[OpenRISC] ensure dma_alloc_coherent always returns zeroed memory

[OpenRISC] ensure dma_alloc_coherent always returns zeroed memory

[Christoph Hellwig]

For security reasons we already returned zeroed memory from
dma_alloc_coherent on most common platforms, but some implementation
missed out.  Make sure we provide a consistent behavior.

[OpenRISC] [PATCH 1/2] dma-mapping: zero memory returned from dma_alloc_*

[Christoph Hellwig]

If we want to map memory from the DMA allocator to userspace it must be
zeroed at allocation time to prevent stale data leaks.   We already do
this on most common architectures, but some architectures don't do this
yet, fix them up, either by passing GFP_ZERO when we use the normal page
allocator or doing a manual memset otherwise.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 arch/alpha/kernel/pci_iommu.c    | 2 +-
 arch/arc/mm/dma.c                | 2 +-
 arch/c6x/mm/dma-coherent.c       | 5 ++++-
 arch/m68k/kernel/dma.c           | 2 +-
 arch/microblaze/mm/consistent.c  | 2 +-
 arch/openrisc/kernel/dma.c       | 2 +-
 arch/parisc/kernel/pci-dma.c     | 4 ++--
 arch/s390/pci/pci_dma.c          | 2 +-
 arch/sparc/kernel/ioport.c       | 2 +-
 arch/sparc/mm/io-unit.c          | 2 +-
 arch/sparc/mm/iommu.c            | 2 +-
 arch/xtensa/kernel/pci-dma.c     | 2 +-
 drivers/misc/mic/host/mic_boot.c | 2 +-
 kernel/dma/virt.c                | 2 +-
 14 files changed, 18 insertions(+), 15 deletions(-)

diff --git a/arch/alpha/kernel/pci_iommu.c b/arch/alpha/kernel/pci_iommu.c
index e1716e0d92fd..28a025eda80d 100644
--- a/arch/alpha/kernel/pci_iommu.c
+++ b/arch/alpha/kernel/pci_iommu.c
@@ -443,7 +443,7 @@ static void *alpha_pci_alloc_coherent(struct device *dev, size_t size,
 	gfp &= ~GFP_DMA;
 
 try_again:
-	cpu_addr = (void *)__get_free_pages(gfp, order);
+	cpu_addr = (void *)__get_free_pages(gfp | GFP_ZERO, order);
 	if (! cpu_addr) {
 		printk(KERN_INFO "pci_alloc_consistent: "
 		       "get_free_pages failed from %pf\n",
diff --git a/arch/arc/mm/dma.c b/arch/arc/mm/dma.c
index db203ff69ccf..b0754581efc6 100644
--- a/arch/arc/mm/dma.c
+++ b/arch/arc/mm/dma.c
@@ -33,7 +33,7 @@ void *arch_dma_alloc(struct device *dev, size_t size, dma_addr_t *dma_handle,
 	 */
 	BUG_ON(gfp & __GFP_HIGHMEM);
 
-	page = alloc_pages(gfp, order);
+	page = alloc_pages(gfp | GFP_ZERO, order);
 	if (!page)
 		return NULL;
 
diff --git a/arch/c6x/mm/dma-coherent.c b/arch/c6x/mm/dma-coherent.c
index 01305c787201..75b79571732c 100644
--- a/arch/c6x/mm/dma-coherent.c
+++ b/arch/c6x/mm/dma-coherent.c
@@ -78,6 +78,7 @@ static void __free_dma_pages(u32 addr, int order)
 void *arch_dma_alloc(struct device *dev, size_t size, dma_addr_t *handle,
 		gfp_t gfp, unsigned long attrs)
 {
+	void *ret;
 	u32 paddr;
 	int order;
 
@@ -94,7 +95,9 @@ void *arch_dma_alloc(struct device *dev, size_t size, dma_addr_t *handle,
 	if (!paddr)
 		return NULL;
 
-	return phys_to_virt(paddr);
+	ret = phys_to_virt(paddr);
+	memset(ret, 0, 1 << order);
+	return ret;
 }
 
 /*
diff --git a/arch/m68k/kernel/dma.c b/arch/m68k/kernel/dma.c
index e99993c57d6b..dafe99d08a6a 100644
--- a/arch/m68k/kernel/dma.c
+++ b/arch/m68k/kernel/dma.c
@@ -32,7 +32,7 @@ void *arch_dma_alloc(struct device *dev, size_t size, dma_addr_t *handle,
 	size = PAGE_ALIGN(size);
 	order = get_order(size);
 
-	page = alloc_pages(flag, order);
+	page = alloc_pages(flag | GFP_ZERO, order);
 	if (!page)
 		return NULL;
 
diff --git a/arch/microblaze/mm/consistent.c b/arch/microblaze/mm/consistent.c
index 45e0a1aa9357..79b9f4695a1b 100644
--- a/arch/microblaze/mm/consistent.c
+++ b/arch/microblaze/mm/consistent.c
@@ -81,7 +81,7 @@ void *arch_dma_alloc(struct device *dev, size_t size, dma_addr_t *dma_handle,
 	size = PAGE_ALIGN(size);
 	order = get_order(size);
 
