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Date: Thu, 02 Apr 2009 00:12:44 -0700
From: Jeremy Fitzhardinge <jeremy@...p.org>
To: FUJITA Tomonori <fujita.tomonori@....ntt.co.jp>
CC: x86@...nel.org, mingo@...e.hu, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] swiotlb updates for Xen dom0
FUJITA Tomonori wrote:
> On Tue, 31 Mar 2009 15:52:06 -0700
> Jeremy Fitzhardinge <jeremy@...p.org> wrote:
>
>
>> This series adds Xen support to x86 swiotlb. This is mostly a matter of
>> adding some Xen code into the existing hooks in pci-swiotlb_64.c:
>> - swiotlb_alloc_boot
>> - swiotlb_arch_range_needs_mapping
>> - swiotlb_phys_to_bus/bus_to_phys
>>
>> These hooks are conditional on xen_pv_domain(), which compiles to a
>> constant 0 when CONFIG_XEN is not enabled (and is a simple variable
>> read when it is).
>>
>> All the Xen-specific code is in xen-iommu.c.
>>
>> This series is just the patches which touch lib/swiotlb.c or
>> pci-swiotlb_64.c. You can see them with more context in:
>> git://git.kernel.org/pub/scm/linux/kernel/git/jeremy/xen.git for-linus/xen/dom0/swiotlb
>>
>> Thanks,
>> J
>>
>> arch/x86/kernel/pci-swiotlb_64.c | 31 ++++++++++++++++-
>> arch/x86/xen/Kconfig | 1
>> drivers/pci/xen-iommu.c | 68 ++++++++++++++++++++++++++++++++++++---
>> include/xen/swiotlb.h | 38 +++++++++++++++++++++
>> lib/swiotlb.c | 3 +
>> 5 files changed, 133 insertions(+), 8 deletions(-)
>>
>
> This patchset looks ugly.
>
> You add 'if we are Xen, we do A. We do B if not' code into 6 functions
> though pic-swiotlb_64.c has only 8 functions. In addition, 5 of 8
> functions were added for Xen.
>
> Why can't you have something like arch/x86/xen/pci-swiotlb.c, which
> works as arch/x86/kernel/pci-swiotlb_64.c? That should be much
> cleaner.
>
Sure. Something like this? (Applied on top of the rest of the series,
after kernel/pci-swiotlb_64.c => pci_swiotlb.c) It leaves one if(xen)
in the init function, but its consistent with the other clauses setting
swiotlb=1.
My only concern with this scheme is that if there's ever a non-Xen x86
user who wants to override these functions, we'll need to move them back
out into a common file because its not possible to have two overriding
definitions for a weak function (one hopes that the linker will warn if
that arises).
J
Subject: [PATCH] xen/swiotlb: move all Xen-specific swiotlb operations to separate file
Most of these functions are no-ops on non-Xen systems, so we can fall
back to the default functions if CONFIG_XEN is not defined.
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@...rix.com>
diff --git a/arch/x86/kernel/pci-swiotlb.c b/arch/x86/kernel/pci-swiotlb.c
index ead556f..2d8dd35 100644
--- a/arch/x86/kernel/pci-swiotlb.c
+++ b/arch/x86/kernel/pci-swiotlb.c
@@ -12,54 +12,9 @@
#include <asm/dma.h>
#include <xen/swiotlb.h>
-#include <asm/xen/hypervisor.h>
int swiotlb __read_mostly;
-void * __init swiotlb_alloc_boot(size_t size, unsigned long nslabs)
-{
- void *ret = alloc_bootmem_low_pages(size);
-
- if (ret && xen_pv_domain())
- xen_swiotlb_fixup(ret, size, nslabs);
-
- return ret;
-}
-
-void *swiotlb_alloc(unsigned order, unsigned long nslabs)
-{
- void *ret = (void *)__get_free_pages(GFP_DMA | __GFP_NOWARN, order);
-
- if (ret && xen_pv_domain())
- xen_swiotlb_fixup(ret, 1u << order, nslabs);
-
- return ret;
-}
-
-dma_addr_t swiotlb_phys_to_bus(struct device *hwdev, phys_addr_t paddr)
-{
- if (xen_pv_domain())
- return xen_phys_to_bus(paddr);
-
- return paddr;
-}
-
-phys_addr_t swiotlb_bus_to_phys(dma_addr_t baddr)
-{
- if (xen_pv_domain())
- return xen_bus_to_phys(baddr);
-
- return baddr;
-}
-
-int swiotlb_arch_range_needs_mapping(phys_addr_t paddr, size_t size)
-{
- if (xen_pv_domain())
- return xen_range_needs_mapping(paddr, size);
-
- return 0;
-}
-
static void *x86_swiotlb_alloc_coherent(struct device *hwdev, size_t size,
dma_addr_t *dma_handle, gfp_t flags)
{
diff --git a/arch/x86/xen/Makefile b/arch/x86/xen/Makefile
index 639965a..b021e72 100644
--- a/arch/x86/xen/Makefile
+++ b/arch/x86/xen/Makefile
@@ -12,4 +12,4 @@ obj-y := enlighten.o setup.o multicalls.o mmu.o irq.o \
obj-$(CONFIG_SMP) += smp.o spinlock.o
obj-$(CONFIG_XEN_DEBUG_FS) += debugfs.o
obj-$(CONFIG_XEN_DOM0) += vga.o apic.o
-obj-$(CONFIG_XEN_DOM0_PCI) += pci.o
\ No newline at end of file
+obj-$(CONFIG_XEN_DOM0_PCI) += pci.o pci-swiotlb.o
\ No newline at end of file
diff --git a/arch/x86/xen/pci-swiotlb.c b/arch/x86/xen/pci-swiotlb.c
new file mode 100644
index 0000000..82b2291
--- /dev/null
+++ b/arch/x86/xen/pci-swiotlb.c
@@ -0,0 +1,51 @@
+#include <linux/bootmem.h>
+#include <linux/gfp.h>
+
+#include <xen/swiotlb.h>
+#include <asm/xen/hypervisor.h>
+
+/*
+ * This file defines overrides for weak functions with default
+ * implementations in lib/swiotlb.c.
+ */
+
+void * __init swiotlb_alloc_boot(size_t size, unsigned long nslabs)
+{
+ void *ret = alloc_bootmem_low_pages(size);
+
+ if (ret && xen_pv_domain())
+ xen_swiotlb_fixup(ret, size, nslabs);
+
+ return ret;
+}
+
+void *swiotlb_alloc(unsigned order, unsigned long nslabs)
+{
+ /* Never called on x86. Warn, just in case. */
+ WARN_ON(1);
+ return NULL;
+}
+
+dma_addr_t swiotlb_phys_to_bus(struct device *hwdev, phys_addr_t paddr)
+{
+ if (xen_pv_domain())
+ return xen_phys_to_bus(paddr);
+
+ return paddr;
+}
+
+phys_addr_t swiotlb_bus_to_phys(dma_addr_t baddr)
+{
+ if (xen_pv_domain())
+ return xen_bus_to_phys(baddr);
+
+ return baddr;
+}
+
+int swiotlb_arch_range_needs_mapping(phys_addr_t paddr, size_t size)
+{
+ if (xen_pv_domain())
+ return xen_range_needs_mapping(paddr, size);
+
+ return 0;
+}
--
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