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[mirror_edk2.git] / OvmfPkg / Include / IndustryStandard / Xen / grant_table.h

/******************************************************************************\r
 * grant_table.h\r
 *\r
 * Interface for granting foreign access to page frames, and receiving\r
 * page-ownership transfers.\r
 *\r
 * SPDX-License-Identifier: MIT\r
 *\r
 * Copyright (c) 2004, K A Fraser\r
 */\r
\r
#ifndef __XEN_PUBLIC_GRANT_TABLE_H__\r
#define __XEN_PUBLIC_GRANT_TABLE_H__\r
\r
#include "xen.h"\r
\r
/*\r
 * `incontents 150 gnttab Grant Tables\r
 *\r
 * Xen's grant tables provide a generic mechanism to memory sharing\r
 * between domains. This shared memory interface underpins the split\r
 * device drivers for block and network IO.\r
 *\r
 * Each domain has its own grant table. This is a data structure that\r
 * is shared with Xen; it allows the domain to tell Xen what kind of\r
 * permissions other domains have on its pages. Entries in the grant\r
 * table are identified by grant references. A grant reference is an\r
 * integer, which indexes into the grant table. It acts as a\r
 * capability which the grantee can use to perform operations on the\r
 * granter's memory.\r
 *\r
 * This capability-based system allows shared-memory communications\r
 * between unprivileged domains. A grant reference also encapsulates\r
 * the details of a shared page, removing the need for a domain to\r
 * know the real machine address of a page it is sharing. This makes\r
 * it possible to share memory correctly with domains running in\r
 * fully virtualised memory.\r
 */\r
\r
/***********************************\r
 * GRANT TABLE REPRESENTATION\r
 */\r
\r
/* Some rough guidelines on accessing and updating grant-table entries\r
 * in a concurrency-safe manner. For more information, Linux contains a\r
 * reference implementation for guest OSes (drivers/xen/grant_table.c, see\r
 * http://git.kernel.org/?p=linux/kernel/git/torvalds/linux.git;a=blob;f=drivers/xen/grant-table.c;hb=HEAD\r
 *\r
 * NB. WMB is a no-op on current-generation x86 processors. However, a\r
 *     compiler barrier will still be required.\r
 *\r
 * Introducing a valid entry into the grant table:\r
 *  1. Write ent->domid.\r
 *  2. Write ent->frame:\r
 *      GTF_permit_access:   Frame to which access is permitted.\r
 *      GTF_accept_transfer: Pseudo-phys frame slot being filled by new\r
 *                           frame, or zero if none.\r
 *  3. Write memory barrier (WMB).\r
 *  4. Write ent->flags, inc. valid type.\r
 *\r
 * Invalidating an unused GTF_permit_access entry:\r
 *  1. flags = ent->flags.\r
 *  2. Observe that !(flags & (GTF_reading|GTF_writing)).\r
 *  3. Check result of SMP-safe CMPXCHG(&ent->flags, flags, 0).\r
 *  NB. No need for WMB as reuse of entry is control-dependent on success of\r
 *      step 3, and all architectures guarantee ordering of ctrl-dep writes.\r
 *\r
 * Invalidating an in-use GTF_permit_access entry:\r
 *  This cannot be done directly. Request assistance from the domain controller\r
 *  which can set a timeout on the use of a grant entry and take necessary\r
 *  action. (NB. This is not yet implemented!).\r
 *\r
 * Invalidating an unused GTF_accept_transfer entry:\r
 *  1. flags = ent->flags.\r
 *  2. Observe that !(flags & GTF_transfer_committed). [*]\r
 *  3. Check result of SMP-safe CMPXCHG(&ent->flags, flags, 0).\r