-	vaddr = __get_free_pages(gfp, order);
+	vaddr = __get_free_pages(gfp | GFP_ZERO, order);
 	if (!vaddr)
 		return NULL;
 
diff --git a/arch/openrisc/kernel/dma.c b/arch/openrisc/kernel/dma.c
index 159336adfa2f..cdd03f63207c 100644
--- a/arch/openrisc/kernel/dma.c
+++ b/arch/openrisc/kernel/dma.c
@@ -89,7 +89,7 @@ arch_dma_alloc(struct device *dev, size_t size, dma_addr_t *dma_handle,
 		.mm = &init_mm
 	};
 
-	page = alloc_pages_exact(size, gfp);
+	page = alloc_pages_exact(size, gfp | GFP_ZERO);
 	if (!page)
 		return NULL;
 
diff --git a/arch/parisc/kernel/pci-dma.c b/arch/parisc/kernel/pci-dma.c
index 04c48f1ef3fb..7fa396714b5a 100644
--- a/arch/parisc/kernel/pci-dma.c
+++ b/arch/parisc/kernel/pci-dma.c
@@ -404,7 +404,7 @@ static void *pcxl_dma_alloc(struct device *dev, size_t size,
 	order = get_order(size);
 	size = 1 << (order + PAGE_SHIFT);
 	vaddr = pcxl_alloc_range(size);
-	paddr = __get_free_pages(flag, order);
+	paddr = __get_free_pages(flag | GFP_ZERO, order);
 	flush_kernel_dcache_range(paddr, size);
 	paddr = __pa(paddr);
 	map_uncached_pages(vaddr, size, paddr);
@@ -429,7 +429,7 @@ static void *pcx_dma_alloc(struct device *dev, size_t size,
 	if ((attrs & DMA_ATTR_NON_CONSISTENT) == 0)
 		return NULL;
 
-	addr = (void *)__get_free_pages(flag, get_order(size));
+	addr = (void *)__get_free_pages(flag | GFP_ZERO, get_order(size));
 	if (addr)
 		*dma_handle = (dma_addr_t)virt_to_phys(addr);
 
diff --git a/arch/s390/pci/pci_dma.c b/arch/s390/pci/pci_dma.c
index 346ba382193a..2578d9567d86 100644
--- a/arch/s390/pci/pci_dma.c
+++ b/arch/s390/pci/pci_dma.c
@@ -404,7 +404,7 @@ static void *s390_dma_alloc(struct device *dev, size_t size,
 	dma_addr_t map;
 
 	size = PAGE_ALIGN(size);
-	page = alloc_pages(flag, get_order(size));
+	page = alloc_pages(flag | GFP_ZERO, get_order(size));
 	if (!page)
 		return NULL;
 
diff --git a/arch/sparc/kernel/ioport.c b/arch/sparc/kernel/ioport.c
index baa235652c27..b3a0c5adeed5 100644
--- a/arch/sparc/kernel/ioport.c
+++ b/arch/sparc/kernel/ioport.c
@@ -325,7 +325,7 @@ void *arch_dma_alloc(struct device *dev, size_t size, dma_addr_t *dma_handle,
 		return NULL;
 
 	size = PAGE_ALIGN(size);
-	va = (void *) __get_free_pages(gfp, get_order(size));
+	va = (void *) __get_free_pages(gfp | GFP_ZERO, get_order(size));
 	if (!va) {
 		printk("%s: no %zd pages\n", __func__, size >> PAGE_SHIFT);
 		return NULL;
diff --git a/arch/sparc/mm/io-unit.c b/arch/sparc/mm/io-unit.c
index 2088d292c6e5..d1729c8b0bf9 100644
--- a/arch/sparc/mm/io-unit.c
+++ b/arch/sparc/mm/io-unit.c
@@ -225,7 +225,7 @@ static void *iounit_alloc(struct device *dev, size_t len,
 		return NULL;
 
 	len = PAGE_ALIGN(len);
-	va = __get_free_pages(gfp, get_order(len));
+	va = __get_free_pages(gfp | GFP_ZERO, get_order(len));
 	if (!va)
 		return NULL;
 
diff --git a/arch/sparc/mm/iommu.c b/arch/sparc/mm/iommu.c
index 3599485717e7..25c83078ece7 100644
--- a/arch/sparc/mm/iommu.c
+++ b/arch/sparc/mm/iommu.c
@@ -347,7 +347,7 @@ static void *sbus_iommu_alloc(struct device *dev, size_t len,
 		return NULL;
 
 	len = PAGE_ALIGN(len);
-	va = __get_free_pages(gfp, get_order(len));
+	va = __get_free_pages(gfp | GFP_ZERO, get_order(len));
 	if (va == 0)
 		return NULL;
 
