[PATCH 2/8] xen: Make clear that swiotlb and biomerge are dealing with DMA address
Julien Grall
julien.grall at citrix.com
Tue Jul 28 08:02:43 PDT 2015
The swiotlb is required when programming a DMA address on ARM when a
device is not protected by an IOMMU.
In this case, the DMA address should always be equal to the machine address.
For DOM0 memory, Xen ensure it by have an identity mapping between the
guest address and host address. However, when mapping a foreign grant
reference, the 1:1 model doesn't work.
For ARM guest, most of the callers of pfn_to_mfn expects to get a GFN
(Guest Frame Number), i.e a PFN (Page Frame Number) from the Linux point
of view given that all ARM guest are auto-translated.
Even though the name pfn_to_mfn is misleading, we need to ensure that
those caller get a GFN and not by mistake a MFN. In pratical, I haven't
seen error related to this but we should fix it for the sake of
correctness.
In order to fix the implementation of pfn_to_mfn on ARM in a follow-up
patch, we have to introduce new helpers to return the DMA from a PFN and
the invert.
On x86, the new helpers will be an alias of pfn_to_mfn and mfn_to_pfn.
The helpers will be used in swiotlb and xen_biovec_phys_mergeable.
This is necessary in the latter because we have to ensure that the
biovec code will not try to merge a biovec using foreign page and
another using Linux memory.
Lastly, the helper mfn_to_local_pfn has been renamed to dnf_to_local_pfn
given that the only usage was in swiotlb.
Signed-off-by: Julien Grall <julien.grall at citrix.com>
Cc: Stefano Stabellini <stefano.stabellini at eu.citrix.com>
Cc: Russell King <linux at arm.linux.org.uk>
Cc: Konrad Rzeszutek Wilk <konrad.wilk at oracle.com>
Cc: Boris Ostrovsky <boris.ostrovsky at oracle.com>
Cc: David Vrabel <david.vrabel at citrix.com>
Cc: Thomas Gleixner <tglx at linutronix.de>
Cc: Ingo Molnar <mingo at redhat.com>
Cc: "H. Peter Anvin" <hpa at zytor.com>
Cc: x86 at kernel.org
Cc: linux-arm-kernel at lists.infradead.org
---
arch/arm/include/asm/xen/page.h | 23 +++++++++++++++++++++--
arch/arm/xen/mm.c | 4 ++--
arch/x86/include/asm/xen/page.h | 8 ++++++--
drivers/xen/biomerge.c | 6 +++---
drivers/xen/swiotlb-xen.c | 16 ++++++++--------
5 files changed, 40 insertions(+), 17 deletions(-)
diff --git a/arch/arm/include/asm/xen/page.h b/arch/arm/include/asm/xen/page.h
index c2e9dcd..6c9f6d2 100644
--- a/arch/arm/include/asm/xen/page.h
+++ b/arch/arm/include/asm/xen/page.h
@@ -52,7 +52,26 @@ static inline unsigned long mfn_to_pfn(unsigned long mfn)
return mfn;
}
-#define mfn_to_local_pfn(mfn) mfn_to_pfn(mfn)
+/* Pseudo-physical <-> DMA conversion */
+static inline unsigned long pfn_to_dfn(unsigned long pfn)
+{
+ unsigned long mfn;
+
+ if (phys_to_mach.rb_node != NULL) {
+ mfn = __pfn_to_mfn(pfn);
+ if (mfn != INVALID_P2M_ENTRY)
+ return mfn;
+ }
+
+ return pfn;
+}
+
+static inline unsigned long dfn_to_pfn(unsigned long dfn)
+{
+ return dfn;
+}
+
+#define dfn_to_local_pfn(dfn) dfn_to_pfn(dfn)
/* VIRT <-> MACHINE conversion */
#define virt_to_mfn(v) (pfn_to_mfn(virt_to_pfn(v)))
@@ -96,7 +115,7 @@ static inline bool set_phys_to_machine(unsigned long pfn, unsigned long mfn)
bool xen_arch_need_swiotlb(struct device *dev,
unsigned long pfn,
- unsigned long mfn);
+ unsigned long dfn);
unsigned long xen_get_swiotlb_free_pages(unsigned int order);
#endif /* _ASM_ARM_XEN_PAGE_H */
diff --git a/arch/arm/xen/mm.c b/arch/arm/xen/mm.c
index 03e75fe..12bde72 100644
--- a/arch/arm/xen/mm.c
+++ b/arch/arm/xen/mm.c
@@ -139,9 +139,9 @@ void __xen_dma_sync_single_for_device(struct device *hwdev,
bool xen_arch_need_swiotlb(struct device *dev,
unsigned long pfn,
- unsigned long mfn)
+ unsigned long dfn)
{
- return (!hypercall_cflush && (pfn != mfn) && !is_device_dma_coherent(dev));
+ return (!hypercall_cflush && (pfn != dfn) && !is_device_dma_coherent(dev));
}
int xen_create_contiguous_region(phys_addr_t pstart, unsigned int order,
diff --git a/arch/x86/include/asm/xen/page.h b/arch/x86/include/asm/xen/page.h
index c44a5d5..046e91a 100644
--- a/arch/x86/include/asm/xen/page.h
+++ b/arch/x86/include/asm/xen/page.h
@@ -178,6 +178,10 @@ static inline xpaddr_t machine_to_phys(xmaddr_t machine)
return XPADDR(PFN_PHYS(mfn_to_pfn(PFN_DOWN(machine.maddr))) | offset);
}
+/* Pseudo-physical <-> DMA conversion */
+#define pfn_to_dfn(pfn) pfn_to_mfn(pfn)
+#define dfn_to_pfn(dfn) mfn_to_pfn(dfn)
+
/*
* We detect special mappings in one of two ways:
* 1. If the MFN is an I/O page then Xen will set the m2p entry
@@ -198,7 +202,7 @@ static inline xpaddr_t machine_to_phys(xmaddr_t machine)
* require. In all the cases we care about, the FOREIGN_FRAME bit is
* masked (e.g., pfn_to_mfn()) so behaviour there is correct.
