* [PATCH 0/3] virtio-iommu on non-devicetree platforms
@ 2020-02-14 16:04 Jean-Philippe Brucker
2020-02-14 16:04 ` [PATCH 1/3] iommu/virtio: Add topology description to virtio-iommu config space Jean-Philippe Brucker
` (2 more replies)
0 siblings, 3 replies; 13+ messages in thread
From: Jean-Philippe Brucker @ 2020-02-14 16:04 UTC (permalink / raw)
To: iommu, virtualization, linux-pci
Cc: joro, bhelgaas, mst, jasowang, kevin.tian, sebastien.boeuf,
eric.auger, jacob.jun.pan
Add topology description to the virtio-iommu driver and enable x86
platforms. Since the RFC [1] I've mostly given up on ACPI tables, since
the internal discussions seem to have reached a dead end. The built-in
topology description presented here isn't ideal, but it is simple to
implement and doesn't impose a dependency on ACPI or device-tree, which
can be beneficial to lightweight hypervisors.
The built-in description is an array in the virtio config space. The
driver parses the config space early and postpones endpoint probe until
the virtio-iommu device is ready. Each element in the array describes
either a PCI range or a single MMIO endpoint, and their associated
endpoint IDs:
struct virtio_iommu_topo_pci_range {
__le16 type; /* 1: PCI range */
__le16 hierarchy; /* PCI domain number */
__le16 requester_start; /* First BDF */
__le16 requester_end; /* Last BDF */
__le32 endpoint_start; /* First endpoint ID */
};
struct virtio_iommu_topo_endpoint {
__le16 type; /* 2: Endpoint */
__le16 reserved; /* 0 */
__le32 endpoint; /* Endpoint ID */
__le64 address; /* First MMIO address */
};
You can find the QEMU patches based on Eric's latest device on my
virtio-iommu/devel branch [2]. I test on both x86 q35, and aarch64 virt
machine with edk2.
[1] https://lore.kernel.org/linux-iommu/20191122105000.800410-1-jean-philippe@linaro.org/
[2] https://jpbrucker.net/git/qemu virtio-iommu/devel
Jean-Philippe Brucker (3):
iommu/virtio: Add topology description to virtio-iommu config space
PCI: Add DMA configuration for virtual platforms
iommu/virtio: Enable x86 support
MAINTAINERS | 2 +
drivers/iommu/Kconfig | 13 +-
drivers/iommu/Makefile | 1 +
drivers/iommu/virtio-iommu-topology.c | 343 ++++++++++++++++++++++++++
drivers/iommu/virtio-iommu.c | 3 +
drivers/pci/pci-driver.c | 5 +
include/linux/virt_iommu.h | 19 ++
include/uapi/linux/virtio_iommu.h | 26 ++
8 files changed, 411 insertions(+), 1 deletion(-)
create mode 100644 drivers/iommu/virtio-iommu-topology.c
create mode 100644 include/linux/virt_iommu.h
--
2.25.0
^ permalink raw reply [flat|nested] 13+ messages in thread* [PATCH 1/3] iommu/virtio: Add topology description to virtio-iommu config space 2020-02-14 16:04 [PATCH 0/3] virtio-iommu on non-devicetree platforms Jean-Philippe Brucker @ 2020-02-14 16:04 ` Jean-Philippe Brucker 2020-02-14 16:04 ` [PATCH 2/3] PCI: Add DMA configuration for virtual platforms Jean-Philippe Brucker 2020-02-14 16:04 ` [PATCH 3/3] iommu/virtio: Enable x86 support Jean-Philippe Brucker 2 siblings, 0 replies; 13+ messages in thread From: Jean-Philippe Brucker @ 2020-02-14 16:04 UTC (permalink / raw) To: iommu, virtualization, linux-pci Cc: joro, bhelgaas, mst, jasowang, kevin.tian, sebastien.boeuf, eric.auger, jacob.jun.pan Platforms without device-tree do not currently have a method for describing the vIOMMU topology. Provide a topology description embedded into the virtio device. Use PCI FIXUP to probe the config space early, because we need to discover the topology before any DMA configuration takes place, and the virtio driver may be loaded much later. Since we discover the topology description when probing the PCI hierarchy, the virtual IOMMU cannot manage other platform devices discovered earlier. This solution isn't elegant nor foolproof, but is the best we can do at the moment and works with existing virtio-iommu implementations. It also enables an IOMMU for lightweight hypervisors that do not rely on firmware methods for booting. Signed-off-by: Eric Auger <eric.auger@redhat.com> Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org> --- MAINTAINERS | 2 + drivers/iommu/Kconfig | 10 + drivers/iommu/Makefile | 1 + drivers/iommu/virtio-iommu-topology.c | 343 ++++++++++++++++++++++++++ drivers/iommu/virtio-iommu.c | 3 + include/linux/virt_iommu.h | 19 ++ include/uapi/linux/virtio_iommu.h | 26 ++ 7 files changed, 404 insertions(+) create mode 100644 drivers/iommu/virtio-iommu-topology.c create mode 100644 include/linux/virt_iommu.h diff --git a/MAINTAINERS b/MAINTAINERS index 38fe2f3f7b6f..6b978b0d0c90 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -17780,6 +17780,8 @@ M: Jean-Philippe Brucker <jean-philippe@linaro.org> L: virtualization@lists.linux-foundation.org S: Maintained F: drivers/iommu/virtio-iommu.c +F: drivers/iommu/virtio-iommu-topology.c +F: include/linux/virt_iommu.h F: include/uapi/linux/virtio_iommu.h VIRTUAL BOX GUEST DEVICE DRIVER diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig index d2fade984999..068d4e0e3541 100644 --- a/drivers/iommu/Kconfig +++ b/drivers/iommu/Kconfig @@ -516,4 +516,14 @@ config VIRTIO_IOMMU Say Y here if you intend to run this kernel as a guest. +config VIRTIO_IOMMU_TOPOLOGY + bool "Topology properties for the virtio-iommu" + depends on VIRTIO_IOMMU + default y + help + Enable early probing of the virtio-iommu device, to detect the + built-in topology description. + + Say Y here if you intend to run this kernel as a guest. + endif # IOMMU_SUPPORT diff --git a/drivers/iommu/Makefile b/drivers/iommu/Makefile index 2104fb8afc06..f295cacf9c6e 100644 --- a/drivers/iommu/Makefile +++ b/drivers/iommu/Makefile @@ -37,3 +37,4 @@ obj-$(CONFIG_S390_IOMMU) += s390-iommu.o obj-$(CONFIG_QCOM_IOMMU) += qcom_iommu.o