Re: [PATCH v8 15/17] KVM: arm64: implement ITS command queue command handlers

Marc Zyngier
2016-07-11T17:17:38Z

On 05/07/16 12:23, Andre Przywara wrote:
> The connection between a device, an event ID, the LPI number and the
> allocated CPU is stored in in-memory tables in a GICv3, but their
> format is not specified by the spec. Instead software uses a command
> queue in a ring buffer to let the ITS implementation use their own
> format.
> Implement handlers for the various ITS commands and let them store
> the requested relation into our own data structures. Those data
> structures are protected by the its_lock mutex.
> Our internal ring buffer read and write pointers are protected by the
> its_cmd mutex, so that at most one VCPU per ITS can handle commands at
> any given time.
> Error handling is very basic at the moment, as we don't have a good
> way of communicating errors to the guest (usually a SError).
> The INT command handler is missing at this point, as we gain the
> capability of actually injecting MSIs into the guest only later on.
>
> Signed-off-by: Andre Przywara <andre.przywara@arm.com>
> ---
> virt/kvm/arm/vgic/vgic-its.c | 609 ++++++++++++++++++++++++++++++++++++++++++-
> 1 file changed, 605 insertions(+), 4 deletions(-)
>
> diff --git a/virt/kvm/arm/vgic/vgic-its.c b/virt/kvm/arm/vgic/vgic-its.c
> index 5de71bd..432daed 100644
> --- a/virt/kvm/arm/vgic/vgic-its.c
> +++ b/virt/kvm/arm/vgic/vgic-its.c
> @@ -58,6 +58,43 @@ out_unlock:
> return irq;
> }
>
> +/*
> + * 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
> + * and return a pointer to the existing structure.
> + * If this is a "new" LPI, we allocate and initialize a new struct vgic_irq.
> + * This function returns a pointer to the _unlocked_ structure.
> + */
> +static struct vgic_irq *vgic_add_lpi(struct kvm *kvm, u32 intid)
> +{
> + struct vgic_dist *dist = &kvm->arch.vgic;
> + struct vgic_irq *irq = vgic_its_get_lpi(kvm, intid);

So this thing doesn't return with any lock held...

> +
> + /* In this case there is no put, since we keep the reference. */
> + if (irq)
> + return irq;
> +
> + irq = kzalloc(sizeof(struct vgic_irq), GFP_KERNEL);
> +
> + if (!irq)
> + return NULL;
> +
> + INIT_LIST_HEAD(&irq->lpi_entry);
> + INIT_LIST_HEAD(&irq->ap_list);
> + spin_lock_init(&irq->irq_lock);
> +
> + irq->config = VGIC_CONFIG_EDGE;
> + kref_init(&irq->refcount);
> + irq->intid = intid;

which means that two callers can allocate their own irq structure...

> +
> + spin_lock(&dist->lpi_list_lock);
> + list_add_tail(&irq->lpi_entry, &dist->lpi_list_head);
> + dist->lpi_list_count++;
> + spin_unlock(&dist->lpi_list_lock);

and insert it. Not too bad if they are different LPIs, but leading to
Armageddon if they are the same. You absolutely need to check for the
the presence of the interrupt in this list *while holding the lock*.

