On 21-02-10 16:17:07, Jonathan Cameron wrote: > On Tue, 9 Feb 2021 16:02:52 -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 initial driver boiler-plate and Documentation/ > > infrastructure. > > > > Link: https://www.computeexpresslink.org/download-the-specification > > Cc: Jonathan Corbet <corbet@xxxxxxx> > > Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx> > > Signed-off-by: Ben Widawsky <ben.widawsky@xxxxxxxxx> > > Acked-by: David Rientjes <rientjes@xxxxxxxxxx> (v1) > > A few trivial bits inline but nothing that I feel that strongly about. > It is probably a good idea to add a note about generic dvsec code > somewhere in this patch description (to avoid people raising it on > future versions!) > > With the define of PCI_EXT_CAP_ID_DVSEC dropped (it's in the generic > header already). > > Reviewed-by: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx> > > > --- > > Documentation/driver-api/cxl/index.rst | 12 ++++ > > .../driver-api/cxl/memory-devices.rst | 29 +++++++++ > > Documentation/driver-api/index.rst | 1 + > > drivers/Kconfig | 1 + > > drivers/Makefile | 1 + > > drivers/cxl/Kconfig | 35 +++++++++++ > > drivers/cxl/Makefile | 4 ++ > > drivers/cxl/mem.c | 63 +++++++++++++++++++ > > drivers/cxl/pci.h | 18 ++++++ > > include/linux/pci_ids.h | 1 + > > 10 files changed, 165 insertions(+) > > create mode 100644 Documentation/driver-api/cxl/index.rst > > create mode 100644 Documentation/driver-api/cxl/memory-devices.rst > > create mode 100644 drivers/cxl/Kconfig > > create mode 100644 drivers/cxl/Makefile > > create mode 100644 drivers/cxl/mem.c > > create mode 100644 drivers/cxl/pci.h > > > > diff --git a/Documentation/driver-api/cxl/index.rst b/Documentation/driver-api/cxl/index.rst > > new file mode 100644 > > index 000000000000..036e49553542 > > --- /dev/null > > +++ b/Documentation/driver-api/cxl/index.rst > > @@ -0,0 +1,12 @@ > > +.. SPDX-License-Identifier: GPL-2.0 > > + > > +==================== > > +Compute Express Link > > +==================== > > + > > +.. toctree:: > > + :maxdepth: 1 > > + > > + memory-devices > > + > > +.. only:: subproject and html > > diff --git a/Documentation/driver-api/cxl/memory-devices.rst b/Documentation/driver-api/cxl/memory-devices.rst > > new file mode 100644 > > index 000000000000..43177e700d62 > > --- /dev/null > > +++ b/Documentation/driver-api/cxl/memory-devices.rst > > @@ -0,0 +1,29 @@ > > +.. SPDX-License-Identifier: GPL-2.0 > > +.. include:: <isonum.txt> > > + > > +=================================== > > +Compute Express Link Memory Devices > > +=================================== > > + > > +A Compute Express Link Memory Device is a CXL component that implements the > > +CXL.mem protocol. It contains some amount of volatile memory, persistent memory, > > +or both. It is enumerated as a PCI device for configuration and passing > > +messages over an MMIO mailbox. Its contribution to the System Physical > > +Address space is handled via HDM (Host Managed Device Memory) decoders > > +that optionally define a device's contribution to an interleaved address > > +range across multiple devices underneath a host-bridge or interleaved > > +across host-bridges. > > + > > +Driver Infrastructure > > +===================== > > + > > +This section covers the driver infrastructure for a CXL memory device. > > + > > +CXL Memory Device > > +----------------- > > + > > +.. kernel-doc:: drivers/cxl/mem.c > > + :doc: cxl mem > > + > > +.. kernel-doc:: drivers/cxl/mem.c > > + :internal: > > diff --git a/Documentation/driver-api/index.rst