11. Overview 2----------- 3 4This document describes the driver set for Unisys Secure Partitioning 5(s-Par(R)). 6 7s-Par is firmware that provides hardware partitioning capabilities for 8splitting large-scale Intel x86 servers into multiple isolated 9partitions. s-Par provides a set of para-virtualized device drivers to 10allow guest partitions on the same server to share devices that would 11normally be unsharable, specifically: 12 13* visornic - network interface 14* visorhba - scsi disk adapter 15* visorinput - keyboard and mouse 16 17These drivers conform to the standard Linux bus/device model described 18within Documentation/driver-model/, and utilize a driver named visorbus to 19present the virtual busses involved. Drivers in the 'visor*' driver set are 20commonly referred to as "guest drivers" or "client drivers". All drivers 21except visorbus expose a device of a specific usable class to the Linux guest 22environment (e.g., block, network, or input), and are collectively referred 23to as "function drivers". 24 25The back-end for each device is owned and managed by a small, 26single-purpose service partition in the s-Par firmware, which communicates 27with each guest partition sharing that device through an area of shared memory 28called a "channel". In s-Par nomenclature, the back-end is often referred to 29as the "service partition", "IO partition" (for virtual network and scsi disk 30devices), or "console partition" (for virtual keyboard and mouse devices). 31 32Each virtual device requires exactly 1 dedicated channel, which the guest 33driver and back-end use to communicate. The hypervisor need not intervene 34(other than normal interrupt handling) in the interactions that occur across 35this channel. 36 37NOT covered in this document: 38 39* s-Par also supports sharing physical PCI adapters via SR-IOV, but 40 because this requires no specific support in the guest partitions, it will 41 not be discussed in this document. Shared SR-IOV devices should be used 42 wherever possible for highest performance. 43 44* Because the s-Par back-end provides a standard EFI framebuffer to each 45 guest, the already-existing efifb Linux driver is used to provide guest 46 video access. Thus, the only s-Par-unique support that is necessary to 47 provide a guest graphics console are for keyboard and mouse (via visorinput). 48 49 502. Driver Descriptions 51---------------------- 52 532.1. visorbus 54------------- 55 562.1.1. Overview 57--------------- 58 59The visorbus driver handles the virtual busses on which all of the virtual 60devices reside. It provides a registration function named 61visorbus_register_visor_driver() that is called by each of the function 62drivers at initialization time, which the function driver uses to tell 63visorbus about the device classes (via specifying a list of device type 64GUIDs) it wants to handle. For use by function drivers, visorbus provides 65implementation for struct visor_driver and struct visor_device, as well 66as utility functions for communicating with the back-end. 67 68visorbus is associated with ACPI id "PNP0A07" in modules.alias, so if built 69as a module it will typically be loaded automatically via standard udev or 70systemd (God help us) configurations. 71 72visorbus can similarly force auto-loading of function drivers for virtual 73devices it discovers, as it includes a MODALIAS environment variable of this 74form in the hotplug uevent environment when each virtual device is 75discovered: 76 77 visorbus:<device type GUID> 78 79visorbus notifies each function driver when a device of its registered class 80arrives and departs, by calling the function driver's probe() and remove() 81methods. 82 83The actual struct device objects that correspond to each virtual bus and 84each virtual device are created and owned by visorbus. These device objects 85are created in response to messages from the s-Par back-end received on a 86special control channel called the "controlvm channel" (each guest partition 87has access to exactly 1 controlvm channel), and have a lifetime that is 88independent of the function drivers that control them. 89 902.1.2. "struct visor device" Function Driver Interfaces 91------------------------------------------------------- 92 93The interface between visorbus and its function drivers is defined in 94visorbus.h, and described below. 95 96When a visor function driver loads, it calls visorbus_register_visor_driver() 97to register itself with visorbus. The significant information passed in this 98exchange is as follows: 99 100* the GUID(s) of the channel type(s) that are handled by this driver, as 101 well as a "friendly name" identifying each (this will be published under 102 /sys/devices/visorbus<x>/dev<y>) 103 104* the addresses of callback functions to be called whenever a virtual 105 device/channel with the appropriate channel-type GUID(s) appears or 106 disappears 107 108* the address of a "channel_interrupt" function, which will be automatically 109 called at specific intervals to enable the driver to poll the device 110 channel for activity 111 112The following functions implemented within each function driver will be 113called automatically by the visorbus driver at appropriate times: 114 115* The probe() function notifies about the creation of each new virtual 116 device/channel instance. 