> +
> + return irq;
> +}
> +
> struct its_device {
> struct list_head dev_list;
>
> @@ -87,6 +124,43 @@ struct its_itte {
> u32 event_id;
> };
>
> +/*
> + * Find and returns a device in the device table for an ITS.
> + * Must be called with the its_lock held.
> + */
> +static struct its_device *find_its_device(struct vgic_its *its, u32 device_id)
> +{
> + struct its_device *device;
> +
> + list_for_each_entry(device, &its->device_list, dev_list)
> + if (device_id == device->device_id)
> + return device;
> +
> + return NULL;
> +}
> +
> +/*
> + * Find and returns an interrupt translation table entry (ITTE) for a given
> + * Device ID/Event ID pair on an ITS.
> + * Must be called with the its_lock held.
> + */
> +static struct its_itte *find_itte(struct vgic_its *its, u32 device_id,
> + u32 event_id)
> +{
> + struct its_device *device;
> + struct its_itte *itte;
> +
> + device = find_its_device(its, device_id);
> + if (device == NULL)
> + return NULL;
> +
> + list_for_each_entry(itte, &device->itt_head, itte_list)
> + if (itte->event_id == event_id)
> + return itte;
> +
> + return NULL;
> +}
> +
> /* To be used as an iterator this macro misses the enclosing parentheses */
> #define for_each_lpi_its(dev, itte, its) \
> list_for_each_entry(dev, &(its)->device_list, dev_list) \
> @@ -98,6 +172,22 @@ struct its_itte {
>
> #define GIC_LPI_OFFSET 8192
>
> +/*
> + * Finds and returns a collection in the ITS collection table.
> + * Must be called with the its_lock held.
> + */
> +static struct its_collection *find_collection(struct vgic_its *its, int coll_id)
> +{
> + struct its_collection *collection;
> +
> + list_for_each_entry(collection, &its->collection_list, coll_list) {
> + if (coll_id == collection->collection_id)
> + return collection;
> + }
> +
> + return NULL;
> +}
> +
> #define LPI_PROP_ENABLE_BIT(p) ((p) & LPI_PROP_ENABLED)
> #define LPI_PROP_PRIORITY(p) ((p) & 0xfc)
>
> @@ -135,7 +225,7 @@ static int update_lpi_config_filtered(struct kvm *kvm, struct vgic_irq *irq,
> }
>
> /* Updates the priority and enable bit for a given LPI. */
> -int update_lpi_config(struct kvm *kvm, struct vgic_irq *irq)
> +static int update_lpi_config(struct kvm *kvm, struct vgic_irq *irq)
> {
> return update_lpi_config_filtered(kvm, irq, NULL);
> }
> @@ -174,6 +264,48 @@ static int vgic_its_copy_lpi_list(struct kvm *kvm, u32 **intid_ptr)
> }
>
> /*
> + * Promotes the ITS view of affinity of an ITTE (which redistributor this LPI
> + * is targeting) to the VGIC's view, which deals with target VCPUs.
> + * Needs to be called whenever either the collection for a LPIs has
> + * changed or the collection itself got retargeted.
> + */
> +static void update_affinity_itte(struct kvm *kvm, struct its_itte *itte)
> +{
> + struct kvm_vcpu *vcpu;
> +
> + vcpu = kvm_get_vcpu(kvm, itte->collection->target_addr);
> +
> + spin_lock(&itte->irq->irq_lock);
> + itte->irq->target_vcpu = vcpu;
> + spin_unlock(&itte->irq->irq_lock);
> +}
> +
> +/*
> + * Updates the target VCPU for every LPI targeting this collection.
> + * Must be called with the its_lock held.
> + */
> +static void update_affinity_collection(struct kvm *kvm, struct vgic_its *its,
> + struct its_collection *coll)
> +{
> + struct its_device *device;
> + struct its_itte *itte;
> +
> + for_each_lpi_its(device, itte, its) {
> + if (!itte->collection || coll != itte->collection)
> + continue;
> +
> + update_affinity_itte(kvm, itte);
> + }
> +}
> +
> +static u32 max_lpis_propbaser(u64 propbaser)
> +{
> + int nr_idbits = (propbaser & 0x1f) + 1;
> +
> + return 1U << min(nr_idbits, INTERRUPT_ID_BITS_ITS);
> +}
> +
