--- /dev/null
+.. SPDX-License-Identifier: GPL-2.0
+
+===========================================================
+POWER9 eXternal Interrupt Virtualization Engine (XIVE Gen1)
+===========================================================
+
+Device types supported:
+ - KVM_DEV_TYPE_XIVE POWER9 XIVE Interrupt Controller generation 1
+
+This device acts as a VM interrupt controller. It provides the KVM
+interface to configure the interrupt sources of a VM in the underlying
+POWER9 XIVE interrupt controller.
+
+Only one XIVE instance may be instantiated. A guest XIVE device
+requires a POWER9 host and the guest OS should have support for the
+XIVE native exploitation interrupt mode. If not, it should run using
+the legacy interrupt mode, referred as XICS (POWER7/8).
+
+* Device Mappings
+
+ The KVM device exposes different MMIO ranges of the XIVE HW which
+ are required for interrupt management. These are exposed to the
+ guest in VMAs populated with a custom VM fault handler.
+
+ 1. Thread Interrupt Management Area (TIMA)
+
+ Each thread has an associated Thread Interrupt Management context
+ composed of a set of registers. These registers let the thread
+ handle priority management and interrupt acknowledgment. The most
+ important are :
+
+ - Interrupt Pending Buffer (IPB)
+ - Current Processor Priority (CPPR)
+ - Notification Source Register (NSR)
+
+ They are exposed to software in four different pages each proposing
+ a view with a different privilege. The first page is for the
+ physical thread context and the second for the hypervisor. Only the
+ third (operating system) and the fourth (user level) are exposed the
+ guest.
+
+ 2. Event State Buffer (ESB)
+
+ Each source is associated with an Event State Buffer (ESB) with
+ either a pair of even/odd pair of pages which provides commands to
+ manage the source: to trigger, to EOI, to turn off the source for
+ instance.
+
+ 3. Device pass-through
+
+ When a device is passed-through into the guest, the source
+ interrupts are from a different HW controller (PHB4) and the ESB
+ pages exposed to the guest should accommadate this change.
+
+ The passthru_irq helpers, kvmppc_xive_set_mapped() and
+ kvmppc_xive_clr_mapped() are called when the device HW irqs are
+ mapped into or unmapped from the guest IRQ number space. The KVM
+ device extends these helpers to clear the ESB pages of the guest IRQ
+ number being mapped and then lets the VM fault handler repopulate.
+ The handler will insert the ESB page corresponding to the HW
+ interrupt of the device being passed-through or the initial IPI ESB
+ page if the device has being removed.
+
+ The ESB remapping is fully transparent to the guest and the OS
+ device driver. All handling is done within VFIO and the above
+ helpers in KVM-PPC.
+
+* Groups:
+
+1. KVM_DEV_XIVE_GRP_CTRL
+ Provides global controls on the device
+
+ Attributes:
+ 1.1 KVM_DEV_XIVE_RESET (write only)
+ Resets the interrupt controller configuration for sources and event
+ queues. To be used by kexec and kdump.
+
+ Errors: none
+
+ 1.2 KVM_DEV_XIVE_EQ_SYNC (write only)
+ Sync all the sources and queues and mark the EQ pages dirty. This
+ to make sure that a consistent memory state is captured when
+ migrating the VM.
+
+ Errors: none
+
+ 1.3 KVM_DEV_XIVE_NR_SERVERS (write only)
+ The kvm_device_attr.addr points to a __u32 value which is the number of
+ interrupt server numbers (ie, highest possible vcpu id plus one).
+
+ Errors:
+
+ ======= ==========================================
+ -EINVAL Value greater than KVM_MAX_VCPU_ID.
+ -EFAULT Invalid user pointer for attr->addr.
+ -EBUSY A vCPU is already connected to the device.
+ ======= ==========================================
+
+2. KVM_DEV_XIVE_GRP_SOURCE (write only)
+ Initializes a new source in the XIVE device and mask it.
+
+ Attributes:
+ Interrupt source number (64-bit)
+
+ The kvm_device_attr.addr points to a __u64 value::
+
+ bits: | 63 .... 2 | 1 | 0
+ values: | unused | level | type
+
+ - type: 0:MSI 1:LSI
+ - level: assertion level in case of an LSI.