117 118* The remove() function notifies about the destruction of a virtual 119 device/channel instance. 120 121* The channel_interrupt() function is called at frequent intervals to 122 give the function driver an opportunity to poll the virtual device channel 123 for requests. Information is passed to this function to enable the 124 function driver to use the visorchannel_signalinsert() and 125 visorchannel_signalremove() functions to respond to and initiate activity 126 over the channel. (Note that since it is the visorbus driver that 127 determines when this is called, it is very easy to switch to 128 interrupt-driven mechanisms when available for particular virtual device 129 types.) 130 131* The pause() function is called should it ever be necessary to direct the 132 function driver to temporarily stop accessing the device channel. An 133 example of when this is needed is when the service partition implementing 134 the back-end of the virtual device needs to be recovered. After a 135 successful return of pause(), the function driver must not access the 136 device channel until a subsequent resume() occurs. 137 138* The resume() function is the "book-end" to pause(), and is described above. 139 1402.1.3. sysfs Advertised Information 141----------------------------------- 142 143Because visorbus is a standard Linux bus driver in the model described in 144Documentation/driver-model/, the hierarchy of s-Par virtual devices is 145published in the sysfs tree beneath /bus/visorbus/, e.g., 146/sys/bus/visorbus/devices/ might look like: 147 148 vbus1:dev1 -> ../../../devices/visorbus1/vbus1:dev1 149 vbus1:dev2 -> ../../../devices/visorbus1/vbus1:dev2 150 vbus1:dev3 -> ../../../devices/visorbus1/vbus1:dev3 151 vbus2:dev0 -> ../../../devices/visorbus2/vbus2:dev0 152 vbus2:dev1 -> ../../../devices/visorbus2/vbus2:dev1 153 vbus2:dev2 -> ../../../devices/visorbus2/vbus2:dev2 154 visorbus1 -> ../../../devices/visorbus1 155 visorbus2 -> ../../../devices/visorbus2 156 157visor_device notes: 158 159* Each visorbus<n> entry denotes the existence of a struct visor_device 160 denoting virtual bus #<n>. A unique s-Par channel exists for each such 161 virtual bus. 162 163* Virtual bus numbers uniquely identify s-Par back-end service partitions. 164 In this example, bus 1 corresponds to the s-Par console partition 165 (controls keyboard, video, and mouse), whereas bus 2 corresponds to the 166 s-Par IO partition (controls network and disk). 167 168* Each vbus<x>:dev<y> entry denotes the existence of a struct visor_device 169 denoting virtual device #<y> outboard of virtual bus #<x>. A unique s-Par 170 channel exists for each such virtual device. 171 172* If a function driver has loaded and claimed a particular device, the 173 bus/visorbus/devices/vbus<x>:dev<y>/driver symlink will indicate that 174 function driver. 175 176Every active visorbus device will have a sysfs subtree under: 177 178 /sys/devices/visorbus<x>/vbus<x>:dev<y>/ 179 180The following files exist under /sys/devices/visorbus<x>/vbus<x>:dev<y>: 181 182 subsystem link to sysfs tree that describes the 183 visorbus bus type; e.g.: 184 ../../../bus/visorbus 185 186 driver link to sysfs tree that describes the 187 function driver controlling this device; 188 e.g.: 189 ../../../bus/visorbus/drivers/visorhba 190 Note that this "driver" link will not exist 191 if the appropriate function driver has not 192 been loaded yet. 193 194 channel properties of the device channel (all in 195 ascii text format) 196 197 clientpartition handle identifying the guest (client) side 198 of this channel, e.g. 0x10000000. 199 200 nbytes total size of this channel in bytes 201 202 physaddr the guest physical address for the base of 203 the channel 204 205 typeguid a GUID identifying the channel type, in 206 xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx notation 207 208 typename a "friendly name" for this channel type, e.g., 209 "keyboard". Note that this name is provided by 210 a particular function driver, so "typename" 211 will return an empty string until AFTER the 212 appropriate function driver controlling this 213 channel type is loaded 214 215 zoneguid a GUID identifying the channel zone, in 216 xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx notation 217 218 2192.2. visorhba 220------------- 221 222The visorhba driver registers with visorbus as the function driver to 223handle virtual scsi disk devices, specified using the 224VISOR_VHBA_CHANNEL_GUID type in the visorbus_register_visor_driver() 225call. visorhba uses scsi_add_host() to expose a Linux block device 226(e.g., /sys/block/) in the guest environment for each s-Par virtual device. 