 *  NB. No need for WMB as reuse of entry is control-dependent on success of\r
 *      step 3, and all architectures guarantee ordering of ctrl-dep writes.\r
 *  [*] If GTF_transfer_committed is set then the grant entry is 'committed'.\r
 *      The guest must /not/ modify the grant entry until the address of the\r
 *      transferred frame is written. It is safe for the guest to spin waiting\r
 *      for this to occur (detect by observing GTF_transfer_completed in\r
 *      ent->flags).\r
 *\r
 * Invalidating a committed GTF_accept_transfer entry:\r
 *  1. Wait for (ent->flags & GTF_transfer_completed).\r
 *\r
 * Changing a GTF_permit_access from writable to read-only:\r
 *  Use SMP-safe CMPXCHG to set GTF_readonly, while checking !GTF_writing.\r
 *\r
 * Changing a GTF_permit_access from read-only to writable:\r
 *  Use SMP-safe bit-setting instruction.\r
 */\r
\r
/*\r
 * Reference to a grant entry in a specified domain's grant table.\r
 */\r
typedef UINT32 grant_ref_t;\r
\r
/*\r
 * A grant table comprises a packed array of grant entries in one or more\r
 * page frames shared between Xen and a guest.\r
 * [XEN]: This field is written by Xen and read by the sharing guest.\r
 * [GST]: This field is written by the guest and read by Xen.\r
 */\r
\r
/*\r
 * Version 1 of the grant table entry structure is maintained purely\r
 * for backwards compatibility.  New guests should use version 2.\r
 */\r
#if __XEN_INTERFACE_VERSION__ < 0x0003020a\r
#define grant_entry_v1    grant_entry\r
#define grant_entry_v1_t  grant_entry_t\r
#endif\r
struct grant_entry_v1 {\r
  /* GTF_xxx: various type and flag information.  [XEN,GST] */\r
  UINT16     flags;\r
  /* The domain being granted foreign privileges. [GST] */\r
  domid_t    domid;\r
\r
  /*\r
   * GTF_permit_access: Frame that @domid is allowed to map and access. [GST]\r
   * GTF_accept_transfer: Frame whose ownership transferred by @domid. [XEN]\r
   */\r
  UINT32     frame;\r
};\r
\r
typedef struct grant_entry_v1 grant_entry_v1_t;\r
\r
/* The first few grant table entries will be preserved across grant table\r
 * version changes and may be pre-populated at domain creation by tools.\r
 */\r
#define GNTTAB_NR_RESERVED_ENTRIES  8\r
#define GNTTAB_RESERVED_CONSOLE     0\r
#define GNTTAB_RESERVED_XENSTORE    1\r
\r
/*\r
 * Type of grant entry.\r
 *  GTF_invalid: This grant entry grants no privileges.\r
 *  GTF_permit_access: Allow @domid to map/access @frame.\r
 *  GTF_accept_transfer: Allow @domid to transfer ownership of one page frame\r
 *                       to this guest. Xen writes the page number to @frame.\r
 *  GTF_transitive: Allow @domid to transitively access a subrange of\r
 *                  @trans_grant in @trans_domid.  No mappings are allowed.\r
 */\r
#define GTF_invalid          (0U<<0)\r
#define GTF_permit_access    (1U<<0)\r
#define GTF_accept_transfer  (2U<<0)\r
#define GTF_transitive       (3U<<0)\r
#define GTF_type_mask        (3U<<0)\r
\r
/*\r
 * Subflags for GTF_permit_access.\r
 *  GTF_readonly: Restrict @domid to read-only mappings and accesses. [GST]\r
 *  GTF_reading: Grant entry is currently mapped for reading by @domid. [XEN]\r
 *  GTF_writing: Grant entry is currently mapped for writing by @domid. [XEN]\r
 *  GTF_PAT, GTF_PWT, GTF_PCD: (x86) cache attribute flags for the grant [GST]\r
 *  GTF_sub_page: Grant access to only a subrange of the page.  @domid\r
 *                will only be allowed to copy from the grant, and not\r