+
+ Errors:
+
+ ======= ==========================================
+ -E2BIG Interrupt source number is out of range
+ -ENOMEM Could not create a new source block
+ -EFAULT Invalid user pointer for attr->addr.
+ -ENXIO Could not allocate underlying HW interrupt
+ ======= ==========================================
+
+3. KVM_DEV_XIVE_GRP_SOURCE_CONFIG (write only)
+ Configures source targeting
+
+ Attributes:
+ Interrupt source number (64-bit)
+
+ The kvm_device_attr.addr points to a __u64 value::
+
+ bits: | 63 .... 33 | 32 | 31 .. 3 | 2 .. 0
+ values: | eisn | mask | server | priority
+
+ - priority: 0-7 interrupt priority level
+ - server: CPU number chosen to handle the interrupt
+ - mask: mask flag (unused)
+ - eisn: Effective Interrupt Source Number
+
+ Errors:
+
+ ======= =======================================================
+ -ENOENT Unknown source number
+ -EINVAL Not initialized source number
+ -EINVAL Invalid priority
+ -EINVAL Invalid CPU number.
+ -EFAULT Invalid user pointer for attr->addr.
+ -ENXIO CPU event queues not configured or configuration of the
+ underlying HW interrupt failed
+ -EBUSY No CPU available to serve interrupt
+ ======= =======================================================
+
+4. KVM_DEV_XIVE_GRP_EQ_CONFIG (read-write)
+ Configures an event queue of a CPU
+
+ Attributes:
+ EQ descriptor identifier (64-bit)
+
+ The EQ descriptor identifier is a tuple (server, priority)::
+
+ bits: | 63 .... 32 | 31 .. 3 | 2 .. 0
+ values: | unused | server | priority
+
+ The kvm_device_attr.addr points to::
+
+ struct kvm_ppc_xive_eq {
+ __u32 flags;
+ __u32 qshift;
+ __u64 qaddr;
+ __u32 qtoggle;
+ __u32 qindex;
+ __u8 pad[40];
+ };
+
+ - flags: queue flags
+ KVM_XIVE_EQ_ALWAYS_NOTIFY (required)
+ forces notification without using the coalescing mechanism
+ provided by the XIVE END ESBs.
+ - qshift: queue size (power of 2)
+ - qaddr: real address of queue
+ - qtoggle: current queue toggle bit
+ - qindex: current queue index
+ - pad: reserved for future use
+
+ Errors:
+
+ ======= =========================================
+ -ENOENT Invalid CPU number
+ -EINVAL Invalid priority
+ -EINVAL Invalid flags
+ -EINVAL Invalid queue size
+ -EINVAL Invalid queue address
+ -EFAULT Invalid user pointer for attr->addr.
+ -EIO Configuration of the underlying HW failed
+ ======= =========================================
+
+5. KVM_DEV_XIVE_GRP_SOURCE_SYNC (write only)
+ Synchronize the source to flush event notifications
+
+ Attributes:
+ Interrupt source number (64-bit)
+
+ Errors:
+
+ ======= =============================
+ -ENOENT Unknown source number
+ -EINVAL Not initialized source number
+ ======= =============================
+
+* VCPU state
+
+ The XIVE IC maintains VP interrupt state in an internal structure
+ called the NVT. When a VP is not dispatched on a HW processor
+ thread, this structure can be updated by HW if the VP is the target
+ of an event notification.
+
+ It is important for migration to capture the cached IPB from the NVT
+ as it synthesizes the priorities of the pending interrupts. We
+ capture a bit more to report debug information.
+
+ KVM_REG_PPC_VP_STATE (2 * 64bits)::
+
+ bits: | 63 .... 32 | 31 .... 0 |
+ values: | TIMA word0 | TIMA word1 |
+ bits: | 127 .......... 64 |
+ values: | unused |
+
+* Migration:
+
+ Saving the state of a VM using the XIVE native exploitation mode
+ should follow a specific sequence. When the VM is stopped :
+
+ 1. Mask all sources (PQ=01) to stop the flow of events.
+
+ 2. Sync the XIVE device with the KVM control KVM_DEV_XIVE_EQ_SYNC to
+ flush any in-flight event notification and to stabilize the EQs. At
+ this stage, the EQ pages are marked dirty to make sure they are
+ transferred in the migration sequence.
