linux-kernel - Re: [RFC v2 06/15] vfio/cxl: introduce vfio-cxl core preludes

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Message-ID: <20251222135400.000041d6@huawei.com>
Date: Mon, 22 Dec 2025 13:54:00 +0000
From: Jonathan Cameron <jonathan.cameron@...wei.com>
To: <mhonap@...dia.com>
CC: <aniketa@...dia.com>, <ankita@...dia.com>, <alwilliamson@...dia.com>,
	<vsethi@...dia.com>, <jgg@...dia.com>, <mochs@...dia.com>,
	<skolothumtho@...dia.com>, <alejandro.lucero-palau@....com>,
	<dave@...olabs.net>, <dave.jiang@...el.com>, <alison.schofield@...el.com>,
	<vishal.l.verma@...el.com>, <ira.weiny@...el.com>,
	<dan.j.williams@...el.com>, <jgg@...pe.ca>, <yishaih@...dia.com>,
	<kevin.tian@...el.com>, <cjia@...dia.com>, <kwankhede@...dia.com>,
	<targupta@...dia.com>, <zhiw@...dia.com>, <kjaju@...dia.com>,
	<linux-kernel@...r.kernel.org>, <linux-cxl@...r.kernel.org>,
	<kvm@...r.kernel.org>
Subject: Re: [RFC v2 06/15] vfio/cxl: introduce vfio-cxl core preludes

On Tue, 9 Dec 2025 22:20:10 +0530
mhonap@...dia.com wrote:

> From: Manish Honap <mhonap@...dia.com>
> 
> In VFIO, common functions that used by VFIO variant drivers are managed
> in a set of "core" functions. E.g. the vfio-pci-core provides the common
> functions used by VFIO variant drviers to support PCI device
> passhthrough.
> 
> Although the CXL type-2 device has a PCI-compatible interface for device
> configuration and programming, they still needs special handlings when
> initialize the device:
> 
> - Probing the CXL DVSECs in the configuration.
> - Probing the CXL register groups implemented by the device.
> - Configuring the CXL device state required by the kernel CXL core.
> - Create the CXL region.
> - Special handlings of the CXL MMIO BAR.
> 
> Introduce vfio-cxl core preludes to hold all the common functions used
> by VFIO variant drivers to support CXL device passthrough.
> 
> Co-developed-by: Zhi Wang <zhiw@...dia.com>
> Signed-off-by: Zhi Wang <zhiw@...dia.com>
> Signed-off-by: Manish Honap <mhonap@...dia.com>

One trivial thing from a first look.

> diff --git a/drivers/vfio/pci/vfio_cxl_core.c b/drivers/vfio/pci/vfio_cxl_core.c
> new file mode 100644
> index 000000000000..cf53720c0cb7
> --- /dev/null
> +++ b/drivers/vfio/pci/vfio_cxl_core.c
> @@ -0,0 +1,238 @@

> +
> +int vfio_cxl_core_create_cxl_region(struct vfio_cxl_core_device *cxl, u64 size)
> +{
> +	struct cxl_region *region;
> +	struct range range;
> +	int ret;
> +	struct vfio_cxl *cxl_core = cxl->cxl_core;
> +
> +	if (WARN_ON(cxl_core->region.region))
> +		return -EEXIST;
> +
> +	ret = get_hpa_and_request_dpa(cxl, size);
> +	if (ret)
> +		return ret;
> +
> +	region = cxl_create_region(cxl_core->cxlrd, &cxl_core->cxled, true);
> +	if (IS_ERR(region)) {
> +		ret = PTR_ERR(region);
> +		cxl_dpa_free(cxl_core->cxled);
> +		return ret;

Trivial but might as well do:

		return PTR_ERR(region);

and save a line.

> +	}
> +
> +	cxl_get_region_range(region, &range);
> +
> +	cxl_core->region.addr = range.start;
> +	cxl_core->region.size = size;
> +	cxl_core->region.region = region;
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(vfio_cxl_core_create_cxl_region);