/******************************************************************************
* grant_table.h
*
* Interface for granting foreign access to page frames, and receiving
* page-ownership transfers.
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to
* deal in the Software without restriction, including without limitation the
* rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
* sell copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
* DEALINGS IN THE SOFTWARE.
*
* Copyright (c) 2004, K A Fraser
*/
#ifndef __XEN_PUBLIC_GRANT_TABLE_H__
#define __XEN_PUBLIC_GRANT_TABLE_H__
#include "xen.h"
/*
* `incontents 150 gnttab Grant Tables
*
* Xen's grant tables provide a generic mechanism to memory sharing
* between domains. This shared memory interface underpins the split
* device drivers for block and network IO.
*
* Each domain has its own grant table. This is a data structure that
* is shared with Xen; it allows the domain to tell Xen what kind of
* permissions other domains have on its pages. Entries in the grant
* table are identified by grant references. A grant reference is an
* integer, which indexes into the grant table. It acts as a
* capability which the grantee can use to perform operations on the
* granter's memory.
*
* This capability-based system allows shared-memory communications
* between unprivileged domains. A grant reference also encapsulates
* the details of a shared page, removing the need for a domain to
* know the real machine address of a page it is sharing. This makes
* it possible to share memory correctly with domains running in
* fully virtualised memory.
*/
/***********************************
* 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 (drivers/xen/grant_table.c, see
* http://git.kernel.org/?p=linux/kernel/git/torvalds/linux.git;a=blob;f=drivers/xen/grant-table.c;hb=HEAD
*
* 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.
*/
/*
* Reference to a grant entry in a specified domain's grant table.
*/
typedef UINT32 grant_ref_t;
/*
* 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.
*/
/*
* Version 1 of the grant table entry structure is maintained purely
* for backwards compatibility. New guests should use version 2.
*/
#if __XEN_INTERFACE_VERSION__ < 0x0003020a
#define grant_entry_v1 grant_entry
#define grant_entry_v1_t grant_entry_t
#endif
struct grant_entry_v1 {
/* GTF_xxx: various type and flag information. [XEN,GST] */
UINT16 flags;
/* The domain being granted foreign privileges. [GST] */
domid_t domid;
/*
* GTF_permit_access: Frame that @domid is allowed to map and access. [GST]
* GTF_accept_transfer: Frame whose ownership transferred by @domid. [XEN]
*/
UINT32 frame;
};
typedef struct grant_entry_v1 grant_entry_v1_t;
/* The first few grant table entries will be preserved across grant table
* version changes and may be pre-populated at domain creation by tools.
*/
#define GNTTAB_NR_RESERVED_ENTRIES 8
#define GNTTAB_RESERVED_CONSOLE 0
#define GNTTAB_RESERVED_XENSTORE 1
/*
* 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.
* GTF_transitive: Allow @domid to transitively access a subrange of
* @trans_grant in @trans_domid. No mappings are allowed.
*/
#define GTF_invalid (0U<<0)
#define GTF_permit_access (1U<<0)
#define GTF_accept_transfer (2U<<0)
#define GTF_transitive (3U<<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]
* GTF_PAT, GTF_PWT, GTF_PCD: (x86) cache attribute flags for the grant [GST]
* GTF_sub_page: Grant access to only a subrange of the page. @domid
* will only be allowed to copy from the grant, and not
* map it. [GST]
*/
#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)
#define _GTF_PWT (5)
#define GTF_PWT (1U<<_GTF_PWT)
#define _GTF_PCD (6)
#define GTF_PCD (1U<<_GTF_PCD)
#define _GTF_PAT (7)
#define GTF_PAT (1U<<_GTF_PAT)
#define _GTF_sub_page (8)
#define GTF_sub_page (1U<<_GTF_sub_page)
/*
* 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)
/*
* Version 2 grant table entries. These fulfil the same role as
* version 1 entries, but can represent more complicated operations.
* Any given domain will have either a version 1 or a version 2 table,
* and every entry in the table will be the same version.
*
* The interface by which domains use grant references does not depend
* on the grant table version in use by the other domain.
*/
#if __XEN_INTERFACE_VERSION__ >= 0x0003020a
/*
* Version 1 and version 2 grant entries share a common prefix. The
* fields of the prefix are documented as part of struct
* grant_entry_v1.
*/
struct grant_entry_header {
UINT16 flags;
domid_t domid;
};
typedef struct grant_entry_header grant_entry_header_t;
/*
* Version 2 of the grant entry structure.
*/
union grant_entry_v2 {
grant_entry_header_t hdr;
/*
* This member is used for V1-style full page grants, where either:
*
* -- hdr.type is GTF_accept_transfer, or
* -- hdr.type is GTF_permit_access and GTF_sub_page is not set.
*
* In that case, the frame field has the same semantics as the
* field of the same name in the V1 entry structure.