diff --git a/arch/xtensa/kernel/pci-dma.c b/arch/xtensa/kernel/pci-dma.c
index 1fc138b6bc0a..e9fbec5f6ec2 100644
--- a/arch/xtensa/kernel/pci-dma.c
+++ b/arch/xtensa/kernel/pci-dma.c
@@ -160,7 +160,7 @@ void *arch_dma_alloc(struct device *dev, size_t size, dma_addr_t *handle,
 						 flag & __GFP_NOWARN);
 
 	if (!page)
-		page = alloc_pages(flag, get_order(size));
+		page = alloc_pages(flag | GFP_ZERO, get_order(size));
 
 	if (!page)
 		return NULL;
diff --git a/drivers/misc/mic/host/mic_boot.c b/drivers/misc/mic/host/mic_boot.c
index c327985c9523..7e5bd8654fd4 100644
--- a/drivers/misc/mic/host/mic_boot.c
+++ b/drivers/misc/mic/host/mic_boot.c
@@ -149,7 +149,7 @@ static void *__mic_dma_alloc(struct device *dev, size_t size,
 	struct scif_hw_dev *scdev = dev_get_drvdata(dev);
 	struct mic_device *mdev = scdev_to_mdev(scdev);
 	dma_addr_t tmp;
-	void *va = kmalloc(size, gfp);
+	void *va = kmalloc(size, gfp | GFP_ZERO);
 
 	if (va) {
 		tmp = mic_map_single(mdev, va, size);
diff --git a/kernel/dma/virt.c b/kernel/dma/virt.c
index 631ddec4b60a..f80990f882a6 100644
--- a/kernel/dma/virt.c
+++ b/kernel/dma/virt.c
@@ -13,7 +13,7 @@ static void *dma_virt_alloc(struct device *dev, size_t size,
 {
 	void *ret;
 
-	ret = (void *)__get_free_pages(gfp, get_order(size));
+	ret = (void *)__get_free_pages(gfp | GFP_ZERO, get_order(size));
 	if (ret)
 		*dma_handle = (uintptr_t)ret;
 	return ret;
-- 
2.19.2

[OpenRISC] [PATCH 1/2] dma-mapping: zero memory returned from dma_alloc_*

[Geert Uytterhoeven]

Hi Christoph,

On Fri, Dec 14, 2018 at 9:26 AM Christoph Hellwig <hch@lst.de> wrote:
> If we want to map memory from the DMA allocator to userspace it must be
> zeroed at allocation time to prevent stale data leaks.   We already do
> this on most common architectures, but some architectures don't do this
> yet, fix them up, either by passing GFP_ZERO when we use the normal page
> allocator or doing a manual memset otherwise.
>
> Signed-off-by: Christoph Hellwig <hch@lst.de>

Thanks for your patch!

> --- a/arch/m68k/kernel/dma.c
> +++ b/arch/m68k/kernel/dma.c
> @@ -32,7 +32,7 @@ void *arch_dma_alloc(struct device *dev, size_t size, dma_addr_t *handle,
>         size = PAGE_ALIGN(size);
>         order = get_order(size);
>
> -       page = alloc_pages(flag, order);
> +       page = alloc_pages(flag | GFP_ZERO, order);
>         if (!page)
>                 return NULL;

There's second implementation below, which calls __get_free_pages() and
does an explicit memset().  As __get_free_pages() calls alloc_pages(), perhaps
it makes sense to replace the memset() by GFP_ZERO, to increase consistency?

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert at linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds

[OpenRISC] [PATCH 1/2] dma-mapping: zero memory returned from dma_alloc_*

[Geert Uytterhoeven]

On Fri, Dec 14, 2018 at 10:54 AM Geert Uytterhoeven
<geert@linux-m68k.org> wrote:
> On Fri, Dec 14, 2018 at 9:26 AM Christoph Hellwig <hch@lst.de> wrote:
> > If we want to map memory from the DMA allocator to userspace it must be
> > zeroed at allocation time to prevent stale data leaks.   We already do
> > this on most common architectures, but some architectures don't do this
> > yet, fix them up, either by passing GFP_ZERO when we use the normal page
> > allocator or doing a manual memset otherwise.
> >
> > Signed-off-by: Christoph Hellwig <hch@lst.de>
>
> Thanks for your patch!
>
> > --- a/arch/m68k/kernel/dma.c
> > +++ b/arch/m68k/kernel/dma.c
> > @@ -32,7 +32,7 @@ void *arch_dma_alloc(struct device *dev, size_t size, dma_addr_t *handle,
> >         size = PAGE_ALIGN(size);
> >         order = get_order(size);
> >
> > -       page = alloc_pages(flag, order);
> > +       page = alloc_pages(flag | GFP_ZERO, order);
> >         if (!page)
> >                 return NULL;
>
> There's second implementation below, which calls __get_free_pages() and
> does an explicit memset().  As __get_free_pages() calls alloc_pages(), perhaps
> it makes sense to replace the memset() by GFP_ZERO, to increase consistency?

