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Date: Tue, 11 Apr 2023 10:21:20 -0700
From: Brett Creeley <bcreeley@....com>
To: Alex Williamson <alex.williamson@...hat.com>,
Brett Creeley <brett.creeley@....com>
Cc: kvm@...r.kernel.org, netdev@...r.kernel.org, jgg@...dia.com,
yishaih@...dia.com, shameerali.kolothum.thodi@...wei.com,
kevin.tian@...el.com, shannon.nelson@....com, drivers@...sando.io,
simon.horman@...igine.com
Subject: Re: [PATCH v8 vfio 4/7] vfio/pds: Add VFIO live migration support
On 4/10/2023 3:05 PM, Alex Williamson wrote:
> Caution: This message originated from an External Source. Use proper caution when opening attachments, clicking links, or responding.
>
>
> On Tue, 4 Apr 2023 12:01:38 -0700
> Brett Creeley <brett.creeley@....com> wrote:
>> diff --git a/drivers/vfio/pci/pds/lm.c b/drivers/vfio/pci/pds/lm.c
>> new file mode 100644
>> index 000000000000..855f5da9b99a
>> --- /dev/null
>> +++ b/drivers/vfio/pci/pds/lm.c
>> @@ -0,0 +1,479 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +/* Copyright(c) 2023 Advanced Micro Devices, Inc. */
>> +
>> +#include <linux/anon_inodes.h>
>> +#include <linux/file.h>
>> +#include <linux/fs.h>
>> +#include <linux/highmem.h>
>> +#include <linux/vfio.h>
>> +#include <linux/vfio_pci_core.h>
>> +
>> +#include "vfio_dev.h"
>> +#include "cmds.h"
>> +
>> +#define PDS_VFIO_LM_FILENAME "pds_vfio_lm"
>> +
>> +const char *
>> +pds_vfio_lm_state(enum vfio_device_mig_state state)
>> +{
>> + switch (state) {
>> + case VFIO_DEVICE_STATE_ERROR:
>> + return "VFIO_DEVICE_STATE_ERROR";
>> + case VFIO_DEVICE_STATE_STOP:
>> + return "VFIO_DEVICE_STATE_STOP";
>> + case VFIO_DEVICE_STATE_RUNNING:
>> + return "VFIO_DEVICE_STATE_RUNNING";
>> + case VFIO_DEVICE_STATE_STOP_COPY:
>> + return "VFIO_DEVICE_STATE_STOP_COPY";
>> + case VFIO_DEVICE_STATE_RESUMING:
>> + return "VFIO_DEVICE_STATE_RESUMING";
>> + case VFIO_DEVICE_STATE_RUNNING_P2P:
>> + return "VFIO_DEVICE_STATE_RUNNING_P2P";
>> + default:
>> + return "VFIO_DEVICE_STATE_INVALID";
>> + }
>> +
>> + return "VFIO_DEVICE_STATE_INVALID";
>
> Seems a tad redundant.
I can remove this on the next revision. However, it is nice to be able
to see the state transitions via enabling the dynamic debug statement in
pds_vfio_step_device_state_locked(), but maybe this would make more
sense in the layer above the device specific VFIO drivers?
>
>> +}
>> +
> [snip]
>> +struct file *
>> +pds_vfio_step_device_state_locked(struct pds_vfio_pci_device *pds_vfio,
>> + enum vfio_device_mig_state next)
>> +{
>> + enum vfio_device_mig_state cur = pds_vfio->state;
>> + struct device *dev = &pds_vfio->pdev->dev;
>> + int err = 0;
>> +
>> + dev_dbg(dev, "%s => %s\n",
>> + pds_vfio_lm_state(cur), pds_vfio_lm_state(next));
>> +
>> + if (cur == VFIO_DEVICE_STATE_STOP && next == VFIO_DEVICE_STATE_STOP_COPY) {
>> + /* Device is already stopped
>> + * create save device data file & get device state from firmware
>> + */
>
> Standard multi-line comment style please, we're not under net/ here.