+
+ 3. Capture the state of the source targeting, the EQs configuration
+ and the state of thread interrupt context registers.
+
+ Restore is similar:
+
+ 1. Restore the EQ configuration. As targeting depends on it.
+ 2. Restore targeting
+ 3. Restore the thread interrupt contexts
+ 4. Restore the source states
+ 5. Let the vCPU run
+++ /dev/null
-POWER9 eXternal Interrupt Virtualization Engine (XIVE Gen1)
-==========================================================
-
-Device types supported:
- KVM_DEV_TYPE_XIVE POWER9 XIVE Interrupt Controller generation 1
-
-This device acts as a VM interrupt controller. It provides the KVM
-interface to configure the interrupt sources of a VM in the underlying
-POWER9 XIVE interrupt controller.
-
-Only one XIVE instance may be instantiated. A guest XIVE device
-requires a POWER9 host and the guest OS should have support for the
-XIVE native exploitation interrupt mode. If not, it should run using
-the legacy interrupt mode, referred as XICS (POWER7/8).
-
-* Device Mappings
-
- The KVM device exposes different MMIO ranges of the XIVE HW which
- are required for interrupt management. These are exposed to the
- guest in VMAs populated with a custom VM fault handler.
-
- 1. Thread Interrupt Management Area (TIMA)
-
- Each thread has an associated Thread Interrupt Management context
- composed of a set of registers. These registers let the thread
- handle priority management and interrupt acknowledgment. The most
- important are :
-
- - Interrupt Pending Buffer (IPB)
- - Current Processor Priority (CPPR)
- - Notification Source Register (NSR)
-
- They are exposed to software in four different pages each proposing
- a view with a different privilege. The first page is for the
- physical thread context and the second for the hypervisor. Only the
- third (operating system) and the fourth (user level) are exposed the
- guest.
-
- 2. Event State Buffer (ESB)
-
- Each source is associated with an Event State Buffer (ESB) with
- either a pair of even/odd pair of pages which provides commands to
- manage the source: to trigger, to EOI, to turn off the source for
- instance.
-
- 3. Device pass-through
-
- When a device is passed-through into the guest, the source
- interrupts are from a different HW controller (PHB4) and the ESB
- pages exposed to the guest should accommadate this change.
-
- The passthru_irq helpers, kvmppc_xive_set_mapped() and
- kvmppc_xive_clr_mapped() are called when the device HW irqs are
- mapped into or unmapped from the guest IRQ number space. The KVM
- device extends these helpers to clear the ESB pages of the guest IRQ
- number being mapped and then lets the VM fault handler repopulate.
- The handler will insert the ESB page corresponding to the HW
- interrupt of the device being passed-through or the initial IPI ESB
- page if the device has being removed.
-
- The ESB remapping is fully transparent to the guest and the OS
- device driver. All handling is done within VFIO and the above
- helpers in KVM-PPC.
-
-* Groups:
-
- 1. KVM_DEV_XIVE_GRP_CTRL
- Provides global controls on the device
- Attributes:
- 1.1 KVM_DEV_XIVE_RESET (write only)
- Resets the interrupt controller configuration for sources and event
- queues. To be used by kexec and kdump.
- Errors: none
-
- 1.2 KVM_DEV_XIVE_EQ_SYNC (write only)
- Sync all the sources and queues and mark the EQ pages dirty. This
- to make sure that a consistent memory state is captured when
- migrating the VM.
- Errors: none
-
- 1.3 KVM_DEV_XIVE_NR_SERVERS (write only)
- The kvm_device_attr.addr points to a __u32 value which is the number of
- interrupt server numbers (ie, highest possible vcpu id plus one).
- Errors:
- -EINVAL: Value greater than KVM_MAX_VCPU_ID.
- -EFAULT: Invalid user pointer for attr->addr.
- -EBUSY: A vCPU is already connected to the device.
-
- 2. KVM_DEV_XIVE_GRP_SOURCE (write only)
- Initializes a new source in the XIVE device and mask it.
- Attributes:
- Interrupt source number (64-bit)
- The kvm_device_attr.addr points to a __u64 value:
- bits: | 63 .... 2 | 1 | 0
- values: | unused | level | type
- - type: 0:MSI 1:LSI
- - level: assertion level in case of an LSI.