Regardless, for m68k:
Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert at linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds

[OpenRISC] [PATCH 1/2] dma-mapping: zero memory returned from dma_alloc_*

[Christoph Hellwig]

On Fri, Dec 14, 2018 at 10:54:32AM +0100, Geert Uytterhoeven wrote:
> > -       page = alloc_pages(flag, order);
> > +       page = alloc_pages(flag | GFP_ZERO, order);
> >         if (!page)
> >                 return NULL;
> 
> There's second implementation below, which calls __get_free_pages() and
> does an explicit memset().  As __get_free_pages() calls alloc_pages(), perhaps
> it makes sense to replace the memset() by GFP_ZERO, to increase consistency?

It would, but this patch really tries to be minimally invasive to just
provide the zeroing everywhere.  There is plenty of opportunity
to improve the m68k dma allocator if I can get enough reviewers/testers:

 - for one the coldfire/nommu case absolutely does not make sense to
   me as there is not work done at all to make sure the memory is
   mapped uncached despite the architecture implementing cache
   flushing for the map interface.  So this whole implementation
   looks broken to me and will need some major work (I had a previous
   discussion with Greg on that which needs to be dug out)
 - the "regular" implementation in this patch should probably be replaced
   with the generic remapping helpers that have been added for the 4.21
   merge window:

	http://git.infradead.org/users/hch/dma-mapping.git/commitdiff/0c3b3171ceccb8830c2bb5adff1b4e9b204c1450

Compile tested only patch below:

--
From ade86dc75b9850daf9111ebf9ce15825a6144f2d Mon Sep 17 00:00:00 2001
From: Christoph Hellwig <hch@lst.de>
Date: Fri, 14 Dec 2018 12:41:45 +0100
Subject: m68k: use the generic dma coherent remap allocator

This switche to using common code for the DMA allocations, including
potential use of the CMA allocator if configure.  Also add a few
comments where the existing behavior seems to be lacking.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 arch/m68k/Kconfig      |  2 ++
 arch/m68k/kernel/dma.c | 64 ++++++++++++------------------------------
 2 files changed, 20 insertions(+), 46 deletions(-)

diff --git a/arch/m68k/Kconfig b/arch/m68k/Kconfig
index 8a5868e9a3a0..60788cf02fbc 100644
--- a/arch/m68k/Kconfig
+++ b/arch/m68k/Kconfig
@@ -2,10 +2,12 @@
 config M68K
 	bool
 	default y
+	select ARCH_HAS_DMA_MMAP_PGPROT if MMU && !COLDFIRE
 	select ARCH_HAS_SYNC_DMA_FOR_DEVICE if HAS_DMA
 	select ARCH_MIGHT_HAVE_PC_PARPORT if ISA
 	select ARCH_NO_COHERENT_DMA_MMAP if !MMU
 	select ARCH_NO_PREEMPT if !COLDFIRE
+	select DMA_DIRECT_REMAP if MMU && !COLDFIRE
 	select HAVE_IDE
 	select HAVE_AOUT if MMU
 	select HAVE_DEBUG_BUGVERBOSE
diff --git a/arch/m68k/kernel/dma.c b/arch/m68k/kernel/dma.c
index dafe99d08a6a..16da5d96e228 100644
--- a/arch/m68k/kernel/dma.c
+++ b/arch/m68k/kernel/dma.c
@@ -18,57 +18,29 @@
 #include <asm/pgalloc.h>
 
 #if defined(CONFIG_MMU) && !defined(CONFIG_COLDFIRE)
-
-void *arch_dma_alloc(struct device *dev, size_t size, dma_addr_t *handle,
-		gfp_t flag, unsigned long attrs)
+void arch_dma_prep_coherent(struct page *page, size_t size)
 {
-	struct page *page, **map;
-	pgprot_t pgprot;
-	void *addr;
-	int i, order;
-
-	pr_debug("dma_alloc_coherent: %d,%x\n", size, flag);
-
-	size = PAGE_ALIGN(size);
-	order = get_order(size);
-
-	page = alloc_pages(flag | GFP_ZERO, order);
-	if (!page)
-		return NULL;
-
-	*handle = page_to_phys(page);
-	map = kmalloc(sizeof(struct page *) << order, flag & ~__GFP_DMA);
-	if (!map) {
-		__free_pages(page, order);
-		return NULL;
-	}
-	split_page(page, order);
-
-	order = 1 << order;
-	size >>= PAGE_SHIFT;
-	map[0] = page;
-	for (i = 1; i < size; i++)
-		map[i] = page + i;
-	for (; i < order; i++)
-		__free_page(page + i);
-	pgprot = __pgprot(_PAGE_PRESENT | _PAGE_ACCESSED | _PAGE_DIRTY);
-	if (CPU_IS_040_OR_060)
-		pgprot_val(pgprot) |= _PAGE_GLOBAL040 | _PAGE_NOCACHE_S;
-	else
-		pgprot_val(pgprot) |= _PAGE_NOCACHE030;
-	addr = vmap(map, size, VM_MAP, pgprot);
-	kfree(map);
-
-	return addr;
+	/*
+	 * XXX: don't we need to flush and invalidate the caches before
+	 * creating a coherent mapping?
+	 * coherent?
+	 */
 }
 
