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Message-ID: <1344265686.2486.13.camel@lorien2>
Date: Mon, 06 Aug 2012 09:08:06 -0600
From: Shuah Khan <shuah.khan@...com>
To: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
Cc: fujita.tomonori@....ntt.co.jp, akpm@...ux-foundation.org,
paul.gortmaker@...driver.com, bhelgaas@...gle.com,
amwang@...hat.com, rob@...dley.net, linux-kernel@...r.kernel.org,
linux-doc@...r.kernel.org, shuahkhan@...il.com
Subject: Re: [PATCH RESEND] swiotlb: Disable swiotlb overflow support when
CONFIG_ISA is disabled
On Tue, 2012-07-24 at 20:48 -0400, Konrad Rzeszutek Wilk wrote:
> On Tue, Jul 24, 2012 at 01:46:27PM -0600, Shuah Khan wrote:
> > Disable iotlb overflow support when CONFIG_ISA is disabled. Add deprecation
>
> You need to check one more thing. In the email I mentioned that the bulk
> of the drivers that utilize this are ISA, but there are also some that
> are PCI dependent.
>
> So I grepped for anything that does 'dma_map_page' and some of them are
> even PCIe, for example: drivers/net/ethernet/intel/ixgbevf/ixgbevf_main.c
>
> Which means that the check for CONFIG_ISA is not sufficient.
Thanks for the review and comments. Got back from a two week vacation
and going to start work on this. I started sending fixes to drivers I
can find that don't check dma mapping errors as well.
-- Shuah
>
> > notice warning message and deprecation schedule documentation. This is the
> > first step towards removing overflow support, to be consistent with other
> > iommu implementations and return DMA_ERROR_CODE. This disabling step is for
> > finding drivers that don't call dma_mapping_error to check for errors returned
> > by the mapping interface. Once drivers are fixed overflow support can be
> > removed.
> >
> > Signed-off-by: Shuah Khan <shuah.khan@...com>
>
> Did you do a cross compile on IA64 just to double check? Comments below.
>
> > ---
> > Documentation/feature-removal-schedule.txt | 22 ++++++--
> > lib/swiotlb.c | 79 +++++++++++++++++++++-------
> > 2 files changed, 79 insertions(+), 22 deletions(-)
> >
> > diff --git a/Documentation/feature-removal-schedule.txt b/Documentation/feature-removal-schedule.txt
> > index 5979c3e..ce6c0ae 100644
> > --- a/Documentation/feature-removal-schedule.txt
> > +++ b/Documentation/feature-removal-schedule.txt
> > @@ -35,7 +35,7 @@ What: x86_32 "no-hlt" cmdline param
> > When: 2012
> > Why: remove a branch from idle path, simplify code used by everybody.
> > This option disabled the use of HLT in idle and machine_halt()
> > - for hardware that was flakey 15-years ago. Today we have
> > + for hardware that was flaky 15-years ago. Today we have
>
> Ummm, that is not part of what this patch should be doing.
>
> > "idle=poll" that removed HLT from idle, and so if such a machine
> > is still running the upstream kernel, "idle=poll" is likely sufficient.
> > Who: Len Brown <len.brown@...el.com>
> > @@ -160,7 +160,7 @@ Files: arch/*/kernel/*_ksyms.c
> > Check: kernel_thread
> > Why: kernel_thread is a low-level implementation detail. Drivers should
> > use the <linux/kthread.h> API instead which shields them from
> > - implementation details and provides a higherlevel interface that
> > + implementation details and provides a higher level interface that
>
> Neither is this.
> > prevents bugs and code duplication
> > Who: Christoph Hellwig <hch@....de>
> >
> > @@ -236,7 +236,7 @@ Who: David Brownell <dbrownell@...rs.sourceforge.net>
> >
> > What: b43 support for firmware revision < 410
> > When: The schedule was July 2008, but it was decided that we are going to keep the
> > - code as long as there are no major maintanance headaches.
> > + code as long as there are no major maintenance headaches.
>
> Or this.
>
> > So it _could_ be removed _any_ time now, if it conflicts with something new.
> > Why: The support code for the old firmware hurts code readability/maintainability
> > and slightly hurts runtime performance. Bugfixes for the old firmware
> > @@ -608,3 +608,19 @@ When: June 2013
> > Why: Unsupported/unmaintained/unused since 2.6
> >
> > ----------------------------
> > +
> > +What: SWIOTLB overflow buffer support.