- Errors:
- -E2BIG: Interrupt source number is out of range
- -ENOMEM: Could not create a new source block
- -EFAULT: Invalid user pointer for attr->addr.
- -ENXIO: Could not allocate underlying HW interrupt
-
- 3. KVM_DEV_XIVE_GRP_SOURCE_CONFIG (write only)
- Configures source targeting
- Attributes:
- Interrupt source number (64-bit)
- The kvm_device_attr.addr points to a __u64 value:
- bits: | 63 .... 33 | 32 | 31 .. 3 | 2 .. 0
- values: | eisn | mask | server | priority
- - priority: 0-7 interrupt priority level
- - server: CPU number chosen to handle the interrupt
- - mask: mask flag (unused)
- - eisn: Effective Interrupt Source Number
- Errors:
- -ENOENT: Unknown source number
- -EINVAL: Not initialized source number
- -EINVAL: Invalid priority
- -EINVAL: Invalid CPU number.
- -EFAULT: Invalid user pointer for attr->addr.
- -ENXIO: CPU event queues not configured or configuration of the
- underlying HW interrupt failed
- -EBUSY: No CPU available to serve interrupt
-
- 4. KVM_DEV_XIVE_GRP_EQ_CONFIG (read-write)
- Configures an event queue of a CPU
- Attributes:
- EQ descriptor identifier (64-bit)
- The EQ descriptor identifier is a tuple (server, priority) :
- bits: | 63 .... 32 | 31 .. 3 | 2 .. 0
- values: | unused | server | priority
- The kvm_device_attr.addr points to :
- struct kvm_ppc_xive_eq {
- __u32 flags;
- __u32 qshift;
- __u64 qaddr;
- __u32 qtoggle;
- __u32 qindex;
- __u8 pad[40];
- };
- - flags: queue flags
- KVM_XIVE_EQ_ALWAYS_NOTIFY (required)
- forces notification without using the coalescing mechanism
- provided by the XIVE END ESBs.
- - qshift: queue size (power of 2)
- - qaddr: real address of queue
- - qtoggle: current queue toggle bit
- - qindex: current queue index
- - pad: reserved for future use
- Errors:
- -ENOENT: Invalid CPU number
- -EINVAL: Invalid priority
- -EINVAL: Invalid flags
- -EINVAL: Invalid queue size
- -EINVAL: Invalid queue address
- -EFAULT: Invalid user pointer for attr->addr.
- -EIO: Configuration of the underlying HW failed
-
- 5. KVM_DEV_XIVE_GRP_SOURCE_SYNC (write only)
- Synchronize the source to flush event notifications
- Attributes:
- Interrupt source number (64-bit)
- Errors:
- -ENOENT: Unknown source number
- -EINVAL: Not initialized source number
-
-* VCPU state
-
- The XIVE IC maintains VP interrupt state in an internal structure
- called the NVT. When a VP is not dispatched on a HW processor
- thread, this structure can be updated by HW if the VP is the target
- of an event notification.
-
- It is important for migration to capture the cached IPB from the NVT
- as it synthesizes the priorities of the pending interrupts. We
- capture a bit more to report debug information.
-
- KVM_REG_PPC_VP_STATE (2 * 64bits)
- bits: | 63 .... 32 | 31 .... 0 |
- values: | TIMA word0 | TIMA word1 |
- bits: | 127 .......... 64 |
- values: | unused |
-
-* Migration:
-
- Saving the state of a VM using the XIVE native exploitation mode
- should follow a specific sequence. When the VM is stopped :
-
- 1. Mask all sources (PQ=01) to stop the flow of events.
-
- 2. Sync the XIVE device with the KVM control KVM_DEV_XIVE_EQ_SYNC to
- flush any in-flight event notification and to stabilize the EQs. At
- this stage, the EQ pages are marked dirty to make sure they are
- transferred in the migration sequence.
-
- 3. Capture the state of the source targeting, the EQs configuration
- and the state of thread interrupt context registers.
-
- Restore is similar :
-
- 1. Restore the EQ configuration. As targeting depends on it.
- 2. Restore targeting
- 3. Restore the thread interrupt contexts
- 4. Restore the source states
- 5. Let the vCPU run
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