Re: [Xen-devel] [RFC PATCH 19/24] ARM: vITS: handle DISCARD command

[Stefano Stabellini]

On Wed, 28 Sep 2016, Andre Przywara wrote:
> The DISCARD command drops the connection between a DeviceID/EventID
> and an LPI/collection pair.
> We mark the respective structure entries as not allocated and make
> sure that any queued IRQs are removed.
> 
> Signed-off-by: Andre Przywara 
> ---
>  xen/arch/arm/gic-its.c| 21 +++
>  xen/arch/arm/vgic-its.c   | 48 
> +++
>  xen/include/asm-arm/gic-its.h |  5 +
>  3 files changed, 74 insertions(+)
> 
> diff --git a/xen/arch/arm/gic-its.c b/xen/arch/arm/gic-its.c
> index d1b1cbb..766a7cb 100644
> --- a/xen/arch/arm/gic-its.c
> +++ b/xen/arch/arm/gic-its.c
> @@ -634,6 +634,27 @@ int gicv3_lpi_change_vcpu(struct domain *d, uint32_t 
> host_lpi, int new_vcpu_id)
>  return 0;
>  }
>  
> +/* Looks up a given host LPI assigned to that domain and returns the
> + * connected virtual LPI number. Also stores the target vcpu ID in
> + * the passed vcpu_id pointer.
> + * Returns 0 if no host LPI could be found for that domain, or the
> + * virtual LPI number (>= 8192) if the lookup succeeded.
> + */
> +uint32_t gicv3_lpi_lookup_lpi(struct domain *d, uint32_t host_lpi, int 
> *vcpu_id)
> +{
> +union host_lpi *hlpip, hlpi;
> +
> +hlpip = gic_find_host_lpi(host_lpi, d);
> +if ( !hlpip )
> +return 0;
> +
> +hlpi.data = hlpip->data;
> +if ( vcpu_id )
> +*vcpu_id = hlpi.vcpu_id;
> +
> +return hlpi.virt_lpi;
> +}
> +
>  void gicv3_its_dt_init(const struct dt_device_node *node)
>  {
>  const struct dt_device_node *its = NULL;
> diff --git a/xen/arch/arm/vgic-its.c b/xen/arch/arm/vgic-its.c
> index c0a60ad..028d234 100644
> --- a/xen/arch/arm/vgic-its.c
> +++ b/xen/arch/arm/vgic-its.c
> @@ -367,6 +367,51 @@ out_unlock:
>  return 0;
>  }
>  
> +static int its_handle_discard(struct virt_its *its, uint64_t *cmdptr)
> +{
> +uint32_t devid = its_cmd_get_deviceid(cmdptr);
> +uint32_t eventid = its_cmd_get_id(cmdptr);
> +struct pending_irq *pirq;
> +struct vits_itte *itte;
> +struct vcpu *vcpu;
> +uint32_t vlpi;
> +int ret = -1, vcpu_id;
> +
> +spin_lock(>its_lock);
> +itte = get_devid_evid(its, devid, eventid);
> +if ( !itte )
> +goto out_unlock;
> +
> +vlpi = gicv3_lpi_lookup_lpi(its->d, itte->hlpi, _id);
> +if ( !vlpi )
> +goto out_unlock;

Using itte->hlpi like that is very dangerous because the guest could be
modifying that field while we run gicv3_lpi_lookup_lpi or
gicv3_lpi_drop_host_lpi. Actually we need a compiler barrier after
reading all guest accessible fields and before using them to access our
own data structures.