> > +When: 3.8
> > +Why: Remove SWIOTLB overflow buffer support and return DMA_ERROR_CODE
> > + (a value of zero) to make it consistent with iommu implementation
> > + on Intel, AMD, and swiotlb-xen. In 3.6, Disable iotlb overflow
> > + support when CONFIG_ISA is disabled with the intent to find drivers
> > + that don't call dma_mapping_error to check for errors returned by the
> > + mapping interface. Once drivers are fixed overflow support can be
> > + removed.
> > + If you see any problems related to disabling SWIOTLB overflow buffer,
> > + please report to us!
> > + E-mail us at: linux-kernel@...r.kernel.org
> > +Who: Shuah Khan <shuah.khan@...com> <shuahkhan@...il.com>
> > +
> > +----------------------------
> > diff --git a/lib/swiotlb.c b/lib/swiotlb.c
> > index 45bc1f8..0123bb8 100644
> > --- a/lib/swiotlb.c
> > +++ b/lib/swiotlb.c
> > @@ -15,6 +15,9 @@
> > * 05/09/10 linville Add support for syncing ranges, support syncing for
> > * DMA_BIDIRECTIONAL mappings, miscellaneous cleanup.
> > * 08/12/11 beckyb Add highmem support
> > + * 07/2012 shuahkhan Disable iotlb overflow support when CONFIG_ISA
> > + * is enabled. Remove it for all configs when drivers
> > + * that don't check for mapping errors are fixed.
>
> Don't bother. The changelog is now in the git commit.
>
> > */
> >
> > #include <linux/cache.h>
> > @@ -68,7 +71,11 @@ static unsigned long io_tlb_nslabs;
> > /*
> > * When the IOMMU overflows we return a fallback buffer. This sets the size.
> > */
> > +#if defined(CONFIG_ISA)
> > static unsigned long io_tlb_overflow = 32*1024;
> > +#else
> > +static unsigned long io_tlb_overflow;
> > +#endif
> >
> > static void *io_tlb_overflow_buffer;
> >
> > @@ -92,6 +99,24 @@ static DEFINE_SPINLOCK(io_tlb_lock);
> >
> > static int late_alloc;
> >
> > +static void swiotlb_print_overflow_deprecation_notice(void)
> > +{
> > + if (io_tlb_overflow) {
> > + pr_warn("SWIOTLB overflow buffer will be deprecated.\n"
> > + " If you have a driver that depends on this feature\n"
> > + " please Email us at: linux-kernel@...r.kernel.org,\n"
> > + " Shuah Khan (shuahkhan@...il.com), and\n"
> > + " Konrad Wilk (konrad.wilk@...cle.com)\n");
> > + } else {
> > + pr_warn("SWIOTLB overflow buffer is disabled and will be\n"
> > + " deprecated. Please report problems related to\n"
> > + " disabling overflow buffer to\n"
> > + " linux-kernel@...r.kernel.org,\n"
> > + " Shuah Khan (shuahkhan@...il.com), and\n"
> > + " Konrad Wilk (konrad.wilk@...cle.com)\n");
> > + }
> > +}
> > +
> > static int __init
> > setup_io_tlb_npages(char *str)
> > {
> > @@ -108,7 +133,6 @@ setup_io_tlb_npages(char *str)
> > return 1;
> > }
> > __setup("swiotlb=", setup_io_tlb_npages);
> > -/* make io_tlb_overflow tunable too? */
> >
> > unsigned long swiotlb_nr_tbl(void)
> > {
> > @@ -156,12 +180,18 @@ void __init swiotlb_init_with_tbl(char *tlb, unsigned long nslabs, int verbose)
> > io_tlb_index = 0;
> > io_tlb_orig_addr = alloc_bootmem_pages(PAGE_ALIGN(io_tlb_nslabs * sizeof(phys_addr_t)));
> >
> > - /*
> > - * Get the overflow emergency buffer
> > - */
> > - io_tlb_overflow_buffer = alloc_bootmem_low_pages(PAGE_ALIGN(io_tlb_overflow));
> > - if (!io_tlb_overflow_buffer)
> > - panic("Cannot allocate SWIOTLB overflow buffer!\n");