obj-$(CONFIG_HYPERV_IOMMU) += hyperv-iommu.o obj-$(CONFIG_VIRTIO_IOMMU) += virtio-iommu.o +obj-$(CONFIG_VIRTIO_IOMMU_TOPOLOGY) += virtio-iommu-topology.o diff --git a/drivers/iommu/virtio-iommu-topology.c b/drivers/iommu/virtio-iommu-topology.c new file mode 100644 index 000000000000..e4ab49701df5 --- /dev/null +++ b/drivers/iommu/virtio-iommu-topology.c @@ -0,0 +1,343 @@ +// SPDX-License-Identifier: GPL-2.0 +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt + +#include <linux/dma-iommu.h> +#include <linux/list.h> +#include <linux/pci.h> +#include <linux/virt_iommu.h> +#include <linux/virtio_ids.h> +#include <linux/virtio_pci.h> +#include <uapi/linux/virtio_iommu.h> + +struct viommu_cap_config { + u8 bar; + u32 length; /* structure size */ + u32 offset; /* structure offset within the bar */ +}; + +union viommu_topo_cfg { + __le16 type; + struct virtio_iommu_topo_pci_range pci; + struct virtio_iommu_topo_endpoint ep; +}; + +struct viommu_spec { + struct device *dev; /* transport device */ + struct fwnode_handle *fwnode; + struct iommu_ops *ops; + struct list_head list; + size_t num_items; + /* The config array of length num_items follows */ + union viommu_topo_cfg cfg[]; +}; + +static LIST_HEAD(viommus); +static DEFINE_MUTEX(viommus_lock); + +#define VPCI_FIELD(field) offsetof(struct virtio_pci_cap, field) + +static inline int viommu_pci_find_capability(struct pci_dev *dev, u8 cfg_type, + struct viommu_cap_config *cap) +{ + int pos; + u8 bar; + + for (pos = pci_find_capability(dev, PCI_CAP_ID_VNDR); + pos > 0; + pos = pci_find_next_capability(dev, pos, PCI_CAP_ID_VNDR)) { + u8 type; + + pci_read_config_byte(dev, pos + VPCI_FIELD(cfg_type), &type); + if (type != cfg_type) + continue; + + pci_read_config_byte(dev, pos + VPCI_FIELD(bar), &bar); + + /* Ignore structures with reserved BAR values */ + if (type != VIRTIO_PCI_CAP_PCI_CFG && bar > 0x5) + continue; + + cap->bar = bar; + pci_read_config_dword(dev, pos + VPCI_FIELD(length), + &cap->length); + pci_read_config_dword(dev, pos + VPCI_FIELD(offset), + &cap->offset); + + return pos; + } + return 0; +} + +static void viommu_ccopy(__le32 *dst, u32 __iomem *src, size_t length) +{ + size_t i; + + /* For the moment all our config structures align on 32b */ + if (WARN_ON(length % 4)) + return; + + for (i = 0; i < length / 4; i++) + /* Keep little-endian data */ + dst[i] = cpu_to_le32(ioread32(src + i)); +} + +static int viommu_parse_topology(struct device *dev, + struct virtio_iommu_config __iomem *cfg) +{ + size_t i; + size_t spec_length; + struct viommu_spec *viommu_spec; + u32 offset, item_length, num_items; + + offset = ioread32(&cfg->topo_config.offset); + item_length = ioread32(&cfg->topo_config.item_length); + num_items = ioread32(&cfg->topo_config.num_items); + if (!offset || !num_items || !item_length) + return 0; + + spec_length = sizeof(*viommu_spec) + num_items * + sizeof(union viommu_topo_cfg); + viommu_spec = kzalloc(spec_length, GFP_KERNEL); + if (!viommu_spec) + return -ENOMEM; + + viommu_spec->dev = dev; + + /* Copy in the whole array, sort it out later */ + for (i = 0; i < num_items; i++) { + size_t read_length = min_t(size_t, item_length, + sizeof(union viommu_topo_cfg)); + + viommu_ccopy((__le32 *)&viommu_spec->cfg[i], + (void __iomem *)cfg + offset, + read_length); + + offset += item_length; + } + viommu_spec->num_items = num_items; + + mutex_lock(&viommus_lock); + list_add(&viommu_spec->list, &viommus); + mutex_unlock(&viommus_lock); + + return 0; +} + +static void viommu_pci_parse_topology(struct pci_dev *dev) +{ + int pos; + u32 features; + void __iomem *regs; + struct viommu_cap_config cap = {0}; + struct virtio_pci_common_cfg __iomem *common_cfg; + + /* + * The virtio infrastructure might not be loaded at this point. we need + * to access the BARs ourselves. + */ + pos = viommu_pci_find_capability(dev, VIRTIO_PCI_CAP_COMMON_CFG, &cap); + if (!pos) { + pci_warn(dev, "common capability not found\n"); + return; + } + + if (pci_enable_device_mem(dev)) + return; + + regs = pci_iomap(dev, cap.bar, 0); + if (!regs) + return; + + common_cfg = regs + cap.offset; + + /* Find out if the device supports topology description */ + writel(0, &common_cfg->device_feature_select); + features = ioread32(&common_cfg->device_feature); + + pci_iounmap(dev, regs); + + if (!(features & BIT(VIRTIO_IOMMU_F_TOPOLOGY))) { + pci_dbg(dev, "device doesn't have topology description"); + return; + } + + pos = viommu_pci_find_capability(dev, VIRTIO_PCI_CAP_DEVICE_CFG, &cap); + if (!pos) { + pci_warn(dev, "device config capability not found\n"); + return; + } + + regs = pci_iomap(dev, cap.bar, 0); + if (!regs) + return; + + pci_info(dev, "parsing virtio-iommu topology\n"); + viommu_parse_topology(&dev->dev, regs + cap.offset); + pci_iounmap(dev, regs); +} + +/* + * Catch a PCI virtio-iommu implementation early to get the topology description + * before we start probing other endpoints. + */ +DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_REDHAT_QUMRANET, 0x1040 + VIRTIO_ID_IOMMU, + viommu_pci_parse_topology); + +/* + * Return true if the device matches this topology structure. Write the endpoint + * ID into epid if it's the case. + */ +static bool viommu_parse_pci(struct pci_dev *pdev, union viommu_topo_cfg *cfg, + u32 *epid) +{ + u32 endpoint_start; + u16 start, end, domain; + u16 devid = pci_dev_id(pdev); + u16 type = le16_to_cpu(cfg->type); + + if (type != VIRTIO_IOMMU_TOPO_PCI_RANGE) + return false; + + start = le16_to_cpu(cfg->pci.requester_start); + end = le16_to_cpu(cfg->pci.requester_end); + domain = le16_to_cpu(cfg->pci.hierarchy); + endpoint_start = le32_to_cpu(cfg->pci.endpoint_start); + + if (pci_domain_nr(pdev->bus) == domain && + devid >= start && devid <= end) { + *epid = devid - start + endpoint_start; + return true; + } + return false; +} + +static const struct iommu_ops *virt_iommu_setup(struct device *dev) +{ + struct iommu_fwspec *fwspec = dev_iommu_fwspec_get(dev); + const struct iommu_ops *viommu_ops = NULL; + struct fwnode_handle *viommu_fwnode; + struct viommu_spec *viommu_spec; + struct pci_dev *pci_dev = NULL; + struct device *viommu_dev; + bool found = false; + size_t i; + u32 epid; + int ret; + + /* Already translated? */ + if (fwspec && fwspec->ops) + return fwspec->ops; + + if (dev_is_pci(dev)) { + pci_dev = to_pci_dev(dev); + } else { + /* At the moment we don't support platform devices */ + return NULL; + } + + mutex_lock(&viommus_lock); + list_for_each_entry(viommu_spec, &viommus, list) { + for (i = 0; i < viommu_spec->num_items; i++) { + union viommu_topo_cfg *cfg = &viommu_spec->cfg[i]; + + found = viommu_parse_pci(pci_dev, cfg, &epid); + if (found) + break; + } + if (found) { + viommu_ops = viommu_spec->ops; + viommu_fwnode = viommu_spec->fwnode; + viommu_dev = viommu_spec->dev; + break; + } + } + mutex_unlock(&viommus_lock); + if (!found) + return NULL; + + /* We're not translating ourselves. */ + if (viommu_dev == dev) + return NULL; + + /* + * If we found a PCI range managed by the viommu, we're the ones that + * have to request ACS. + */ + if (pci_dev) + pci_request_acs(); + + if (!viommu_ops) + return ERR_PTR(-EPROBE_DEFER); + + ret = iommu_fwspec_init(dev, viommu_fwnode, viommu_ops); + if (ret) + return ERR_PTR(ret); + + iommu_fwspec_add_ids(dev, &epid, 1); + + return viommu_ops; +} + +/** + * virt_dma_configure - Configure DMA of virtualized devices + * @dev: the endpoint + * + * Setup the DMA and IOMMU ops of a virtual device, for platforms without DT or + * ACPI. + * + * Return: -EPROBE_DEFER if the device is managed by an IOMMU that hasn't been + * probed yet, 0 otherwise + */ +int virt_dma_configure(struct device *dev) +{ + const struct iommu_ops *iommu_ops; + + iommu_ops = virt_iommu_setup(dev); + if (IS_ERR_OR_NULL(iommu_ops)) { + int ret = PTR_ERR(iommu_ops); + + if (ret == -EPROBE_DEFER || ret == 0) + return ret; + dev_err(dev, "error %d while setting up virt IOMMU\n", ret); + return 0; + } + + /* + * If we have reason to believe the IOMMU driver missed the initial + * add_device callback for dev, replay it to get things in order. + */ + if (dev->bus && !device_iommu_mapped(dev)) + iommu_probe_device(dev); + + /* Assume coherent, as well as full 64-bit addresses. */ +#ifdef CONFIG_ARCH_HAS_SETUP_DMA_OPS + arch_setup_dma_ops(dev, 0, ~0ULL, iommu_ops, true); +#else + iommu_setup_dma_ops(dev, 0, ~0ULL); +#endif + return 0; +} + +/** + * virt_set_iommu_ops - Set the IOMMU ops of a virtual IOMMU device + * @dev: the IOMMU device (transport) + * @ops: the new IOMMU ops or NULL + * + * Setup the iommu_ops associated to a viommu_spec, once the driver is loaded + * and the device probed. + */ +void virt_set_iommu_ops(struct device *dev, struct iommu_ops *ops) +{ + struct viommu_spec *viommu_spec; + + mutex_lock(&viommus_lock); + list_for_each_entry(viommu_spec, &viommus, list) { + if (viommu_spec->dev == dev) { + viommu_spec->ops = ops; + viommu_spec->fwnode = ops ? dev->fwnode : NULL; + break; + } + } + mutex_unlock(&viommus_lock); +} +EXPORT_SYMBOL_GPL(virt_set_iommu_ops); diff --git a/drivers/iommu/virtio-iommu.c b/drivers/iommu/virtio-iommu.c index cce329d71fba..f18ba8e22ebd 100644 --- a/drivers/iommu/virtio-iommu.c +++ b/drivers/iommu/virtio-iommu.c @@ -21,6 +21,7 @@ #include <linux/virtio.h> #include <linux/virtio_config.h> #include <linux/virtio_ids.h> +#include <linux/virt_iommu.h> #include <linux/wait.h> #include <uapi/linux/virtio_iommu.h> @@ -1075,6 +1076,7 @@ static int viommu_probe(struct virtio_device *vdev) if (ret) goto err_free_vqs; + virt_set_iommu_ops(dev->parent, &viommu_ops); iommu_device_set_ops(&viommu->iommu, &viommu_ops); iommu_device_set_fwnode(&viommu->iommu, parent_dev->fwnode); @@ -1122,6 +1124,7 @@ static void viommu_remove(struct virtio_device *vdev) { struct viommu_dev *viommu = vdev->priv; + virt_set_iommu_ops(vdev->dev.parent, NULL); iommu_device_sysfs_remove(&viommu->iommu); iommu_device_unregister(&viommu->iommu); diff --git a/include/linux/virt_iommu.h b/include/linux/virt_iommu.h new file mode 100644 index 000000000000..c68b03ec75ba --- /dev/null +++ b/include/linux/virt_iommu.h @@ -0,0 +1,19 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef VIRTIO_IOMMU_H_ +#define VIRTIO_IOMMU_H_ + +#if IS_ENABLED(CONFIG_VIRTIO_IOMMU_TOPOLOGY) +int virt_dma_configure(struct device *dev); +void virt_set_iommu_ops(struct device *dev, struct iommu_ops *ops); +#else /* !CONFIG_VIRTIO_IOMMU_TOPOLOGY */ +static inline int virt_dma_configure(struct device *dev) +{ + /* Don't disturb the normal DMA configuration methods */ + return 0; +} + +static inline void virt_set_iommu_ops(struct device *dev, struct iommu_ops *ops) +{ } +#endif /* !CONFIG_VIRTIO_IOMMU_TOPOLOGY */ + +#endif /* VIRTIO_IOMMU_H_ */ diff --git a/include/uapi/linux/virtio_iommu.h b/include/uapi/linux/virtio_iommu.h index 237e36a280cb..ec57d215086a 100644 --- a/include/uapi/linux/virtio_iommu.h +++ b/include/uapi/linux/virtio_iommu.h @@ -16,6 +16,7 @@ #define VIRTIO_IOMMU_F_BYPASS 3 #define VIRTIO_IOMMU_F_PROBE 4 #define VIRTIO_IOMMU_F_MMIO 5 +#define VIRTIO_IOMMU_F_TOPOLOGY 6 struct virtio_iommu_range_64 { __le64 start; @@ -27,6 +28,12 @@ struct virtio_iommu_range_32 { __le32 end; }; +struct virtio_iommu_topo_config { + __le32 offset; + __le32 num_items; + __le32 item_length; +}; + struct virtio_iommu_config { /* Supported page sizes */ __le64 page_size_mask; @@ -36,6 +43,25 @@ struct virtio_iommu_config { struct virtio_iommu_range_32 domain_range; /* Probe buffer size */ __le32 probe_size; + struct virtio_iommu_topo_config topo_config; +}; + +#define VIRTIO_IOMMU_TOPO_PCI_RANGE 0x1 +#define VIRTIO_IOMMU_TOPO_ENDPOINT 0x2 + +struct virtio_iommu_topo_pci_range { + __le16 type; + __le16 hierarchy; + __le16 requester_start; + __le16 requester_end; + __le32 endpoint_start; +}; + +struct virtio_iommu_topo_endpoint { + __le16 type; + __le16 reserved; + __le32 endpoint; + __le64 address; }; /* Request types */ -- 2.25.0 ^ permalink raw reply related [flat|nested] 13+ messages in thread
