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grant_table.h
/* SPDX-License-Identifier: MIT */ /****************************************************************************** * 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__ #include <xen/interface/xen.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 (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_t 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 largely for * backwards compatibility. New guests are recommended to support using * version 2 to overcome version 1 limitations, but to default to version 1. */ struct grant_entry_v1 { /* GTF_xxx: various type and flag information. [XEN,GST] */ uint16_t flags; /* The domain being granted foreign privileges. [GST] */ domid_t domid; /* * GTF_permit_access: GFN that @domid is allowed to map and access. [GST] * GTF_accept_transfer: GFN that @domid is allowed to transfer into. [GST] * GTF_transfer_completed: MFN whose ownership transferred by @domid * (non-translated guests only). [XEN] */ uint32_t frame; }; /* 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 and GTF_transitive. * 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] * Further subflags for GTF_permit_access only. * GTF_PAT, GTF_PWT, GTF_PCD: (x86) cache attribute flags to be used for * mappings of 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. */ /* * 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_t flags; domid_t domid; }; /* * Version 2 of the grant entry structure. */ union grant_entry_v2 { struct grant_entry_header 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 { struct grant_entry_header hdr; uint32_t pad0; uint64_t 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 { struct grant_entry_header hdr; uint16_t page_off; uint16_t length; uint64_t 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 { struct grant_entry_header hdr; domid_t trans_domid; uint16_t pad0; grant_ref_t gref; } transitive; uint32_t __spacer[4]; /* Pad to a power of two */ }; typedef uint16_t grant_status_t; /*********************************** * GRANT TABLE QUERIES AND USES */ #define GNTTABOP_map_grant_ref 0 #define GNTTABOP_unmap_grant_ref 1 #define GNTTABOP_setup_table 2 #define GNTTABOP_dump_table 3 #define GNTTABOP_transfer 4 #define GNTTABOP_copy 5 #define GNTTABOP_query_size 6 #define GNTTABOP_unmap_and_replace 7 #define GNTTABOP_set_version 8 #define GNTTABOP_get_status_frames 9 #define GNTTABOP_get_version 10 #define GNTTABOP_swap_grant_ref 11 #define GNTTABOP_cache_flush 12 /* ` } */ /* * Handle to track a mapping created via a grant reference. */ typedef uint32_t 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, <status> * 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_t host_addr; uint32_t flags; /* GNTMAP_* */ grant_ref_t ref; domid_t dom; /* OUT parameters. */ int16_t status; /* GNTST_* */ grant_handle_t handle; uint64_t dev_bus_addr; }; DEFINE_GUEST_HANDLE_STRUCT(gnttab_map_grant_ref); /* * 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_t host_addr; uint64_t dev_bus_addr; grant_handle_t handle; /* OUT parameters. */ int16_t status; /* GNTST_* */ }; DEFINE_GUEST_HANDLE_STRUCT(gnttab_unmap_grant_ref); /* * 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. */ struct gnttab_setup_table { /* IN parameters. */ domid_t dom; uint32_t nr_frames; /* OUT parameters. */ int16_t status; /* GNTST_* */ GUEST_HANDLE(xen_pfn_t) frame_list; }; DEFINE_GUEST_HANDLE_STRUCT(gnttab_setup_table); /* * GNTTABOP_dump_table: Dump the contents of the grant table to the * xen console. Debugging use only. */ struct gnttab_dump_table { /* IN parameters. */ domid_t dom; /* OUT parameters. */ int16_t status; /* GNTST_* */ }; DEFINE_GUEST_HANDLE_STRUCT(gnttab_dump_table); /* * GNTTABOP_transfer: Transfer <frame> to a foreign domain. The foreign domain * has previously registered its interest in the transfer via <domid, ref>. * * Note that, even if the transfer fails, the specified page no longer belongs * to the calling domain *unless* the error is GNTST_bad_page. * * Note further that only PV guests can use this operation. */ struct gnttab_transfer { /* IN parameters. */ xen_pfn_t mfn; domid_t domid; grant_ref_t ref; /* OUT parameters. */ int16_t status; }; DEFINE_GUEST_HANDLE_STRUCT(gnttab_transfer); /* * GNTTABOP_copy: Hypervisor based copy * source and destinations can be eithers MFNs or, for foreign domains, * grant references. the foreign domain has to grant read/write access * in its grant table. * * The flags specify what type source and destinations are (either MFN * or grant