Will fix. Thanks.
>
>> + err = pds_vfio_get_save_file(pds_vfio);
>> + if (err)
>> + return ERR_PTR(err);
>> +
>> + /* Get device state */
>> + err = pds_vfio_get_lm_state_cmd(pds_vfio);
>> + if (err) {
>> + pds_vfio_put_save_file(pds_vfio);
>> + return ERR_PTR(err);
>> + }
>> +
>> + return pds_vfio->save_file->filep;
>> + }
>> +
>> + if (cur == VFIO_DEVICE_STATE_STOP_COPY && next == VFIO_DEVICE_STATE_STOP) {
>> + /* Device is already stopped
>> + * delete the save device state file
>> + */
>> + pds_vfio_put_save_file(pds_vfio);
>> + pds_vfio_send_host_vf_lm_status_cmd(pds_vfio,
>> + PDS_LM_STA_NONE);
>> + return NULL;
>> + }
>> +
>> + if (cur == VFIO_DEVICE_STATE_STOP && next == VFIO_DEVICE_STATE_RESUMING) {
>> + /* create resume device data file */
>> + err = pds_vfio_get_restore_file(pds_vfio);
>> + if (err)
>> + return ERR_PTR(err);
>> +
>> + return pds_vfio->restore_file->filep;
>> + }
>> +
>> + if (cur == VFIO_DEVICE_STATE_RESUMING && next == VFIO_DEVICE_STATE_STOP) {
>> + /* Set device state */
>> + err = pds_vfio_set_lm_state_cmd(pds_vfio);
>> + if (err)
>> + return ERR_PTR(err);
>> +
>> + /* delete resume device data file */
>> + pds_vfio_put_restore_file(pds_vfio);
>> + return NULL;
>> + }
>> +
>> + if (cur == VFIO_DEVICE_STATE_RUNNING && next == VFIO_DEVICE_STATE_RUNNING_P2P) {
>> + pds_vfio_send_host_vf_lm_status_cmd(pds_vfio, PDS_LM_STA_IN_PROGRESS);
>> + /* Device should be stopped
>> + * no interrupts, dma or change in internal state
>> + */
>> + err = pds_vfio_suspend_device_cmd(pds_vfio);
>> + if (err)
>> + return ERR_PTR(err);
>> +
>> + return NULL;
>> + }
>
> The comment here, as well as the no-op transitions from STOP->P2P and
> P2P->STOP has me concerned whether a device in this suspend state
> really meets the definition of our P2P state. The RUNNING_P2P state is
> a quiescent state where the device must accept access, including
> peer-to-peer DMA, but it cannot initiate DMA or interrupts. Is that
> consistent with this suspend state? Thanks,
>
> Alex
Yeah, these comments are misleading. Our device in the suspend state
does meet the definition of the P2P and STOP states based on how you
described them here and how they are defined in the VFIO header file.
I will remove the comments here as they are redundant since the states
align with the documentation.
Thanks,
Brett
>
>> +
>> + if (cur == VFIO_DEVICE_STATE_RUNNING_P2P && next == VFIO_DEVICE_STATE_RUNNING) {
>> + /* Device should be functional
>> + * interrupts, dma, mmio or changes to internal state is allowed
>> + */
>> + err = pds_vfio_resume_device_cmd(pds_vfio);
>> + if (err)
>> + return ERR_PTR(err);
>> +
>> + pds_vfio_send_host_vf_lm_status_cmd(pds_vfio,
>> + PDS_LM_STA_NONE);
>> + return NULL;
>> + }
>> +
>> + if (cur == VFIO_DEVICE_STATE_STOP && next == VFIO_DEVICE_STATE_RUNNING_P2P)
>> + return NULL;
>> +
>> + if (cur == VFIO_DEVICE_STATE_RUNNING_P2P && next == VFIO_DEVICE_STATE_STOP)
>> + return NULL;
>> +
>> + return ERR_PTR(-EINVAL);
>> +}
>
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