*/
-static inline unsigned long mfn_to_local_pfn(unsigned long mfn)
+static inline unsigned long dfn_to_local_pfn(unsigned long mfn)
{
unsigned long pfn;
@@ -264,7 +268,7 @@ void make_lowmem_page_readwrite(void *vaddr);
static inline bool xen_arch_need_swiotlb(struct device *dev,
unsigned long pfn,
- unsigned long mfn)
+ unsigned long dfn)
{
return false;
}
diff --git a/drivers/xen/biomerge.c b/drivers/xen/biomerge.c
index 0edb91c..4bc5866 100644
--- a/drivers/xen/biomerge.c
+++ b/drivers/xen/biomerge.c
@@ -6,10 +6,10 @@
bool xen_biovec_phys_mergeable(const struct bio_vec *vec1,
const struct bio_vec *vec2)
{
- unsigned long mfn1 = pfn_to_mfn(page_to_pfn(vec1->bv_page));
- unsigned long mfn2 = pfn_to_mfn(page_to_pfn(vec2->bv_page));
+ unsigned long dfn1 = pfn_to_dfn(page_to_pfn(vec1->bv_page));
+ unsigned long dfn2 = pfn_to_dfn(page_to_pfn(vec2->bv_page));
return __BIOVEC_PHYS_MERGEABLE(vec1, vec2) &&
- ((mfn1 == mfn2) || ((mfn1+1) == mfn2));
+ ((dfn1 == dfn2) || ((dfn1+1) == dfn2));
}
EXPORT_SYMBOL(xen_biovec_phys_mergeable);
diff --git a/drivers/xen/swiotlb-xen.c b/drivers/xen/swiotlb-xen.c
index 4c54932..52c3138 100644
--- a/drivers/xen/swiotlb-xen.c
+++ b/drivers/xen/swiotlb-xen.c
@@ -82,8 +82,8 @@ static u64 start_dma_addr;
*/
static inline dma_addr_t xen_phys_to_bus(phys_addr_t paddr)
{
- unsigned long mfn = pfn_to_mfn(PFN_DOWN(paddr));
- dma_addr_t dma = (dma_addr_t)mfn << PAGE_SHIFT;
+ unsigned long dfn = pfn_to_dfn(PFN_DOWN(paddr));
+ dma_addr_t dma = (dma_addr_t)dfn << PAGE_SHIFT;
dma |= paddr & ~PAGE_MASK;
@@ -92,7 +92,7 @@ static inline dma_addr_t xen_phys_to_bus(phys_addr_t paddr)
static inline phys_addr_t xen_bus_to_phys(dma_addr_t baddr)
{
- unsigned long pfn = mfn_to_pfn(PFN_DOWN(baddr));
+ unsigned long pfn = dfn_to_pfn(PFN_DOWN(baddr));
dma_addr_t dma = (dma_addr_t)pfn << PAGE_SHIFT;
phys_addr_t paddr = dma;
@@ -110,15 +110,15 @@ static int check_pages_physically_contiguous(unsigned long pfn,
unsigned int offset,
size_t length)
{
- unsigned long next_mfn;
+ unsigned long next_dfn;
int i;
int nr_pages;
- next_mfn = pfn_to_mfn(pfn);
+ next_dfn = pfn_to_dfn(pfn);
nr_pages = (offset + length + PAGE_SIZE-1) >> PAGE_SHIFT;
for (i = 1; i < nr_pages; i++) {
- if (pfn_to_mfn(++pfn) != ++next_mfn)
+ if (pfn_to_dfn(++pfn) != ++next_dfn)
return 0;
}
return 1;
@@ -138,8 +138,8 @@ static inline int range_straddles_page_boundary(phys_addr_t p, size_t size)
static int is_xen_swiotlb_buffer(dma_addr_t dma_addr)
{
- unsigned long mfn = PFN_DOWN(dma_addr);
- unsigned long pfn = mfn_to_local_pfn(mfn);
+ unsigned long dfn = PFN_DOWN(dma_addr);
+ unsigned long pfn = dfn_to_local_pfn(dfn);
phys_addr_t paddr;
/* If the address is outside our domain, it CAN
--
2.1.4
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