* [PATCH 2/3] PCI: Add DMA configuration for virtual platforms 2020-02-14 16:04 [PATCH 0/3] virtio-iommu on non-devicetree platforms Jean-Philippe Brucker 2020-02-14 16:04 ` [PATCH 1/3] iommu/virtio: Add topology description to virtio-iommu config space Jean-Philippe Brucker @ 2020-02-14 16:04 ` Jean-Philippe Brucker 2020-02-14 17:03 ` Robin Murphy 2020-02-14 16:04 ` [PATCH 3/3] iommu/virtio: Enable x86 support Jean-Philippe Brucker 2 siblings, 1 reply; 13+ messages in thread From: Jean-Philippe Brucker @ 2020-02-14 16:04 UTC (permalink / raw) To: iommu, virtualization, linux-pci Cc: joro, bhelgaas, mst, jasowang, kevin.tian, sebastien.boeuf, eric.auger, jacob.jun.pan Hardware platforms usually describe the IOMMU topology using either device-tree pointers or vendor-specific ACPI tables. For virtual platforms that don't provide a device-tree, the virtio-iommu device contains a description of the endpoints it manages. That information allows us to probe endpoints after the IOMMU is probed (possibly as late as userspace modprobe), provided it is discovered early enough. Add a hook to pci_dma_configure(), which returns -EPROBE_DEFER if the endpoint is managed by a vIOMMU that will be loaded later, or 0 in any other case to avoid disturbing the normal DMA configuration methods. When CONFIG_VIRTIO_IOMMU_TOPOLOGY isn't selected, the call to virt_dma_configure() is compiled out. As long as the information is consistent, platforms can provide both a device-tree and a built-in topology, and the IOMMU infrastructure is able to deal with multiple DMA configuration methods. Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org> --- drivers/pci/pci-driver.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c index 0454ca0e4e3f..69303a814f21 100644 --- a/drivers/pci/pci-driver.c +++ b/drivers/pci/pci-driver.c @@ -18,6 +18,7 @@ #include <linux/kexec.h> #include <linux/of_device.h> #include <linux/acpi.h> +#include <linux/virt_iommu.h> #include "pci.h" #include "pcie/portdrv.h" @@ -1602,6 +1603,10 @@ static int pci_dma_configure(struct device *dev) struct device *bridge; int ret = 0; + ret = virt_dma_configure(dev); + if (ret) + return ret; + bridge = pci_get_host_bridge_device(to_pci_dev(dev)); if (IS_ENABLED(CONFIG_OF) && bridge->parent && -- 2.25.0 ^ permalink raw reply related [flat|nested] 13+ messages in thread
* Re: [PATCH 2/3] PCI: Add DMA configuration for virtual platforms 2020-02-14 16:04 ` [PATCH 2/3] PCI: Add DMA configuration for virtual platforms Jean-Philippe Brucker @ 2020-02-14 17:03 ` Robin Murphy 2020-02-17 9:12 ` Jean-Philippe Brucker 0 siblings, 1 reply; 13+ messages in thread From: Robin Murphy @ 2020-02-14 17:03 UTC (permalink / raw) To: Jean-Philippe Brucker, iommu, virtualization, linux-pci Cc: kevin.tian, mst, sebastien.boeuf, jacob.jun.pan, bhelgaas, jasowang On 14/02/2020 4:04 pm, Jean-Philippe Brucker wrote: > Hardware platforms usually describe the IOMMU topology using either > device-tree pointers or vendor-specific ACPI tables. For virtual > platforms that don't provide a device-tree, the virtio-iommu device > contains a description of the endpoints it manages. That information > allows us to probe endpoints after the IOMMU is probed (possibly as late > as userspace modprobe), provided it is discovered early enough. > > Add a hook to pci_dma_configure(), which returns -EPROBE_DEFER if the > endpoint is managed by a vIOMMU that will be loaded later, or 0 in any > other case to avoid disturbing the normal DMA configuration methods. > When CONFIG_VIRTIO_IOMMU_TOPOLOGY isn't selected, the call to > virt_dma_configure() is compiled out. > > As long as the information is consistent, platforms can provide both a > device-tree and a built-in topology, and the IOMMU infrastructure is > able to deal with multiple DMA configuration methods. Urgh, it's already been established[1] that having IOMMU setup tied to DMA configuration at driver probe time is not just conceptually wrong but actually broken, so the concept here worries me a bit. In a world where of_iommu_configure() and friends are being called much earlier around iommu_probe_device() time, how badly will this fall apart? Robin. [1] https://lore.kernel.org/linux-iommu/9625faf4-48ef-2dd3-d82f-931d9cf26976@huawei.com/ > Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org> > --- > drivers/pci/pci-driver.c | 5 +++++ > 1 file changed, 5 insertions(+) > > diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c > index 0454ca0e4e3f..69303a814f21 100644 > --- a/drivers/pci/pci-driver.c > +++ b/drivers/pci/pci-driver.c > @@ -18,6 +18,7 @@ > #include <linux/kexec.h> > #include <linux/of_device.h> > #include <linux/acpi.h> > +#include <linux/virt_iommu.h> > #include "pci.h" > #include "pcie/portdrv.h" > > @@ -1602,6 +1603,10 @@ static int pci_dma_configure(struct device *dev) > struct device *bridge; > int ret = 0; > > + ret = virt_dma_configure(dev); > + if (ret) > + return ret; > + > bridge = pci_get_host_bridge_device(to_pci_dev(dev)); > > if (IS_ENABLED(CONFIG_OF) && bridge->parent && > ^ permalink raw reply [flat|nested] 13+ messages in thread
