Re: [Qemu-devel] [PATCH v4 36/47] Page request: Process incoming page request

[David Gibson]

On Fri, Oct 03, 2014 at 06:47:42PM +0100, Dr. David Alan Gilbert (git) wrote:
> From: "Dr. David Alan Gilbert" <address@hidden>
> 
> On receiving MIG_RPCOMM_REQPAGES look up the address and
> queue the page.
> 
> Signed-off-by: Dr. David Alan Gilbert <address@hidden>
> ---
>  arch_init.c                   | 52 
> +++++++++++++++++++++++++++++++++++++++++++
>  include/migration/migration.h | 21 +++++++++++++++++
>  include/qemu/typedefs.h       |  3 ++-
>  migration.c                   | 34 +++++++++++++++++++++++++++-
>  4 files changed, 108 insertions(+), 2 deletions(-)
> 
> diff --git a/arch_init.c b/arch_init.c
> index 4a03171..72f9e17 100644
> --- a/arch_init.c
> +++ b/arch_init.c
> @@ -660,6 +660,58 @@ static int ram_save_page(QEMUFile *f, RAMBlock* block, 
> ram_addr_t offset,
>  }
>  
>  /*
> + * Queue the pages for transmission, e.g. a request from postcopy destination
> + *   ms: MigrationStatus in which the queue is held
> + *   rbname: The RAMBlock the request is for - may be NULL (to mean reuse 
> last)
> + *   start: Offset from the start of the RAMBlock
> + *   len: Length (in bytes) to send
> + *   Return: 0 on success
> + */
> +int ram_save_queue_pages(MigrationState *ms, const char *rbname,
> +                         ram_addr_t start, ram_addr_t len)
> +{
> +    RAMBlock *ramblock;
> +
> +    if (!rbname) {
> +        /* Reuse last RAMBlock */
> +        ramblock = ms->last_req_rb;
> +
> +        if (!ramblock) {
> +            error_report("ram_save_queue_pages no previous block");
> +            return -1;

This should be an assert() shouldn't it?

> +        }
> +    } else {
> +        ramblock = ram_find_block(rbname);
> +
> +        if (!ramblock) {
> +            error_report("ram_save_queue_pages no block '%s'", rbname);
> +            return -1;
> +        }

And maybe this one too - I would have expected the rb names to have
already been validated on the source machine at this stage.