-void arch_dma_free(struct device *dev, size_t size, void *addr,
-		dma_addr_t handle, unsigned long attrs)
+pgprot_t arch_dma_mmap_pgprot(struct device *dev, pgprot_t prot,
+		unsigned long attrs)
 {
-	pr_debug("dma_free_coherent: %p, %x\n", addr, handle);
-	vfree(addr);
+	/*
+	 * XXX: this doesn't seem to handle the sun3 MMU@all.
+	 */
+	if (CPU_IS_040_OR_060) {
+		pgprot_val(prot) &= ~_PAGE_CACHE040;
+		pgprot_val(prot) |= _PAGE_GLOBAL040 | _PAGE_NOCACHE_S;
+	} else {
+		pgprot_val(prot) |= _PAGE_NOCACHE030;
+	}
+	return prot;
 }
-
 #else
 
 #include <asm/cacheflush.h>
-- 
2.19.2

[OpenRISC] [PATCH 1/2] dma-mapping: zero memory returned from dma_alloc_*

[Geert Uytterhoeven]

Hi Christoph,

On Fri, Dec 14, 2018 at 12:47 PM Christoph Hellwig <hch@lst.de> wrote:
>
> On Fri, Dec 14, 2018 at 10:54:32AM +0100, Geert Uytterhoeven wrote:
> > > -       page = alloc_pages(flag, order);
> > > +       page = alloc_pages(flag | GFP_ZERO, order);
> > >         if (!page)
> > >                 return NULL;
> >
> > There's second implementation below, which calls __get_free_pages() and
> > does an explicit memset().  As __get_free_pages() calls alloc_pages(), perhaps
> > it makes sense to replace the memset() by GFP_ZERO, to increase consistency?
>
> It would, but this patch really tries to be minimally invasive to just
> provide the zeroing everywhere.

Fair enough.

> There is plenty of opportunity
> to improve the m68k dma allocator if I can get enough reviewers/testers:
>
>  - for one the coldfire/nommu case absolutely does not make sense to
>    me as there is not work done at all to make sure the memory is
>    mapped uncached despite the architecture implementing cache
>    flushing for the map interface.  So this whole implementation
>    looks broken to me and will need some major work (I had a previous
>    discussion with Greg on that which needs to be dug out)
>  - the "regular" implementation in this patch should probably be replaced
>    with the generic remapping helpers that have been added for the 4.21
>    merge window:
>
>         http://git.infradead.org/users/hch/dma-mapping.git/commitdiff/0c3b3171ceccb8830c2bb5adff1b4e9b204c1450
>
> Compile tested only patch below:
>
> --
> From ade86dc75b9850daf9111ebf9ce15825a6144f2d Mon Sep 17 00:00:00 2001
> From: Christoph Hellwig <hch@lst.de>
> Date: Fri, 14 Dec 2018 12:41:45 +0100
> Subject: m68k: use the generic dma coherent remap allocator
>
> This switche to using common code for the DMA allocations, including
> potential use of the CMA allocator if configure.  Also add a few
> comments where the existing behavior seems to be lacking.
>
> Signed-off-by: Christoph Hellwig <hch@lst.de>

Thanks, looks OK to me.
M68k doesn't have many drivers using the DMA framework, as most of them
predated that framework.

> --- a/arch/m68k/kernel/dma.c
> +++ b/arch/m68k/kernel/dma.c

>
> -void arch_dma_free(struct device *dev, size_t size, void *addr,
> -               dma_addr_t handle, unsigned long attrs)
> +pgprot_t arch_dma_mmap_pgprot(struct device *dev, pgprot_t prot,
> +               unsigned long attrs)
>  {
> -       pr_debug("dma_free_coherent: %p, %x\n", addr, handle);
> -       vfree(addr);
> +       /*
> +        * XXX: this doesn't seem to handle the sun3 MMU at all.

Sun-3 selects NO_DMA, and this file is compiled for the HAS_DMA case only.

> +        */
> +       if (CPU_IS_040_OR_060) {
> +               pgprot_val(prot) &= ~_PAGE_CACHE040;
> +               pgprot_val(prot) |= _PAGE_GLOBAL040 | _PAGE_NOCACHE_S;
> +       } else {
> +               pgprot_val(prot) |= _PAGE_NOCACHE030;
> +       }
> +       return prot;
>  }

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert at linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds

[OpenRISC] [PATCH 1/2] dma-mapping: zero memory returned from dma_alloc_*

[Greg Ungerer]

On 14/12/18 9:47 pm, Christoph Hellwig wrote:
> On Fri, Dec 14, 2018 at 10:54:32AM +0100, Geert Uytterhoeven wrote:
>>> -       page = alloc_pages(flag, order);
>>> +       page = alloc_pages(flag | GFP_ZERO, order);
>>>          if (!page)
>>>                  return NULL;
>>
>> There's second implementation below, which calls __get_free_pages() and
>> does an explicit memset().  As __get_free_pages() calls alloc_pages(), perhaps
>> it makes sense to replace the memset() by GFP_ZERO, to increase consistency?
> 
> It would, but this patch really tries to be minimally invasive to just
> provide the zeroing everywhere.  There is plenty of opportunity
> to improve the m68k dma allocator if I can get enough reviewers/testers:
> 
>   - for one the coldfire/nommu case absolutely does not make sense to
>     me as there is not work done at all to make sure the memory is
>     mapped uncached despite the architecture implementing cache
>     flushing for the map interface.  So this whole implementation
>     looks broken to me and will need some major work (I had a previous
>     discussion with Greg on that which needs to be dug out)

Yep, that is right. Certainly the MMU case is broken. Some noMMU cases work
by virtue of the SoC only having an instruction cache (the older V2 cores).