* Re: [PATCH 2/3] PCI: Add DMA configuration for virtual platforms 2020-02-14 17:03 ` Robin Murphy @ 2020-02-17 9:12 ` Jean-Philippe Brucker 0 siblings, 0 replies; 13+ messages in thread From: Jean-Philippe Brucker @ 2020-02-17 9:12 UTC (permalink / raw) To: Robin Murphy Cc: iommu, virtualization, linux-pci, kevin.tian, mst, sebastien.boeuf, jacob.jun.pan, bhelgaas, jasowang On Fri, Feb 14, 2020 at 05:03:16PM +0000, Robin Murphy wrote: > On 14/02/2020 4:04 pm, Jean-Philippe Brucker wrote: > > Hardware platforms usually describe the IOMMU topology using either > > device-tree pointers or vendor-specific ACPI tables. For virtual > > platforms that don't provide a device-tree, the virtio-iommu device > > contains a description of the endpoints it manages. That information > > allows us to probe endpoints after the IOMMU is probed (possibly as late > > as userspace modprobe), provided it is discovered early enough. > > > > Add a hook to pci_dma_configure(), which returns -EPROBE_DEFER if the > > endpoint is managed by a vIOMMU that will be loaded later, or 0 in any > > other case to avoid disturbing the normal DMA configuration methods. > > When CONFIG_VIRTIO_IOMMU_TOPOLOGY isn't selected, the call to > > virt_dma_configure() is compiled out. > > > > As long as the information is consistent, platforms can provide both a > > device-tree and a built-in topology, and the IOMMU infrastructure is > > able to deal with multiple DMA configuration methods. > > Urgh, it's already been established[1] that having IOMMU setup tied to DMA > configuration at driver probe time is not just conceptually wrong but > actually broken, so the concept here worries me a bit. In a world where > of_iommu_configure() and friends are being called much earlier around > iommu_probe_device() time, how badly will this fall apart? If present the DT configuration should take precedence over this built-in method, so the earlier it is called the better. virt_dma_configure() currently gives up if the device already has iommu_ops (well, still calls setup_dma_ops() which is safe enough, but I think I'll change that to have virt_iommu_setup() return NULL if iommu_ops are present). I don't have the full picture of the changes you intend for {of,acpi}_iommu_configure(), do you think checking the validity of dev->iommu_fwspec will remain sufficient to have both methods coexist? Thanks, Jean ^ permalink raw reply [flat|nested] 13+ messages in thread
* [PATCH 3/3] iommu/virtio: Enable x86 support 2020-02-14 16:04 [PATCH 0/3] virtio-iommu on non-devicetree platforms Jean-Philippe Brucker 2020-02-14 16:04 ` [PATCH 1/3] iommu/virtio: Add topology description to virtio-iommu config space Jean-Philippe Brucker 2020-02-14 16:04 ` [PATCH 2/3] PCI: Add DMA configuration for virtual platforms Jean-Philippe Brucker @ 2020-02-14 16:04 ` Jean-Philippe Brucker 2020-02-14 16:57 ` Robin Murphy 2 siblings, 1 reply; 13+ messages in thread From: Jean-Philippe Brucker @ 2020-02-14 16:04 UTC (permalink / raw) To: iommu, virtualization, linux-pci Cc: joro, bhelgaas, mst, jasowang, kevin.tian, sebastien.boeuf, eric.auger, jacob.jun.pan With the built-in topology description in place, x86 platforms can now use the virtio-iommu. Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org> --- drivers/iommu/Kconfig | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig index 068d4e0e3541..adcbda44d473 100644 --- a/drivers/iommu/Kconfig +++ b/drivers/iommu/Kconfig @@ -508,8 +508,9 @@ config HYPERV_IOMMU config VIRTIO_IOMMU bool "Virtio IOMMU driver" depends on VIRTIO=y - depends on ARM64 + depends on (ARM64 || X86) select IOMMU_API + select IOMMU_DMA select INTERVAL_TREE help Para-virtualised IOMMU driver with virtio. -- 2.25.0 ^ permalink raw reply related [flat|nested] 13+ messages in thread
* Re: [PATCH 3/3] iommu/virtio: Enable x86 support 2020-02-14 16:04 ` [PATCH 3/3] iommu/virtio: Enable x86 support Jean-Philippe Brucker @ 2020-02-14 16:57 ` Robin Murphy 2020-02-16 9:50 ` Michael S. Tsirkin 0 siblings, 1 reply; 13+ messages in thread From: Robin Murphy @ 2020-02-14 16:57 UTC (permalink / raw) To: Jean-Philippe Brucker, iommu, virtualization, linux-pci Cc: kevin.tian, mst, sebastien.boeuf, jacob.jun.pan, bhelgaas, jasowang On 14/02/2020 4:04 pm, Jean-Philippe Brucker wrote: > With the built-in topology description in place, x86 platforms can now > use the virtio-iommu. > > Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org> > --- > drivers/iommu/Kconfig | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig > index 068d4e0e3541..adcbda44d473 100644 > --- a/drivers/iommu/Kconfig > +++ b/drivers/iommu/Kconfig > @@ -508,8 +508,9 @@ config HYPERV_IOMMU > config VIRTIO_IOMMU > bool "Virtio IOMMU driver" > depends on VIRTIO=y > - depends on ARM64 > + depends on (ARM64 || X86) > select IOMMU_API > + select IOMMU_DMA Can that have an "if X86" for clarity? AIUI it's not necessary for virtio-iommu itself (and really shouldn't be), but is merely to satisfy the x86 arch code's expectation that IOMMU drivers bring their own DMA ops, right? Robin. > select INTERVAL_TREE > help > Para-virtualised IOMMU driver with virtio. > ^ permalink raw reply [flat|nested] 13+ messages in thread
