Subject: Re: [PATCH v5 13/27] cxl: prepare memdev creation for type2

From: Zhi Wang <[email-masked]>
Date: Thu, 21 Nov 2024 09:43:58 +0200

On Wed, 20 Nov 2024 10:15:59 -0700
Dave Jiang <[email-masked]> wrote:

> 
> 
> On 11/20/24 6:57 AM, Alejandro Lucero Palau wrote:
> > 
> > On 11/19/24 21:27, Dave Jiang wrote:
> >>
> >> On 11/19/24 1:06 PM, Zhi Wang wrote:
> >>> On Tue, 19 Nov 2024 11:24:44 -0700
> >>> Dave Jiang <[email-masked]> wrote:
> >>>
> >>>>
> >>>> On 11/18/24 9:44 AM, [email-masked] wrote:
> >>>>> From: Alejandro Lucero <[email-masked]>
> >>>>>
> >>>>> Current cxl core is relying on a CXL_DEVTYPE_CLASSMEM type device
> >>>>> when creating a memdev leading to problems when obtaining
> >>>>> cxl_memdev_state references from a CXL_DEVTYPE_DEVMEM type. This
> >>>>> last device type is managed by a specific vendor driver and does
> >>>>> not need same sysfs files since not userspace intervention is
> >>>>> expected.
> >>>>>
> >>>>> Create a new cxl_mem device type with no attributes for Type2.
> >>>>>
> >>>>> Avoid debugfs files relying on existence of clx_memdev_state.
> >>>>>
> >>>>> Make devm_cxl_add_memdev accesible from a accel driver.
> >>>>>
> >>>>> Signed-off-by: Alejandro Lucero <[email-masked]>
> >>>>> ---
> >>>>>   drivers/cxl/core/cdat.c   |  3 +++
> >>>>>   drivers/cxl/core/memdev.c | 15 +++++++++++++--
> >>>>>   drivers/cxl/core/region.c |  3 ++-
> >>>>>   drivers/cxl/mem.c         | 25 +++++++++++++++++++------
> >>>>>   include/cxl/cxl.h         |  2 ++
> >>>>>   5 files changed, 39 insertions(+), 9 deletions(-)
> >>>>>
> >>>>> diff --git a/drivers/cxl/core/cdat.c b/drivers/cxl/core/cdat.c
> >>>>> index e9cd7939c407..192cff18ea25 100644
> >>>>> --- a/drivers/cxl/core/cdat.c
> >>>>> +++ b/drivers/cxl/core/cdat.c
> >>>>> @@ -577,6 +577,9 @@ static struct cxl_dpa_perf
> >>>>> *cxled_get_dpa_perf(struct cxl_endpoint_decoder *cxle struct
> >>>>> cxl_memdev_state *mds = to_cxl_memdev_state(cxlmd->cxlds); struct
> >>>>> cxl_dpa_perf *perf;
> >>>>> +    if (!mds)
> >>>>> +        return ERR_PTR(-EINVAL);
> >>>>> +
> >>>>>       switch (mode) {
> >>>>>       case CXL_DECODER_RAM:
> >>>>>           perf = &mds->ram_perf;
> >>>>> diff --git a/drivers/cxl/core/memdev.c b/drivers/cxl/core/memdev.c
> >>>>> index d746c8a1021c..df31eea0c06b 100644
> >>>>> --- a/drivers/cxl/core/memdev.c
> >>>>> +++ b/drivers/cxl/core/memdev.c
> >>>>> @@ -547,9 +547,17 @@ static const struct device_type
> >>>>> cxl_memdev_type = { .groups = cxl_memdev_attribute_groups,
> >>>>>   };
> >>>>>   +static const struct device_type cxl_accel_memdev_type = {
> >>>>> +    .name = "cxl_memdev",
> >>>>> +    .release = cxl_memdev_release,
> >>>>> +    .devnode = cxl_memdev_devnode,
> >>>>> +};
> >>>>> +
> >>>>>   bool is_cxl_memdev(const struct device *dev)
> >>>>>   {
> >>>>> -    return dev->type == &cxl_memdev_type;
> >>>>> +    return (dev->type == &cxl_memdev_type ||
> >>>>> +        dev->type == &cxl_accel_memdev_type);
> >>>>> +
> >>>>>   }
> >>>>>   EXPORT_SYMBOL_NS_GPL(is_cxl_memdev, CXL);
> >>>> Does type2 device also exports a CDAT?
> >>>>
> >>> Yes. Type2 can also export a CDAT.
> >> Thanks! Probably should have the split out helpers regardless.
> > 
> > 
> > Maybe, but should not we wait until that is required? I did not see the need for adding them with this patchset.
> 
> Sure. I think my concern is with paths that apply only to one type but not the other. If you have not encountered any then we can wait.
> 

Agree.

I was thinking that for long-term, maybe CDAT routines shouldn't be tied to
device type, for me, it is like a cap that can be probed-and-used. E.g.
when talking with DOE, the core knows if CDAT is available or not, similar
case when the core tries to reach it via mailbox.