> > + if (io_tlb_overflow) {
> > + /*
> > + * Get the overflow emergency buffer
> > + */
> > + io_tlb_overflow_buffer = alloc_bootmem_low_pages(
> > + PAGE_ALIGN(io_tlb_overflow));
> > + if (!io_tlb_overflow_buffer)
> > + panic("Cannot allocate SWIOTLB overflow buffer!\n");
> > + }
> > +
> > + swiotlb_print_overflow_deprecation_notice();
> > +
> > if (verbose)
> > swiotlb_print_info();
> > }
> > @@ -264,14 +294,17 @@ swiotlb_late_init_with_default_size(size_t default_size)
> >
> > memset(io_tlb_orig_addr, 0, io_tlb_nslabs * sizeof(phys_addr_t));
> >
> > - /*
> > - * Get the overflow emergency buffer
> > - */
> > - io_tlb_overflow_buffer = (void *)__get_free_pages(GFP_DMA,
> > - get_order(io_tlb_overflow));
> > - if (!io_tlb_overflow_buffer)
> > - goto cleanup4;
> > + if (io_tlb_overflow) {
> > + /*
> > + * Get the overflow emergency buffer
> > + */
> > + io_tlb_overflow_buffer = (void *)
> > + __get_free_pages(GFP_DMA, get_order(io_tlb_overflow));
> > + if (!io_tlb_overflow_buffer)
> > + goto cleanup4;
> > + }
> >
> > + swiotlb_print_overflow_deprecation_notice();
> > swiotlb_print_info();
> >
> > late_alloc = 1;
> > @@ -297,12 +330,13 @@ cleanup1:
> >
> > void __init swiotlb_free(void)
> > {
> > - if (!io_tlb_overflow_buffer)
> > + if (!io_tlb_orig_addr)
> > return;
> >
> > if (late_alloc) {
> > - free_pages((unsigned long)io_tlb_overflow_buffer,
> > - get_order(io_tlb_overflow));
> > + if (io_tlb_overflow_buffer)
> > + free_pages((unsigned long)io_tlb_overflow_buffer,
> > + get_order(io_tlb_overflow));
> > free_pages((unsigned long)io_tlb_orig_addr,
> > get_order(io_tlb_nslabs * sizeof(phys_addr_t)));
> > free_pages((unsigned long)io_tlb_list, get_order(io_tlb_nslabs *
> > @@ -310,8 +344,9 @@ void __init swiotlb_free(void)
> > free_pages((unsigned long)io_tlb_start,
> > get_order(io_tlb_nslabs << IO_TLB_SHIFT));
> > } else {
> > - free_bootmem_late(__pa(io_tlb_overflow_buffer),
> > - PAGE_ALIGN(io_tlb_overflow));
> > + if (io_tlb_overflow_buffer)
> > + free_bootmem_late(__pa(io_tlb_overflow_buffer),
> > + PAGE_ALIGN(io_tlb_overflow));
> > free_bootmem_late(__pa(io_tlb_orig_addr),
> > PAGE_ALIGN(io_tlb_nslabs * sizeof(phys_addr_t)));
> > free_bootmem_late(__pa(io_tlb_list),
> > @@ -681,6 +716,8 @@ dma_addr_t swiotlb_map_page(struct device *dev, struct page *page,
> > map = map_single(dev, phys, size, dir);
> > if (!map) {
> > swiotlb_full(dev, size, dir, 1);
> > + if (!io_tlb_overflow)
> > + return DMA_ERROR_CODE;
> > map = io_tlb_overflow_buffer;
> > }
> >
> > @@ -691,6 +728,8 @@ dma_addr_t swiotlb_map_page(struct device *dev, struct page *page,
> > */
> > if (!dma_capable(dev, dev_addr, size)) {
> > swiotlb_tbl_unmap_single(dev, map, size, dir);
> > + if (!io_tlb_overflow)
> > + return DMA_ERROR_CODE;
> > dev_addr = swiotlb_virt_to_bus(dev, io_tlb_overflow_buffer);
> > }
> >
> > @@ -910,6 +949,8 @@ EXPORT_SYMBOL(swiotlb_sync_sg_for_device);
> > int
> > swiotlb_dma_mapping_error(struct device *hwdev, dma_addr_t dma_addr)
> > {
> > + if (!io_tlb_overflow)
> > + return DMA_ERROR_CODE;
> > return (dma_addr == swiotlb_virt_to_bus(hwdev, io_tlb_overflow_buffer));
> > }
> > EXPORT_SYMBOL(swiotlb_dma_mapping_error);
> > --
> > 1.7.9.5
> >
> >
> >
> > --
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