[PATCH -mm] ia64: make IOMMU respect the segment boundary limits

[PATCH -mm] ia64: make IOMMU respect the segment boundary limits

[FUJITA Tomonori]

This patch is another sequel to my patchset that fixes iommu segment
boundary problems, that is, IOMMUs allocate memory areas without
considering a low level driver's segment boundary limits:

http://www.mail-archive.com/linux-scsi@vger.kernel.org/msg11919.html

This patchset fixes the IA64 IOMMU code.

This assumes that ioc->ibase is on iovp_size boundary. If not, please
let me know. I'll fix the patch.

From: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Subject: [PATCH -mm] ia64: make IOMMU respect the segment boundary limits

This makes IA64's IOMMU implementation not allocate a memory area
spanning LLD's segment boundary.

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
---
 arch/ia64/Kconfig               |    3 ++
 arch/ia64/hp/common/sba_iommu.c |   56 +++++++++++++++++++++++++++------------
 2 files changed, 42 insertions(+), 17 deletions(-)

diff --git a/arch/ia64/Kconfig b/arch/ia64/Kconfig
index 8fa3faf..1b73ffe 100644
--- a/arch/ia64/Kconfig
+++ b/arch/ia64/Kconfig
@@ -611,6 +611,9 @@ config IRQ_PER_CPU
 	bool
 	default y
 
+config IOMMU_HELPER
+	def_bool (IA64_HP_ZX1 || IA64_HP_ZX1_SWIOTLB || IA64_GENERIC)
+
 source "arch/ia64/hp/sim/Kconfig"
 
 source "arch/ia64/Kconfig.debug"
diff --git a/arch/ia64/hp/common/sba_iommu.c b/arch/ia64/hp/common/sba_iommu.c
index 523eae6..9409de5 100644
--- a/arch/ia64/hp/common/sba_iommu.c
+++ b/arch/ia64/hp/common/sba_iommu.c
@@ -35,6 +35,7 @@
 #include <linux/nodemask.h>
 #include <linux/bitops.h>         /* hweight64() */
 #include <linux/crash_dump.h>
+#include <linux/iommu-helper.h>
 
 #include <asm/delay.h>		/* ia64_get_itc() */
 #include <asm/io.h>
@@ -460,6 +461,13 @@ get_iovp_order (unsigned long size)
 	return order;
 }
 
+static unsigned long ptr_to_pide(struct ioc *ioc, unsigned long *res_ptr,
+				 unsigned int bitshiftcnt)
+{
+	return (((unsigned long)res_ptr - (unsigned long)ioc->res_map) << 3)
+		+ bitshiftcnt;
+}
+
 /**
  * sba_search_bitmap - find free space in IO PDIR resource bitmap
  * @ioc: IO MMU structure which owns the pdir we are interested in.
@@ -471,15 +479,25 @@ get_iovp_order (unsigned long size)
  * Cool perf optimization: search for log2(size) bits at a time.
  */
 static SBA_INLINE unsigned long
-sba_search_bitmap(struct ioc *ioc, unsigned long bits_wanted, int use_hint)
+sba_search_bitmap(struct ioc *ioc, struct device *dev,
+		  unsigned long bits_wanted, int use_hint)
 {
 	unsigned long *res_ptr;
 	unsigned long *res_end = (unsigned long *) &(ioc->res_map[ioc->res_size]);
-	unsigned long flags, pide = ~0UL;
+	unsigned long flags, pide = ~0UL, tpide;
+	unsigned long boundary_size;
+	unsigned long shift;
+	int ret;
 
 	ASSERT(((unsigned long) ioc->res_hint & (sizeof(unsigned long) - 1UL)) = 0);
 	ASSERT(res_ptr < res_end);
 
+	boundary_size = (unsigned long long)dma_get_seg_boundary(dev) + 1;
+	boundary_size = ALIGN(boundary_size, 1ULL << iovp_shift) >> iovp_shift;
+
+	BUG_ON(ioc->ibase & ~iovp_mask);
+	shift = ioc->ibase >> iovp_shift;
+
 	spin_lock_irqsave(&ioc->res_lock, flags);
 
