linux/drivers/pci/ecam.c
Russell King 8fe55ef233 PCI: Dynamically map ECAM regions
Attempting to boot 32-bit ARM kernels under QEMU's 3.x virt models fails
when we have more than 512M of RAM in the model as we run out of vmalloc
space for the PCI ECAM regions. This failure will be silent when running
libvirt, as the console in that situation is a PCI device.

In this configuration, the kernel maps the whole ECAM, which QEMU sets up
for 256 buses, even when maybe only seven buses are in use.  Each bus uses
1M of ECAM space, and ioremap() adds an additional guard page between
allocations. The kernel vmap allocator will align these regions to 512K,
resulting in each mapping eating 1.5M of vmalloc space. This means we need
384M of vmalloc space just to map all of these, which is very wasteful of
resources.

Fix this by only mapping the ECAM for buses we are going to be using.  In
my setups, this is around seven buses in most guests, which is 10.5M of
vmalloc space - way smaller than the 384M that would otherwise be required.
This also means that the kernel can boot without forcing extra RAM into
highmem with the vmalloc= argument, or decreasing the virtual RAM available
to the guest.

Suggested-by: Arnd Bergmann <arnd@arndb.de>
Link: https://lore.kernel.org/r/E1lhCAV-0002yb-50@rmk-PC.armlinux.org.uk
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
2021-06-16 17:20:40 -05:00