Z.
> DJ
> 
> > 
> > 
> >>>> I'm also wondering if we should have distinctive helpers:
> >>>> is_cxl_type3_memdev()
> >>>> is_cxl_type2_memdev()
> >>>>
> >>>> and is_cxl_memdev() is just calling those two helpers above.
> >>>>
> >>>> And if no CDAT is exported, we should change the is_cxl_memdev() to
> >>>> is_cxl_type3_memdev() in read_cdat_data().
> >>>>
> >>>> DJ
> >>>>
> >>>>>   @@ -660,7 +668,10 @@ static struct cxl_memdev
> >>>>> *cxl_memdev_alloc(struct cxl_dev_state *cxlds, dev->parent =
> >>>>> cxlds->dev; dev->bus = &cxl_bus_type;
> >>>>>       dev->devt = MKDEV(cxl_mem_major, cxlmd->id);
> >>>>> -    dev->type = &cxl_memdev_type;
> >>>>> +    if (cxlds->type == CXL_DEVTYPE_DEVMEM)
> >>>>> +        dev->type = &cxl_accel_memdev_type;
> >>>>> +    else
> >>>>> +        dev->type = &cxl_memdev_type;
> >>>>>       device_set_pm_not_required(dev);
> >>>>>       INIT_WORK(&cxlmd->detach_work, detach_memdev);
> >>>>>   diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
> >>>>> index dff618c708dc..622e3bb2e04b 100644
> >>>>> --- a/drivers/cxl/core/region.c
> >>>>> +++ b/drivers/cxl/core/region.c
> >>>>> @@ -1948,7 +1948,8 @@ static int cxl_region_attach(struct
> >>>>> cxl_region *cxlr, return -EINVAL;
> >>>>>       }
> >>>>>   -    cxl_region_perf_data_calculate(cxlr, cxled);
> >>>>> +    if (cxlr->type == CXL_DECODER_HOSTONLYMEM)
> >>>>> +        cxl_region_perf_data_calculate(cxlr, cxled);
> >>>>>         if (test_bit(CXL_REGION_F_AUTO, &cxlr->flags)) {
> >>>>>           int i;
> >>>>> diff --git a/drivers/cxl/mem.c b/drivers/cxl/mem.c
> >>>>> index a9fd5cd5a0d2..cb771bf196cd 100644
> >>>>> --- a/drivers/cxl/mem.c
> >>>>> +++ b/drivers/cxl/mem.c
> >>>>> @@ -130,12 +130,18 @@ static int cxl_mem_probe(struct device *dev)
> >>>>>       dentry = cxl_debugfs_create_dir(dev_name(dev));
> >>>>>       debugfs_create_devm_seqfile(dev, "dpamem", dentry,
> >>>>> cxl_mem_dpa_show);
> >>>>> -    if (test_bit(CXL_POISON_ENABLED_INJECT,
> >>>>> mds->poison.enabled_cmds))
> >>>>> -        debugfs_create_file("inject_poison", 0200, dentry,
> >>>>> cxlmd,
> >>>>> -                    &cxl_poison_inject_fops);
> >>>>> -    if (test_bit(CXL_POISON_ENABLED_CLEAR,
> >>>>> mds->poison.enabled_cmds))
> >>>>> -        debugfs_create_file("clear_poison", 0200, dentry,
> >>>>> cxlmd,
> >>>>> -                    &cxl_poison_clear_fops);
> >>>>> +    /*
> >>>>> +     * Avoid poison debugfs files for Type2 devices as they
> >>>>> rely on
> >>>>> +     * cxl_memdev_state.
> >>>>> +     */
> >>>>> +    if (mds) {
> >>>>> +        if (test_bit(CXL_POISON_ENABLED_INJECT,
> >>>>> mds->poison.enabled_cmds))
> >>>>> +            debugfs_create_file("inject_poison", 0200,
> >>>>> dentry, cxlmd,
> >>>>> +
> >>>>> &cxl_poison_inject_fops);
> >>>>> +        if (test_bit(CXL_POISON_ENABLED_CLEAR,
> >>>>> mds->poison.enabled_cmds))
> >>>>> +            debugfs_create_file("clear_poison", 0200,
> >>>>> dentry, cxlmd,
> >>>>> +
> >>>>> &cxl_poison_clear_fops);
> >>>>> +    }
> >>>>>         rc = devm_add_action_or_reset(dev, remove_debugfs, dentry);
> >>>>>       if (rc)
> >>>>> @@ -219,6 +225,13 @@ static umode_t cxl_mem_visible(struct kobject
> >>>>> *kobj, struct attribute *a, int n) struct cxl_memdev *cxlmd =
> >>>>> to_cxl_memdev(dev); struct cxl_memdev_state *mds =
> >>>>> to_cxl_memdev_state(cxlmd->cxlds);
> >>>>> +    /*
> >>>>> +     * Avoid poison sysfs files for Type2 devices as they rely
> >>>>> on
> >>>>> +     * cxl_memdev_state.
> >>>>> +     */
> >>>>> +    if (!mds)
> >>>>> +        return 0;
> >>>>> +
> >>>>>       if (a == &dev_attr_trigger_poison_list.attr)
> >>>>>           if (!test_bit(CXL_POISON_ENABLED_LIST,
> >>>>>                     mds->poison.enabled_cmds))
> >>>>> diff --git a/include/cxl/cxl.h b/include/cxl/cxl.h
> >>>>> index 6033ce84b3d3..5608ed0f5f15 100644
> >>>>> --- a/include/cxl/cxl.h
> >>>>> +++ b/include/cxl/cxl.h
> >>>>> @@ -57,4 +57,6 @@ int cxl_pci_accel_setup_regs(struct pci_dev
> >>>>> *pdev, struct cxl_dev_state *cxlds); int
> >>>>> cxl_request_resource(struct cxl_dev_state *cxlds, enum cxl_resource
> >>>>> type); int cxl_release_resource(struct cxl_dev_state *cxlds, enum
> >>>>> cxl_resource type); void cxl_set_media_ready(struct cxl_dev_state
> >>>>> *cxlds); +struct cxl_memdev *devm_cxl_add_memdev(struct device
> >>>>> *host,
> >>>>> +                       struct cxl_dev_state
> >>>>> *cxlds); #endif
> >>>>
> 
>