227 228visorhba provides access to a shared SCSI host bus adapter and one or more 229disk devices, by proxying SCSI commands between the guest and the service 230partition that owns the shared SCSI adapter, using a channel between the 231guest and the service partition. The disks that appear on the shared bus 232are defined by the s-Par configuration and enforced by the service partition, 233while the guest driver handles sending commands and handling responses. Each 234disk is shared as a whole to a guest. Sharing the bus adapter in this way 235provides resiliency; should the device encounter an error, only the service 236partition is rebooted, and the device is reinitialized. This allows 237guests to continue running and to recover from the error. 238 239When compiled as a module, visorhba can be autoloaded by visorbus in 240standard udev/systemd environments, as it includes the modules.alias 241definition: 242 243 "visorbus:"+VISOR_VHBA_CHANNEL_GUID_STR 244 245i.e.: 246 247 alias visorbus:414815ed-c58c-11da-95a9-00e08161165f visorhba 248 249 2502.3. visornic 251------------- 252 253The visornic driver registers with visorbus as the function driver to 254handle virtual network devices, specified using the 255VISOR_VNIC_CHANNEL_GUID type in the visorbus_register_visor_driver() 256call. visornic uses register_netdev() to expose a Linux device of class net 257(e.g., /sys/class/net/) in the guest environment for each s-Par virtual 258device. 259 260visornic provides a paravirtualized network interface to a 261guest by proxying buffer information between the guest and the service 262partition that owns the shared network interface, using a channel 263between the guest and the service partition. The connectivity of this 264interface with the shared interface and possibly other guest 265partitions is defined by the s-Par configuration and enforced by the 266service partition; the guest driver handles communication and link 267status. 268 269When compiled as a module, visornic can be autoloaded by visorbus in 270standard udev/systemd environments, as it includes the modules.alias 271definition: 272 273 "visorbus:"+VISOR_VNIC_CHANNEL_GUID_STR 274 275i.e.: 276 277 alias visorbus:8cd5994d-c58e-11da-95a9-00e08161165f visornic 278 279 2802.4. visorinput 281--------------- 282 283The visorinput driver registers with visorbus as the function driver to 284handle human input devices, specified using the 285VISOR_KEYBOARD_CHANNEL_GUID and VISOR_MOUSE_CHANNEL_GUID 286types in the visorbus_register_visor_driver() call. visorinput uses 287input_register_device() to expose devices of class input 288(e.g., /sys/class/input/) for virtual keyboard and virtual mouse devices. 289A s-Par virtual keyboard device maps 1-to-1 with a Linux input device 290named "visor Keyboard", while a s-Par virtual mouse device has 2 Linux input 291devices created for it: 1 named "visor Wheel", and 1 named "visor Mouse". 292 293By registering as input class devices, modern versions of X will 294automatically find and properly use s-Par virtual keyboard and mouse devices. 295As the s-Par back-end reports keyboard and mouse activity via events on the 296virtual device channel, the visorinput driver delivers the activity to the 297Linux environment by calling input_report_key() and input_report_abs(). 298 299You can interact with the guest console using the usyscon Partition Desktop 300(a.k.a., "pd") application, provided as part of s-Par. After installing the 301usyscon Partition Desktop into a Linux environment via the 302usyscon_partitiondesktop-*.rpm, or into a Windows environment via 303PartitionDesktop.msi, you will be able to launch a console for your guest 304Linux environment by clicking the console icon in the s-Par web UI. 305 306When compiled as a module, visorinput can be autoloaded by visorbus in 307standard udev/systemd environments, as it includes the modules.alias 308definition: 309 310 "visorbus:"+VISOR_MOUSE_CHANNEL_GUID_STR 311 "visorbus:"+VISOR_KEYBOARD_CHANNEL_GUID_STR 312 313i.e.: 314 315 alias visorbus:c73416d0-b0b8-44af-b304-9d2ae99f1b3d visorinput 316 alias visorbus:addf07d4-94a9-46e2-81c3-61abcdbdbd87 visorinput 317 318 3193. Minimum Required Driver Set 320------------------------------ 321 322visorbus is required for every Linux guest running under s-Par. 323 324visorhba is typically required for a Linux guest running under s-Par, as it 325is required if your guest boot disk is a virtual device provided by the s-Par 326back-end, which is the default configuration. However, for advanced 327configurations where the Linux guest boots via an SR-IOV-provided HBA or 328SAN disk for example, visorhba is not technically required. 329 330visornic is typically required for a Linux guest running under s-Par, as it 331is required if your guest network interface is a virtual device provided by 332the s-Par back-end, which is the default configuration. However, for 333configurations where the Linux guest is provided with an SR-IOV NIC 334for example, visornic is not technically required. 335 336visorinput is only required for a Linux guest running under s-Par if you 337require graphics-mode access to your guest console. 338
