Commit 696ed9a9 authored by Dr. David Alan Gilbert's avatar Dr. David Alan Gilbert Committed by Juan Quintela
Browse files

postcopy_ram.c: place_page and helpers 



postcopy_place_page (etc) provide a way for postcopy to place a page
into guests memory atomically (using the copy ioctl on the ufd).

Signed-off-by: default avatarDr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: default avatarAmit Shah <amit.shah@redhat.com>
Reviewed-by: default avatarJuan Quintela <quintela@redhat.com>
Signed-off-by: default avatarJuan Quintela <quintela@redhat.com>
parent a82d593b

include/migration/migration.h

+1 −0
Original line number Diff line number Diff line
@@ -96,6 +96,7 @@ struct MigrationIncomingState { 
    int       userfault_fd;

    QEMUFile *to_src_file;

    QemuMutex rp_mutex;    /* We send replies from multiple threads */

    void     *postcopy_tmp_page;



    /* See savevm.c */

    LoadStateEntry_Head loadvm_handlers;

include/migration/postcopy-ram.h

+21 −0
Original line number Diff line number Diff line
@@ -69,4 +69,25 @@ void postcopy_discard_send_range(MigrationState *ms, PostcopyDiscardState *pds, 
void postcopy_discard_send_finish(MigrationState *ms,

                                  PostcopyDiscardState *pds);



/*

 * Place a page (from) at (host) efficiently

 *    There are restrictions on how 'from' must be mapped, in general best

 *    to use other postcopy_ routines to allocate.

 * returns 0 on success

 */

int postcopy_place_page(MigrationIncomingState *mis, void *host, void *from);



/*

 * Place a zero page at (host) atomically

 * returns 0 on success

 */

int postcopy_place_page_zero(MigrationIncomingState *mis, void *host);



/*

 * Allocate a page of memory that can be mapped at a later point in time

 * using postcopy_place_page

 * Returns: Pointer to allocated page

 */

void *postcopy_get_tmp_page(MigrationIncomingState *mis);



#endif

migration/postcopy-ram.c

+100 −0
Original line number Diff line number Diff line
@@ -272,6 +272,10 @@ int postcopy_ram_incoming_cleanup(MigrationIncomingState *mis) 
        return -1;

    }



    if (mis->postcopy_tmp_page) {

        munmap(mis->postcopy_tmp_page, getpagesize());

        mis->postcopy_tmp_page = NULL;

    }

    return 0;

}
@@ -338,6 +342,83 @@ int postcopy_ram_enable_notify(MigrationIncomingState *mis) 
    return 0;

}



/*

 * Place a host page (from) at (host) atomically

 * returns 0 on success

 */

int postcopy_place_page(MigrationIncomingState *mis, void *host, void *from)

{

    struct uffdio_copy copy_struct;



    copy_struct.dst = (uint64_t)(uintptr_t)host;

    copy_struct.src = (uint64_t)(uintptr_t)from;

    copy_struct.len = getpagesize();

    copy_struct.mode = 0;



    /* copy also acks to the kernel waking the stalled thread up

     * TODO: We can inhibit that ack and only do it if it was requested

     * which would be slightly cheaper, but we'd have to be careful

     * of the order of updating our page state.

     */

    if (ioctl(mis->userfault_fd, UFFDIO_COPY, &copy_struct)) {

        int e = errno;

        error_report("%s: %s copy host: %p from: %p",

                     __func__, strerror(e), host, from);



        return -e;

    }



    trace_postcopy_place_page(host);

    return 0;

}



/*

 * Place a zero page at (host) atomically

 * returns 0 on success

 */

int postcopy_place_page_zero(MigrationIncomingState *mis, void *host)

{

    struct uffdio_zeropage zero_struct;



    zero_struct.range.start = (uint64_t)(uintptr_t)host;

    zero_struct.range.len = getpagesize();

    zero_struct.mode = 0;



    if (ioctl(mis->userfault_fd, UFFDIO_ZEROPAGE, &zero_struct)) {

        int e = errno;

        error_report("%s: %s zero host: %p",

                     __func__, strerror(e), host);



        return -e;

    }



    trace_postcopy_place_page_zero(host);

    return 0;

}



/*

 * Returns a target page of memory that can be mapped at a later point in time

 * using postcopy_place_page

 * The same address is used repeatedly, postcopy_place_page just takes the

 * backing page away.

 * Returns: Pointer to allocated page

 *

 */

void *postcopy_get_tmp_page(MigrationIncomingState *mis)

{

    if (!mis->postcopy_tmp_page) {

        mis->postcopy_tmp_page = mmap(NULL, getpagesize(),

                             PROT_READ | PROT_WRITE, MAP_PRIVATE |

                             MAP_ANONYMOUS, -1, 0);

        if (!mis->postcopy_tmp_page) {

            error_report("%s: %s", __func__, strerror(errno));

            return NULL;

        }

    }



    return mis->postcopy_tmp_page;

}



#else

/* No target OS support, stubs just fail */

bool postcopy_ram_supported_by_host(void)
@@ -370,6 +451,25 @@ int postcopy_ram_enable_notify(MigrationIncomingState *mis) 
    assert(0);

    return -1;

}



int postcopy_place_page(MigrationIncomingState *mis, void *host, void *from)

{

    assert(0);

    return -1;

}



int postcopy_place_page_zero(MigrationIncomingState *mis, void *host)

{

    assert(0);

    return -1;

}



void *postcopy_get_tmp_page(MigrationIncomingState *mis)

{

    assert(0);

    return NULL;

}



#endif



/* ------------------------------------------------------------------------- */

trace-events

+2 −0
Original line number Diff line number Diff line
@@ -1551,6 +1551,8 @@ postcopy_discard_send_range(const char *ramblock, unsigned long start, unsigned 
postcopy_ram_discard_range(void *start, size_t length) "%p,+%zx"

postcopy_cleanup_range(const char *ramblock, void *host_addr, size_t offset, size_t length) "%s: %p offset=%zx length=%zx"

postcopy_init_range(const char *ramblock, void *host_addr, size_t offset, size_t length) "%s: %p offset=%zx length=%zx"

postcopy_place_page(void *host_addr) "host=%p"

postcopy_place_page_zero(void *host_addr) "host=%p"



# kvm-all.c

kvm_ioctl(int type, void *arg) "type 0x%x, arg %p"