> +vcpu = its->d->vcpu[vcpu_id];
> +
> +pirq = lpi_to_pending(vcpu, vlpi, false);
> +if ( pirq )
> +{
> +clear_bit(GIC_IRQ_GUEST_QUEUED, >status);
> +gic_remove_from_queues(vcpu, vlpi);
> +
> +/* Mark this pending IRQ struct as availabe again. */
> +if ( !test_bit(GIC_IRQ_GUEST_VISIBLE, >status) )
> +pirq->irq = 0;

We need to do something in case the vlpi is in a GICH_LR register


> +}
> +
> +gicv3_lpi_drop_host_lpi(its->hw_its, devid, eventid, itte->hlpi);

Same here regarding itte->hlpi


> +itte->hlpi = 0; /* Mark this ITTE as unused. */
> +ret = 0;
> +
> +put_devid_evid(its, itte);
> +
> +out_unlock:
> +spin_unlock(>its_lock);
> +
> +return ret;
> +}
> +
>  #define ITS_CMD_BUFFER_SIZE(baser)  baser) & 0xff) + 1) << 12)
>  
>  static int vgic_its_handle_cmds(struct domain *d, struct virt_its *its,
> @@ -390,6 +435,9 @@ static int vgic_its_handle_cmds(struct domain *d, struct 
> virt_its *its,
>  case GITS_CMD_CLEAR:
>  its_handle_clear(its, cmdptr);
>  break;
> +case GITS_CMD_DISCARD:
> +its_handle_discard(its, cmdptr);
> +break;
>  case GITS_CMD_INT:
>  its_handle_int(its, cmdptr);
>  break;
> diff --git a/xen/include/asm-arm/gic-its.h b/xen/include/asm-arm/gic-its.h
> index 7e1142f..3f5698d 100644
> --- a/xen/include/asm-arm/gic-its.h
> +++ b/xen/include/asm-arm/gic-its.h
> @@ -133,6 +133,11 @@ int gicv3_its_map_device(struct host_its *hw_its, struct 
> domain *d,
>  int gicv3_lpi_allocate_host_lpi(struct host_its *its,
>  uint32_t devid, uint32_t eventid,
>  struct vcpu *v, int virt_lpi);
> +/* Given a physical LPI, looks up and returns the associated virtual LPI
> + * and the target VCPU in the given domain.
> + */
> +uint32_t gicv3_lpi_lookup_lpi(struct domain *d, uint32_t host_lpi,
> +  int *vcpu_id);
>  int gicv3_lpi_change_vcpu(struct domain *d, uint32_t host_lpi, int 
> new_vcpu_id);
>  int gicv3_lpi_drop_host_lpi(struct host_its *its,
>  uint32_t devid, uint32_t eventid,
> -- 
> 2.9.0
> 

[Xen-devel] [RFC PATCH 19/24] ARM: vITS: handle DISCARD command

[Andre Przywara]

The DISCARD command drops the connection between a DeviceID/EventID
and an LPI/collection pair.
We mark the respective structure entries as not allocated and make
sure that any queued IRQs are removed.

Signed-off-by: Andre Przywara 
---
 xen/arch/arm/gic-its.c| 21 +++
 xen/arch/arm/vgic-its.c   | 48 +++
 xen/include/asm-arm/gic-its.h |  5 +
 3 files changed, 74 insertions(+)

diff --git a/xen/arch/arm/gic-its.c b/xen/arch/arm/gic-its.c
index d1b1cbb..766a7cb 100644
--- a/xen/arch/arm/gic-its.c
+++ b/xen/arch/arm/gic-its.c
@@ -634,6 +634,27 @@ int gicv3_lpi_change_vcpu(struct domain *d, uint32_t 
host_lpi, int new_vcpu_id)
 return 0;
 }
 