 *                map it. [GST]\r
 */\r
#define _GTF_readonly  (2)\r
#define GTF_readonly   (1U<<_GTF_readonly)\r
#define _GTF_reading   (3)\r
#define GTF_reading    (1U<<_GTF_reading)\r
#define _GTF_writing   (4)\r
#define GTF_writing    (1U<<_GTF_writing)\r
#define _GTF_PWT       (5)\r
#define GTF_PWT        (1U<<_GTF_PWT)\r
#define _GTF_PCD       (6)\r
#define GTF_PCD        (1U<<_GTF_PCD)\r
#define _GTF_PAT       (7)\r
#define GTF_PAT        (1U<<_GTF_PAT)\r
#define _GTF_sub_page  (8)\r
#define GTF_sub_page   (1U<<_GTF_sub_page)\r
\r
/*\r
 * Subflags for GTF_accept_transfer:\r
 *  GTF_transfer_committed: Xen sets this flag to indicate that it is committed\r
 *      to transferring ownership of a page frame. When a guest sees this flag\r
 *      it must /not/ modify the grant entry until GTF_transfer_completed is\r
 *      set by Xen.\r
 *  GTF_transfer_completed: It is safe for the guest to spin-wait on this flag\r
 *      after reading GTF_transfer_committed. Xen will always write the frame\r
 *      address, followed by ORing this flag, in a timely manner.\r
 */\r
#define _GTF_transfer_committed  (2)\r
#define GTF_transfer_committed   (1U<<_GTF_transfer_committed)\r
#define _GTF_transfer_completed  (3)\r
#define GTF_transfer_completed   (1U<<_GTF_transfer_completed)\r
\r
/*\r
 * Version 2 grant table entries.  These fulfil the same role as\r
 * version 1 entries, but can represent more complicated operations.\r
 * Any given domain will have either a version 1 or a version 2 table,\r
 * and every entry in the table will be the same version.\r
 *\r
 * The interface by which domains use grant references does not depend\r
 * on the grant table version in use by the other domain.\r
 */\r
#if __XEN_INTERFACE_VERSION__ >= 0x0003020a\r
\r
/*\r
 * Version 1 and version 2 grant entries share a common prefix.  The\r
 * fields of the prefix are documented as part of struct\r
 * grant_entry_v1.\r
 */\r
struct grant_entry_header {\r
  UINT16     flags;\r
  domid_t    domid;\r
};\r
\r
typedef struct grant_entry_header grant_entry_header_t;\r
\r
/*\r
 * Version 2 of the grant entry structure.\r
 */\r
union grant_entry_v2 {\r
  grant_entry_header_t    hdr;\r
\r
  /*\r
   * This member is used for V1-style full page grants, where either:\r
   *\r
   * -- hdr.type is GTF_accept_transfer, or\r
   * -- hdr.type is GTF_permit_access and GTF_sub_page is not set.\r
   *\r
   * In that case, the frame field has the same semantics as the\r
   * field of the same name in the V1 entry structure.\r
   */\r
  struct {\r
    grant_entry_header_t    hdr;\r
    UINT32                  pad0;\r
    UINT64                  frame;\r
  } full_page;\r
\r
  /*\r
   * If the grant type is GTF_grant_access and GTF_sub_page is set,\r
   * @domid is allowed to access bytes [@page_off,@page_off+@length)\r
   * in frame @frame.\r
   */\r
  struct {\r
    grant_entry_header_t    hdr;\r
    UINT16                  page_off;\r
    UINT16                  length;\r
    UINT64                  frame;\r
  } sub_page;\r
\r
  /*\r
   * If the grant is GTF_transitive, @domid is allowed to use the\r
   * grant @gref in domain @trans_domid, as if it was the local\r
   * domain.  Obviously, the transitive access must be compatible\r
   * with the original grant.\r
   *\r
   * The current version of Xen does not allow transitive grants\r
   * to be mapped.\r
   */\r
  struct {\r
    grant_entry_header_t    hdr;\r
    domid_t                 trans_domid;\r