 	/* Allow caller to force a search through the entire resource space */
@@ -504,9 +522,7 @@ sba_search_bitmap(struct ioc *ioc, unsigned long bits_wanted, int use_hint)
 			if (likely(*res_ptr != ~0UL)) {
 				bitshiftcnt = ffz(*res_ptr);
 				*res_ptr |= (1UL << bitshiftcnt);
-				pide = ((unsigned long)res_ptr - (unsigned long)ioc->res_map);
-				pide <<= 3;	/* convert to bit address */
-				pide += bitshiftcnt;
+				pide = ptr_to_pide(ioc, res_ptr, bitshiftcnt);
 				ioc->res_bitshift = bitshiftcnt + bits_wanted;
 				goto found_it;
 			}
@@ -535,11 +551,13 @@ sba_search_bitmap(struct ioc *ioc, unsigned long bits_wanted, int use_hint)
 			DBG_RES("    %p %lx %lx\n", res_ptr, mask, *res_ptr);
 			ASSERT(0 != mask);
 			for (; mask ; mask <<= o, bitshiftcnt += o) {
-				if(0 = ((*res_ptr) & mask)) {
+				tpide = ptr_to_pide(ioc, res_ptr, bitshiftcnt);
+				ret = iommu_is_span_boundary(tpide, bits_wanted,
+							     shift,
+							     boundary_size);
+				if ((0 = ((*res_ptr) & mask)) && !ret) {
 					*res_ptr |= mask;     /* mark resources busy! */
-					pide = ((unsigned long)res_ptr - (unsigned long)ioc->res_map);
-					pide <<= 3;	/* convert to bit address */
-					pide += bitshiftcnt;
+					pide = tpide;
 					ioc->res_bitshift = bitshiftcnt + bits_wanted;
 					goto found_it;
 				}
@@ -560,6 +578,11 @@ sba_search_bitmap(struct ioc *ioc, unsigned long bits_wanted, int use_hint)
 		end = res_end - qwords;
 
 		for (; res_ptr < end; res_ptr++) {
+			tpide = ptr_to_pide(ioc, res_ptr, 0);
+			ret = iommu_is_span_boundary(tpide, bits_wanted,
+						     shift, boundary_size);
+			if (ret)
+				goto next_ptr;
 			for (i = 0 ; i < qwords ; i++) {
 				if (res_ptr[i] != 0)
 					goto next_ptr;
@@ -572,8 +595,7 @@ sba_search_bitmap(struct ioc *ioc, unsigned long bits_wanted, int use_hint)
 				res_ptr[i] = ~0UL;
 			res_ptr[i] |= RESMAP_MASK(bits);
 
-			pide = ((unsigned long)res_ptr - (unsigned long)ioc->res_map);
-			pide <<= 3;	/* convert to bit address */
+			pide = tpide;
 			res_ptr += qwords;
 			ioc->res_bitshift = bits;
 			goto found_it;
@@ -605,7 +627,7 @@ found_it:
  * resource bit map.
  */
 static int
-sba_alloc_range(struct ioc *ioc, size_t size)
+sba_alloc_range(struct ioc *ioc, struct device *dev, size_t size)
 {
 	unsigned int pages_needed = size >> iovp_shift;
 #ifdef PDIR_SEARCH_TIMING
@@ -622,9 +644,9 @@ sba_alloc_range(struct ioc *ioc, size_t size)
 	/*
 	** "seek and ye shall find"...praying never hurts either...
 	*/
-	pide = sba_search_bitmap(ioc, pages_needed, 1);
+	pide = sba_search_bitmap(ioc, dev, pages_needed, 1);
 	if (unlikely(pide >= (ioc->res_size << 3))) {
-		pide = sba_search_bitmap(ioc, pages_needed, 0);
+		pide = sba_search_bitmap(ioc, dev, pages_needed, 0);
 		if (unlikely(pide >= (ioc->res_size << 3))) {
 #if DELAYED_RESOURCE_CNT > 0
 			unsigned long flags;
@@ -653,7 +675,7 @@ sba_alloc_range(struct ioc *ioc, size_t size)
 			}
 			spin_unlock_irqrestore(&ioc->saved_lock, flags);
 
