fenghua.yu at intel
Jun 18, 2009, 11:05 AM
Views: 197
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[PATCH 1/2] IOMMU Identity Mapping Support: iommu_identity_mapping definition
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IOMMU Identity Mapping Support: iommu_identity_mapping definition
Identity mapping for IOMMU defines a single domain to 1:1 map all pci devices
to all usable memory.
This will reduces map/unmap overhead in DMA API's and improve IOMMU performance.
On 10Gb network cards, Netperf shows no performance degradation compared to
non-IOMMU performance.
This method may lose some of DMA remapping benefits like isolation.
The first patch defines iommu_identity_mapping varialbe which controls the
identity mapping code and is 0 by default.
Signed-off-by: Fenghua Yu <fenghua.yu[at]intel.com>
---
Documentation/kernel-parameters.txt | 1 +
arch/ia64/include/asm/iommu.h | 2 ++
arch/ia64/kernel/pci-dma.c | 1 +
arch/x86/include/asm/iommu.h | 1 +
arch/x86/kernel/pci-dma.c | 5 +++++
5 files changed, 10 insertions(+)
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 4b78797..6b1d7b4 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -988,6 +988,7 @@ and is between 256 and 4096 characters. It is defined in the file
forcesac
soft
pt [x86, IA64]
+ identity [x86, IA64]
io7= [HW] IO7 for Marvel based alpha systems
See comment before marvel_specify_io7 in
diff --git a/arch/ia64/include/asm/iommu.h b/arch/ia64/include/asm/iommu.h
index 745e095..cc6d59f 100644
--- a/arch/ia64/include/asm/iommu.h
+++ b/arch/ia64/include/asm/iommu.h
@@ -11,8 +11,10 @@ extern int force_iommu, no_iommu;
extern int iommu_detected;
#ifdef CONFIG_DMAR
extern int iommu_pass_through;
+extern int iommu_identity_mapping;
#else
#define iommu_pass_through (0)
+#define iommu_identity_mapping (0)
#endif
extern void iommu_dma_init(void);
extern void machvec_init(const char *name);
diff --git a/arch/ia64/kernel/pci-dma.c b/arch/ia64/kernel/pci-dma.c
index 0569596..15b8555 100644
--- a/arch/ia64/kernel/pci-dma.c
+++ b/arch/ia64/kernel/pci-dma.c
@@ -33,6 +33,7 @@ int force_iommu __read_mostly;
#endif
int iommu_pass_through;
+int iommu_identity_mapping;
/* Dummy device used for NULL arguments (normally ISA). Better would
be probably a smaller DMA mask, but this is bug-to-bug compatible
diff --git a/arch/x86/include/asm/iommu.h b/arch/x86/include/asm/iommu.h
index fd6d21b..d2aee4a 100644
--- a/arch/x86/include/asm/iommu.h
+++ b/arch/x86/include/asm/iommu.h
@@ -7,6 +7,7 @@ extern struct dma_map_ops nommu_dma_ops;
extern int force_iommu, no_iommu;
extern int iommu_detected;
extern int iommu_pass_through;
+extern int iommu_identity_mapping;
/* 10 seconds */
#define DMAR_OPERATION_TIMEOUT ((cycles_t) tsc_khz*10*1000)
diff --git a/arch/x86/kernel/pci-dma.c b/arch/x86/kernel/pci-dma.c
index 049005e..489179a 100644
--- a/arch/x86/kernel/pci-dma.c
+++ b/arch/x86/kernel/pci-dma.c
@@ -33,6 +33,7 @@ int no_iommu __read_mostly;
int iommu_detected __read_mostly = 0;
int iommu_pass_through;
+int iommu_identity_mapping;
dma_addr_t bad_dma_address __read_mostly = 0;
EXPORT_SYMBOL(bad_dma_address);
@@ -208,6 +209,10 @@ static __init int iommu_setup(char *p)
forbid_dac = -1;
return 1;
}
+ if (!strncmp(p, "identity", 8)) {
+ iommu_identity_mapping = 1;
+ return 1;
+ }
#ifdef CONFIG_SWIOTLB
if (!strncmp(p, "soft", 4))
swiotlb = 1;
--
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[PATCH 1/2] IOMMU Identity Mapping Support: iommu_identity_mapping definition
