/* 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. */ 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 { … }; /* 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 … #define GNTTAB_RESERVED_CONSOLE … #define GNTTAB_RESERVED_XENSTORE … /* * 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 … #define GTF_permit_access … #define GTF_accept_transfer … #define GTF_transitive … #define GTF_type_mask … /* * 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 … #define GTF_readonly … #define _GTF_reading … #define GTF_reading … #define _GTF_writing … #define GTF_writing … #define _GTF_PWT … #define GTF_PWT … #define _GTF_PCD … #define GTF_PCD … #define _GTF_PAT … #define GTF_PAT … #define _GTF_sub_page … #define 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 … #define GTF_transfer_committed … #define _GTF_transfer_completed … #define 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 { … }; /* * Version 2 of the grant entry structure. */ grant_entry_v2; grant_status_t; /*********************************** * GRANT TABLE QUERIES AND USES */ #define GNTTABOP_map_grant_ref … #define GNTTABOP_unmap_grant_ref … #define GNTTABOP_setup_table … #define GNTTABOP_dump_table … #define GNTTABOP_transfer … #define GNTTABOP_copy … #define GNTTABOP_query_size … #define GNTTABOP_unmap_and_replace … #define GNTTABOP_set_version … #define GNTTABOP_get_status_frames … #define GNTTABOP_get_version … #define GNTTABOP_swap_grant_ref … #define GNTTABOP_cache_flush … /* ` } */ /* * Handle to track a mapping created via a grant reference. */ 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 { … }; DEFINE_GUEST_HANDLE_STRUCT(…); /* * 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 { … }; DEFINE_GUEST_HANDLE_STRUCT(…); /* * 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 { … }; DEFINE_GUEST_HANDLE_STRUCT(…); /* * GNTTABOP_dump_table: Dump the contents of the grant table to the * xen console. Debugging use only. */ struct gnttab_dump_table { … }; DEFINE_GUEST_HANDLE_STRUCT(…); /* * 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 { … }; DEFINE_GUEST_HANDLE_STRUCT(…); /* * 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 … #define GNTCOPY_source_gref … #define _GNTCOPY_dest_gref … #define GNTCOPY_dest_gref … struct gnttab_copy { … }; DEFINE_GUEST_HANDLE_STRUCT(…); /* * 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 { … }; DEFINE_GUEST_HANDLE_STRUCT(…); /* * 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 { … }; DEFINE_GUEST_HANDLE_STRUCT(…); /* * 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 { … }; DEFINE_GUEST_HANDLE_STRUCT(…); /* * 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 { … }; DEFINE_GUEST_HANDLE_STRUCT(…); /* * GNTTABOP_get_version: Get the grant table version which is in * effect for domain <dom>. */ struct gnttab_get_version { … }; DEFINE_GUEST_HANDLE_STRUCT(…); /* * GNTTABOP_swap_grant_ref: Swap the contents of two grant entries. */ struct gnttab_swap_grant_ref { … }; DEFINE_GUEST_HANDLE_STRUCT(…); /* * 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 { … }; DEFINE_GUEST_HANDLE_STRUCT(…); /* * Bitfield values for gnttab_map_grant_ref.flags. */ /* Map the grant entry for access by I/O devices. */ #define _GNTMAP_device_map … #define GNTMAP_device_map … /* Map the grant entry for access by host CPUs. */ #define _GNTMAP_host_map … #define GNTMAP_host_map … /* Accesses to the granted frame will be restricted to read-only access. */ #define _GNTMAP_readonly … #define 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 … #define 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 … #define 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 … #define GNTMAP_guest_avail_mask … /* * Values for error status returns. All errors are -ve. */ #define GNTST_okay … #define GNTST_general_error … #define GNTST_bad_domain … #define GNTST_bad_gntref … #define GNTST_bad_handle … #define GNTST_bad_virt_addr … #define GNTST_bad_dev_addr … #define GNTST_no_device_space … #define GNTST_permission_denied … #define GNTST_bad_page … #define GNTST_bad_copy_arg … #define GNTST_address_too_big … #define GNTST_eagain … #define GNTST_no_space … #define GNTTABOP_error_msgs … #endif /* __XEN_PUBLIC_GRANT_TABLE_H__ */
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