/****************************************************************************** * grant_table.h * * Interface for granting foreign access to page frames, and receiving * page-ownership transfers. * * Copyright (c) 2004, K A Fraser */ #ifndef __XEN_PUBLIC_GRANT_TABLE_H__ #define __XEN_PUBLIC_GRANT_TABLE_H__ /*********************************** * GRANT TABLE REPRESENTATION */ /* Some rough guidelines on accessing and updating grant-table entries * in a concurrency-safe manner. For more information, Linux contains a * reference implementation for guest OSes (arch/xen/kernel/grant_table.c). * * NB. WMB is a no-op on current-generation x86 processors. However, a * compiler barrier will still be required. * * Introducing a valid entry into the grant table: * 1. Write ent->domid. * 2. Write ent->frame: * GTF_permit_access: Frame to which access is permitted. * GTF_accept_transfer: Pseudo-phys frame slot being filled by new * frame, or zero if none. * 3. Write memory barrier (WMB). * 4. Write ent->flags, inc. valid type. * * Invalidating an unused GTF_permit_access entry: * 1. flags = ent->flags. * 2. Observe that !(flags & (GTF_reading|GTF_writing)). * 3. Check result of SMP-safe CMPXCHG(&ent->flags, flags, 0). * NB. No need for WMB as reuse of entry is control-dependent on success of * step 3, and all architectures guarantee ordering of ctrl-dep writes. * * Invalidating an in-use GTF_permit_access entry: * This cannot be done directly. Request assistance from the domain controller * which can set a timeout on the use of a grant entry and take necessary * action. (NB. This is not yet implemented!). * * Invalidating an unused GTF_accept_transfer entry: * 1. flags = ent->flags. * 2. Observe that !(flags & GTF_transfer_committed). [*] * 3. Check result of SMP-safe CMPXCHG(&ent->flags, flags, 0). * NB. No need for WMB as reuse of entry is control-dependent on success of * step 3, and all architectures guarantee ordering of ctrl-dep writes. * [*] If GTF_transfer_committed is set then the grant entry is 'committed'. * The guest must /not/ modify the grant entry until the address of the * transferred frame is written. It is safe for the guest to spin waiting * for this to occur (detect by observing GTF_transfer_completed in * ent->flags). * * Invalidating a committed GTF_accept_transfer entry: * 1. Wait for (ent->flags & GTF_transfer_completed). * * Changing a GTF_permit_access from writable to read-only: * Use SMP-safe CMPXCHG to set GTF_readonly, while checking !GTF_writing. * * Changing a GTF_permit_access from read-only to writable: * Use SMP-safe bit-setting instruction. */ /* * A grant table comprises a packed array of grant entries in one or more * page frames shared between Xen and a guest. * [XEN]: This field is written by Xen and read by the sharing guest. * [GST]: This field is written by the guest and read by Xen. */ typedef struct { /* GTF_xxx: various type and flag information. [XEN,GST] */ u16 flags; /* 0 */ /* The domain being granted foreign privileges. [GST] */ domid_t domid; /* 2 */ /* * GTF_permit_access: Frame that @domid is allowed to map and access. [GST] * GTF_accept_transfer: Frame whose ownership transferred by @domid. [XEN] */ u32 frame; /* 4 */ } PACKED grant_entry_t; /* 8 bytes */ /* * Type of grant entry. * GTF_invalid: This grant entry grants no privileges. * GTF_permit_access: Allow @domid to map/access @frame. * GTF_accept_transfer: Allow @domid to transfer ownership of one page frame * to this guest. Xen writes the page number to @frame. */ #define GTF_invalid (0U<<0) #define GTF_permit_access (1U<<0) #define GTF_accept_transfer (2U<<0) #define GTF_type_mask (3U<<0) /* * Subflags for GTF_permit_access. * GTF_readonly: Restrict @domid to read-only mappings and accesses. [GST] * GTF_reading: Grant entry is currently mapped for reading by @domid. [XEN] * GTF_writing: Grant entry is currently mapped for writing by @domid. [XEN] */ #define _GTF_readonly (2) #define GTF_readonly (1U<<_GTF_readonly) #define _GTF_reading (3) #define GTF_reading (1U<<_GTF_reading) #define _GTF_writing (4) #define GTF_writing (1U<<_GTF_writing) /* * Subflags for GTF_accept_transfer: * GTF_transfer_committed: Xen sets this flag to indicate that it is committed * to transferring ownership of a page frame. When a guest sees this flag * it must /not/ modify the grant entry until GTF_transfer_completed is * set by Xen. * GTF_transfer_completed: It is safe for the guest to spin-wait on this flag * after reading GTF_transfer_committed. Xen will always write the frame * address, followed by ORing this flag, in a timely manner. */ #define _GTF_transfer_committed (2) #define GTF_transfer_committed (1U<<_GTF_transfer_committed) #define _GTF_transfer_completed (3) #define GTF_transfer_completed (1U<<_GTF_transfer_completed) /*********************************** * GRANT