* Re: [PATCH 3/3] iommu/virtio: Enable x86 support 2020-02-14 16:57 ` Robin Murphy @ 2020-02-16 9:50 ` Michael S. Tsirkin 2020-02-17 9:01 ` Jean-Philippe Brucker 0 siblings, 1 reply; 13+ messages in thread From: Michael S. Tsirkin @ 2020-02-16 9:50 UTC (permalink / raw) To: Robin Murphy Cc: Jean-Philippe Brucker, iommu, virtualization, linux-pci, kevin.tian, sebastien.boeuf, jacob.jun.pan, bhelgaas, jasowang On Fri, Feb 14, 2020 at 04:57:11PM +0000, Robin Murphy wrote: > On 14/02/2020 4:04 pm, Jean-Philippe Brucker wrote: > > With the built-in topology description in place, x86 platforms can now > > use the virtio-iommu. > > > > Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org> > > --- > > drivers/iommu/Kconfig | 3 ++- > > 1 file changed, 2 insertions(+), 1 deletion(-) > > > > diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig > > index 068d4e0e3541..adcbda44d473 100644 > > --- a/drivers/iommu/Kconfig > > +++ b/drivers/iommu/Kconfig > > @@ -508,8 +508,9 @@ config HYPERV_IOMMU > > config VIRTIO_IOMMU > > bool "Virtio IOMMU driver" > > depends on VIRTIO=y > > - depends on ARM64 > > + depends on (ARM64 || X86) > > select IOMMU_API > > + select IOMMU_DMA > > Can that have an "if X86" for clarity? AIUI it's not necessary for > virtio-iommu itself (and really shouldn't be), but is merely to satisfy the > x86 arch code's expectation that IOMMU drivers bring their own DMA ops, > right? > > Robin. In fact does not this work on any platform now? > > select INTERVAL_TREE > > help > > Para-virtualised IOMMU driver with virtio. > > ^ permalink raw reply [flat|nested] 13+ messages in thread
* Re: [PATCH 3/3] iommu/virtio: Enable x86 support 2020-02-16 9:50 ` Michael S. Tsirkin @ 2020-02-17 9:01 ` Jean-Philippe Brucker 2020-02-17 13:01 ` Michael S. Tsirkin 0 siblings, 1 reply; 13+ messages in thread From: Jean-Philippe Brucker @ 2020-02-17 9:01 UTC (permalink / raw) To: Michael S. Tsirkin Cc: Robin Murphy, iommu, virtualization, linux-pci, kevin.tian, sebastien.boeuf, jacob.jun.pan, bhelgaas, jasowang On Sun, Feb 16, 2020 at 04:50:33AM -0500, Michael S. Tsirkin wrote: > On Fri, Feb 14, 2020 at 04:57:11PM +0000, Robin Murphy wrote: > > On 14/02/2020 4:04 pm, Jean-Philippe Brucker wrote: > > > With the built-in topology description in place, x86 platforms can now > > > use the virtio-iommu. > > > > > > Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org> > > > --- > > > drivers/iommu/Kconfig | 3 ++- > > > 1 file changed, 2 insertions(+), 1 deletion(-) > > > > > > diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig > > > index 068d4e0e3541..adcbda44d473 100644 > > > --- a/drivers/iommu/Kconfig > > > +++ b/drivers/iommu/Kconfig > > > @@ -508,8 +508,9 @@ config HYPERV_IOMMU > > > config VIRTIO_IOMMU > > > bool "Virtio IOMMU driver" > > > depends on VIRTIO=y > > > - depends on ARM64 > > > + depends on (ARM64 || X86) > > > select IOMMU_API > > > + select IOMMU_DMA > > > > Can that have an "if X86" for clarity? AIUI it's not necessary for > > virtio-iommu itself (and really shouldn't be), but is merely to satisfy the > > x86 arch code's expectation that IOMMU drivers bring their own DMA ops, > > right? > > > > Robin. > > In fact does not this work on any platform now? There is ongoing work to use the generic IOMMU_DMA ops on X86. AMD IOMMU has been converted recently [1] but VT-d still implements its own DMA ops (conversion patches are on the list [2]). On Arm the arch Kconfig selects IOMMU_DMA, and I assume we'll have the same on X86 once Tom's work is complete. Until then I can add a "if X86" here for clarity. Thanks, Jean [1] https://lore.kernel.org/linux-iommu/20190613223901.9523-1-murphyt7@tcd.ie/ [2] https://lore.kernel.org/linux-iommu/20191221150402.13868-1-murphyt7@tcd.ie/ ^ permalink raw reply [flat|nested] 13+ messages in thread
* Re: [PATCH 3/3] iommu/virtio: Enable x86 support 2020-02-17 9:01 ` Jean-Philippe Brucker @ 2020-02-17 13:01 ` Michael S. Tsirkin 2020-02-17 13:22 ` Robin Murphy 0 siblings, 1 reply; 13+ messages in thread From: Michael S. Tsirkin @ 2020-02-17 13:01 UTC (permalink / raw) To: Jean-Philippe Brucker Cc: Robin Murphy, iommu, virtualization, linux-pci, kevin.tian, sebastien.boeuf, jacob.jun.pan, bhelgaas, jasowang On Mon, Feb 17, 2020 at 10:01:07AM +0100, Jean-Philippe Brucker wrote: > On Sun, Feb 16, 2020 at 04:50:33AM -0500, Michael S. Tsirkin wrote: > > On Fri, Feb 14, 2020 at 04:57:11PM +0000, Robin Murphy wrote: > > > On 14/02/2020 4:04 pm, Jean-Philippe Brucker wrote: > > > > With the built-in topology description in place, x86 platforms can now > > > > use the virtio-iommu. > > > > > > > > Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org> > > > > --- > > > > drivers/iommu/Kconfig | 3 ++- > > > > 1 file changed, 2 insertions(+), 1 deletion(-) > > > > > > > > diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig > > > > index 068d4e0e3541..adcbda44d473 100644 > > > > --- a/drivers/iommu/Kconfig > > > > +++ b/drivers/iommu/Kconfig > > > > @@ -508,8 +508,9 @@ config HYPERV_IOMMU > > > > config VIRTIO_IOMMU > > > > bool "Virtio IOMMU driver" > > > > depends on VIRTIO=y > > > > - depends on ARM64 > > > > + depends on (ARM64 || X86) > > > > select IOMMU_API > > > > + select IOMMU_DMA > > > > > > Can that have an "if X86" for clarity? AIUI it's not necessary for > > > virtio-iommu itself (and really shouldn't be), but is merely to satisfy the > > > x86 arch code's expectation that IOMMU drivers bring their own DMA ops, > > > right? > > > > > > Robin. > > > > In fact does not this work on any platform now? > > There is ongoing work to use the generic IOMMU_DMA ops on X86. AMD IOMMU > has been converted recently [1] but VT-d still implements its own DMA ops > (conversion patches are on the list [2]). On Arm the arch Kconfig selects > IOMMU_DMA, and I assume we'll have the same on X86 once Tom's work is > complete. Until then I can add a "if X86" here for clarity. > > Thanks, > Jean > > [1] https://lore.kernel.org/linux-iommu/20190613223901.9523-1-murphyt7@tcd.ie/ > [2] https://lore.kernel.org/linux-iommu/20191221150402.13868-1-murphyt7@tcd.ie/ What about others? E.g. PPC? -- MST ^ permalink raw reply [flat|nested] 13+ messages in thread
