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From: Juan Quintela <quintela@redhat.com>
In-Reply-To: <1443515898-3594-39-git-send-email-dgilbert@redhat.com> (David
	Alan Gilbert's message of "Tue, 29 Sep 2015 09:38:02 +0100")
References: <1443515898-3594-1-git-send-email-dgilbert@redhat.com>
	<1443515898-3594-39-git-send-email-dgilbert@redhat.com>
Date: Wed, 21 Oct 2015 13:12:42 +0200
Message-ID: <87r3koa311.fsf@neno.neno>
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Subject: Re: [Qemu-devel] [PATCH v8 38/54] Page request: Add
	MIG_RP_MSG_REQ_PAGES reverse command
Reply-To: quintela@redhat.com
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To: "Dr. David Alan Gilbert (git)" <dgilbert@redhat.com>
Cc: aarcange@redhat.com, liang.z.li@intel.com, qemu-devel@nongnu.org, luis@cs.umu.se, bharata@linux.vnet.ibm.com, amit.shah@redhat.com, pbonzini@redhat.com

"Dr. David Alan Gilbert (git)" <dgilbert@redhat.com> wrote:
> From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
>
> Add MIG_RP_MSG_REQ_PAGES command on Return path for the postcopy
> destination to request a page from the source.
>
> Two versions exist:
>    MIG_RP_MSG_REQ_PAGES_ID that includes a RAMBlock name and start/len
>    MIG_RP_MSG_REQ_PAGES that just has start/len for use with the same
>                         RAMBlock as a previous MIG_RP_MSG_REQ_PAGES_ID
>
> Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>


Reviewed-by: Juan Quintela <quintela@redhat.com>


> diff --git a/migration/migration.c b/migration/migration.c
> index 4f8ef6f..e994164 100644
> --- a/migration/migration.c
> +++ b/migration/migration.c
> @@ -251,6 +251,35 @@ static void deferred_incoming_migration(Error **errp)
>      deferred_incoming = true;
>  }
>  
> +/* Request a range of pages from the source VM at the given
> + * start address.
> + *   rbname: Name of the RAMBlock to request the page in, if NULL it's the same
> + *           as the last request (a name must have been given previously)
> + *   Start: Address offset within the RB
> + *   Len: Length in bytes required - must be a multiple of pagesize
> + */
> +void migrate_send_rp_req_pages(MigrationIncomingState *mis, const char *rbname,
> +                               ram_addr_t start, size_t len)
> +{
> +    uint8_t bufc[12 + 1 + 255]; /* start (8), len (4), rbname upto 256 */
> +    size_t msglen = 12; /* start + len */
> +
> +    *(uint64_t *)bufc = cpu_to_be64((uint64_t)start);
> +    *(uint32_t *)(bufc + 8) = cpu_to_be32((uint32_t)len);

struct foo {
     uint64_t start;
     uint32_t len;
     char msg[];
}

As we are supposed to have the same qemu on both sides, this should
work, no?

Reviewed by anyways, because I am not sure that proposed solution is
(even) better than current code.

Later, Juan.