TABLE QUERIES AND USES */ /* * Reference to a grant entry in a specified domain's grant table. */ typedef u16 grant_ref_t; /* * GNTTABOP_map_grant_ref: Map the grant entry (,) for access * by devices and/or host CPUs. If successful, is a tracking number * that must be presented later to destroy the mapping(s). On error, * is a negative status code. * NOTES: * 1. If GNTPIN_map_for_dev is specified then is the address * via which I/O devices may access the granted frame. * 2. If GNTPIN_map_for_host is specified then a mapping will be added at * virtual address in the current address space. * 3. Mappings should only be destroyed via GNTTABOP_unmap_grant_ref. If a * host mapping is destroyed by other means then it is *NOT* guaranteed * to be accounted to the correct grant reference! */ #define GNTTABOP_map_grant_ref 0 typedef struct { /* IN parameters. */ memory_t host_virt_addr; /* 0 */ MEMORY_PADDING; domid_t dom; /* 8 */ grant_ref_t ref; /* 10 */ u16 flags; /* 12: GNTMAP_* */ /* OUT parameters. */ s16 handle; /* 14: +ve: handle; -ve: GNTST_* */ memory_t dev_bus_addr; /* 16 */ MEMORY_PADDING; } PACKED gnttab_map_grant_ref_t; /* 24 bytes */ /* * GNTTABOP_unmap_grant_ref: Destroy one or more grant-reference mappings * tracked by . If or is zero, that * field is ignored. If non-zero, they must refer to a device/host mapping * that is tracked by * NOTES: * 1. The call may fail in an undefined manner if either mapping is not * tracked by . * 3. After executing a batch of unmaps, it is guaranteed that no stale * mappings will remain in the device or host TLBs. */ #define GNTTABOP_unmap_grant_ref 1 typedef struct { /* IN parameters. */ memory_t host_virt_addr; /* 0 */ MEMORY_PADDING; memory_t dev_bus_addr; /* 8 */ MEMORY_PADDING; u16 handle; /* 16 */ /* OUT parameters. */ s16 status; /* 18: GNTST_* */ u32 __pad; } PACKED gnttab_unmap_grant_ref_t; /* 24 bytes */ #define GNTUNMAP_DEV_FROM_VIRT (~0U) /* * GNTTABOP_setup_table: Set up a grant table for comprising at least * pages. The frame addresses are written to the . * Only addresses are written, even if the table is larger. * NOTES: * 1. may be specified as DOMID_SELF. * 2. Only a sufficiently-privileged domain may specify != DOMID_SELF. * 3. Xen may not support more than a single grant-table page per domain. */ #define GNTTABOP_setup_table 2 typedef struct { /* IN parameters. */ domid_t dom; /* 0 */ u16 nr_frames; /* 2 */ u16 __pad; /* OUT parameters. */ s16 status; /* 6: GNTST_* */ unsigned long *frame_list; /* 8 */ MEMORY_PADDING; } PACKED gnttab_setup_table_t; /* 16 bytes */ /* * GNTTABOP_dump_table: Dump the contents of the grant table to the * xen console. Debugging use only. */ #define GNTTABOP_dump_table 3 typedef struct { /* IN parameters. */ domid_t dom; /* 0 */ /* OUT parameters. */ s16 status; /* 2: GNTST_* */ } PACKED gnttab_dump_table_t; /* 4 bytes */ /* * Bitfield values for update_pin_status.flags. */ /* Map the grant entry for access by I/O devices. */ #define _GNTMAP_device_map (0) #define GNTMAP_device_map (1<<_GNTMAP_device_map) /* Map the grant entry for access by host CPUs. */ #define _GNTMAP_host_map (1) #define GNTMAP_host_map (1<<_GNTMAP_host_map) /* Accesses to the granted frame will be restricted to read-only access. */ #define _GNTMAP_readonly (2) #define GNTMAP_readonly (1<<_GNTMAP_readonly) /* * GNTMAP_host_map subflag: * 0 => The host mapping is usable only by the guest OS. * 1 => The host mapping is usable by guest OS + current application. */ #define _GNTMAP_application_map (3) #define GNTMAP_application_map (1<<_GNTMAP_application_map) /* * Values for error status returns. All errors are -ve. */ #define GNTST_okay (0) #define GNTST_general_error (-1) /* General undefined error. */ #define GNTST_bad_domain (-2) /* Unrecognsed domain id. */ #define GNTST_bad_gntref (-3) /* Unrecognised or inappropriate gntref. */ #define GNTST_bad_handle (-4) /* Unrecognised or inappropriate handle. */ #define GNTST_bad_virt_addr (-5) /* Inappropriate virtual address to map. */ #define GNTST_bad_dev_addr (-6) /* Inappropriate device address to unmap.*/ #define GNTST_no_device_space (-7) /* Out of space in I/O MMU. */ #define GNTST_permission_denied (-8) /* Not enough privilege for operation. */ #define GNTTABOP_error_msgs { \ "okay", \ "undefined error", \ "unrecognised domain id", \ "invalid grant reference", \ "invalid mapping handle", \ "invalid virtual address", \ "invalid device address", \ "no spare translation slot in the I/O MMU", \ "permission denied" \ } typedef struct { union { /* 0 */ gnttab_map_grant_ref_t map_grant_ref; gnttab_unmap_grant_ref_t unmap_grant_ref; gnttab_setup_table_t setup_table; gnttab_dump_table_t dump_table; u8 __dummy[24]; } PACKED u; } PACKED gnttab_op_t; /* 32 bytes */ #endif /* __XEN_PUBLIC_GRANT_TABLE_H__ */