* Re: [PATCH 3/3] iommu/virtio: Enable x86 support 2020-02-17 13:01 ` Michael S. Tsirkin @ 2020-02-17 13:22 ` Robin Murphy 2020-02-17 13:31 ` Michael S. Tsirkin 0 siblings, 1 reply; 13+ messages in thread From: Robin Murphy @ 2020-02-17 13:22 UTC (permalink / raw) To: Michael S. Tsirkin, Jean-Philippe Brucker Cc: iommu, virtualization, linux-pci, kevin.tian, sebastien.boeuf, jacob.jun.pan, bhelgaas, jasowang On 17/02/2020 1:01 pm, Michael S. Tsirkin wrote: > On Mon, Feb 17, 2020 at 10:01:07AM +0100, Jean-Philippe Brucker wrote: >> On Sun, Feb 16, 2020 at 04:50:33AM -0500, Michael S. Tsirkin wrote: >>> On Fri, Feb 14, 2020 at 04:57:11PM +0000, Robin Murphy wrote: >>>> On 14/02/2020 4:04 pm, Jean-Philippe Brucker wrote: >>>>> With the built-in topology description in place, x86 platforms can now >>>>> use the virtio-iommu. >>>>> >>>>> Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org> >>>>> --- >>>>> drivers/iommu/Kconfig | 3 ++- >>>>> 1 file changed, 2 insertions(+), 1 deletion(-) >>>>> >>>>> diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig >>>>> index 068d4e0e3541..adcbda44d473 100644 >>>>> --- a/drivers/iommu/Kconfig >>>>> +++ b/drivers/iommu/Kconfig >>>>> @@ -508,8 +508,9 @@ config HYPERV_IOMMU >>>>> config VIRTIO_IOMMU >>>>> bool "Virtio IOMMU driver" >>>>> depends on VIRTIO=y >>>>> - depends on ARM64 >>>>> + depends on (ARM64 || X86) >>>>> select IOMMU_API >>>>> + select IOMMU_DMA >>>> >>>> Can that have an "if X86" for clarity? AIUI it's not necessary for >>>> virtio-iommu itself (and really shouldn't be), but is merely to satisfy the >>>> x86 arch code's expectation that IOMMU drivers bring their own DMA ops, >>>> right? >>>> >>>> Robin. >>> >>> In fact does not this work on any platform now? >> >> There is ongoing work to use the generic IOMMU_DMA ops on X86. AMD IOMMU >> has been converted recently [1] but VT-d still implements its own DMA ops >> (conversion patches are on the list [2]). On Arm the arch Kconfig selects >> IOMMU_DMA, and I assume we'll have the same on X86 once Tom's work is >> complete. Until then I can add a "if X86" here for clarity. >> >> Thanks, >> Jean >> >> [1] https://lore.kernel.org/linux-iommu/20190613223901.9523-1-murphyt7@tcd.ie/ >> [2] https://lore.kernel.org/linux-iommu/20191221150402.13868-1-murphyt7@tcd.ie/ > > What about others? E.g. PPC? That was the point I was getting at - while iommu-dma should build just fine for the likes of PPC, s390, 32-bit Arm, etc., they have no architecture code to correctly wire up iommu_dma_ops to devices. Thus there's currently no point pulling it in and pretending it's anything more than a waste of space for architectures other than arm64 and x86. It's merely a historical artefact of the x86 DMA API implementation that when the IOMMU drivers were split out to form drivers/iommu they took some of their relevant arch code with them. Robin. ^ permalink raw reply [flat|nested] 13+ messages in thread
* Re: [PATCH 3/3] iommu/virtio: Enable x86 support 2020-02-17 13:22 ` Robin Murphy @ 2020-02-17 13:31 ` Michael S. Tsirkin 2020-02-17 14:10 ` Robin Murphy 0 siblings, 1 reply; 13+ messages in thread From: Michael S. Tsirkin @ 2020-02-17 13:31 UTC (permalink / raw) To: Robin Murphy Cc: Jean-Philippe Brucker, iommu, virtualization, linux-pci, kevin.tian, sebastien.boeuf, jacob.jun.pan, bhelgaas, jasowang On Mon, Feb 17, 2020 at 01:22:44PM +0000, Robin Murphy wrote: > On 17/02/2020 1:01 pm, Michael S. Tsirkin wrote: > > On Mon, Feb 17, 2020 at 10:01:07AM +0100, Jean-Philippe Brucker wrote: > > > On Sun, Feb 16, 2020 at 04:50:33AM -0500, Michael S. Tsirkin wrote: > > > > On Fri, Feb 14, 2020 at 04:57:11PM +0000, Robin Murphy wrote: > > > > > On 14/02/2020 4:04 pm, Jean-Philippe Brucker wrote: > > > > > > With the built-in topology description in place, x86 platforms can now > > > > > > use the virtio-iommu. > > > > > > > > > > > > Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org> > > > > > > --- > > > > > > drivers/iommu/Kconfig | 3 ++- > > > > > > 1 file changed, 2 insertions(+), 1 deletion(-) > > > > > > > > > > > > diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig > > > > > > index 068d4e0e3541..adcbda44d473 100644 > > > > > > --- a/drivers/iommu/Kconfig > > > > > > +++ b/drivers/iommu/Kconfig > > > > > > @@ -508,8 +508,9 @@ config HYPERV_IOMMU > > > > > > config VIRTIO_IOMMU > > > > > > bool "Virtio IOMMU driver" > > > > > > depends on VIRTIO=y > > > > > > - depends on ARM64 > > > > > > + depends on (ARM64 || X86) > > > > > > select IOMMU_API > > > > > > + select IOMMU_DMA > > > > > > > > > > Can that have an "if X86" for clarity? AIUI it's not necessary for > > > > > virtio-iommu itself (and really shouldn't be), but is merely to satisfy the > > > > > x86 arch code's expectation that IOMMU drivers bring their own DMA ops, > > > > > right? > > > > > > > > > > Robin. > > > > > > > > In fact does not this work on any platform now? > > > > > > There is ongoing work to use the generic IOMMU_DMA ops on X86. AMD IOMMU > > > has been converted recently [1] but VT-d still implements its own DMA ops > > > (conversion patches are on the list [2]). On Arm the arch Kconfig selects > > > IOMMU_DMA, and I assume we'll have the same on X86 once Tom's work is > > > complete. Until then I can add a "if X86" here for clarity. > > > > > > Thanks, > > > Jean > > > > > > [1] https://lore.kernel.org/linux-iommu/20190613223901.9523-1-murphyt7@tcd.ie/ > > > [2] https://lore.kernel.org/linux-iommu/20191221150402.13868-1-murphyt7@tcd.ie/ > > > > What about others? E.g. PPC? > > That was the point I was getting at - while iommu-dma should build just fine > for the likes of PPC, s390, 32-bit Arm, etc., they have no architecture code > to correctly wire up iommu_dma_ops to devices. Thus there's currently no > point pulling it in and pretending it's anything more than a waste of space > for architectures other than arm64 and x86. It's merely a historical > artefact of the x86 DMA API implementation that when the IOMMU drivers were > split out to form drivers/iommu they took some of their relevant arch code > with them. > > Robin. Rather than white-listing architectures, how about making the architectures in question set some kind of symbol, and depend on it? -- MST ^ permalink raw reply [flat|nested] 13+ messages in thread