234 lines
5.6 KiB
C

// SPDX-License-Identifier: GPL-2.0
/*
* Copyright 2016 Broadcom
*/
#include <linux/device.h>
#include <linux/io.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/pci.h>
#include <linux/pci-ecam.h>
#include <linux/slab.h>
/*
* On 64-bit systems, we do a single ioremap for the whole config space
* since we have enough virtual address range available. On 32-bit, we
* ioremap the config space for each bus individually.
*/
static const bool per_bus_mapping = !IS_ENABLED(CONFIG_64BIT);
/*
* Create a PCI config space window
* - reserve mem region
* - alloc struct pci_config_window with space for all mappings
* - ioremap the config space
*/
struct pci_config_window *pci_ecam_create(struct device *dev,
struct resource *cfgres, struct resource *busr,
const struct pci_ecam_ops *ops)
{
unsigned int bus_shift = ops->bus_shift;
struct pci_config_window *cfg;
unsigned int bus_range, bus_range_max, bsz;
struct resource *conflict;
int err;
if (busr->start > busr->end)
return ERR_PTR(-EINVAL);
cfg = kzalloc(sizeof(*cfg), GFP_KERNEL);
if (!cfg)
return ERR_PTR(-ENOMEM);
/* ECAM-compliant platforms need not supply ops->bus_shift */
if (!bus_shift)
bus_shift = PCIE_ECAM_BUS_SHIFT;
cfg->parent = dev;
cfg->ops = ops;
cfg->busr.start = busr->start;
cfg->busr.end = busr->end;
cfg->busr.flags = IORESOURCE_BUS;
cfg->bus_shift = bus_shift;
bus_range = resource_size(&cfg->busr);
bus_range_max = resource_size(cfgres) >> bus_shift;
if (bus_range > bus_range_max) {
bus_range = bus_range_max;
cfg->busr.end = busr->start + bus_range - 1;
dev_warn(dev, "ECAM area %pR can only accommodate %pR (reduced from %pR desired)\n",
cfgres, &cfg->busr, busr);
}
bsz = 1 << bus_shift;
cfg->res.start = cfgres->start;
cfg->res.end = cfgres->end;
cfg->res.flags = IORESOURCE_MEM | IORESOURCE_BUSY;
cfg->res.name = "PCI ECAM";
conflict = request_resource_conflict(&iomem_resource, &cfg->res);
if (conflict) {
err = -EBUSY;
dev_err(dev, "can't claim ECAM area %pR: address conflict with %s %pR\n",
&cfg->res, conflict->name, conflict);
goto err_exit;
}
if (per_bus_mapping) {
cfg->winp = kcalloc(bus_range, sizeof(*cfg->winp), GFP_KERNEL);
if (!cfg->winp)
goto err_exit_malloc;
} else {
cfg->win = pci_remap_cfgspace(cfgres->start, bus_range * bsz);
if (!cfg->win)
goto err_exit_iomap;
}
if (ops->init) {
err = ops->init(cfg);
if (err)
goto err_exit;
}
dev_info(dev, "ECAM at %pR for %pR\n", &cfg->res, &cfg->busr);
return cfg;
err_exit_iomap:
dev_err(dev, "ECAM ioremap failed\n");
err_exit_malloc:
err = -ENOMEM;
err_exit:
pci_ecam_free(cfg);
return ERR_PTR(err);
}
EXPORT_SYMBOL_GPL(pci_ecam_create);
void pci_ecam_free(struct pci_config_window *cfg)
{
int i;
if (per_bus_mapping) {
if (cfg->winp) {
for (i = 0; i < resource_size(&cfg->busr); i++)
if (cfg->winp[i])
iounmap(cfg->winp[i]);
kfree(cfg->winp);
}
} else {
if (cfg->win)
iounmap(cfg->win);
}
if (cfg->res.parent)
release_resource(&cfg->res);
kfree(cfg);
}
EXPORT_SYMBOL_GPL(pci_ecam_free);
static int pci_ecam_add_bus(struct pci_bus *bus)
{
struct pci_config_window *cfg = bus->sysdata;
unsigned int bsz = 1 << cfg->bus_shift;
unsigned int busn = bus->number;
phys_addr_t start;
if (!per_bus_mapping)
return 0;
if (busn < cfg->busr.start || busn > cfg->busr.end)
return -EINVAL;
busn -= cfg->busr.start;
start = cfg->res.start + busn * bsz;
cfg->winp[busn] = pci_remap_cfgspace(start, bsz);
if (!cfg->winp[busn])
return -ENOMEM;
return 0;
}
static void pci_ecam_remove_bus(struct pci_bus *bus)
{
struct pci_config_window *cfg = bus->sysdata;
unsigned int busn = bus->number;
if (!per_bus_mapping || busn < cfg->busr.start || busn > cfg->busr.end)
return;
busn -= cfg->busr.start;
if (cfg->winp[busn]) {
iounmap(cfg->winp[busn]);
cfg->winp[busn] = NULL;
}
}
/*
* Function to implement the pci_ops ->map_bus method
*/
void __iomem *pci_ecam_map_bus(struct pci_bus *bus, unsigned int devfn,
int where)
{
struct pci_config_window *cfg = bus->sysdata;
unsigned int bus_shift = cfg->ops->bus_shift;
unsigned int devfn_shift = cfg->ops->bus_shift - 8;
unsigned int busn = bus->number;
void __iomem *base;
u32 bus_offset, devfn_offset;
if (busn < cfg->busr.start || busn > cfg->busr.end)
return NULL;
busn -= cfg->busr.start;
if (per_bus_mapping) {
base = cfg->winp[busn];
busn = 0;
} else
base = cfg->win;
if (cfg->ops->bus_shift) {
bus_offset = (busn & PCIE_ECAM_BUS_MASK) << bus_shift;
devfn_offset = (devfn & PCIE_ECAM_DEVFN_MASK) << devfn_shift;
where &= PCIE_ECAM_REG_MASK;
return base + (bus_offset | devfn_offset | where);
}
return base + PCIE_ECAM_OFFSET(busn, devfn, where);
}
EXPORT_SYMBOL_GPL(pci_ecam_map_bus);
/* ECAM ops */
const struct pci_ecam_ops pci_generic_ecam_ops = {
.pci_ops = {
.add_bus = pci_ecam_add_bus,
.remove_bus = pci_ecam_remove_bus,
.map_bus = pci_ecam_map_bus,
.read = pci_generic_config_read,
.write = pci_generic_config_write,
}
};
EXPORT_SYMBOL_GPL(pci_generic_ecam_ops);
#if defined(CONFIG_ACPI) && defined(CONFIG_PCI_QUIRKS)
/* ECAM ops for 32-bit access only (non-compliant) */
const struct pci_ecam_ops pci_32b_ops = {
.pci_ops = {
.add_bus = pci_ecam_add_bus,
.remove_bus = pci_ecam_remove_bus,
.map_bus = pci_ecam_map_bus,
.read = pci_generic_config_read32,
.write = pci_generic_config_write32,
}
};
/* ECAM ops for 32-bit read only (non-compliant) */
const struct pci_ecam_ops pci_32b_read_ops = {
.pci_ops = {
.add_bus = pci_ecam_add_bus,
.remove_bus = pci_ecam_remove_bus,
.map_bus = pci_ecam_map_bus,
.read = pci_generic_config_read32,
.write = pci_generic_config_write,
}
};
#endif