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hw/xen: Add gnttab operations to allow redirection to internal emulation

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Move the existing code using libxengnttab to xen-operations.c and allow
the operations to be redirected so that we can add emulation of grant
table mapping for backend drivers.

In emulation, mapping more than one grant ref to be virtually contiguous
would be fairly difficult. The best way to do it might be to make the
ram_block mappings actually backed by a file (shmem or a deleted file,
perhaps) so that we can have multiple *shared* mappings of it. But that
would be fairly intrusive.

Making the backend drivers cope with page *lists* instead of expecting
the mapping to be contiguous is also non-trivial, since some structures
would actually *cross* page boundaries (e.g. the 32-bit blkif responses
which are 12 bytes).

So for now, we'll support only single-page mappings in emulation. Add a
XEN_GNTTAB_OP_FEATURE_MAP_MULTIPLE flag to indicate that the native Xen
implementation *does* support multi-page maps, and a helper function to
query it.

Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Reviewed-by: Paul Durrant <paul@xen.org>
This commit is contained in:
David Woodhouse 2023-01-01 21:31:37 +00:00
parent b6cacfea0b
commit c412ba47b2
9 changed files with 280 additions and 272 deletions
Download patch file Download diff file Expand all files Collapse all files

39
include/hw/xen/xen_common.h
View file

@ -28,17 +28,6 @@ extern xc_interface *xen_xc;
#if CONFIG_XEN_CTRL_INTERFACE_VERSION < 40701
typedef xc_interface xenforeignmemory_handle;
typedef xc_gnttab xengnttab_handle;
#define xengnttab_open(l, f) xc_gnttab_open(l, f)
#define xengnttab_close(h) xc_gnttab_close(h)
#define xengnttab_set_max_grants(h, n) xc_gnttab_set_max_grants(h, n)
#define xengnttab_map_grant_ref(h, d, r, p) xc_gnttab_map_grant_ref(h, d, r, p)
#define xengnttab_unmap(h, a, n) xc_gnttab_munmap(h, a, n)
#define xengnttab_map_grant_refs(h, c, d, r, p) \
xc_gnttab_map_grant_refs(h, c, d, r, p)
#define xengnttab_map_domain_grant_refs(h, c, d, r, p) \
xc_gnttab_map_domain_grant_refs(h, c, d, r, p)
#define xenforeignmemory_open(l, f) xen_xc
#define xenforeignmemory_close(h)
@ -58,7 +47,6 @@ static inline void *xenforeignmemory_map(xc_interface *h, uint32_t dom,
#else /* CONFIG_XEN_CTRL_INTERFACE_VERSION >= 40701 */
#include <xengnttab.h>
#include <xenforeignmemory.h>
#endif
@ -648,31 +636,4 @@ static inline int xen_set_ioreq_server_state(domid_t dom,
#endif
/* Xen before 4.8 */
#if CONFIG_XEN_CTRL_INTERFACE_VERSION < 40800
struct xengnttab_grant_copy_segment {
union xengnttab_copy_ptr {
void *virt;
struct {
uint32_t ref;
uint16_t offset;
uint16_t domid;
} foreign;
} source, dest;
uint16_t len;
uint16_t flags;
int16_t status;
};
typedef struct xengnttab_grant_copy_segment xengnttab_grant_copy_segment_t;
static inline int xengnttab_grant_copy(xengnttab_handle *xgt, uint32_t count,
xengnttab_grant_copy_segment_t *segs)
{
return -ENOSYS;
}
#endif
#endif /* QEMU_HW_XEN_COMMON_H */