> +/*
> * 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.
> @@ -299,10 +431,479 @@ static void its_free_itte(struct kvm *kvm, struct its_itte *itte)
> kfree(itte);
> }
>
> -static int vits_handle_command(struct kvm *kvm, struct vgic_its *its,
> +static u64 its_cmd_mask_field(u64 *its_cmd, int word, int shift, int size)
> +{
> + return (le64_to_cpu(its_cmd[word]) >> shift) & (BIT_ULL(size) - 1);
> +}
> +
> +#define its_cmd_get_command(cmd) its_cmd_mask_field(cmd, 0, 0, 8)
> +#define its_cmd_get_deviceid(cmd) its_cmd_mask_field(cmd, 0, 32, 32)
> +#define its_cmd_get_id(cmd) its_cmd_mask_field(cmd, 1, 0, 32)
> +#define its_cmd_get_physical_id(cmd) its_cmd_mask_field(cmd, 1, 32, 32)
> +#define its_cmd_get_collection(cmd) its_cmd_mask_field(cmd, 2, 0, 16)
> +#define its_cmd_get_target_addr(cmd) its_cmd_mask_field(cmd, 2, 16, 32)
> +#define its_cmd_get_validbit(cmd) its_cmd_mask_field(cmd, 2, 63, 1)
> +
> +/* The DISCARD command frees an Interrupt Translation Table Entry (ITTE). */
> +static int vgic_its_cmd_handle_discard(struct kvm *kvm, struct vgic_its *its,
> + u64 *its_cmd)
> +{
> + u32 device_id;
> + u32 event_id;
> + struct its_itte *itte;
> + int ret = E_ITS_DISCARD_UNMAPPED_INTERRUPT;
> +
> + device_id = its_cmd_get_deviceid(its_cmd);
> + event_id = its_cmd_get_id(its_cmd);
> +
> + mutex_lock(&its->its_lock);
> + itte = find_itte(its, device_id, event_id);
> + if (itte && itte->collection) {
> + /*
> + * Though the spec talks about removing the pending state, we
> + * don't bother here since we clear the ITTE anyway and the
> + * pending state is a property of the ITTE struct.
> + */
> + its_free_itte(kvm, itte);
> + ret = 0;
> + }
> +
> + mutex_unlock(&its->its_lock);
> + return ret;
> +}
> +
> +/* The MOVI command moves an ITTE to a different collection. */
> +static int vgic_its_cmd_handle_movi(struct kvm *kvm, struct vgic_its *its,
> + u64 *its_cmd)
> +{
> + u32 device_id = its_cmd_get_deviceid(its_cmd);
> + u32 event_id = its_cmd_get_id(its_cmd);
> + u32 coll_id = its_cmd_get_collection(its_cmd);
> + struct kvm_vcpu *vcpu;
> + struct its_itte *itte;
> + struct its_collection *collection;
> + int ret = 0;
> +
> + mutex_lock(&its->its_lock);
> + itte = find_itte(its, device_id, event_id);
> + if (!itte) {
> + ret = E_ITS_MOVI_UNMAPPED_INTERRUPT;
> + goto out_unlock;
> + }
> + if (!its_is_collection_mapped(itte->collection)) {
> + ret = E_ITS_MOVI_UNMAPPED_COLLECTION;
> + goto out_unlock;
> + }
> +
> + collection = find_collection(its, coll_id);
> + if (!its_is_collection_mapped(collection)) {
> + ret = E_ITS_MOVI_UNMAPPED_COLLECTION;
> + goto out_unlock;
> + }
> +
> + itte->collection = collection;
> + vcpu = kvm_get_vcpu(kvm, collection->target_addr);
> +
> + spin_lock(&itte->irq->irq_lock);
> + itte->irq->target_vcpu = vcpu;
> + spin_unlock(&itte->irq->irq_lock);
> +
> +out_unlock:
> + mutex_unlock(&its->its_lock);
> + return ret;
> +}
> +
> +static void vgic_its_init_collection(struct vgic_its *its,
> + struct its_collection *collection,
> + u32 coll_id)
> +{
> + collection->collection_id = coll_id;
> + collection->target_addr = COLLECTION_NOT_MAPPED;
> +
> + list_add_tail(&collection->coll_list, &its->collection_list);
> +}
> +
> +/* The MAPTI and MAPI commands map LPIs to ITTEs. */
> +static int vgic_its_cmd_handle_mapi(struct kvm *kvm, struct vgic_its *its,
> + u64 *its_cmd, u8 subcmd)
> +{
> + u32 device_id = its_cmd_get_deviceid(its_cmd);
> + u32 event_id = its_cmd_get_id(its_cmd);
> + u32 coll_id = its_cmd_get_collection(its_cmd);
> + struct its_itte *itte;
> + struct its_device *device;
