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Date: Wed, 9 Jan 2013 08:24:09 -0500
From: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
To: Yinghai Lu <yinghai@...nel.org>
Cc: "Eric W. Biederman" <ebiederm@...ssion.com>,
Shuah Khan <shuahkhan@...il.com>,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...e.hu>, "H. Peter Anvin" <hpa@...or.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Borislav Petkov <bp@...en8.de>, Jan Kiszka <jan.kiszka@....de>,
Jason Wessel <jason.wessel@...driver.com>,
linux-kernel@...r.kernel.org, Joerg Roedel <joro@...tes.org>
Subject: Re: [PATCH v7u1 26/31] x86: Don't enable swiotlb if there is not
enough ram for it
On Tue, Jan 08, 2013 at 05:12:02PM -0800, Yinghai Lu wrote:
> On Tue, Jan 8, 2013 at 5:07 PM, Yinghai Lu <yinghai@...nel.org> wrote:
> > On Tue, Jan 8, 2013 at 4:58 PM, Eric W. Biederman <ebiederm@...ssion.com> wrote:
> >
> >>
> >> So instead we need to say?
> >>
> >> + if (no_iotlb_memory)
> >> + panic("Cannot allocate SWIOTLB buffer");
> >> +
> >>
> >> Which is just making the panic a little later than it used to be and
> >> seems completely reasonable.
> >
> > yes, looks some driver just use map_single without checking results.
>
> update one.
Please make it inline.
Anyhow, comments:
> Subject: [PATCH] x86: Don't panic if can not alloc buffer for swiotlb
>
> Normal boot path on system with iommu support:
> swiotlb buffer will be allocated early at first and then try to initialize
> iommu, if iommu for intel or amd could setup properly, swiotlb buffer
Intel or AMD
> will be freed.
>
> The early allocating is with bootmem, and could panic when we try to use
> kdump with buffer above 4G only, or with memmap to limit mem under 4G.
Can you provide the memmap example in here, please.
>
> According to Eric, add _nopanic version and no_iotlb_memory to fail
> map single later if swiotlb is still needed.
>
> -v2: don't pass nopanic, and use -ENOMEM return value according to Eric.
> panic early instead of using swiotlb_full to panic...according to Eric/Konrad.
>
> Suggested-by: Eric W. Biederman <ebiederm@...ssion.com>
> Signed-off-by: Yinghai Lu <yinghai@...nel.org>
> Cc: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
> Cc: Joerg Roedel <joro@...tes.org>
>
> ---
> arch/x86/kernel/pci-swiotlb.c | 2 -
> include/linux/swiotlb.h | 1
> lib/swiotlb.c | 54 +++++++++++++++++++++++++++++++++++-------
> 3 files changed, 47 insertions(+), 10 deletions(-)
>
> Index: linux-2.6/include/linux/swiotlb.h
> ===================================================================
> --- linux-2.6.orig/include/linux/swiotlb.h
> +++ linux-2.6/include/linux/swiotlb.h
> @@ -22,6 +22,7 @@ extern int swiotlb_force;
> */
> #define IO_TLB_SHIFT 11
>
> +void swiotlb_init_nopanic(int verbose);
No need for that, lets just use the swiotlb_init version.
> extern void swiotlb_init(int verbose);
> extern void swiotlb_init_with_tbl(char *tlb, unsigned long nslabs, int verbose);
> extern unsigned long swiotlb_nr_tbl(void);
> Index: linux-2.6/lib/swiotlb.c
> ===================================================================
> --- linux-2.6.orig/lib/swiotlb.c
> +++ linux-2.6/lib/swiotlb.c
> @@ -122,11 +122,18 @@ static dma_addr_t swiotlb_virt_to_bus(st
> return phys_to_dma(hwdev, virt_to_phys(address));
> }
>
> +static bool no_iotlb_memory;
> +
> void swiotlb_print_info(void)
> {
> unsigned long bytes = io_tlb_nslabs << IO_TLB_SHIFT;
> unsigned char *vstart, *vend;
>
> + if (no_iotlb_memory) {
> + printk(KERN_INFO "software IO TLB: No low mem\n");
KERN_ERROR or KERN_WARN
> + return;
> + }
> +
> vstart = phys_to_virt(io_tlb_start);
> vend = phys_to_virt(io_tlb_end);
>
> @@ -136,7 +143,8 @@ void swiotlb_print_info(void)
> bytes >> 20, vstart, vend - 1);
> }
>
> -void __init swiotlb_init_with_tbl(char *tlb, unsigned long nslabs, int verbose)
> +static int __init __swiotlb_init_with_tbl(char *tlb, unsigned long nslabs,
> + int verbose)
Collapse it in. Meaning make swiotlb_init_with_tbl return an int. This will
require altering the Xen version of Xen-SWIOTLB but that should be fairly easy.