-			pide = sba_search_bitmap(ioc, pages_needed, 0);
+			pide = sba_search_bitmap(ioc, dev, pages_needed, 0);
 			if (unlikely(pide >= (ioc->res_size << 3)))
 				panic(__FILE__ ": I/O MMU @ %p is out of mapping resources\n",
 				      ioc->ioc_hpa);
@@ -936,7 +958,7 @@ sba_map_single(struct device *dev, void *addr, size_t size, int dir)
 	spin_unlock_irqrestore(&ioc->res_lock, flags);
 #endif
 
-	pide = sba_alloc_range(ioc, size);
+	pide = sba_alloc_range(ioc, dev, size);
 
 	iovp = (dma_addr_t) pide << iovp_shift;
 
@@ -1373,7 +1395,7 @@ sba_coalesce_chunks(struct ioc *ioc, struct device *dev,
 		dma_len = (dma_len + dma_offset + ~iovp_mask) & iovp_mask;
 		ASSERT(dma_len <= DMA_CHUNK_SIZE);
 		dma_sg->dma_address = (dma_addr_t) (PIDE_FLAG
-			| (sba_alloc_range(ioc, dma_len) << iovp_shift)
+			| (sba_alloc_range(ioc, dev, dma_len) << iovp_shift)
 			| dma_offset);
 		n_mappings++;
 	}
-- 
1.5.3.7

[PATCH -mm] ia64: make IOMMU respect the segment boundary limits

[FUJITA Tomonori]

This patch is another sequel to my patchset that fixes iommu segment
boundary problems, that is, IOMMUs allocate memory areas without
considering a low level driver's segment boundary limits:

http://www.mail-archive.com/linux-scsi@vger.kernel.org/msg11919.html

This patchset fixes the IA64 IOMMU code.

This assumes that ioc->ibase is on iovp_size boundary. If not, please
let me know. I'll fix the patch.

=
From: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Subject: [PATCH -mm] ia64: make IOMMU respect the segment boundary limits

This makes IA64's IOMMU implementation not allocate a memory area
spanning LLD's segment boundary.

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
---
 arch/ia64/Kconfig               |    3 ++
 arch/ia64/hp/common/sba_iommu.c |   56 +++++++++++++++++++++++++++------------
 2 files changed, 42 insertions(+), 17 deletions(-)

diff --git a/arch/ia64/Kconfig b/arch/ia64/Kconfig
index 8fa3faf..1b73ffe 100644
--- a/arch/ia64/Kconfig
+++ b/arch/ia64/Kconfig
@@ -611,6 +611,9 @@ config IRQ_PER_CPU
 	bool
 	default y
 
+config IOMMU_HELPER
+	def_bool (IA64_HP_ZX1 || IA64_HP_ZX1_SWIOTLB || IA64_GENERIC)
+
 source "arch/ia64/hp/sim/Kconfig"
 
 source "arch/ia64/Kconfig.debug"
diff --git a/arch/ia64/hp/common/sba_iommu.c b/arch/ia64/hp/common/sba_iommu.c
index 523eae6..9409de5 100644
--- a/arch/ia64/hp/common/sba_iommu.c
+++ b/arch/ia64/hp/common/sba_iommu.c
@@ -35,6 +35,7 @@
 #include <linux/nodemask.h>
 #include <linux/bitops.h>         /* hweight64() */
 #include <linux/crash_dump.h>
+#include <linux/iommu-helper.h>
 
 #include <asm/delay.h>		/* ia64_get_itc() */
 #include <asm/io.h>
@@ -460,6 +461,13 @@ get_iovp_order (unsigned long size)
 	return order;
 }
 
