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/******************************************************************************
* grant_table.h
*
* Interface for granting foreign access to page frames, and receiving
* page-ownership transfers.
*
* Copyright (c) 2004, K A Fraser
*/
#ifndef __HYPERVISOR_IFS_GRANT_TABLE_H__
#define __HYPERVISOR_IFS_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 (<dom>,<ref>) for access
* by devices and/or host CPUs. If successful, <handle> is a tracking number
* that must be presented later to destroy the mapping(s). On error, <handle>
* is a negative status code.
* NOTES:
* 1. If GNTPIN_map_for_dev is specified then <dev_bus_addr> 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 <host_virt_addr> 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 <handle>. If <host_virt_addr> or <dev_bus_addr> is zero, that
* field is ignored. If non-zero, they must refer to a device/host mapping
* that is tracked by <handle>
* NOTES:
* 1. The call may fail in an undefined manner if either mapping is not
* tracked by <handle>.
* 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 */
/*
* GNTTABOP_setup_table: Set up a grant table for <dom> comprising at least
* <nr_frames> pages. The frame addresses are written to the <frame_list>.
* Only <nr_frames> addresses are written, even if the table is larger.
* NOTES:
* 1. <dom> may be specified as DOMID_SELF.
* 2. Only a sufficiently-privileged domain may specify <dom> != 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 */
/*
* 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 (-3) /* Unrecognised or inappropriate handle. */
#define GNTST_no_device_space (-4) /* Out of space in I/O MMU. */
#define GNTST_permission_denied (-5) /* Not enough privilege for operation. */
#define GNTTABOP_error_msgs { \
"okay", \
"undefined error", \
"unrecognised domain id", \
"invalid grant reference", \
"invalid mapping handle", \
"no spare translation slot in the I/O MMU", \
"permission denied" \
}
#endif /* __HYPERVISOR_IFS_GRANT_TABLE_H__ */
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