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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH] tools/migrate: Fix regression when migrating from older version of Xen
On Wed, 2013-07-10 at 20:19 +0100, Andrew Cooper wrote:
> Commit 00a4b65f8534c9e6521eab2e6ce796ae36037774 Sep 7 2010
> "libxc: provide notification of final checkpoint to restore end"
> broke migration from any version of Xen using tools from prior to that commit
>
> Older tools have no idea about an XC_SAVE_ID_LAST_CHECKPOINT, causing newer
> tools xc_domain_restore() to start reading the qemu save record, as
> ctx->last_checkpoint is 0.
Can the receive not distinguish the case where it is receiving a
checkpoint stream from a regular one? Either via some property of the
stream or the parameters with which it was called?
ctx->last_checkpoint should (be made to) only matter if you are doing
check pointing and I think we can mandate that checking pointing is only
supported between like versions of Xen. TBH it's a bit odd to send the
LAST_CHECKPOINT in anon-checkpoint stream anyway, but what's done is
done.
Ian.
>
> The failure looks like:
> xc: error: Max batch size exceeded (1970103633). Giving up.
> where 1970103633 = 0x756d6551 = *(uint32_t*)"Qemu"
>
> Sadly, the simple fix of just setting ctx->last_checkpoint = 1 will cause an
> opposite function regresson for anyone using the current behaviour of
> save_callbacks->checkpoint().
>
> The only safe fix is to rely on the toolstack to provide this information.
>
> Passing 0 results in unchanged behaviour, while passing nonzero means "the
> other end of the migration stream does not know about
> XC_SAVE_ID_LAST_CHECKPOINT but is performing a normal migrate"
>
> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> ---
> tools/libxc/xc_domain_restore.c | 3 ++-
> tools/libxc/xc_nomigrate.c | 2 +-
> tools/libxc/xenguest.h | 4 +++-
> tools/libxl/libxl_save_helper.c | 2 +-
> tools/xcutils/xc_restore.c | 2 +-
> 5 files changed, 8 insertions(+), 5 deletions(-)
>
> diff --git a/tools/libxc/xc_domain_restore.c b/tools/libxc/xc_domain_restore.c
> index 63d36cd..40c9282 100644
> --- a/tools/libxc/xc_domain_restore.c
> +++ b/tools/libxc/xc_domain_restore.c
> @@ -1401,7 +1401,7 @@ int xc_domain_restore(xc_interface *xch, int io_fd,
> uint32_t dom,
> domid_t store_domid, unsigned int console_evtchn,
> unsigned long *console_mfn, domid_t console_domid,
> unsigned int hvm, unsigned int pae, int superpages,
> - int no_incr_generationid,
> + int no_incr_generationid, int last_checkpoint_unaware,
> unsigned long *vm_generationid_addr,
> struct restore_callbacks *callbacks)
> {
> @@ -1472,6 +1472,7 @@ int xc_domain_restore(xc_interface *xch, int io_fd,
> uint32_t dom,
>
> ctx->superpages = superpages;
> ctx->hvm = hvm;
> + ctx->last_checkpoint = !!last_checkpoint_unaware;
>
> ctxt = xc_hypercall_buffer_alloc(xch, ctxt, sizeof(*ctxt));
>
> diff --git a/tools/libxc/xc_nomigrate.c b/tools/libxc/xc_nomigrate.c
> index 73e7566..1d3aec5 100644
> --- a/tools/libxc/xc_nomigrate.c
> +++ b/tools/libxc/xc_nomigrate.c
> @@ -35,7 +35,7 @@ int xc_domain_restore(xc_interface *xch, int io_fd,
> uint32_t dom,
> domid_t store_domid, unsigned int console_evtchn,
> unsigned long *console_mfn, domid_t console_domid,
> unsigned int hvm, unsigned int pae, int superpages,
> - int no_incr_generationid,
> + int no_incr_generationid, int last_checkpoint_unaware,
> unsigned long *vm_generationid_addr,
> struct restore_callbacks *callbacks)
> {
> diff --git a/tools/libxc/xenguest.h b/tools/libxc/xenguest.h
> index 4714bd2..977dde3 100644
> --- a/tools/libxc/xenguest.h
> +++ b/tools/libxc/xenguest.h
> @@ -114,6 +114,8 @@ struct restore_callbacks {
> * @parm pae non-zero if this HVM domain has PAE support enabled
> * @parm superpages non-zero to allocate guest memory with superpages
> * @parm no_incr_generationid non-zero if generation id is NOT to be
> incremented
> + * @parm last_checkpoint_unaware non-zero if far end of the migration is
> unaware
> + * of the XC_SAVE_ID_LAST_CHECKPOINT hunk in the migration stream.
> * @parm vm_generationid_addr returned with the address of the generation id
> buffer
> * @parm callbacks non-NULL to receive a callback to restore toolstack
> * specific data
> @@ -124,7 +126,7 @@ int xc_domain_restore(xc_interface *xch, int io_fd,
> uint32_t dom,
> domid_t store_domid, unsigned int console_evtchn,
> unsigned long *console_mfn, domid_t console_domid,
> unsigned int hvm, unsigned int pae, int superpages,
> - int no_incr_generationid,
> + int no_incr_generationid, int last_checkpoint_unaware,
> unsigned long *vm_generationid_addr,
> struct restore_callbacks *callbacks);
> /**
> diff --git a/tools/libxl/libxl_save_helper.c b/tools/libxl/libxl_save_helper.c
> index 772251a..8f14b8b 100644
> --- a/tools/libxl/libxl_save_helper.c
> +++ b/tools/libxl/libxl_save_helper.c
> @@ -264,7 +264,7 @@ int main(int argc, char **argv)
> r = xc_domain_restore(xch, io_fd, dom, store_evtchn, &store_mfn,
> store_domid, console_evtchn, &console_mfn,
> console_domid, hvm, pae, superpages,
> - no_incr_genidad, &genidad,
> + no_incr_genidad, 0, &genidad,
> &helper_restore_callbacks);
> helper_stub_restore_results(store_mfn,console_mfn,genidad,0);
> complete(r);
> diff --git a/tools/xcutils/xc_restore.c b/tools/xcutils/xc_restore.c
> index 35d725c..e657c7f 100644
> --- a/tools/xcutils/xc_restore.c
> +++ b/tools/xcutils/xc_restore.c
> @@ -52,7 +52,7 @@ main(int argc, char **argv)
>
> ret = xc_domain_restore(xch, io_fd, domid, store_evtchn, &store_mfn, 0,
> console_evtchn, &console_mfn, 0, hvm, pae,
> superpages,
> - 0, NULL, NULL);
> + 0, 0, NULL, NULL);
>
> if ( ret == 0 )
> {
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