+static unsigned long ptr_to_pide(struct ioc *ioc, unsigned long *res_ptr,
+				 unsigned int bitshiftcnt)
+{
+	return (((unsigned long)res_ptr - (unsigned long)ioc->res_map) << 3)
+		+ bitshiftcnt;
+}
+
 /**
  * sba_search_bitmap - find free space in IO PDIR resource bitmap
  * @ioc: IO MMU structure which owns the pdir we are interested in.
@@ -471,15 +479,25 @@ get_iovp_order (unsigned long size)
  * Cool perf optimization: search for log2(size) bits at a time.
  */
 static SBA_INLINE unsigned long
-sba_search_bitmap(struct ioc *ioc, unsigned long bits_wanted, int use_hint)
+sba_search_bitmap(struct ioc *ioc, struct device *dev,
+		  unsigned long bits_wanted, int use_hint)
 {
 	unsigned long *res_ptr;
 	unsigned long *res_end = (unsigned long *) &(ioc->res_map[ioc->res_size]);
-	unsigned long flags, pide = ~0UL;
+	unsigned long flags, pide = ~0UL, tpide;
+	unsigned long boundary_size;
+	unsigned long shift;
+	int ret;
 
 	ASSERT(((unsigned long) ioc->res_hint & (sizeof(unsigned long) - 1UL)) == 0);
 	ASSERT(res_ptr < res_end);
 
+	boundary_size = (unsigned long long)dma_get_seg_boundary(dev) + 1;
+	boundary_size = ALIGN(boundary_size, 1ULL << iovp_shift) >> iovp_shift;
+
+	BUG_ON(ioc->ibase & ~iovp_mask);
+	shift = ioc->ibase >> iovp_shift;
+
 	spin_lock_irqsave(&ioc->res_lock, flags);
 
 	/* Allow caller to force a search through the entire resource space */
@@ -504,9 +522,7 @@ sba_search_bitmap(struct ioc *ioc, unsigned long bits_wanted, int use_hint)
 			if (likely(*res_ptr != ~0UL)) {
 				bitshiftcnt = ffz(*res_ptr);
 				*res_ptr |= (1UL << bitshiftcnt);
-				pide = ((unsigned long)res_ptr - (unsigned long)ioc->res_map);
-				pide <<= 3;	/* convert to bit address */
-				pide += bitshiftcnt;
+				pide = ptr_to_pide(ioc, res_ptr, bitshiftcnt);
 				ioc->res_bitshift = bitshiftcnt + bits_wanted;
 				goto found_it;
 			}
@@ -535,11 +551,13 @@ sba_search_bitmap(struct ioc *ioc, unsigned long bits_wanted, int use_hint)
 			DBG_RES("    %p %lx %lx\n", res_ptr, mask, *res_ptr);
 			ASSERT(0 != mask);
 			for (; mask ; mask <<= o, bitshiftcnt += o) {
-				if(0 == ((*res_ptr) & mask)) {
+				tpide = ptr_to_pide(ioc, res_ptr, bitshiftcnt);
+				ret = iommu_is_span_boundary(tpide, bits_wanted,
+							     shift,
+							     boundary_size);
+				if ((0 == ((*res_ptr) & mask)) && !ret) {
 					*res_ptr |= mask;     /* mark resources busy! */
-					pide = ((unsigned long)res_ptr - (unsigned long)ioc->res_map);
-					pide <<= 3;	/* convert to bit address */
-					pide += bitshiftcnt;
+					pide = tpide;
 					ioc->res_bitshift = bitshiftcnt + bits_wanted;
 					goto found_it;
 				}
@@ -560,6 +578,11 @@ sba_search_bitmap(struct ioc *ioc, unsigned long bits_wanted, int use_hint)
 		end = res_end - qwords;
 
 		for (; res_ptr < end; res_ptr++) {
+			tpide = ptr_to_pide(ioc, res_ptr, 0);
+			ret = iommu_is_span_boundary(tpide, bits_wanted,
+						     shift, boundary_size);
+			if (ret)
+				goto next_ptr;
 			for (i = 0 ; i < qwords ; i++) {
 				if (res_ptr[i] != 0)
 					goto next_ptr;
@@ -572,8 +595,7 @@ sba_search_bitmap(struct ioc *ioc, unsigned long bits_wanted, int use_hint)
 				res_ptr[i] = ~0UL;
 			res_ptr[i] |= RESMAP_MASK(bits);
 