> + struct its_collection *collection, *new_coll = NULL;
> + int lpi_nr;
> + int ret = 0;
> +
> + mutex_lock(&its->its_lock);
> +
> + device = find_its_device(its, device_id);
> + if (!device) {
> + ret = E_ITS_MAPTI_UNMAPPED_DEVICE;
> + goto out_unlock;
> + }
> +
> + collection = find_collection(its, coll_id);
> + if (!collection) {
> + new_coll = kzalloc(sizeof(struct its_collection), GFP_KERNEL);
> + if (!new_coll) {
> + ret = -ENOMEM;
> + goto out_unlock;
> + }
> + }
> +
> + if (subcmd == GITS_CMD_MAPTI)
> + lpi_nr = its_cmd_get_physical_id(its_cmd);
> + else
> + lpi_nr = event_id;
> + if (lpi_nr < GIC_LPI_OFFSET ||
> + lpi_nr >= max_lpis_propbaser(kvm->arch.vgic.propbaser))
> + return E_ITS_MAPTI_PHYSICALID_OOR;
> +
> + itte = find_itte(its, device_id, event_id);
> + if (!itte) {
> + itte = kzalloc(sizeof(struct its_itte), GFP_KERNEL);
> + if (!itte) {
> + kfree(new_coll);
> + ret = -ENOMEM;
> + goto out_unlock;
> + }
> +
> + itte->event_id = event_id;
> + list_add_tail(&itte->itte_list, &device->itt_head);
> + }
> +
> + if (!collection) {
> + collection = new_coll;
> + vgic_its_init_collection(its, collection, coll_id);
> + }
> +
> + itte->collection = collection;
> + itte->lpi = lpi_nr;
> + itte->irq = vgic_add_lpi(kvm, lpi_nr);
> + update_affinity_itte(kvm, itte);
> +
> + /*
> + * We "cache" the configuration table entries in out struct vgic_irq's.
> + * However we only have those structs for mapped IRQs, so we read in
> + * the respective config data from memory here upon mapping the LPI.
> + */
> + update_lpi_config(kvm, itte->irq);
> +
> +out_unlock:
> + mutex_unlock(&its->its_lock);
> +
> + return 0;
> +}
> +
> +/* Requires the its_lock to be held. */
> +static void vgic_its_unmap_device(struct kvm *kvm, struct its_device *device)
> +{
> + struct its_itte *itte, *temp;
> +
> + /*
> + * The spec says that unmapping a device with still valid
> + * ITTEs associated is UNPREDICTABLE. We remove all ITTEs,
> + * since we cannot leave the memory unreferenced.
> + */
> + list_for_each_entry_safe(itte, temp, &device->itt_head, itte_list)
> + its_free_itte(kvm, itte);
> +
> + list_del(&device->dev_list);
> + kfree(device);
> +}
> +
> +/* MAPD maps or unmaps a device ID to Interrupt Translation Tables (ITTs). */
> +static int vgic_its_cmd_handle_mapd(struct kvm *kvm, struct vgic_its *its,
> + u64 *its_cmd)
> +{
> + bool valid = its_cmd_get_validbit(its_cmd);
> + u32 device_id = its_cmd_get_deviceid(its_cmd);
> + struct its_device *device;
> + int ret = 0;
> +
> + mutex_lock(&its->its_lock);
> +
> + device = find_its_device(its, device_id);
> + if (device)
> + vgic_its_unmap_device(kvm, device);
> +
> + /*
> + * The spec does not say whether unmapping a not-mapped device
> + * is an error, so we are done in any case.
> + */
> + if (!valid)
> + goto out_unlock;
> +
> + device = kzalloc(sizeof(struct its_device), GFP_KERNEL);
> + if (!device) {
> + ret = -ENOMEM;
> + goto out_unlock;
> + }
> +
> + device->device_id = device_id;
> + INIT_LIST_HEAD(&device->itt_head);
> +
> + list_add_tail(&device->dev_list, &its->device_list);
> +
> +out_unlock:
> + mutex_unlock(&its->its_lock);
> + return ret;
> +}
> +
> +/* The MAPC command maps collection IDs to redistributors. */
> +static int vgic_its_cmd_handle_mapc(struct kvm *kvm, struct vgic_its *its,
> + u64 *its_cmd)
> +{
> + u16 coll_id;
> + u32 target_addr;
> + struct its_collection *collection;
> + bool valid;
> + int ret = 0;
> +
> + valid = its_cmd_get_validbit(its_cmd);
> + coll_id = its_cmd_get_collection(its_cmd);
> + target_addr = its_cmd_get_target_addr(its_cmd);
> +