The MMU case is fixable, but I think it will mean changing away from
the fall-back virtual:physical 1:1 mapping it uses for the kernel address
space. So not completely trivial. Either that or a dedicated area of RAM
for coherent allocations that we can mark as non-cachable via the really
course grained and limited ACR registers - not really very appealing.

The noMMU case in general is probably limited to something like that same
type of dedicated RAM/ACR register mechamism.

The most commonly used periperal with DMA is the FEC ethernet module,
and it has some "special" (used very loosely) cache flushing for
parts like the 532x family which probably makes it mostly work right.
There is a PCI bus on the 54xx family of parts, and I know general
ethernet cards on it (like e1000's) have problems I am sure are
related to the fact that coherent memory allocations aren't.

I do plan to have a look at this for the MMU case some time soon.

Regards
Greg




>   - the "regular" implementation in this patch should probably be replaced
>     with the generic remapping helpers that have been added for the 4.21
>     merge window:
> 
> 	http://git.infradead.org/users/hch/dma-mapping.git/commitdiff/0c3b3171ceccb8830c2bb5adff1b4e9b204c1450
> 
> Compile tested only patch below:
> 
> --
>>From ade86dc75b9850daf9111ebf9ce15825a6144f2d Mon Sep 17 00:00:00 2001
> From: Christoph Hellwig <hch@lst.de>
> Date: Fri, 14 Dec 2018 12:41:45 +0100
> Subject: m68k: use the generic dma coherent remap allocator
> 
> This switche to using common code for the DMA allocations, including
> potential use of the CMA allocator if configure.  Also add a few
> comments where the existing behavior seems to be lacking.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
>   arch/m68k/Kconfig      |  2 ++
>   arch/m68k/kernel/dma.c | 64 ++++++++++++------------------------------
>   2 files changed, 20 insertions(+), 46 deletions(-)
> 
> diff --git a/arch/m68k/Kconfig b/arch/m68k/Kconfig
> index 8a5868e9a3a0..60788cf02fbc 100644
> --- a/arch/m68k/Kconfig
> +++ b/arch/m68k/Kconfig
> @@ -2,10 +2,12 @@
>   config M68K
>   	bool
>   	default y
> +	select ARCH_HAS_DMA_MMAP_PGPROT if MMU && !COLDFIRE
>   	select ARCH_HAS_SYNC_DMA_FOR_DEVICE if HAS_DMA
>   	select ARCH_MIGHT_HAVE_PC_PARPORT if ISA
>   	select ARCH_NO_COHERENT_DMA_MMAP if !MMU
>   	select ARCH_NO_PREEMPT if !COLDFIRE
> +	select DMA_DIRECT_REMAP if MMU && !COLDFIRE
>   	select HAVE_IDE
>   	select HAVE_AOUT if MMU
>   	select HAVE_DEBUG_BUGVERBOSE
> diff --git a/arch/m68k/kernel/dma.c b/arch/m68k/kernel/dma.c
> index dafe99d08a6a..16da5d96e228 100644
> --- a/arch/m68k/kernel/dma.c
> +++ b/arch/m68k/kernel/dma.c
> @@ -18,57 +18,29 @@
>   #include <asm/pgalloc.h>
>   
>   #if defined(CONFIG_MMU) && !defined(CONFIG_COLDFIRE)
> -
> -void *arch_dma_alloc(struct device *dev, size_t size, dma_addr_t *handle,
> -		gfp_t flag, unsigned long attrs)
> +void arch_dma_prep_coherent(struct page *page, size_t size)
>   {
> -	struct page *page, **map;
> -	pgprot_t pgprot;
> -	void *addr;
> -	int i, order;
> -
> -	pr_debug("dma_alloc_coherent: %d,%x\n", size, flag);
> -
> -	size = PAGE_ALIGN(size);
> -	order = get_order(size);
> -
> -	page = alloc_pages(flag | GFP_ZERO, order);
> -	if (!page)
> -		return NULL;
> -
> -	*handle = page_to_phys(page);
> -	map = kmalloc(sizeof(struct page *) << order, flag & ~__GFP_DMA);
> -	if (!map) {
> -		__free_pages(page, order);
> -		return NULL;
> -	}
> -	split_page(page, order);
> -
> -	order = 1 << order;
> -	size >>= PAGE_SHIFT;
> -	map[0] = page;
> -	for (i = 1; i < size; i++)
> -		map[i] = page + i;
> -	for (; i < order; i++)
> -		__free_page(page + i);
> -	pgprot = __pgprot(_PAGE_PRESENT | _PAGE_ACCESSED | _PAGE_DIRTY);
> -	if (CPU_IS_040_OR_060)
> -		pgprot_val(pgprot) |= _PAGE_GLOBAL040 | _PAGE_NOCACHE_S;
> -	else
> -		pgprot_val(pgprot) |= _PAGE_NOCACHE030;
> -	addr = vmap(map, size, VM_MAP, pgprot);
> -	kfree(map);
> -
> -	return addr;
> +	/*
> +	 * XXX: don't we need to flush and invalidate the caches before
> +	 * creating a coherent mapping?
> +	 * coherent?
> +	 */
>   }
>   
> -void arch_dma_free(struct device *dev, size_t size, void *addr,
> -		dma_addr_t handle, unsigned long attrs)
> +pgprot_t arch_dma_mmap_pgprot(struct device *dev, pgprot_t prot,
> +		unsigned long attrs)
>   {
> -	pr_debug("dma_free_coherent: %p, %x\n", addr, handle);
> -	vfree(addr);
> +	/*
> +	 * XXX: this doesn't seem to handle the sun3 MMU at all.
> +	 */
> +	if (CPU_IS_040_OR_060) {
> +		pgprot_val(prot) &= ~_PAGE_CACHE040;
> +		pgprot_val(prot) |= _PAGE_GLOBAL040 | _PAGE_NOCACHE_S;
> +	} else {
> +		pgprot_val(prot) |= _PAGE_NOCACHE030;
> +	}
> +	return prot;
>   }
> -
>   #else
>   
>   #include <asm/cacheflush.h>
> 

