On Tue, Jan 12, 2021 at 11:03 AM Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx> wrote: > > On Mon, 11 Jan 2021 14:51:08 -0800 > Ben Widawsky <ben.widawsky@xxxxxxxxx> wrote: > > > From: Dan Williams <dan.j.williams@xxxxxxxxx> > > > > The CXL.mem protocol allows a device to act as a provider of "System > > RAM" and/or "Persistent Memory" that is fully coherent as if the memory > > was attached to the typical CPU memory controller. > > > > With the CXL-2.0 specification a PCI endpoint can implement a "Type-3" > > device interface and give the operating system control over "Host > > Managed Device Memory". See section 2.3 Type 3 CXL Device. > > > > The memory range exported by the device may optionally be described by > > the platform firmware memory map, or by infrastructure like LIBNVDIMM to > > provision persistent memory capacity from one, or more, CXL.mem devices. > > > > A pre-requisite for Linux-managed memory-capacity provisioning is this > > cxl_mem driver that can speak the mailbox protocol defined in section > > 8.2.8.4 Mailbox Registers. > > > > For now just land the driver boiler-plate and fill it in with > > functionality in subsequent commits. > > > > Link: https://www.computeexpresslink.org/download-the-specification > > Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx> > > Signed-off-by: Ben Widawsky <ben.widawsky@xxxxxxxxx> > > Just one passing comment inline. > > > diff --git a/drivers/cxl/mem.c b/drivers/cxl/mem.c > > new file mode 100644 > > index 000000000000..005404888942 > > --- /dev/null > > +++ b/drivers/cxl/mem.c > > @@ -0,0 +1,69 @@ > > +// SPDX-License-Identifier: GPL-2.0-only > > +/* Copyright(c) 2020 Intel Corporation. All rights reserved. */ > > +#include <linux/module.h> > > +#include <linux/pci.h> > > +#include <linux/io.h> > > +#include "acpi.h" > > +#include "pci.h" > > + > > +static int cxl_mem_dvsec(struct pci_dev *pdev, int dvsec) > > Is it worth pulling this out to a utility library now as we are going > to keep needing this for CXL devices? > Arguably, with a vendor_id parameter it might make sense to have > it as a utility function for pci rather than CXL alone. Sure, cxl_mem_dvsec() can move to a central location, but I'd wait for the first incremental user to split it out.
