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([2a01:e0a:280:24f0:576b:abc6:6396:ed4a]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-46d1f3e1b03sm52436745e9.23.2025.09.22.09.00.38 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 22 Sep 2025 09:00:39 -0700 (PDT) Message-ID: <15399e70-fa4b-4792-9881-9dec59f0c832@redhat.com> Date: Mon, 22 Sep 2025 18:00:38 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH V4 5/8] migration: cpr-exec save and load To: Steve Sistare , qemu-devel@nongnu.org Cc: Fabiano Rosas , Peter Xu , Markus Armbruster , Paolo Bonzini , Eric Blake , "Dr. David Alan Gilbert" , Alex Williamson References: <1758548985-354793-1-git-send-email-steven.sistare@oracle.com> <1758548985-354793-6-git-send-email-steven.sistare@oracle.com> From: =?UTF-8?Q?C=C3=A9dric_Le_Goater?= Content-Language: en-US, fr Autocrypt: addr=clg@redhat.com; keydata= xsFNBFu8o3UBEADP+oJVJaWm5vzZa/iLgpBAuzxSmNYhURZH+guITvSySk30YWfLYGBWQgeo 8NzNXBY3cH7JX3/a0jzmhDc0U61qFxVgrPqs1PQOjp7yRSFuDAnjtRqNvWkvlnRWLFq4+U5t yzYe4SFMjFb6Oc0xkQmaK2flmiJNnnxPttYwKBPd98WfXMmjwAv7QfwW+OL3VlTPADgzkcqj 53bfZ4VblAQrq6Ctbtu7JuUGAxSIL3XqeQlAwwLTfFGrmpY7MroE7n9Rl+hy/kuIrb/TO8n0 ZxYXvvhT7OmRKvbYuc5Jze6o7op/bJHlufY+AquYQ4dPxjPPVUT/DLiUYJ3oVBWFYNbzfOrV RxEwNuRbycttMiZWxgflsQoHF06q/2l4ttS3zsV4TDZudMq0TbCH/uJFPFsbHUN91qwwaN/+ gy1j7o6aWMz+Ib3O9dK2M/j/O/Ube95mdCqN4N/uSnDlca3YDEWrV9jO1mUS/ndOkjxa34ia 70FjwiSQAsyIwqbRO3CGmiOJqDa9qNvd2TJgAaS2WCw/TlBALjVQ7AyoPEoBPj31K74Wc4GS Rm+FSch32ei61yFu6ACdZ12i5Edt+To+hkElzjt6db/UgRUeKfzlMB7PodK7o8NBD8outJGS tsL2GRX24QvvBuusJdMiLGpNz3uqyqwzC5w0Fd34E6G94806fwARAQABzSJDw6lkcmljIExl IEdvYXRlciA8Y2xnQHJlZGhhdC5jb20+wsGRBBMBCAA7FiEEoPZlSPBIlev+awtgUaNDx8/7 7KEFAmTLlVECGwMFCwkIBwICIgIGFQoJCAsCBBYCAwECHgcCF4AACgkQUaNDx8/77KG0eg// S0zIzTcxkrwJ/9XgdcvVTnXLVF9V4/tZPfB7sCp8rpDCEseU6O0TkOVFoGWM39sEMiQBSvyY lHrP7p7E/JYQNNLh441MfaX8RJ5Ul3btluLapm8oHp/vbHKV2IhLcpNCfAqaQKdfk8yazYhh EdxTBlzxPcu+78uE5fF4wusmtutK0JG0sAgq0mHFZX7qKG6LIbdLdaQalZ8CCFMKUhLptW71 xe+aNrn7hScBoOj2kTDRgf9CE7svmjGToJzUxgeh9mIkxAxTu7XU+8lmL28j2L5uNuDOq9vl hM30OT+pfHmyPLtLK8+GXfFDxjea5hZLF+2yolE/ATQFt9AmOmXC+YayrcO2ZvdnKExZS1o8 VUKpZgRnkwMUUReaF/mTauRQGLuS4lDcI4DrARPyLGNbvYlpmJWnGRWCDguQ/LBPpbG7djoy k3NlvoeA757c4DgCzggViqLm0Bae320qEc6z9o0X0ePqSU2f7vcuWN49Uhox5kM5L86DzjEQ RHXndoJkeL8LmHx8DM+kx4aZt0zVfCHwmKTkSTQoAQakLpLte7tWXIio9ZKhUGPv/eHxXEoS 0rOOAZ6np1U/xNR82QbF9qr9TrTVI3GtVe7Vxmff+qoSAxJiZQCo5kt0YlWwti2fFI4xvkOi V7lyhOA3+/3oRKpZYQ86Frlo61HU3r6d9wzOwU0EW7yjdQEQALyDNNMw/08/fsyWEWjfqVhW pOOrX2h+z4q0lOHkjxi/FRIRLfXeZjFfNQNLSoL8j1y2rQOs1j1g+NV3K5hrZYYcMs0xhmrZ KXAHjjDx7FW3sG3jcGjFW5Xk4olTrZwFsZVUcP8XZlArLmkAX3UyrrXEWPSBJCXxDIW1hzwp bV/nVbo/K9XBptT/wPd+RPiOTIIRptjypGY+S23HYBDND3mtfTz/uY0Jytaio9GETj+fFis6 TxFjjbZNUxKpwftu/4RimZ7qL+uM1rG1lLWc9SPtFxRQ8uLvLOUFB1AqHixBcx7LIXSKZEFU CSLB2AE4wXQkJbApye48qnZ09zc929df5gU6hjgqV9Gk1rIfHxvTsYltA1jWalySEScmr0iS YBZjw8Nbd7SxeomAxzBv2l1Fk8fPzR7M616dtb3Z3HLjyvwAwxtfGD7VnvINPbzyibbe9c6g