[OpenRISC] [PATCH 1/2] dma-mapping: zero memory returned from dma_alloc_*

[Christoph Hellwig]

On Sat, Dec 15, 2018 at 12:14:29AM +1000, Greg Ungerer wrote:
> Yep, that is right. Certainly the MMU case is broken. Some noMMU cases work
> by virtue of the SoC only having an instruction cache (the older V2 cores).

Is there a good an easy case to detect if a core has a cache?  Either
runtime or in Kconfig?

> The MMU case is fixable, but I think it will mean changing away from
> the fall-back virtual:physical 1:1 mapping it uses for the kernel address
> space. So not completely trivial. Either that or a dedicated area of RAM
> for coherent allocations that we can mark as non-cachable via the really
> course grained and limited ACR registers - not really very appealing.

What about CF_PAGE_NOCACHE?  Reading arch/m68k/include/asm/mcf_pgtable.h
suggest this would cause an uncached mapping, in which case something
like this should work:

	http://git.infradead.org/users/hch/misc.git/commitdiff/4b8711d436e8d56edbc5ca19aa2be639705bbfef

> The noMMU case in general is probably limited to something like that same
> type of dedicated RAM/ACR register mechamism.
>
> The most commonly used periperal with DMA is the FEC ethernet module,
> and it has some "special" (used very loosely) cache flushing for
> parts like the 532x family which probably makes it mostly work right.
> There is a PCI bus on the 54xx family of parts, and I know general
> ethernet cards on it (like e1000's) have problems I am sure are
> related to the fact that coherent memory allocations aren't.

If we really just care about FEC we can just switch it do use
DMA_ATTR_NON_CONSISTENT and do explicit cache flushing.  But as far
as I can tell FEC only uses DMA coherent allocations for the TSO
headers anyway, is TSO even used on this SOC?

[OpenRISC] [PATCH 1/2] dma-mapping: zero memory returned from dma_alloc_*

[Eugeniy Paltsev]

Hi Christoph,

do you have any public git repository with all your dma changes?

I want to test them for ARC.

Thanks.

On Fri, 2018-12-14 at 09:25 +0100, Christoph Hellwig wrote:
> If we want to map memory from the DMA allocator to userspace it must be
> zeroed at allocation time to prevent stale data leaks.   We already do
> this on most common architectures, but some architectures don't do this
> yet, fix them up, either by passing GFP_ZERO when we use the normal page
> allocator or doing a manual memset otherwise.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
-- 
 Eugeniy Paltsev

[OpenRISC] [PATCH 1/2] dma-mapping: zero memory returned from dma_alloc_*

[hch]

On Fri, Dec 14, 2018 at 12:12:00PM +0000, Eugeniy Paltsev wrote:
> Hi Christoph,
> 
> do you have any public git repository with all your dma changes?

Most of the tree show up in my misc.git repo for testing.

This series is here:

http://git.infradead.org/users/hch/misc.git/shortlog/refs/heads/dma-alloc-always-zero

There current version of the DMA_ATTR_NON_CONSISTENT series is here:

http://git.infradead.org/users/hch/misc.git/shortlog/refs/heads/dma-noncoherent-allocator.2


> I want to test them for ARC.

Thanks a lot!

