302 lines
11 KiB
C
302 lines
11 KiB
C
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/******************************************************************************
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* grant_table.h
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*
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* Interface for granting foreign access to page frames, and receiving
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* page-ownership transfers.
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*
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* Copyright (c) 2004, K A Fraser
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*/
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#ifndef __XEN_PUBLIC_GRANT_TABLE_H__
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#define __XEN_PUBLIC_GRANT_TABLE_H__
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/***********************************
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* GRANT TABLE REPRESENTATION
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*/
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/* Some rough guidelines on accessing and updating grant-table entries
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* in a concurrency-safe manner. For more information, Linux contains a
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* reference implementation for guest OSes (arch/i386/mach-xen/grant_table.c).
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*
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* NB. WMB is a no-op on current-generation x86 processors. However, a
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* compiler barrier will still be required.
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*
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* Introducing a valid entry into the grant table:
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* 1. Write ent->domid.
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* 2. Write ent->frame:
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* GTF_permit_access: Frame to which access is permitted.
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* GTF_accept_transfer: Pseudo-phys frame slot being filled by new
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* frame, or zero if none.
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* 3. Write memory barrier (WMB).
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* 4. Write ent->flags, inc. valid type.
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*
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* Invalidating an unused GTF_permit_access entry:
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* 1. flags = ent->flags.
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* 2. Observe that !(flags & (GTF_reading|GTF_writing)).
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* 3. Check result of SMP-safe CMPXCHG(&ent->flags, flags, 0).
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* NB. No need for WMB as reuse of entry is control-dependent on success of
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* step 3, and all architectures guarantee ordering of ctrl-dep writes.
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*
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* Invalidating an in-use GTF_permit_access entry:
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* This cannot be done directly. Request assistance from the domain controller
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* which can set a timeout on the use of a grant entry and take necessary
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* action. (NB. This is not yet implemented!).
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*
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* Invalidating an unused GTF_accept_transfer entry:
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* 1. flags = ent->flags.
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* 2. Observe that !(flags & GTF_transfer_committed). [*]
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* 3. Check result of SMP-safe CMPXCHG(&ent->flags, flags, 0).
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* NB. No need for WMB as reuse of entry is control-dependent on success of
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* step 3, and all architectures guarantee ordering of ctrl-dep writes.
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* [*] If GTF_transfer_committed is set then the grant entry is 'committed'.
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* The guest must /not/ modify the grant entry until the address of the
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* transferred frame is written. It is safe for the guest to spin waiting
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* for this to occur (detect by observing GTF_transfer_completed in
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* ent->flags).
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*
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* Invalidating a committed GTF_accept_transfer entry:
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* 1. Wait for (ent->flags & GTF_transfer_completed).
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*
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* Changing a GTF_permit_access from writable to read-only:
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* Use SMP-safe CMPXCHG to set GTF_readonly, while checking !GTF_writing.
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*
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* Changing a GTF_permit_access from read-only to writable:
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* Use SMP-safe bit-setting instruction.
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*/
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/*
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* A grant table comprises a packed array of grant entries in one or more
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* page frames shared between Xen and a guest.
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* [XEN]: This field is written by Xen and read by the sharing guest.
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* [GST]: This field is written by the guest and read by Xen.
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*/
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struct grant_entry {
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/* GTF_xxx: various type and flag information. [XEN,GST] */
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uint16_t flags;
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/* The domain being granted foreign privileges. [GST] */
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domid_t domid;
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/*
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* GTF_permit_access: Frame that @domid is allowed to map and access. [GST]
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* GTF_accept_transfer: Frame whose ownership transferred by @domid. [XEN]
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*/
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uint32_t frame;
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};
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/*
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* Type of grant entry.
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* GTF_invalid: This grant entry grants no privileges.
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* GTF_permit_access: Allow @domid to map/access @frame.
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* GTF_accept_transfer: Allow @domid to transfer ownership of one page frame
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* to this guest. Xen writes the page number to @frame.
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*/
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#define GTF_invalid (0U<<0)
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#define GTF_permit_access (1U<<0)
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#define GTF_accept_transfer (2U<<0)
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#define GTF_type_mask (3U<<0)
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/*
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* Subflags for GTF_permit_access.