*/
struct {
grant_entry_header_t hdr;
UINT32 pad0;
UINT64 frame;
} full_page;
/*
* If the grant type is GTF_grant_access and GTF_sub_page is set,
* @domid is allowed to access bytes [@page_off,@page_off+@length)
* in frame @frame.
*/
struct {
grant_entry_header_t hdr;
UINT16 page_off;
UINT16 length;
UINT64 frame;
} sub_page;
/*
* If the grant is GTF_transitive, @domid is allowed to use the
* grant @gref in domain @trans_domid, as if it was the local
* domain. Obviously, the transitive access must be compatible
* with the original grant.
*
* The current version of Xen does not allow transitive grants
* to be mapped.
*/
struct {
grant_entry_header_t hdr;
domid_t trans_domid;
UINT16 pad0;
grant_ref_t gref;
} transitive;
UINT32 __spacer[4]; /* Pad to a power of two */
};
typedef union grant_entry_v2 grant_entry_v2_t;
typedef UINT16 grant_status_t;
#endif /* __XEN_INTERFACE_VERSION__ */
/***********************************
* GRANT TABLE QUERIES AND USES
*/
/* ` enum neg_errnoval
* ` HYPERVISOR_grant_table_op(enum grant_table_op cmd,
* ` VOID *args,
* ` UINT32 count)
* `
*
* @args points to an array of a per-command data structure. The array
* has @count members
*/
/* ` enum grant_table_op { // GNTTABOP_* => struct gnttab_* */
#define GNTTABOP_map_grant_ref 0
#define GNTTABOP_unmap_grant_ref 1
/* ` } */
/*
* Handle to track a mapping created via a grant reference.
*/
typedef UINT32 grant_handle_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 GNTMAP_device_map is specified then <dev_bus_addr> is the address
* via which I/O devices may access the granted frame.
* 2. If GNTMAP_host_map is specified then a mapping will be added at
* either a host virtual address in the current address space, or at
* a PTE at the specified machine address. The type of mapping to
* perform is selected through the GNTMAP_contains_pte flag, and the
* address is specified in <host_addr>.
* 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!
*/
struct gnttab_map_grant_ref {
/* IN parameters. */
UINT64 host_addr;
UINT32 flags; /* GNTMAP_* */
grant_ref_t ref;
domid_t dom;
/* OUT parameters. */
INT16 status; /* => enum grant_status */
grant_handle_t handle;
UINT64 dev_bus_addr;
};
typedef struct gnttab_map_grant_ref gnttab_map_grant_ref_t;
DEFINE_XEN_GUEST_HANDLE(gnttab_map_grant_ref_t);
/*
* GNTTABOP_unmap_grant_ref: Destroy one or more grant-reference mappings
* tracked by <handle>. If <host_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.
*/
struct gnttab_unmap_grant_ref {
/* IN parameters. */
UINT64 host_addr;
UINT64 dev_bus_addr;
grant_handle_t handle;
/* OUT parameters. */
INT16 status; /* => enum grant_status */
};
typedef struct gnttab_unmap_grant_ref gnttab_unmap_grant_ref_t;
DEFINE_XEN_GUEST_HANDLE(gnttab_unmap_grant_ref_t);
/*
* Bitfield values for gnttab_map_grant_ref.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)
/*
* GNTMAP_contains_pte subflag:
* 0 => This map request contains a host virtual address.
* 1 => This map request contains the machine addess of the PTE to update.
*/
#define _GNTMAP_contains_pte (4)
#define GNTMAP_contains_pte (1<<_GNTMAP_contains_pte)
#define _GNTMAP_can_fail (5)
#define GNTMAP_can_fail (1<<_GNTMAP_can_fail)
/*
* Bits to be placed in guest kernel available PTE bits (architecture
* dependent; only supported when XENFEAT_gnttab_map_avail_bits is set).
*/
#define _GNTMAP_guest_avail0 (16)
#define GNTMAP_guest_avail_mask ((UINT32)~0 << _GNTMAP_guest_avail0)
/*
* Values for error status returns. All errors are -ve.
*/
/* ` enum grant_status { */
#define GNTST_okay (0) /* Normal return. */
#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 GNTST_bad_page (-9) /* Specified page was invalid for op. */
#define GNTST_bad_copy_arg (-10) /* copy arguments cross page boundary. */
#define GNTST_address_too_big (-11) /* transfer page address too large. */
#define GNTST_eagain (-12) /* Operation not done; try again. */
/* ` } */
#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", \
"bad page", \
"copy arguments cross page boundary", \
"page address size too large", \
"operation not done; try again" \
}
#endif /* __XEN_PUBLIC_GRANT_TABLE_H__ */
/*
* Local variables:
* mode: C
* c-file-style: "BSD"
* c-basic-offset: 4
* tab-width: 4
* indent-tabs-mode: nil
* End:
*/