b/Documentation/driver-api/index.rst > > index 2456d0a97ed8..d246a18fd78f 100644 > > --- a/Documentation/driver-api/index.rst > > +++ b/Documentation/driver-api/index.rst > > @@ -35,6 +35,7 @@ available subsections can be seen below. > > usb/index > > firewire > > pci/index > > + cxl/index > > spi > > i2c > > ipmb > > diff --git a/drivers/Kconfig b/drivers/Kconfig > > index dcecc9f6e33f..62c753a73651 100644 > > --- a/drivers/Kconfig > > +++ b/drivers/Kconfig > > @@ -6,6 +6,7 @@ menu "Device Drivers" > > source "drivers/amba/Kconfig" > > source "drivers/eisa/Kconfig" > > source "drivers/pci/Kconfig" > > +source "drivers/cxl/Kconfig" > > source "drivers/pcmcia/Kconfig" > > source "drivers/rapidio/Kconfig" > > > > diff --git a/drivers/Makefile b/drivers/Makefile > > index fd11b9ac4cc3..678ea810410f 100644 > > --- a/drivers/Makefile > > +++ b/drivers/Makefile > > @@ -73,6 +73,7 @@ obj-$(CONFIG_NVM) += lightnvm/ > > obj-y += base/ block/ misc/ mfd/ nfc/ > > obj-$(CONFIG_LIBNVDIMM) += nvdimm/ > > obj-$(CONFIG_DAX) += dax/ > > +obj-$(CONFIG_CXL_BUS) += cxl/ > > obj-$(CONFIG_DMA_SHARED_BUFFER) += dma-buf/ > > obj-$(CONFIG_NUBUS) += nubus/ > > obj-y += macintosh/ > > diff --git a/drivers/cxl/Kconfig b/drivers/cxl/Kconfig > > new file mode 100644 > > index 000000000000..9e80b311e928 > > --- /dev/null > > +++ b/drivers/cxl/Kconfig > > @@ -0,0 +1,35 @@ > > +# SPDX-License-Identifier: GPL-2.0-only > > +menuconfig CXL_BUS > > + tristate "CXL (Compute Express Link) Devices Support" > > + depends on PCI > > + help > > + CXL is a bus that is electrically compatible with PCI Express, but > > + layers three protocols on that signalling (CXL.io, CXL.cache, and > > + CXL.mem). The CXL.cache protocol allows devices to hold cachelines > > + locally, the CXL.mem protocol allows devices to be fully coherent > > + memory targets, the CXL.io protocol is equivalent to PCI Express. > > + Say 'y' to enable support for the configuration and management of > > + devices supporting these protocols. > > + > > +if CXL_BUS > > + > > +config CXL_MEM > > + tristate "CXL.mem: Memory Devices" > > + help > > + 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. > > + > > + Say 'y/m' to enable a driver (named "cxl_mem.ko" when built as > > + a module) that will attach to CXL.mem devices for > > + configuration, provisioning, and health monitoring. This > > + driver is required for dynamic provisioning of CXL.mem > > + attached memory which is a prerequisite for persistent memory > > + support. Typically volatile memory is mapped by platform > > + firmware and included in the platform memory map, but in some > > + cases the OS is responsible for mapping that memory. See > > + Chapter 2.3 Type 3 CXL Device in the CXL 2.0 specification. > > + > > + If unsure say 'm'. > > +endif > > diff --git a/drivers/cxl/Makefile b/drivers/cxl/Makefile > > new file mode 100644 > > index 000000000000..4a30f7c3fc4a > > --- /dev/null > > +++ b/drivers/cxl/Makefile > > @@ -0,0 +1,4 @@ > > +# SPDX-License-Identifier: GPL-2.0 > > +obj-$(CONFIG_CXL_MEM) += cxl_mem.o > > + > > +cxl_mem-y := mem.o > > diff --git a/drivers/cxl/mem.c b/drivers/cxl/mem.c > > new file mode 100644 > > index 000000000000..99a6571508df > > --- /dev/null > > +++ b/drivers/cxl/mem.c > > @@ -0,0 +1,63 @@ > > +// 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 "pci.h" > > + > > +static int cxl_mem_dvsec(struct pci_dev *pdev, int dvsec) > > +{ > > + int pos; > > + > > + pos = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_DVSEC); > > + if (!pos) > > + return 0; > > + > > + while (pos) { > > + u16 vendor, id; > > + > > + pci_read_config_word(pdev, pos + PCI_DVSEC_HEADER1, &vendor); > > + pci_read_config_word(pdev, pos + PCI_DVSEC_HEADER2, &id); > > + if (vendor == PCI_DVSEC_VENDOR_ID_CXL && dvsec == id) > > + return pos; > > + > > + pos = pci_find_next_ext_capability(pdev, pos, > > + PCI_EXT_CAP_ID_DVSEC); > > + } > > + > > + return 0; > > Christopher Hellwig raised this in v1. > > https://lore.kernel.org/linux-pci/20201104201141.GA399378@bjorn-Precision-5520/ > > +CC Dave Jiang for update on that. > > This wants to move towards a generic helper. We can do the deduplication > later as Bjorn suggested. > > > +} > > + > > +static int cxl_mem_probe(struct pci_dev *pdev, const struct pci_device_id *id) > > +{ > > + struct device *dev = &pdev->dev; > > + int regloc; > > + > > + regloc = cxl_mem_dvsec(pdev, PCI_DVSEC_ID_CXL_REGLOC_OFFSET); > > + if (!regloc) { > > + dev_err(dev, "register location dvsec not found\n"); > > + return -ENXIO; > > + } > > + > > + return 0; > > +} > > + > > +static const struct pci_device_id cxl_mem_pci_tbl[] = { > > + /* PCI class code for CXL.mem Type-3 Devices */ > > + { PCI_ANY_ID, PCI_ANY_ID, PCI_ANY_ID, PCI_ANY_ID, > > + PCI_CLASS_MEMORY_CXL << 8 | CXL_MEMORY_PROGIF, 0xffffff, 0 }, > > Having looked at this and thought 'thats a bit tricky to check' > I did a quick grep and seems the kernel is split between this approach > and people going with the mor readable c99 style initiators > .class = .. etc > > Personally I'd find the c99 approach easier to read. > Well, it's Dan's patch, but I did modify this last. I took a look around, and the best fit seems to me seems to be: - { PCI_ANY_ID, PCI_ANY_ID, PCI_ANY_ID, PCI_ANY_ID, - PCI_CLASS_MEMORY_CXL << 8 | CXL_MEMORY_PROGIF, 0xffffff, 0 }, + { PCI_DEVICE_CLASS((PCI_CLASS_MEMORY_CXL << 8 | CXL_MEMORY_PROGIF), ~0)}, That work for you? > > + { /* terminate list */ }, > > +}; > > +MODULE_DEVICE_TABLE(pci, cxl_mem_pci_tbl); > > + > > +static struct pci_driver cxl_mem_driver = { > > + .name = KBUILD_MODNAME, > > + .id_table = cxl_mem_pci_tbl, > > + .probe = cxl_mem_probe, > > + .driver = { > > + .probe_type = PROBE_PREFER_ASYNCHRONOUS, > > + }, > > +}; > > + > > +MODULE_LICENSE("GPL v2"); > > +module_pci_driver(cxl_mem_driver); > > diff --git a/drivers/cxl/pci.h b/drivers/cxl/pci.h > > new file mode 100644 > > index 000000000000..f135b9f7bb21 > > --- /dev/null > > +++ b/drivers/cxl/pci.h > > @@ -0,0 +1,18 @@ > > +/* SPDX-License-Identifier: GPL-2.0-only */ > > +/* Copyright(c) 2020 Intel Corporation. All rights reserved. */ > > +#ifndef __CXL_PCI_H__ > > +#define __CXL_PCI_H__ > > + > > +#define CXL_MEMORY_PROGIF 0x10 > > + > > +/* > > + * See section 8.1 Configuration Space Registers in the CXL 2.0 > > + * Specification > > + */ > > +#define PCI_EXT_CAP_ID_DVSEC 0x23 > > This is already in include/uapi/linux/pci_regs.h > > > +#define PCI_DVSEC_VENDOR_ID_CXL 0x1E98 > > +#define PCI_DVSEC_ID_CXL 0x0 > > + > > +#define PCI_DVSEC_ID_CXL_REGLOC_OFFSET 0x8 > > + > > +#endif /* __CXL_PCI_H__ */ > > diff --git a/include/linux/pci_ids.h b/include/linux/pci_ids.h > > index d8156a5dbee8..766260a9b247 100644 > > --- a/include/linux/pci_ids.h > > +++ b/include/linux/pci_ids.h > > @@ -51,6 +51,7 @@ > > #define PCI_BASE_CLASS_MEMORY 0x05 > > #define PCI_CLASS_MEMORY_RAM 0x0500 > > #define PCI_CLASS_MEMORY_FLASH 0x0501 > > +#define PCI_CLASS_MEMORY_CXL 0x0502 > > #define PCI_CLASS_MEMORY_OTHER 0x0580 > > > > #define PCI_BASE_CLASS_BRIDGE 0x06 >