+/* Looks up a given host LPI assigned to that domain and returns the
+ * connected virtual LPI number. Also stores the target vcpu ID in
+ * the passed vcpu_id pointer.
+ * Returns 0 if no host LPI could be found for that domain, or the
+ * virtual LPI number (>= 8192) if the lookup succeeded.
+ */
+uint32_t gicv3_lpi_lookup_lpi(struct domain *d, uint32_t host_lpi, int 
*vcpu_id)
+{
+union host_lpi *hlpip, hlpi;
+
+hlpip = gic_find_host_lpi(host_lpi, d);
+if ( !hlpip )
+return 0;
+
+hlpi.data = hlpip->data;
+if ( vcpu_id )
+*vcpu_id = hlpi.vcpu_id;
+
+return hlpi.virt_lpi;
+}
+
 void gicv3_its_dt_init(const struct dt_device_node *node)
 {
 const struct dt_device_node *its = NULL;
diff --git a/xen/arch/arm/vgic-its.c b/xen/arch/arm/vgic-its.c
index c0a60ad..028d234 100644
--- a/xen/arch/arm/vgic-its.c
+++ b/xen/arch/arm/vgic-its.c
@@ -367,6 +367,51 @@ out_unlock:
 return 0;
 }
 
+static int its_handle_discard(struct virt_its *its, uint64_t *cmdptr)
+{
+uint32_t devid = its_cmd_get_deviceid(cmdptr);
+uint32_t eventid = its_cmd_get_id(cmdptr);
+struct pending_irq *pirq;
+struct vits_itte *itte;
+struct vcpu *vcpu;
+uint32_t vlpi;
+int ret = -1, vcpu_id;
+
+spin_lock(>its_lock);
+itte = get_devid_evid(its, devid, eventid);
+if ( !itte )
+goto out_unlock;
+
+vlpi = gicv3_lpi_lookup_lpi(its->d, itte->hlpi, _id);
+if ( !vlpi )
+goto out_unlock;
+
+vcpu = its->d->vcpu[vcpu_id];
+
+pirq = lpi_to_pending(vcpu, vlpi, false);
+if ( pirq )
+{
+clear_bit(GIC_IRQ_GUEST_QUEUED, >status);
+gic_remove_from_queues(vcpu, vlpi);
+
+/* Mark this pending IRQ struct as availabe again. */
+if ( !test_bit(GIC_IRQ_GUEST_VISIBLE, >status) )
+pirq->irq = 0;
+}
+
+gicv3_lpi_drop_host_lpi(its->hw_its, devid, eventid, itte->hlpi);
+
+itte->hlpi = 0; /* Mark this ITTE as unused. */
+ret = 0;
+
+put_devid_evid(its, itte);
+
+out_unlock:
+spin_unlock(>its_lock);
+
+return ret;
+}
+
 #define ITS_CMD_BUFFER_SIZE(baser)  baser) & 0xff) + 1) << 12)
 
 static int vgic_its_handle_cmds(struct domain *d, struct virt_its *its,
@@ -390,6 +435,9 @@ static int vgic_its_handle_cmds(struct domain *d, struct 
virt_its *its,
 case GITS_CMD_CLEAR:
 its_handle_clear(its, cmdptr);
 break;
+case GITS_CMD_DISCARD:
+its_handle_discard(its, cmdptr);
+break;
 case GITS_CMD_INT:
 its_handle_int(its, cmdptr);
 break;
diff --git a/xen/include/asm-arm/gic-its.h b/xen/include/asm-arm/gic-its.h
index 7e1142f..3f5698d 100644
--- a/xen/include/asm-arm/gic-its.h
+++ b/xen/include/asm-arm/gic-its.h
@@ -133,6 +133,11 @@ int gicv3_its_map_device(struct host_its *hw_its, struct 
domain *d,
 int gicv3_lpi_allocate_host_lpi(struct host_its *its,
 uint32_t devid, uint32_t eventid,
 struct vcpu *v, int virt_lpi);
+/* Given a physical LPI, looks up and returns the associated virtual LPI
+ * and the target VCPU in the given domain.
+ */
+uint32_t gicv3_lpi_lookup_lpi(struct domain *d, uint32_t host_lpi,
+  int *vcpu_id);
 int gicv3_lpi_change_vcpu(struct domain *d, uint32_t host_lpi, int 
new_vcpu_id);
 int gicv3_lpi_drop_host_lpi(struct host_its *its,
 uint32_t devid, uint32_t eventid,
-- 
2.9.0


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