* Re: [PATCH 3/3] iommu/virtio: Enable x86 support 2020-02-17 13:31 ` Michael S. Tsirkin @ 2020-02-17 14:10 ` Robin Murphy 0 siblings, 0 replies; 13+ messages in thread From: Robin Murphy @ 2020-02-17 14:10 UTC (permalink / raw) To: Michael S. Tsirkin Cc: Jean-Philippe Brucker, iommu, virtualization, linux-pci, kevin.tian, sebastien.boeuf, jacob.jun.pan, bhelgaas, jasowang On 17/02/2020 1:31 pm, Michael S. Tsirkin wrote: > On Mon, Feb 17, 2020 at 01:22:44PM +0000, Robin Murphy wrote: >> On 17/02/2020 1:01 pm, Michael S. Tsirkin wrote: >>> On Mon, Feb 17, 2020 at 10:01:07AM +0100, Jean-Philippe Brucker wrote: >>>> On Sun, Feb 16, 2020 at 04:50:33AM -0500, Michael S. Tsirkin wrote: >>>>> On Fri, Feb 14, 2020 at 04:57:11PM +0000, Robin Murphy wrote: >>>>>> On 14/02/2020 4:04 pm, Jean-Philippe Brucker wrote: >>>>>>> With the built-in topology description in place, x86 platforms can now >>>>>>> use the virtio-iommu. >>>>>>> >>>>>>> Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org> >>>>>>> --- >>>>>>> drivers/iommu/Kconfig | 3 ++- >>>>>>> 1 file changed, 2 insertions(+), 1 deletion(-) >>>>>>> >>>>>>> diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig >>>>>>> index 068d4e0e3541..adcbda44d473 100644 >>>>>>> --- a/drivers/iommu/Kconfig >>>>>>> +++ b/drivers/iommu/Kconfig >>>>>>> @@ -508,8 +508,9 @@ config HYPERV_IOMMU >>>>>>> config VIRTIO_IOMMU >>>>>>> bool "Virtio IOMMU driver" >>>>>>> depends on VIRTIO=y >>>>>>> - depends on ARM64 >>>>>>> + depends on (ARM64 || X86) >>>>>>> select IOMMU_API >>>>>>> + select IOMMU_DMA >>>>>> >>>>>> Can that have an "if X86" for clarity? AIUI it's not necessary for >>>>>> virtio-iommu itself (and really shouldn't be), but is merely to satisfy the >>>>>> x86 arch code's expectation that IOMMU drivers bring their own DMA ops, >>>>>> right? >>>>>> >>>>>> Robin. >>>>> >>>>> In fact does not this work on any platform now? >>>> >>>> There is ongoing work to use the generic IOMMU_DMA ops on X86. AMD IOMMU >>>> has been converted recently [1] but VT-d still implements its own DMA ops >>>> (conversion patches are on the list [2]). On Arm the arch Kconfig selects >>>> IOMMU_DMA, and I assume we'll have the same on X86 once Tom's work is >>>> complete. Until then I can add a "if X86" here for clarity. >>>> >>>> Thanks, >>>> Jean >>>> >>>> [1] https://lore.kernel.org/linux-iommu/20190613223901.9523-1-murphyt7@tcd.ie/ >>>> [2] https://lore.kernel.org/linux-iommu/20191221150402.13868-1-murphyt7@tcd.ie/ >>> >>> What about others? E.g. PPC? >> >> That was the point I was getting at - while iommu-dma should build just fine >> for the likes of PPC, s390, 32-bit Arm, etc., they have no architecture code >> to correctly wire up iommu_dma_ops to devices. Thus there's currently no >> point pulling it in and pretending it's anything more than a waste of space >> for architectures other than arm64 and x86. It's merely a historical >> artefact of the x86 DMA API implementation that when the IOMMU drivers were >> split out to form drivers/iommu they took some of their relevant arch code >> with them. >> >> Robin. > > > Rather than white-listing architectures, how about making the > architectures in question set some kind of symbol, and depend on it? Umm, that's basically what we have already? Architectures that use iommu_dma_ops select IOMMU_DMA. The only issue is the oddity of x86 treating IOMMU drivers as part of its arch code, which has never come up against a cross-architecture driver until now. Hence the options of either maintaining that paradigm and having the 'x86 arch code' aspect of this driver "select IOMMU_DMA if x86" such that it works out equivalent to AMD_IOMMU, or a more involved cleanup to move that responsibility out of drivers/iommu/Kconfig entirely and have arch/x86/Kconfig do something like "select IOMMU_DMA if IOMMU_API", as Jean suggested up-thread. In the specific context of IOMMU_DMA we're not talking about any kind of white-list, merely a one-off special case for one particular architecture. Robin. ^ permalink raw reply [flat|nested] 13+ messages in thread
end of thread, other threads:[~2020-02-17 14:10 UTC | newest] Thread overview: 13+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2020-02-14 16:04 [PATCH 0/3] virtio-iommu on non-devicetree platforms Jean-Philippe Brucker 2020-02-14 16:04 ` [PATCH 1/3] iommu/virtio: Add topology description to virtio-iommu config space Jean-Philippe Brucker 2020-02-14 16:04 ` [PATCH 2/3] PCI: Add DMA configuration for virtual platforms Jean-Philippe Brucker 2020-02-14 17:03 ` Robin Murphy 2020-02-17 9:12 ` Jean-Philippe Brucker 2020-02-14 16:04 ` [PATCH 3/3] iommu/virtio: Enable x86 support Jean-Philippe Brucker 2020-02-14 16:57 ` Robin Murphy 2020-02-16 9:50 ` Michael S. Tsirkin 2020-02-17 9:01 ` Jean-Philippe Brucker 2020-02-17 13:01 ` Michael S. Tsirkin 2020-02-17 13:22 ` Robin Murphy 2020-02-17 13:31 ` Michael S. Tsirkin 2020-02-17 14:10 ` Robin Murphy
This is a public inbox, see mirroring instructions for how to clone and mirror all data and code used for this inbox; as well as URLs for NNTP newsgroup(s).