> + if (target_addr >= atomic_read(&kvm->online_vcpus))
> + return E_ITS_MAPC_PROCNUM_OOR;
> +
> + mutex_lock(&its->its_lock);
> +
> + collection = find_collection(its, coll_id);
> +
> + if (!valid) {
> + struct its_device *device;
> + struct its_itte *itte;
> + /*
> + * Clearing the mapping for that collection ID removes the
> + * entry from the list. If there wasn't any before, we can
> + * go home early.
> + */
> + if (!collection)
> + goto out_unlock;
> +
> + for_each_lpi_its(device, itte, its)
> + if (itte->collection &&
> + itte->collection->collection_id == coll_id)
> + itte->collection = NULL;
> +
> + list_del(&collection->coll_list);
> + kfree(collection);
> + } else {
> + if (!collection) {
> + collection = kzalloc(sizeof(struct its_collection),
> + GFP_KERNEL);
> + if (!collection) {
> + ret = -ENOMEM;
> + goto out_unlock;
> + }
> +
> + vgic_its_init_collection(its, collection, coll_id);
> + collection->target_addr = target_addr;
> + } else {
> + collection->target_addr = target_addr;
> + update_affinity_collection(kvm, its, collection);
> + }
> + }
> +
> +out_unlock:
> + mutex_unlock(&its->its_lock);
> +
> + return ret;
> +}
> +
> +/* The CLEAR command removes the pending state for a particular LPI. */
> +static int vgic_its_cmd_handle_clear(struct kvm *kvm, struct vgic_its *its,
> + u64 *its_cmd)
> +{
> + u32 device_id;
> + u32 event_id;
> + struct its_itte *itte;
> + int ret = 0;
> +
> + device_id = its_cmd_get_deviceid(its_cmd);
> + event_id = its_cmd_get_id(its_cmd);
> +
> + mutex_lock(&its->its_lock);
> +
> + itte = find_itte(its, device_id, event_id);
> + if (!itte) {
> + ret = E_ITS_CLEAR_UNMAPPED_INTERRUPT;
> + goto out_unlock;
> + }
> +
> + itte->irq->pending = false;
> +
> +out_unlock:
> + mutex_unlock(&its->its_lock);
> + return ret;
> +}
> +
> +/* The INV command syncs the configuration bits from the memory table. */
> +static int vgic_its_cmd_handle_inv(struct kvm *kvm, struct vgic_its *its,
> + u64 *its_cmd)
> +{
> + u32 device_id;
> + u32 event_id;
> + struct its_itte *itte;
> + int ret;
> +
> + device_id = its_cmd_get_deviceid(its_cmd);
> + event_id = its_cmd_get_id(its_cmd);
> +
> + mutex_lock(&its->its_lock);
> +
> + itte = find_itte(its, device_id, event_id);
> + if (!itte) {
> + ret = E_ITS_INV_UNMAPPED_INTERRUPT;
> + goto out_unlock;
> + }
> +
> + ret = update_lpi_config(kvm, itte->irq);
> +
> +out_unlock:
> + mutex_unlock(&its->its_lock);
> + return ret;
> +}
> +
> +/*
> + * The INVALL command requests flushing of all IRQ data in this collection.
> + * Find the VCPU mapped to that collection, then iterate over the VM's list
> + * of mapped LPIs and update the configuration for each IRQ which targets
> + * the specified vcpu. The configuration will be read from the in-memory
> + * configuration table.
> + */
> +static int vgic_its_cmd_handle_invall(struct kvm *kvm, struct vgic_its *its,
> + u64 *its_cmd)
> +{
> + u32 coll_id = its_cmd_get_collection(its_cmd);
> + struct its_collection *collection;
> + struct kvm_vcpu *vcpu;
> + struct vgic_irq *irq;
> + u32 *intids;
> + int irq_count, i;
> +
> + mutex_lock(&its->its_lock);
> +
> + collection = find_collection(its, coll_id);
> + if (!its_is_collection_mapped(collection))
> + return E_ITS_INVALL_UNMAPPED_COLLECTION;
> +
> + vcpu = kvm_get_vcpu(kvm, collection->target_addr);
> +
> + irq_count = vgic_its_copy_lpi_list(kvm, &intids);
> + if (irq_count < 0)
> + return irq_count;
> +
> + for (i = 0; i < irq_count; i++) {
> + irq = vgic_get_irq(kvm, NULL, intids[i]);
> + if (!irq)
> + continue;
> + update_lpi_config_filtered(kvm, irq, vcpu);
> + vgic_put_irq_locked(kvm, irq);