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* GTF_readonly: Restrict @domid to read-only mappings and accesses. [GST]
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* GTF_reading: Grant entry is currently mapped for reading by @domid. [XEN]
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* GTF_writing: Grant entry is currently mapped for writing by @domid. [XEN]
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*/
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#define _GTF_readonly (2)
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#define GTF_readonly (1U<<_GTF_readonly)
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#define _GTF_reading (3)
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#define GTF_reading (1U<<_GTF_reading)
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#define _GTF_writing (4)
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#define GTF_writing (1U<<_GTF_writing)
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/*
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* Subflags for GTF_accept_transfer:
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* GTF_transfer_committed: Xen sets this flag to indicate that it is committed
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* to transferring ownership of a page frame. When a guest sees this flag
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* it must /not/ modify the grant entry until GTF_transfer_completed is
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* set by Xen.
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* GTF_transfer_completed: It is safe for the guest to spin-wait on this flag
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* after reading GTF_transfer_committed. Xen will always write the frame
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* address, followed by ORing this flag, in a timely manner.
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*/
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#define _GTF_transfer_committed (2)
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#define GTF_transfer_committed (1U<<_GTF_transfer_committed)
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#define _GTF_transfer_completed (3)
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#define GTF_transfer_completed (1U<<_GTF_transfer_completed)
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/***********************************
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* GRANT TABLE QUERIES AND USES
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*/
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/*
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* Reference to a grant entry in a specified domain's grant table.
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*/
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typedef uint32_t grant_ref_t;
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/*
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* Handle to track a mapping created via a grant reference.
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*/
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typedef uint32_t grant_handle_t;
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/*
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* GNTTABOP_map_grant_ref: Map the grant entry (<dom>,<ref>) for access
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* by devices and/or host CPUs. If successful, <handle> is a tracking number
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* that must be presented later to destroy the mapping(s). On error, <handle>
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* is a negative status code.
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* NOTES:
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* 1. If GNTPIN_map_for_dev is specified then <dev_bus_addr> is the address
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* via which I/O devices may access the granted frame.
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* 2. If GNTPIN_map_for_host is specified then a mapping will be added at
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* either a host virtual address in the current address space, or at
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* a PTE at the specified machine address. The type of mapping to
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* perform is selected through the GNTMAP_contains_pte flag, and the
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* address is specified in <host_addr>.
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* 3. Mappings should only be destroyed via GNTTABOP_unmap_grant_ref. If a
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* host mapping is destroyed by other means then it is *NOT* guaranteed
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* to be accounted to the correct grant reference!
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*/
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#define GNTTABOP_map_grant_ref 0
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struct gnttab_map_grant_ref {
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/* IN parameters. */
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uint64_t host_addr;
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uint32_t flags; /* GNTMAP_* */
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grant_ref_t ref;
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domid_t dom;
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/* OUT parameters. */
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int16_t status; /* GNTST_* */
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grant_handle_t handle;
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uint64_t dev_bus_addr;
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};
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DEFINE_GUEST_HANDLE_STRUCT(gnttab_map_grant_ref);
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/*
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* GNTTABOP_unmap_grant_ref: Destroy one or more grant-reference mappings
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* tracked by <handle>. If <host_addr> or <dev_bus_addr> is zero, that
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* field is ignored. If non-zero, they must refer to a device/host mapping
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* that is tracked by <handle>
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* NOTES:
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* 1. The call may fail in an undefined manner if either mapping is not
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* tracked by <handle>.
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* 3. After executing a batch of unmaps, it is guaranteed that no stale
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* mappings will remain in the device or host TLBs.
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*/
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#define GNTTABOP_unmap_grant_ref 1
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struct gnttab_unmap_grant_ref {
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/* IN parameters. */
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uint64_t host_addr;
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uint64_t dev_bus_addr;
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grant_handle_t handle;
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/* OUT parameters. */
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int16_t status; /* GNTST_* */
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};
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DEFINE_GUEST_HANDLE_STRUCT(gnttab_unmap_grant_ref);
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/*
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* GNTTABOP_setup_table: Set up a grant table for <dom> comprising at least
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* <nr_frames> pages. The frame addresses are written to the <frame_list>.
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* Only <nr_frames> addresses are written, even if the table is larger.