reference). * * Note that this can also be used to copy data between two domains * via a third party if the source and destination domains had previously * grant appropriate access to their pages to the third party. * * source_offset specifies an offset in the source frame, dest_offset * the offset in the target frame and len specifies the number of * bytes to be copied. */ #define _GNTCOPY_source_gref (0) #define GNTCOPY_source_gref (1<<_GNTCOPY_source_gref) #define _GNTCOPY_dest_gref (1) #define GNTCOPY_dest_gref (1<<_GNTCOPY_dest_gref) struct gnttab_copy { /* IN parameters. */ struct gnttab_copy_ptr { union { grant_ref_t ref; xen_pfn_t gmfn; } u; domid_t domid; uint16_t offset; } source, dest; uint16_t len; uint16_t flags; /* GNTCOPY_* */ /* OUT parameters. */ int16_t status; }; DEFINE_GUEST_HANDLE_STRUCT(gnttab_copy); /* * GNTTABOP_query_size: Query the current and maximum sizes of the shared * grant table. * NOTES: * 1. <dom> may be specified as DOMID_SELF. * 2. Only a sufficiently-privileged domain may specify <dom> != DOMID_SELF. */ struct gnttab_query_size { /* IN parameters. */ domid_t dom; /* OUT parameters. */ uint32_t nr_frames; uint32_t max_nr_frames; int16_t status; /* GNTST_* */ }; DEFINE_GUEST_HANDLE_STRUCT(gnttab_query_size); /* * GNTTABOP_unmap_and_replace: Destroy one or more grant-reference mappings * tracked by <handle> but atomically replace the page table entry with one * pointing to the machine address under <new_addr>. <new_addr> will be * redirected to the null entry. * NOTES: * 1. The call may fail in an undefined manner if either mapping is not * tracked by <handle>. * 2. After executing a batch of unmaps, it is guaranteed that no stale * mappings will remain in the device or host TLBs. */ struct gnttab_unmap_and_replace { /* IN parameters. */ uint64_t host_addr; uint64_t new_addr; grant_handle_t handle; /* OUT parameters. */ int16_t status; /* GNTST_* */ }; DEFINE_GUEST_HANDLE_STRUCT(gnttab_unmap_and_replace); /* * GNTTABOP_set_version: Request a particular version of the grant * table shared table structure. This operation may be used to toggle * between different versions, but must be performed while no grants * are active. The only defined versions are 1 and 2. */ struct gnttab_set_version { /* IN/OUT parameters */ uint32_t version; }; DEFINE_GUEST_HANDLE_STRUCT(gnttab_set_version); /* * GNTTABOP_get_status_frames: Get the list of frames used to store grant * status for <dom>. In grant format version 2, the status is separated * from the other shared grant fields to allow more efficient synchronization * using barriers instead of atomic cmpexch operations. * <nr_frames> specify the size of vector <frame_list>. * The frame addresses are returned in the <frame_list>. * Only <nr_frames> addresses are returned, 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. */ struct gnttab_get_status_frames { /* IN parameters. */ uint32_t nr_frames; domid_t dom; /* OUT parameters. */ int16_t status; /* GNTST_* */ GUEST_HANDLE(uint64_t) frame_list; }; DEFINE_GUEST_HANDLE_STRUCT(gnttab_get_status_frames); /* * GNTTABOP_get_version: Get the grant table version which is in * effect for domain <dom>. */ struct gnttab_get_version { /* IN parameters */ domid_t dom; uint16_t pad; /* OUT parameters */ uint32_t version; }; DEFINE_GUEST_HANDLE_STRUCT(gnttab_get_version); /* * GNTTABOP_swap_grant_ref: Swap the contents of two grant entries. */ struct gnttab_swap_grant_ref { /* IN parameters */ grant_ref_t ref_a; grant_ref_t ref_b; /* OUT parameters */ int16_t status; /* GNTST_* */ }; DEFINE_GUEST_HANDLE_STRUCT(gnttab_swap_grant_ref); /* * Issue one or more cache maintenance operations on a portion of a * page granted to the calling domain by a foreign domain. */ struct gnttab_cache_flush { union { uint64_t dev_bus_addr; grant_ref_t ref; } a; uint16_t offset; /* offset from start of grant */ uint16_t length; /* size within the grant */ #define GNTTAB_CACHE_CLEAN (1u<<0) #define GNTTAB_CACHE_INVAL (1u<<1) #define GNTTAB_CACHE_SOURCE_GREF (1u<<31) uint32_t op; }; DEFINE_GUEST_HANDLE_STRUCT(gnttab_cache_flush); /* * 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) /* * 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_t)~0 << _GNTMAP_guest_avail0) /* * Values for error status returns. All errors are -ve. */ #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 GNTST_no_space (-13) /* Out of space (handles etc). */ #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", \ "out of space", \ } #endif /* __XEN_PUBLIC_GRANT_TABLE_H__ */
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