    UINT16                  pad0;\r
    grant_ref_t             gref;\r
  } transitive;\r
\r
  UINT32    __spacer[4]; /* Pad to a power of two */\r
};\r
\r
typedef union grant_entry_v2 grant_entry_v2_t;\r
\r
typedef UINT16 grant_status_t;\r
\r
#endif /* __XEN_INTERFACE_VERSION__ */\r
\r
/***********************************\r
 * GRANT TABLE QUERIES AND USES\r
 */\r
\r
/* ` enum neg_errnoval\r
 * ` HYPERVISOR_grant_table_op(enum grant_table_op cmd,\r
 * `                           VOID *args,\r
 * `                           UINT32 count)\r
 * `\r
 *\r
 * @args points to an array of a per-command data structure. The array\r
 * has @count members\r
 */\r
\r
/* ` enum grant_table_op { // GNTTABOP_* => struct gnttab_* */\r
#define GNTTABOP_map_grant_ref    0\r
#define GNTTABOP_unmap_grant_ref  1\r
/* ` } */\r
\r
/*\r
 * Handle to track a mapping created via a grant reference.\r
 */\r
typedef UINT32 grant_handle_t;\r
\r
/*\r
 * GNTTABOP_map_grant_ref: Map the grant entry (<dom>,<ref>) for access\r
 * by devices and/or host CPUs. If successful, <handle> is a tracking number\r
 * that must be presented later to destroy the mapping(s). On error, <handle>\r
 * is a negative status code.\r
 * NOTES:\r
 *  1. If GNTMAP_device_map is specified then <dev_bus_addr> is the address\r
 *     via which I/O devices may access the granted frame.\r
 *  2. If GNTMAP_host_map is specified then a mapping will be added at\r
 *     either a host virtual address in the current address space, or at\r
 *     a PTE at the specified machine address.  The type of mapping to\r
 *     perform is selected through the GNTMAP_contains_pte flag, and the\r
 *     address is specified in <host_addr>.\r
 *  3. Mappings should only be destroyed via GNTTABOP_unmap_grant_ref. If a\r
 *     host mapping is destroyed by other means then it is *NOT* guaranteed\r
 *     to be accounted to the correct grant reference!\r
 */\r
struct gnttab_map_grant_ref {\r
  /* IN parameters. */\r
  UINT64            host_addr;\r
  UINT32            flags;      /* GNTMAP_* */\r
  grant_ref_t       ref;\r
  domid_t           dom;\r
  /* OUT parameters. */\r
  INT16             status;     /* => enum grant_status */\r
  grant_handle_t    handle;\r
  UINT64            dev_bus_addr;\r
};\r
\r
typedef struct gnttab_map_grant_ref gnttab_map_grant_ref_t;\r
DEFINE_XEN_GUEST_HANDLE (gnttab_map_grant_ref_t);\r
\r
/*\r
 * GNTTABOP_unmap_grant_ref: Destroy one or more grant-reference mappings\r
 * tracked by <handle>. If <host_addr> or <dev_bus_addr> is zero, that\r
 * field is ignored. If non-zero, they must refer to a device/host mapping\r
 * that is tracked by <handle>\r
 * NOTES:\r
 *  1. The call may fail in an undefined manner if either mapping is not\r
 *     tracked by <handle>.\r
 *  3. After executing a batch of unmaps, it is guaranteed that no stale\r
 *     mappings will remain in the device or host TLBs.\r
 */\r
struct gnttab_unmap_grant_ref {\r
  /* IN parameters. */\r
  UINT64            host_addr;\r
  UINT64            dev_bus_addr;\r
  grant_handle_t    handle;\r
  /* OUT parameters. */\r
  INT16             status;     /* => enum grant_status */\r
};\r
\r
typedef struct gnttab_unmap_grant_ref gnttab_unmap_grant_ref_t;\r
DEFINE_XEN_GUEST_HANDLE (gnttab_unmap_grant_ref_t);\r
\r
/*\r
 * Bitfield values for gnttab_map_grant_ref.flags.\r
 */\r
/* Map the grant entry for access by I/O devices. */\r
#define _GNTMAP_device_map  (0)\r
