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