/****************************************************************************** | |
* grant_table.h | |
* | |
* Interface for granting foreign access to page frames, and receiving | |
* page-ownership transfers. | |
* | |
* SPDX-License-Identifier: MIT | |
* | |
* 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 address 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) /* Unrecognised 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: | |
*/ |