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PCI: Provide Kconfig option for lockless config space accessors

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The generic PCI configuration space accessors are globally serialized via
pci_lock. On larger systems this causes massive lock contention when the
configuration space has to be accessed frequently. One such access pattern
is the Intel Uncore performance counter unit.

Provide a kernel config option which can be selected by an architecture
when the low level PCI configuration space accessors in the architecture
use their own serialization or can operate completely lockless.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Bjorn Helgaas <helgaas@kernel.org>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: linux-pci@vger.kernel.org
Link: http://lkml.kernel.org/r/20170316215057.205961140@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
This commit is contained in:
Thomas Gleixner 2017-03-16 22:50:06 +01:00
parent bb290fda87
commit 714fe383d6
2 changed files with 15 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
drivers/pci/Kconfig
View File

@ -86,6 +86,9 @@ config PCI_ATS
config PCI_ECAM
bool
config PCI_LOCKLESS_CONFIG
bool
config PCI_IOV
bool "PCI IOV support"
depends on PCI

16
drivers/pci/access.c
View File

@ -25,6 +25,14 @@ DEFINE_RAW_SPINLOCK(pci_lock);
#define PCI_word_BAD (pos & 1)
#define PCI_dword_BAD (pos & 3)
#ifdef CONFIG_PCI_LOCKLESS_CONFIG
# define pci_lock_config(f) do { (void)(f); } while (0)
# define pci_unlock_config(f) do { (void)(f); } while (0)
#else
# define pci_lock_config(f) raw_spin_lock_irqsave(&pci_lock, f)
# define pci_unlock_config(f) raw_spin_unlock_irqrestore(&pci_lock, f)
#endif
#define PCI_OP_READ(size, type, len) \
int pci_bus_read_config_##size \
(struct pci_bus *bus, unsigned int devfn, int pos, type *value) \
@ -33,10 +41,10 @@ int pci_bus_read_config_##size \
unsigned long flags; \
u32 data = 0; \
if (PCI_##size##_BAD) return PCIBIOS_BAD_REGISTER_NUMBER; \
raw_spin_lock_irqsave(&pci_lock, flags); \
pci_lock_config(flags); \
res = bus->ops->read(bus, devfn, pos, len, &data); \
*value = (type)data; \
raw_spin_unlock_irqrestore(&pci_lock, flags); \
pci_unlock_config(flags); \
return res; \
}
@ -47,9 +55,9 @@ int pci_bus_write_config_##size \
int res; \
unsigned long flags; \
if (PCI_##size##_BAD) return PCIBIOS_BAD_REGISTER_NUMBER; \
raw_spin_lock_irqsave(&pci_lock, flags); \
pci_lock_config(flags); \
res = bus->ops->write(bus, devfn, pos, len, value); \
raw_spin_unlock_irqrestore(&pci_lock, flags); \
pci_unlock_config(flags); \
return res; \
}