-			pide = ((unsigned long)res_ptr - (unsigned long)ioc->res_map);
-			pide <<= 3;	/* convert to bit address */
+			pide = tpide;
 			res_ptr += qwords;
 			ioc->res_bitshift = bits;
 			goto found_it;
@@ -605,7 +627,7 @@ found_it:
  * resource bit map.
  */
 static int
-sba_alloc_range(struct ioc *ioc, size_t size)
+sba_alloc_range(struct ioc *ioc, struct device *dev, size_t size)
 {
 	unsigned int pages_needed = size >> iovp_shift;
 #ifdef PDIR_SEARCH_TIMING
@@ -622,9 +644,9 @@ sba_alloc_range(struct ioc *ioc, size_t size)
 	/*
 	** "seek and ye shall find"...praying never hurts either...
 	*/
-	pide = sba_search_bitmap(ioc, pages_needed, 1);
+	pide = sba_search_bitmap(ioc, dev, pages_needed, 1);
 	if (unlikely(pide >= (ioc->res_size << 3))) {
-		pide = sba_search_bitmap(ioc, pages_needed, 0);
+		pide = sba_search_bitmap(ioc, dev, pages_needed, 0);
 		if (unlikely(pide >= (ioc->res_size << 3))) {
 #if DELAYED_RESOURCE_CNT > 0
 			unsigned long flags;
@@ -653,7 +675,7 @@ sba_alloc_range(struct ioc *ioc, size_t size)
 			}
 			spin_unlock_irqrestore(&ioc->saved_lock, flags);
 
-			pide = sba_search_bitmap(ioc, pages_needed, 0);
+			pide = sba_search_bitmap(ioc, dev, pages_needed, 0);
 			if (unlikely(pide >= (ioc->res_size << 3)))
 				panic(__FILE__ ": I/O MMU @ %p is out of mapping resources\n",
 				      ioc->ioc_hpa);
@@ -936,7 +958,7 @@ sba_map_single(struct device *dev, void *addr, size_t size, int dir)
 	spin_unlock_irqrestore(&ioc->res_lock, flags);
 #endif
 
-	pide = sba_alloc_range(ioc, size);
+	pide = sba_alloc_range(ioc, dev, size);
 
 	iovp = (dma_addr_t) pide << iovp_shift;
 
@@ -1373,7 +1395,7 @@ sba_coalesce_chunks(struct ioc *ioc, struct device *dev,
 		dma_len = (dma_len + dma_offset + ~iovp_mask) & iovp_mask;
 		ASSERT(dma_len <= DMA_CHUNK_SIZE);
 		dma_sg->dma_address = (dma_addr_t) (PIDE_FLAG
-			| (sba_alloc_range(ioc, dma_len) << iovp_shift)
+			| (sba_alloc_range(ioc, dev, dma_len) << iovp_shift)
 			| dma_offset);
 		n_mappings++;
 	}
-- 
1.5.3.7

Re: [PATCH -mm] ia64: make IOMMU respect the segment boundary

[Andrew Morton]

On Mon, 10 Mar 2008 22:17:20 +0900 FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp> wrote:

> This patch is another sequel to my patchset that fixes iommu segment
> boundary problems, that is, IOMMUs allocate memory areas without
> considering a low level driver's segment boundary limits:
> 
> http://www.mail-archive.com/linux-scsi@vger.kernel.org/msg11919.html

Please make this easier.

afacit the patches to which you refer are already in mainline, so this is
*not* a "-mm" patch.  It is needed in mainline, correct?

> This patchset fixes the IA64 IOMMU code.

And if it fixes a bug then it is needed in 2.6.25.