LxYCr23c2Ry0UfFXh6UKD83d5ybqnXrEJ5n/t1+TLGCYGzF2erVYGkQrReJe8Mld3iGVldB7 JhuAU1+d88NS3aBpNF6TbGXqlXGF6Yua6n1cOY2Yb4lO/mDKgjXd3aviqlwVlodC8AwI0Sdu jWryzL5/AGEU2sIDQCHuv1QgzmKwhE58d475KdVX/3Vt5I9kTXpvEpfW18TjlFkdHGESM/Jx IqVsqvhAJkalABEBAAHCwV8EGAECAAkFAlu8o3UCGwwACgkQUaNDx8/77KEhwg//WqVopd5k 8hQb9VVdk6RQOCTfo6wHhEqgjbXQGlaxKHoXywEQBi8eULbeMQf5l4+tHJWBxswQ93IHBQjK yKyNr4FXseUI5O20XVNYDJZUrhA4yn0e/Af0IX25d94HXQ5sMTWr1qlSK6Zu79lbH3R57w9j hQm9emQEp785ui3A5U2Lqp6nWYWXz0eUZ0Tad2zC71Gg9VazU9MXyWn749s0nXbVLcLS0yop s302Gf3ZmtgfXTX/W+M25hiVRRKCH88yr6it+OMJBUndQVAA/fE9hYom6t/zqA248j0QAV/p LHH3hSirE1mv+7jpQnhMvatrwUpeXrOiEw1nHzWCqOJUZ4SY+HmGFW0YirWV2mYKoaGO2YBU wYF7O9TI3GEEgRMBIRT98fHa0NPwtlTktVISl73LpgVscdW8yg9Gc82oe8FzU1uHjU8b10lU XOMHpqDDEV9//r4ZhkKZ9C4O+YZcTFu+mvAY3GlqivBNkmYsHYSlFsbxc37E1HpTEaSWsGfA HQoPn9qrDJgsgcbBVc1gkUT6hnxShKPp4PlsZVMNjvPAnr5TEBgHkk54HQRhhwcYv1T2QumQ izDiU6iOrUzBThaMhZO3i927SG2DwWDVzZltKrCMD1aMPvb3NU8FOYRhNmIFR3fcalYr+9gD uVKe8BVz4atMOoktmt0GWTOC8P4= In-Reply-To: <1758548985-354793-6-git-send-email-steven.sistare@oracle.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=170.10.133.124; envelope-from=clg@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -24 X-Spam_score: -2.5 X-Spam_bar: -- X-Spam_report: (-2.5 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.442, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H5=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_VALIDITY_CERTIFIED_BLOCKED=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On 9/22/25 15:49, Steve Sistare wrote: > To preserve CPR state across exec, create a QEMUFile based on a memfd, and > keep the memfd open across exec. Save the value of the memfd in an > environment variable so post-exec QEMU can find it. Couldn't we preserve some memory to hand off to QEMU ? Like firmwares An environment variable is a limited method. Thanks, C. That's a short term hack right ? it's not even documented. I am sure you something else in mind. > These new functions are called in a subsequent patch. > > Signed-off-by: Steve Sistare > --- > include/migration/cpr.h | 5 +++ > migration/cpr-exec.c | 94 +++++++++++++++++++++++++++++++++++++++++++++++++ > migration/meson.build | 1 + > 3 files changed, 100 insertions(+) > create mode 100644 migration/cpr-exec.c > > diff --git a/include/migration/cpr.h b/include/migration/cpr.h > index 2b074d7..b84389f 100644 > --- a/include/migration/cpr.h > +++ b/include/migration/cpr.h > @@ -53,4 +53,9 @@ int cpr_get_fd_param(const char *name, const char *fdname, int index, > QEMUFile *cpr_transfer_output(MigrationChannel *channel, Error **errp); > QEMUFile *cpr_transfer_input(MigrationChannel *channel, Error **errp); > > +QEMUFile *cpr_exec_output(Error **errp); > +QEMUFile *cpr_exec_input(Error **errp); > +void cpr_exec_persist_state(QEMUFile *f); > +bool cpr_exec_has_state(void); > +void cpr_exec_unpersist_state(void); > #endif > diff --git a/migration/cpr-exec.c b/migration/cpr-exec.c > new file mode 100644 > index 0000000..2c32e9c > --- /dev/null > +++ b/migration/cpr-exec.c > @@ -0,0 +1,94 @@ > +/* > + * Copyright (c) 2021-2025 Oracle and/or its affiliates. > + * > + * SPDX-License-Identifier: GPL-2.0-or-later > + */ > + > +#include "qemu/osdep.h" > +#include "qemu/cutils.h" > +#include "qemu/memfd.h" > +#include "qapi/error.h" > +#include "io/channel-file.h" > +#include "io/channel-socket.h" > +#include "migration/cpr.h" > +#include "migration/qemu-file.h" > +#include "migration/misc.h" > +#include "migration/vmstate.h" > +#include "system/runstate.h" > + > +#define CPR_EXEC_STATE_NAME "QEMU_CPR_EXEC_STATE" > + > +static QEMUFile *qemu_file_new_fd_input(int fd, const char *name) > +{ > + g_autoptr(QIOChannelFile) fioc = qio_channel_file_new_fd(fd); > + QIOChannel *ioc = QIO_CHANNEL(fioc); > + qio_channel_set_name(ioc, name); > + return qemu_file_new_input(ioc); > +} > + > +static QEMUFile *qemu_file_new_fd_output(int fd, const char *name) > +{ > + g_autoptr(QIOChannelFile) fioc = qio_channel_file_new_fd(fd); > + QIOChannel *ioc = QIO_CHANNEL(fioc); > + qio_channel_set_name(ioc, name); > + return qemu_file_new_output(ioc); > +} > + > +void cpr_exec_persist_state(QEMUFile *f) > +{ > + QIOChannelFile *fioc = QIO_CHANNEL_FILE(qemu_file_get_ioc(f)); > + int mfd = dup(fioc->fd); > + char val[16]; > + > + /* Remember mfd in environment for post-exec load */ > + qemu_clear_cloexec(mfd); > + snprintf(val, sizeof(val), "%d", mfd); > + g_setenv(CPR_EXEC_STATE_NAME, val, 1); > +} > + > +static int cpr_exec_find_state(void) > +{ > + const char *val = g_getenv(CPR_EXEC_STATE_NAME); > + int mfd; > + > + assert(val); > + g_unsetenv(CPR_EXEC_STATE_NAME); > + assert(!qemu_strtoi(val, NULL, 10, &mfd)); > + return mfd; > +} > + > +bool cpr_exec_has_state(void) > +{ > + return g_getenv(CPR_EXEC_STATE_NAME) != NULL; > +} > + > +void cpr_exec_unpersist_state(void) > +{ > + int mfd; > + const char *val = g_getenv(CPR_EXEC_STATE_NAME); > + > + g_unsetenv(CPR_EXEC_STATE_NAME); > + assert(val); > + assert(!qemu_strtoi(val, NULL, 10, &mfd)); > + close(mfd); > +} > + > +QEMUFile *cpr_exec_output(Error **errp) > +{ > + int mfd = memfd_create(CPR_EXEC_STATE_NAME, 0); The build should be adjusted for Linux only. Thanks, C. > + > + if (mfd < 0) { > + error_setg_errno(errp, errno, "memfd_create failed"); > + return NULL; > + } > + > + return qemu_file_new_fd_output(mfd, CPR_EXEC_STATE_NAME); > +} > + > +QEMUFile *cpr_exec_input(Error **errp) > +{ > + int mfd = cpr_exec_find_state(); > + > + lseek(mfd, 0, SEEK_SET); > + return qemu_file_new_fd_input(mfd, CPR_EXEC_STATE_NAME); > +} > diff --git a/migration/meson.build b/migration/meson.build > index 0f71544..16909d5 100644 > --- a/migration/meson.build > +++ b/migration/meson.build > @@ -16,6 +16,7 @@ system_ss.add(files( > 'channel-block.c', > 'cpr.c', > 'cpr-transfer.c', > + 'cpr-exec.c', > 'cpu-throttle.c', > 'dirtyrate.c', > 'exec.c',