Where is the lpi_list_lock taken? And why would we need it since we've
copied everything already? By the look of it, this vgic_put_irq_locked
should not exist at all, as the only other use case is quite dubious.

> + }
> +
> + kfree(intids);
> +
> + mutex_unlock(&its->its_lock);
> +
> + return 0;
> +}
> +
> +/*
> + * The MOVALL command moves the pending state of all IRQs targeting one
> + * redistributor to another. We don't hold the pending state in the VCPUs,
> + * but in the IRQs instead, so there is really not much to do for us here.
> + * However the spec says that no IRQ must target the old redistributor
> + * afterwards, so we make sure that no LPI is using the associated target_vcpu.
> + * This command affects all LPIs in the system.
> + */
> +static int vgic_its_cmd_handle_movall(struct kvm *kvm, struct vgic_its *its,
> + u64 *its_cmd)
> +{
> + struct vgic_dist *dist = &kvm->arch.vgic;
> + u32 target1_addr = its_cmd_get_target_addr(its_cmd);
> + u32 target2_addr = its_cmd_mask_field(its_cmd, 3, 16, 32);
> + struct kvm_vcpu *vcpu1, *vcpu2;
> + struct vgic_irq *irq;
> +
> + if (target1_addr >= atomic_read(&kvm->online_vcpus) ||
> + target2_addr >= atomic_read(&kvm->online_vcpus))
> + return E_ITS_MOVALL_PROCNUM_OOR;
> +
> + if (target1_addr == target2_addr)
> + return 0;
> +
> + vcpu1 = kvm_get_vcpu(kvm, target1_addr);
> + vcpu2 = kvm_get_vcpu(kvm, target2_addr);
> +
> + spin_lock(&dist->lpi_list_lock);
> +
> + list_for_each_entry(irq, &dist->lpi_list_head, lpi_entry) {
> + spin_lock(&irq->irq_lock);
> +
> + if (irq->target_vcpu == vcpu1)
> + irq->target_vcpu = vcpu2;
> +
> + spin_unlock(&irq->irq_lock);
> + }
> +
> + spin_unlock(&dist->lpi_list_lock);
> +
> + return 0;
> +}
> +
> +/*
> + * This function is called with the its_cmd lock held, but the ITS data
> + * structure lock dropped. It is within the responsibility of the actual
> + * command handlers to take care of proper locking when needed.
> + */
> +static int vgic_its_handle_command(struct kvm *kvm, struct vgic_its *its,
> u64 *its_cmd)
> {
> - return -ENODEV;
> + u8 cmd = its_cmd_get_command(its_cmd);
> + int ret = -ENODEV;
> +
> + switch (cmd) {
> + case GITS_CMD_MAPD:
> + ret = vgic_its_cmd_handle_mapd(kvm, its, its_cmd);
> + break;
> + case GITS_CMD_MAPC:
> + ret = vgic_its_cmd_handle_mapc(kvm, its, its_cmd);
> + break;
> + case GITS_CMD_MAPI:
> + ret = vgic_its_cmd_handle_mapi(kvm, its, its_cmd, cmd);
> + break;
> + case GITS_CMD_MAPTI:
> + ret = vgic_its_cmd_handle_mapi(kvm, its, its_cmd, cmd);
> + break;
> + case GITS_CMD_MOVI:
> + ret = vgic_its_cmd_handle_movi(kvm, its, its_cmd);
> + break;
> + case GITS_CMD_DISCARD:
> + ret = vgic_its_cmd_handle_discard(kvm, its, its_cmd);
> + break;
> + case GITS_CMD_CLEAR:
> + ret = vgic_its_cmd_handle_clear(kvm, its, its_cmd);
> + break;
> + case GITS_CMD_MOVALL:
> + ret = vgic_its_cmd_handle_movall(kvm, its, its_cmd);
> + break;
> + case GITS_CMD_INV:
> + ret = vgic_its_cmd_handle_inv(kvm, its, its_cmd);
> + break;
> + case GITS_CMD_INVALL:
> + ret = vgic_its_cmd_handle_invall(kvm, its, its_cmd);
> + break;
> + case GITS_CMD_SYNC:
> + /* we ignore this command: we are in sync all of the time */
> + ret = 0;
> + break;
> + }

Given that most commands do take the its mutex, it would make a lot of
sense to move the locking here, and remove it from all of the other
commands. This will streamline the code.

> +
> + return ret;
> }
>
> static u64 vgic_sanitise_its_baser(u64 reg)
> @@ -403,7 +1004,7 @@ static void vgic_mmio_write_its_cwriter(struct kvm *kvm, struct vgic_its *its,
> * We just ignore that command then.
> */
> if (!ret)
> - vits_handle_command(kvm, its, cmd_buf);
> + vgic_its_handle_command(kvm, its, cmd_buf);

Care to solve this function renaming nit?

>
> its->creadr += ITS_CMD_SIZE;
> if (its->creadr == ITS_CMD_BUFFER_SIZE(its->cbaser))
>

Thanks,

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