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migration/multifd: Don't send device state packets with zerocopy flag

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If zerocopy is enabled for multifd then QIO_CHANNEL_WRITE_FLAG_ZERO_COPY
flag is forced into all multifd channel write calls via p->write_flags
that was setup in multifd_nocomp_send_setup().

However, device state packets aren't compatible with zerocopy - the data
buffer isn't getting kept pinned until multifd channel flush.

Make sure to mask that QIO_CHANNEL_WRITE_FLAG_ZERO_COPY flag in a multifd
send thread if the data being sent is device state.

Fixes: 0525b91a0b ("migration/multifd: Device state transfer support - send side")
Signed-off-by: Maciej S. Szmigiero <maciej.szmigiero@oracle.com>
Reviewed-by: Fabiano Rosas <farosas@suse.de>
Link: https://lore.kernel.org/r/3bd5f48578e29f3a78f41b1e4fbea3d4b2d9b136.1747403393.git.maciej.szmigiero@oracle.com
Signed-off-by: Peter Xu <peterx@redhat.com>
This commit is contained in:
Maciej S. Szmigiero 2025-05-16 15:53:03 +02:00 • committed by Peter Xu
parent 766bbabac8
commit 6be7696129
1 changed files with 6 additions and 1 deletions
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7
migration/multifd.c
View file

@ -690,6 +690,7 @@ static void *multifd_send_thread(void *opaque)
if (qatomic_load_acquire(&p->pending_job)) {
bool is_device_state = multifd_payload_device_state(p->data);
size_t total_size;
int write_flags_masked = 0;
p->flags = 0;
p->iovs_num = 0;
@ -697,6 +698,9 @@ static void *multifd_send_thread(void *opaque)
if (is_device_state) {
multifd_device_state_send_prepare(p);
/* Device state packets cannot be sent via zerocopy */
write_flags_masked |= QIO_CHANNEL_WRITE_FLAG_ZERO_COPY;
} else {
ret = multifd_send_state->ops->send_prepare(p, &local_err);
if (ret != 0) {
@ -718,7 +722,8 @@ static void *multifd_send_thread(void *opaque)
&p->data->u.ram, &local_err);
} else {
ret = qio_channel_writev_full_all(p->c, p->iov, p->iovs_num,
NULL, 0, p->write_flags,
NULL, 0,
p->write_flags & ~write_flags_masked,
&local_err);
}