> +    }
> +    DPRINTF("ram_save_queue_pages: Block %s start %zx len %zx",
> +                    ramblock->idstr, start, len);
> +
> +    if (start+len > ramblock->length) {
> +        error_report("%s request overrun start=%zx len=%zx blocklen=%zx",
> +                     __func__, start, len, ramblock->length);
> +        return -1;
> +    }
> +
> +    struct MigrationSrcPageRequest *new_entry =
> +        g_malloc0(sizeof(struct MigrationSrcPageRequest));
> +    new_entry->rb = ramblock;
> +    new_entry->offset = start;
> +    new_entry->len = len;
> +    ms->last_req_rb = ramblock;
> +
> +    qemu_mutex_lock(&ms->src_page_req_mutex);
> +    QSIMPLEQ_INSERT_TAIL(&ms->src_page_requests, new_entry, next_req);
> +    qemu_mutex_unlock(&ms->src_page_req_mutex);
> +
> +    return 0;
> +}
> +
> +/*
>   * ram_find_and_save_block: Finds a page to send and sends it to f
>   *
>   * Returns:  The number of bytes written.
> diff --git a/include/migration/migration.h b/include/migration/migration.h
> index 5e0d30d..5bc01d5 100644
> --- a/include/migration/migration.h
> +++ b/include/migration/migration.h
> @@ -102,6 +102,18 @@ MigrationIncomingState 
> *migration_incoming_get_current(void);
>  MigrationIncomingState *migration_incoming_state_init(QEMUFile *f);
>  void migration_incoming_state_destroy(void);
>  
> +/*
> + * An outstanding page request, on the source, having been received
> + * and queued
> + */
> +struct MigrationSrcPageRequest {
> +    RAMBlock *rb;
> +    hwaddr    offset;
> +    hwaddr    len;
> +
> +    QSIMPLEQ_ENTRY(MigrationSrcPageRequest) next_req;
> +};
> +
>  struct MigrationState
>  {
>      int64_t bandwidth_limit;
> @@ -138,6 +150,12 @@ struct MigrationState
>       * of the postcopy phase
>       */
>      unsigned long *sentmap;
> +
> +    /* Queue of outstanding page requests from the destination */
> +    QemuMutex src_page_req_mutex;
> +    QSIMPLEQ_HEAD(src_page_requests, MigrationSrcPageRequest) 
> src_page_requests;
> +    /* The RAMBlock used in the last src_page_request */
> +    RAMBlock *last_req_rb;
>  };
>  
>  void process_incoming_migration(QEMUFile *f);
> @@ -273,4 +291,7 @@ size_t ram_control_save_page(QEMUFile *f, ram_addr_t 
> block_offset,
>                               ram_addr_t offset, size_t size,
>                               int *bytes_sent);
>  
> +int ram_save_queue_pages(MigrationState *ms, const char *rbname,
> +                         ram_addr_t start, ram_addr_t len);
> +
>  #endif
> diff --git a/include/qemu/typedefs.h b/include/qemu/typedefs.h
> index 79f57c0..24c2207 100644
> --- a/include/qemu/typedefs.h
> +++ b/include/qemu/typedefs.h
> @@ -8,6 +8,7 @@ typedef struct QEMUTimerListGroup QEMUTimerListGroup;
>  typedef struct QEMUFile QEMUFile;
>  typedef struct QEMUBH QEMUBH;
>  
> +typedef struct AdapterInfo AdapterInfo;
>  typedef struct AioContext AioContext;
>  
>  typedef struct Visitor Visitor;
> @@ -80,6 +81,6 @@ typedef struct FWCfgState FWCfgState;
>  typedef struct PcGuestInfo PcGuestInfo;
>  typedef struct PostcopyPMI PostcopyPMI;
>  typedef struct Range Range;
> -typedef struct AdapterInfo AdapterInfo;
> +typedef struct RAMBlock RAMBlock;
>  
>  #endif /* QEMU_TYPEDEFS_H */
> diff --git a/migration.c b/migration.c
> index cfdaa52..63d7699 100644
> --- a/migration.c
> +++ b/migration.c
> @@ -26,6 +26,8 @@
>  #include "qemu/thread.h"
>  #include "qmp-commands.h"
>  #include "trace.h"
> +#include "exec/memory.h"
> +#include "exec/address-spaces.h"
>  
>  //#define DEBUG_MIGRATION
>  
> @@ -504,6 +506,15 @@ static void migrate_fd_cleanup(void *opaque)
>  
>      migrate_fd_cleanup_src_rp(s);
>  
> +    /* This queue generally should be empty - but in the case of a failed
> +     * migration might have some droppings in.
> +     */
> +    struct MigrationSrcPageRequest *mspr, *next_mspr;
> +    QSIMPLEQ_FOREACH_SAFE(mspr, &s->src_page_requests, next_req, next_mspr) {
> +        QSIMPLEQ_REMOVE_HEAD(&s->src_page_requests, next_req);
> +        g_free(mspr);
> +    }
> +
>      if (s->file) {
>          trace_migrate_fd_cleanup();
>          qemu_mutex_unlock_iothread();
> @@ -610,6 +621,9 @@ MigrationState *migrate_init(const MigrationParams 
> *params)
>      s->state = MIG_STATE_SETUP;
>      trace_migrate_set_state(MIG_STATE_SETUP);
>  
> +    qemu_mutex_init(&s->src_page_req_mutex);
> +    QSIMPLEQ_INIT(&s->src_page_requests);
> +
>      s->total_time = qemu_clock_get_ms(QEMU_CLOCK_REALTIME);
>      return s;
>  }
> @@ -823,7 +837,25 @@ static void source_return_path_bad(MigrationState *s)
>  static void migrate_handle_rp_reqpages(MigrationState *ms, const char* 
> rbname,
>                                         ram_addr_t start, ram_addr_t len)
>  {
> -    DPRINTF("migrate_handle_rp_reqpages: at %zx for len %zx", start, len);
> +    DPRINTF("migrate_handle_rp_reqpages: in %s start %zx len %zx",
> +            rbname, start, len);
> +
> +    /* Round everything up to our host page size */
> +    long our_host_ps = sysconf(_SC_PAGESIZE);
> +    if (start & (our_host_ps-1)) {
> +        long roundings = start & (our_host_ps-1);
> +        start -= roundings;
> +        len += roundings;
> +    }
> +    if (len & (our_host_ps-1)) {
> +        long roundings = len & (our_host_ps-1);
> +        len -= roundings;
> +        len += our_host_ps;
> +    }
> +
> +    if (ram_save_queue_pages(ms, rbname, start, len)) {
> +        source_return_path_bad(ms);
> +    }
>  }
>  
>  /*

-- 
David Gibson                    | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au  | minimalist, thank you.  NOT _the_ _other_
                                | _way_ _around_!
http://www.ozlabs.org/~dgibson

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