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* NOTES:
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* 1. <dom> may be specified as DOMID_SELF.
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* 2. Only a sufficiently-privileged domain may specify <dom> != DOMID_SELF.
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* 3. Xen may not support more than a single grant-table page per domain.
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*/
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#define GNTTABOP_setup_table 2
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struct gnttab_setup_table {
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/* IN parameters. */
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domid_t dom;
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uint32_t nr_frames;
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/* OUT parameters. */
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int16_t status; /* GNTST_* */
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GUEST_HANDLE(ulong) frame_list;
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};
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DEFINE_GUEST_HANDLE_STRUCT(gnttab_setup_table);
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/*
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* GNTTABOP_dump_table: Dump the contents of the grant table to the
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* xen console. Debugging use only.
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*/
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#define GNTTABOP_dump_table 3
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struct gnttab_dump_table {
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/* IN parameters. */
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domid_t dom;
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/* OUT parameters. */
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int16_t status; /* GNTST_* */
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};
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DEFINE_GUEST_HANDLE_STRUCT(gnttab_dump_table);
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/*
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* GNTTABOP_transfer_grant_ref: Transfer <frame> to a foreign domain. The
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* foreign domain has previously registered its interest in the transfer via
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* <domid, ref>.
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*
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* Note that, even if the transfer fails, the specified page no longer belongs
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* to the calling domain *unless* the error is GNTST_bad_page.
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*/
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#define GNTTABOP_transfer 4
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struct gnttab_transfer {
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/* IN parameters. */
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unsigned long mfn;
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domid_t domid;
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grant_ref_t ref;
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/* OUT parameters. */
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int16_t status;
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};
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DEFINE_GUEST_HANDLE_STRUCT(gnttab_transfer);
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/*
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* Bitfield values for update_pin_status.flags.
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*/
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/* Map the grant entry for access by I/O devices. */
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#define _GNTMAP_device_map (0)
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#define GNTMAP_device_map (1<<_GNTMAP_device_map)
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/* Map the grant entry for access by host CPUs. */
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#define _GNTMAP_host_map (1)
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#define GNTMAP_host_map (1<<_GNTMAP_host_map)
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/* Accesses to the granted frame will be restricted to read-only access. */
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#define _GNTMAP_readonly (2)
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#define GNTMAP_readonly (1<<_GNTMAP_readonly)
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/*
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* GNTMAP_host_map subflag:
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* 0 => The host mapping is usable only by the guest OS.
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* 1 => The host mapping is usable by guest OS + current application.
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*/
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#define _GNTMAP_application_map (3)
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#define GNTMAP_application_map (1<<_GNTMAP_application_map)
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/*
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* GNTMAP_contains_pte subflag:
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* 0 => This map request contains a host virtual address.
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* 1 => This map request contains the machine addess of the PTE to update.
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*/
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#define _GNTMAP_contains_pte (4)
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#define GNTMAP_contains_pte (1<<_GNTMAP_contains_pte)
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/*
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* Values for error status returns. All errors are -ve.
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*/
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#define GNTST_okay (0) /* Normal return. */
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#define GNTST_general_error (-1) /* General undefined error. */
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#define GNTST_bad_domain (-2) /* Unrecognsed domain id. */
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#define GNTST_bad_gntref (-3) /* Unrecognised or inappropriate gntref. */
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#define GNTST_bad_handle (-4) /* Unrecognised or inappropriate handle. */
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#define GNTST_bad_virt_addr (-5) /* Inappropriate virtual address to map. */
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#define GNTST_bad_dev_addr (-6) /* Inappropriate device address to unmap.*/
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#define GNTST_no_device_space (-7) /* Out of space in I/O MMU. */
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#define GNTST_permission_denied (-8) /* Not enough privilege for operation. */
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#define GNTST_bad_page (-9) /* Specified page was invalid for op. */
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#define GNTTABOP_error_msgs { \
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"okay", \
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"undefined error", \
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"unrecognised domain id", \
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"invalid grant reference", \
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"invalid mapping handle", \
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"invalid virtual address", \
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"invalid device address", \
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"no spare translation slot in the I/O MMU", \
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"permission denied", \
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"bad page" \
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}
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#endif /* __XEN_PUBLIC_GRANT_TABLE_H__ */
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