> {
> void *v_overflow_buffer;
> unsigned long i, bytes;
> @@ -150,9 +158,10 @@ void __init swiotlb_init_with_tbl(char *
> /*
> * Get the overflow emergency buffer
> */
> - v_overflow_buffer = alloc_bootmem_low_pages(PAGE_ALIGN(io_tlb_overflow));
> + v_overflow_buffer = alloc_bootmem_low_pages_nopanic(
> + PAGE_ALIGN(io_tlb_overflow));
> if (!v_overflow_buffer)
> - panic("Cannot allocate SWIOTLB overflow buffer!\n");
> + return -ENOMEM;
>
> io_tlb_overflow_buffer = __pa(v_overflow_buffer);
>
> @@ -169,14 +178,22 @@ void __init swiotlb_init_with_tbl(char *
>
> if (verbose)
> swiotlb_print_info();
> +
> + return 0;
> +}
> +
> +void __init swiotlb_init_with_tbl(char *tlb, unsigned long nslabs, int verbose)
> +{
> + if (__swiotlb_init_with_tbl(tlb, nslabs, verbose) == -ENOMEM)
> + panic("Cannot allocate SWIOTLB buffer");
And that way we can get rid of this.
> }
>
> /*
> * Statically reserve bounce buffer space and initialize bounce buffer data
> * structures for the software IO TLB used to implement the DMA API.
> */
> -static void __init
> -swiotlb_init_with_default_size(size_t default_size, int verbose)
> +static __init
> +int swiotlb_init_with_default_size(size_t default_size, int verbose)
> {
> unsigned char *vstart;
> unsigned long bytes;
> @@ -191,17 +208,33 @@ swiotlb_init_with_default_size(size_t de
> /*
> * Get IO TLB memory from the low pages
> */
> - vstart = alloc_bootmem_low_pages(PAGE_ALIGN(bytes));
> + vstart = alloc_bootmem_low_pages_nopanic(PAGE_ALIGN(bytes));
> if (!vstart)
> - panic("Cannot allocate SWIOTLB buffer");
> + return -ENOMEM;
>
> - swiotlb_init_with_tbl(vstart, io_tlb_nslabs, verbose);
> + if (__swiotlb_init_with_tbl(vstart, io_tlb_nslabs, verbose) == -ENOMEM) {
> + free_bootmem(io_tlb_start,
> + PAGE_ALIGN(io_tlb_nslabs << IO_TLB_SHIFT));
> + return -ENOMEM;
> + }
> +
> + return 0;
> +}
> +
> +void __init
> +swiotlb_init_nopanic(int verbose)
> +{
> + /* default to 64MB */
> + if (swiotlb_init_with_default_size(64 * (1<<20), verbose) == -ENOMEM)
> + pr_warn("Cannot allocate SWIOTLB buffer");
> }
And this
>
> void __init
> swiotlb_init(int verbose)
> {
> - swiotlb_init_with_default_size(64 * (1<<20), verbose); /* default to 64MB */
> + /* default to 64MB */
> + if (swiotlb_init_with_default_size(64 * (1<<20), verbose) == -ENOMEM)
> + panic("Cannot allocate SWIOTLB buffer");
> }
And just make this function return 'int'
>
> /*
> @@ -405,6 +438,9 @@ phys_addr_t swiotlb_tbl_map_single(struc
> unsigned long offset_slots;
> unsigned long max_slots;
>
> + if (no_iotlb_memory)
> + panic("Cannot allocate SWIOTLB buffer");
> +
> mask = dma_get_seg_boundary(hwdev);
>
> tbl_dma_addr &= mask;
> Index: linux-2.6/arch/x86/kernel/pci-swiotlb.c
> ===================================================================
> --- linux-2.6.orig/arch/x86/kernel/pci-swiotlb.c
> +++ linux-2.6/arch/x86/kernel/pci-swiotlb.c
> @@ -91,7 +91,7 @@ IOMMU_INIT(pci_swiotlb_detect_4gb,
> void __init pci_swiotlb_init(void)
> {
> if (swiotlb) {
> - swiotlb_init(0);
> + swiotlb_init_nopanic(0);
> dma_ops = &swiotlb_dma_ops;
> }
> }
--
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