#define GNTMAP_device_map   (1<<_GNTMAP_device_map)\r
/* Map the grant entry for access by host CPUs. */\r
#define _GNTMAP_host_map  (1)\r
#define GNTMAP_host_map   (1<<_GNTMAP_host_map)\r
/* Accesses to the granted frame will be restricted to read-only access. */\r
#define _GNTMAP_readonly  (2)\r
#define GNTMAP_readonly   (1<<_GNTMAP_readonly)\r
\r
/*\r
 * GNTMAP_host_map subflag:\r
 *  0 => The host mapping is usable only by the guest OS.\r
 *  1 => The host mapping is usable by guest OS + current application.\r
 */\r
#define _GNTMAP_application_map  (3)\r
#define GNTMAP_application_map   (1<<_GNTMAP_application_map)\r
\r
/*\r
 * GNTMAP_contains_pte subflag:\r
 *  0 => This map request contains a host virtual address.\r
 *  1 => This map request contains the machine address of the PTE to update.\r
 */\r
#define _GNTMAP_contains_pte  (4)\r
#define GNTMAP_contains_pte   (1<<_GNTMAP_contains_pte)\r
\r
#define _GNTMAP_can_fail  (5)\r
#define GNTMAP_can_fail   (1<<_GNTMAP_can_fail)\r
\r
/*\r
 * Bits to be placed in guest kernel available PTE bits (architecture\r
 * dependent; only supported when XENFEAT_gnttab_map_avail_bits is set).\r
 */\r
#define _GNTMAP_guest_avail0     (16)\r
#define GNTMAP_guest_avail_mask  ((UINT32)~0 << _GNTMAP_guest_avail0)\r
\r
/*\r
 * Values for error status returns. All errors are -ve.\r
 */\r
/* ` enum grant_status { */\r
#define GNTST_okay               (0)   /* Normal return.                        */\r
#define GNTST_general_error      (-1)  /* General undefined error.              */\r
#define GNTST_bad_domain         (-2)  /* Unrecognised domain id.               */\r
#define GNTST_bad_gntref         (-3)  /* Unrecognised or inappropriate gntref. */\r
#define GNTST_bad_handle         (-4)  /* Unrecognised or inappropriate handle. */\r
#define GNTST_bad_virt_addr      (-5)  /* Inappropriate virtual address to map. */\r
#define GNTST_bad_dev_addr       (-6)  /* Inappropriate device address to unmap.*/\r
#define GNTST_no_device_space    (-7)  /* Out of space in I/O MMU.              */\r
#define GNTST_permission_denied  (-8)  /* Not enough privilege for operation.  */\r
#define GNTST_bad_page           (-9)  /* Specified page was invalid for op.    */\r
#define GNTST_bad_copy_arg       (-10) /* copy arguments cross page boundary.   */\r
#define GNTST_address_too_big    (-11) /* transfer page address too large.      */\r
#define GNTST_eagain             (-12) /* Operation not done; try again.        */\r
/* ` } */\r
\r
#define GNTTABOP_error_msgs  {                  \\r
    "okay",                                     \\r
    "undefined error",                          \\r
    "unrecognised domain id",                   \\r
    "invalid grant reference",                  \\r
    "invalid mapping handle",                   \\r
    "invalid virtual address",                  \\r
    "invalid device address",                   \\r
    "no spare translation slot in the I/O MMU", \\r
    "permission denied",                        \\r
    "bad page",                                 \\r
    "copy arguments cross page boundary",       \\r
    "page address size too large",              \\r
    "operation not done; try again"             \\r
}\r
\r
#endif /* __XEN_PUBLIC_GRANT_TABLE_H__ */\r
\r
/*\r
 * Local variables:\r
 * mode: C\r
 * c-file-style: "BSD"\r
 * c-basic-offset: 4\r
 * tab-width: 4\r
 * indent-tabs-mode: nil\r
 * End:\r
 */\r