes and create a list of host ITSes out of it. */
>  void gicv3_its_dt_init(const struct dt_device_node *node)
>  {
> diff --git a/xen/arch/arm/vgic-v3-its.c b/xen/arch/arm/vgic-v3-its.c
> index 94c3c44..9dfda59 100644
> --- a/xen/arch/arm/vgic-v3-its.c
> +++ b/xen/arch/arm/vgic-v3-its.c
> @@ -69,10 +69,13 @@ struct vits_itte
>  
>  void vgic_v3_its_init_domain(struct domain *d)
>  {
> +    spin_lock_init(&d->arch.vgic.its_devices_lock);
> +    d->arch.vgic.its_devices = RB_ROOT;
>  }
>  
>  void vgic_v3_its_free_domain(struct domain *d)
>  {
> +    ASSERT(RB_EMPTY_ROOT(&d->arch.vgic.its_devices));
>  }
>  
>  /*
> diff --git a/xen/include/asm-arm/domain.h b/xen/include/asm-arm/domain.h
> index 09fe502..503a3cf 100644
> --- a/xen/include/asm-arm/domain.h
> +++ b/xen/include/asm-arm/domain.h
> @@ -10,6 +10,7 @@
>  #include <asm/gic.h>
>  #include <public/hvm/params.h>
>  #include <xen/serial.h>
> +#include <xen/rbtree.h>
>  
>  struct hvm_domain
>  {
> @@ -108,6 +109,8 @@ struct arch_domain
>          } *rdist_regions;
>          int nr_regions;                     /* Number of rdist regions */
>          uint32_t rdist_stride;              /* Re-Distributor stride */
> +        struct rb_root its_devices;         /* Devices mapped to an ITS */
> +        spinlock_t its_devices_lock;        /* Protects the its_devices tree */
>  #endif
>      } vgic;
>  
> diff --git a/xen/include/asm-arm/gic_v3_its.h b/xen/include/asm-arm/gic_v3_its.h
> index 9b0c0ec..3b7c724 100644
> --- a/xen/include/asm-arm/gic_v3_its.h
> +++ b/xen/include/asm-arm/gic_v3_its.h
> @@ -103,7 +103,10 @@
>  #define GITS_CMD_MOVALL                 0x0e
>  #define GITS_CMD_DISCARD                0x0f
>  
> +#define ITS_DOORBELL_OFFSET             0x10040
> +
>  #include <xen/device_tree.h>
> +#include <xen/rbtree.h>
>  
>  #define HOST_ITS_FLUSH_CMD_QUEUE        (1U << 0)
>  #define HOST_ITS_USES_PTA               (1U << 1)
> @@ -153,6 +156,16 @@ int gicv3_its_setup_collection(unsigned int cpu);
>  void vgic_v3_its_init_domain(struct domain *d);
>  void vgic_v3_its_free_domain(struct domain *d);
>  
> +/*
> + * Map a device on the host by allocating an ITT on the host (ITS).
> + * "nr_event" specifies how many events (interrupts) this device will need.
> + * Setting "valid" to false deallocates the device.
> + */
> +int gicv3_its_map_guest_device(struct domain *d,
> +                               paddr_t host_doorbell, uint32_t host_devid,
> +                               paddr_t guest_doorbell, uint32_t guest_devid,
> +                               uint32_t nr_events, bool valid);
> +
>  int gicv3_allocate_host_lpi_block(struct domain *d, uint32_t *first_lpi);
>  void gicv3_free_host_lpi_block(uint32_t first_lpi);
>  
> -- 
> 2.8.2
> 

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