[OpenRISC] [PATCH 1/2] dma-mapping: zero memory returned from dma_alloc_*

[Sam Ravnborg]

Hi Christoph,

I stumbled upon this one:

#define __get_dma_pages(gfp_mask, order) \
                __get_free_pages((gfp_mask) | GFP_DMA, (order))

(include/linux/gfp.h)
Should it also have the __GFP_ZERO treatment?
Or maybe this is already done in your tree..

As for the sparc bits:
Acked-by: Sam Ravnborg <sam@ravnborg.org> [sparc]

	Sam

[OpenRISC] [PATCH 1/2] dma-mapping: zero memory returned from dma_alloc_*

[Christoph Hellwig]

On Fri, Dec 14, 2018 at 07:10:56PM +0100, Sam Ravnborg wrote:
> Hi Christoph,
> 
> I stumbled upon this one:
> 
> #define __get_dma_pages(gfp_mask, order) \
>                 __get_free_pages((gfp_mask) | GFP_DMA, (order))

This isn't directly related to the dma mapping, but another place
that hides GFP_DMA allocations.  So no need for the treatment,
but we really should kill this obsfucating wrapper..

[OpenRISC] [PATCH 2/2] dma-mapping: deprecate dma_zalloc_coherent

[Christoph Hellwig]

We now always return zeroed memory from dma_alloc_coherent.  Note that
simply passing GFP_ZERO to dma_alloc_coherent wasn't always doing the
right thing to start with given that various allocators are not backed
by the page allocator and thus would ignore GFP_ZERO.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 Documentation/DMA-API.txt   | 9 ---------
 include/linux/dma-mapping.h | 7 ++++---
 2 files changed, 4 insertions(+), 12 deletions(-)

diff --git a/Documentation/DMA-API.txt b/Documentation/DMA-API.txt
index 016eb6909b8a..e133ccd60228 100644
--- a/Documentation/DMA-API.txt
+++ b/Documentation/DMA-API.txt
@@ -58,15 +58,6 @@ specify the ``GFP_`` flags (see kmalloc()) for the allocation (the
 implementation may choose to ignore flags that affect the location of
 the returned memory, like GFP_DMA).
 
-::
-
-	void *
-	dma_zalloc_coherent(struct device *dev, size_t size,
-			    dma_addr_t *dma_handle, gfp_t flag)
-
-Wraps dma_alloc_coherent() and also zeroes the returned memory if the
-allocation attempt succeeded.
-
 ::
 
 	void
diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
index f422aec0f53c..a52c6409bdc2 100644
--- a/include/linux/dma-mapping.h
+++ b/include/linux/dma-mapping.h
@@ -644,12 +644,13 @@ static inline unsigned long dma_max_pfn(struct device *dev)
 }
 #endif
 
+/*
+ * Please always use dma_alloc_coherent instead as it already zeroes the memory!
+ */
 static inline void *dma_zalloc_coherent(struct device *dev, size_t size,
 					dma_addr_t *dma_handle, gfp_t flag)
 {
-	void *ret = dma_alloc_coherent(dev, size, dma_handle,
-				       flag | __GFP_ZERO);
-	return ret;
+	return dma_alloc_coherent(dev, size, dma_handle, flag);
 }
 
 static inline int dma_get_cache_alignment(void)
-- 
2.19.2

[OpenRISC] ensure dma_alloc_coherent always returns zeroed memory

[Christoph Hellwig]

And in various places this used GFP_ZERO instead of __GFP_ZERO,
so won't compile.

The fixed version is available here:

http://git.infradead.org/users/hch/misc.git/shortlog/refs/heads/dma-alloc-always-zero

[OpenRISC] ensure dma_alloc_coherent always returns zeroed memory

[Christoph Hellwig]

FYI, I've picked this up for dma-mapping for-next now.

[OpenRISC] ensure dma_alloc_coherent always returns zeroed memory

[hch]

On Thu, Dec 20, 2018 at 02:32:52PM +0000, Eugeniy Paltsev wrote:
> Hi Christoph,
> 
> I test kernel from your 'dma-alloc-always-zero' branch, and as
> I can see we have DMA peripherals (like USB) broken.

I would be really surprised if that is caused by the patch to add
the zeroing.  Can you check which commit caused the issue by bisecting
from a known good baseline?

[OpenRISC] ensure dma_alloc_coherent always returns zeroed memory

[hch]

On Thu, Dec 20, 2018 at 02:39:20PM +0000, Eugeniy Paltsev wrote:
> > I would be really surprised if that is caused by the patch to add
> > the zeroing. 
> Me too :)
> 
> >  Can you check which commit caused the issue by bisecting
> > from a known good baseline?
> 
> Yep. At least kernel build from v4.20-rc4 (which is base for your branch)
> seems to work fine.

Well, the branch has quite a few commits.  Can you check the commit
just before the zeroing to start, and if that is already broken (which
I suspect) bisect the offending commit?

[OpenRISC] ensure dma_alloc_coherent always returns zeroed memory

[hch]

Btw, can you try wit the very latests dma-mapping-for-next tree
which has a new fix from Thierry Reding that might be related.