116 lines
3.8 KiB
ReStructuredText
116 lines
3.8 KiB
ReStructuredText
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==============================
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VMWare PVSCSI Device Interface
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==============================
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..
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Created by Dmitry Fleytman (dmitry@daynix.com), Daynix Computing LTD.
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This document describes the VMWare PVSCSI device interface specification,
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based on the source code of the PVSCSI Linux driver from kernel 3.0.4.
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Overview
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========
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The interface is based on a memory area shared between hypervisor and VM.
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The memory area is obtained by driver as a device IO memory resource of
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``PVSCSI_MEM_SPACE_SIZE`` length.
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The shared memory consists of a registers area and a rings area.
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The registers area is used to raise hypervisor interrupts and issue device
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commands. The rings area is used to transfer data descriptors and SCSI
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commands from VM to hypervisor and to transfer messages produced by
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hypervisor to VM. Data itself is transferred via virtual scatter-gather DMA.
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PVSCSI Device Registers
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=======================
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The length of the registers area is 1 page
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(``PVSCSI_MEM_SPACE_COMMAND_NUM_PAGES``). The structure of the
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registers area is described by the ``PVSCSIRegOffset`` enum. There
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are registers to issue device commands (with optional short data),
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issue device interrupts, and control interrupt masking.
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PVSCSI Device Rings
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===================
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There are three rings in shared memory:
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Request ring (``struct PVSCSIRingReqDesc *req_ring``)
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ring for OS to device requests
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Completion ring (``struct PVSCSIRingCmpDesc *cmp_ring``)
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ring for device request completions
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Message ring (``struct PVSCSIRingMsgDesc *msg_ring``)
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ring for messages from device. This ring is optional and the
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guest might not configure it.
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There is a control area (``struct PVSCSIRingsState *rings_state``)
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used to control rings operation.
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PVSCSI Device to Host Interrupts
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================================
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The following interrupt types are supported by the PVSCSI device:
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Completion interrupts (completion ring notifications):
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- ``PVSCSI_INTR_CMPL_0``
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- ``PVSCSI_INTR_CMPL_1``
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Message interrupts (message ring notifications):
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- ``PVSCSI_INTR_MSG_0``
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- ``PVSCSI_INTR_MSG_1``
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Interrupts are controlled via the ``PVSCSI_REG_OFFSET_INTR_MASK``
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register. If a bit is set it means the interrupt is enabled, and if
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it is clear then the interrupt is disabled.
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The interrupt modes supported are legacy, MSI and MSI-X.
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In the case of legacy interrupts, the ``PVSCSI_REG_OFFSET_INTR_STATUS``
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register is used to check which interrupt has arrived. Interrupts are
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acknowledged when the corresponding bit is written to the interrupt
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status register.
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PVSCSI Device Operation Sequences
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=================================
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Startup sequence
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----------------
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a. Issue ``PVSCSI_CMD_ADAPTER_RESET`` command
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b. Windows driver reads interrupt status register here
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c. Issue ``PVSCSI_CMD_SETUP_MSG_RING`` command with no additional data,
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check status and disable device messages if error returned
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(Omitted if device messages disabled by driver configuration)
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d. Issue ``PVSCSI_CMD_SETUP_RINGS`` command, provide rings configuration
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as ``struct PVSCSICmdDescSetupRings``
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e. Issue ``PVSCSI_CMD_SETUP_MSG_RING`` command again, provide
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rings configuration as ``struct PVSCSICmdDescSetupMsgRing``
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f. Unmask completion and message (if device messages enabled) interrupts
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Shutdown sequence
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-----------------
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a. Mask interrupts
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b. Flush request ring using ``PVSCSI_REG_OFFSET_KICK_NON_RW_IO``
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c. Issue ``PVSCSI_CMD_ADAPTER_RESET`` command
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Send request
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------------
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a. Fill next free request ring descriptor
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b. Issue ``PVSCSI_REG_OFFSET_KICK_RW_IO`` for R/W operations
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or ``PVSCSI_REG_OFFSET_KICK_NON_RW_IO`` for other operations
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Abort command
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-------------
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a. Issue ``PVSCSI_CMD_ABORT_CMD`` command
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Request completion processing
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-----------------------------
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a. Upon completion interrupt arrival process completion
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and message (if enabled) rings
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