Is that correct?

> This assumes that ioc->ibase is on iovp_size boundary. If not, please
> let me know. I'll fix the patch.

Who is the person who who knows the answer to this?

Does this mean that the patch wasn't runtime tested?  If so, how do you
know there is a bug?

> > From: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
> Subject: [PATCH -mm] ia64: make IOMMU respect the segment boundary limits
> 
> This makes IA64's IOMMU implementation not allocate a memory area
> spanning LLD's segment boundary.

This changelog doesn't actually tell us that this patch fixed a bug.

It should tell us what the bug is, and how it fixed it, please.

> Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
> Cc: Tony Luck <tony.luck@intel.com>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> ---
>  arch/ia64/Kconfig               |    3 ++
>  arch/ia64/hp/common/sba_iommu.c |   56 +++++++++++++++++++++++++++------------

Re: [PATCH -mm] ia64: make IOMMU respect the segment boundary limits

[Andrew Morton]

On Mon, 10 Mar 2008 22:17:20 +0900 FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp> wrote:

> This patch is another sequel to my patchset that fixes iommu segment
> boundary problems, that is, IOMMUs allocate memory areas without
> considering a low level driver's segment boundary limits:
> 
> http://www.mail-archive.com/linux-scsi@vger.kernel.org/msg11919.html

Please make this easier.

afacit the patches to which you refer are already in mainline, so this is
*not* a "-mm" patch.  It is needed in mainline, correct?

> This patchset fixes the IA64 IOMMU code.

And if it fixes a bug then it is needed in 2.6.25.

Is that correct?

> This assumes that ioc->ibase is on iovp_size boundary. If not, please
> let me know. I'll fix the patch.

Who is the person who who knows the answer to this?

Does this mean that the patch wasn't runtime tested?  If so, how do you
know there is a bug?

> =
> From: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
> Subject: [PATCH -mm] ia64: make IOMMU respect the segment boundary limits
> 
> This makes IA64's IOMMU implementation not allocate a memory area
> spanning LLD's segment boundary.

This changelog doesn't actually tell us that this patch fixed a bug.

It should tell us what the bug is, and how it fixed it, please.

> Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
> Cc: Tony Luck <tony.luck@intel.com>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> ---
>  arch/ia64/Kconfig               |    3 ++
>  arch/ia64/hp/common/sba_iommu.c |   56 +++++++++++++++++++++++++++------------

Re: [PATCH -mm] ia64: make IOMMU respect the segment boundary

[FUJITA Tomonori]

On Mon, 10 Mar 2008 20:33:44 -0700
Andrew Morton <akpm@linux-foundation.org> wrote:

> On Mon, 10 Mar 2008 22:17:20 +0900 FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp> wrote:
> 
> > This patch is another sequel to my patchset that fixes iommu segment
> > boundary problems, that is, IOMMUs allocate memory areas without
> > considering a low level driver's segment boundary limits:
> > 
> > http://www.mail-archive.com/linux-scsi@vger.kernel.org/msg11919.html
> 
> Please make this easier.

Very sorry,


> afacit the patches to which you refer are already in mainline, so this is
> *not* a "-mm" patch.  It is needed in mainline, correct?

It's not needed immediately. Please apply it to -mm.


> > This patchset fixes the IA64 IOMMU code.
> 
> And if it fixes a bug then it is needed in 2.6.25.
> 
> Is that correct?

No, it isn't needed in 2.6.25. Sorry, I shouldn't have used 'fixes'.

IOMMUs allocate memory areas without considering a low level driver's
segment boundary limits. Thus low level drivers have a workaround to
adjust scatter lists that IOMMUs build. Duplicating such workaround in
many LLDs and adjusting scatter lists in LLDs again are not good
(because they easily lead to bugs especially after sg chain
introduction and not efficient, etc).

I've been modifying some of the IOMMUs to make them respect low level
drivers' limits.


> > This assumes that ioc->ibase is on iovp_size boundary. If not, please
> > let me know. I'll fix the patch.
> 
> Who is the person who who knows the answer to this?

I expected that someone in IA64 list might konw the answer. I put
BUG_ON so we will know the answer eventually even if nobody knows it.


> Does this mean that the patch wasn't runtime tested?  If so, how do you
> know there is a bug?

Sorry, I don't have IA64. So it's not tested. I read the code and I
learned that IA64's IOMMU ignores segment boundary limits.

I want the patch to be tested in -mm kernels and hope that it will be
merged into 2.6.26.


> > > > From: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
> > Subject: [PATCH -mm] ia64: make IOMMU respect the segment boundary limits
> > 
> > This makes IA64's IOMMU implementation not allocate a memory area
> > spanning LLD's segment boundary.
> 
> This changelog doesn't actually tell us that this patch fixed a bug.
> 
> It should tell us what the bug is, and how it fixed it, please.

How about the following description?


IA64's IOMMU implementation allocates memory areas spanning LLD's
segment boundary limit. It forces low level drivers to have a
workaround to adjust scatter lists that the IOMMU builds.

We are in the process of making all the IOMMUs respect the segment
boundary limits to remove such work around in LLDs. This patch is for
IA64's IOMMU.


Thanks,

Re: [PATCH -mm] ia64: make IOMMU respect the segment boundary limits

[FUJITA Tomonori]

On Mon, 10 Mar 2008 20:33:44 -0700
Andrew Morton <akpm@linux-foundation.org> wrote:

> On Mon, 10 Mar 2008 22:17:20 +0900 FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp> wrote:
> 
> > This patch is another sequel to my patchset that fixes iommu segment
> > boundary problems, that is, IOMMUs allocate memory areas without
> > considering a low level driver's segment boundary limits:
> > 
> > http://www.mail-archive.com/linux-scsi@vger.kernel.org/msg11919.html
> 
> Please make this easier.

Very sorry,


> afacit the patches to which you refer are already in mainline, so this is
> *not* a "-mm" patch.  It is needed in mainline, correct?

It's not needed immediately. Please apply it to -mm.


> > This patchset fixes the IA64 IOMMU code.
> 
> And if it fixes a bug then it is needed in 2.6.25.
> 
> Is that correct?

No, it isn't needed in 2.6.25. Sorry, I shouldn't have used 'fixes'.

IOMMUs allocate memory areas without considering a low level driver's
segment boundary limits. Thus low level drivers have a workaround to
adjust scatter lists that IOMMUs build. Duplicating such workaround in
many LLDs and adjusting scatter lists in LLDs again are not good
(because they easily lead to bugs especially after sg chain
introduction and not efficient, etc).

I've been modifying some of the IOMMUs to make them respect low level
drivers' limits.


> > This assumes that ioc->ibase is on iovp_size boundary. If not, please
> > let me know. I'll fix the patch.
> 
> Who is the person who who knows the answer to this?

I expected that someone in IA64 list might konw the answer. I put
BUG_ON so we will know the answer eventually even if nobody knows it.


> Does this mean that the patch wasn't runtime tested?  If so, how do you
> know there is a bug?

Sorry, I don't have IA64. So it's not tested. I read the code and I
learned that IA64's IOMMU ignores segment boundary limits.

I want the patch to be tested in -mm kernels and hope that it will be
merged into 2.6.26.


> > =
> > From: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
> > Subject: [PATCH -mm] ia64: make IOMMU respect the segment boundary limits
> > 
> > This makes IA64's IOMMU implementation not allocate a memory area
> > spanning LLD's segment boundary.
> 
> This changelog doesn't actually tell us that this patch fixed a bug.
> 
> It should tell us what the bug is, and how it fixed it, please.

How about the following description?


IA64's IOMMU implementation allocates memory areas spanning LLD's
segment boundary limit. It forces low level drivers to have a
workaround to adjust scatter lists that the IOMMU builds.

We are in the process of making all the IOMMUs respect the segment
boundary limits to remove such work around in LLDs. This patch is for
IA64's IOMMU.


Thanks,