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SubjectRe: [PATCH 2/2] gart: reimplement IOMMU_LEAK feature by using DMA_API_DEBUG
On Tue, Apr 14, 2009 at 09:43:19AM +0900, FUJITA Tomonori wrote:
> IOMMU_LEAK, GART's own feature, dumps the used IOMMU entries when
> IOMMU entries is full, which might be useful to find a bad driver that
> eats IOMMU entries.
>
> DMA_API_DEBUG provides the similar feature, debug_dma_dump_mappings,
> and it's better than GART's IOMMU_LEAK feature. GART's IOMMU_LEAK
> feature doesn't say who uses IOMMU entries so it's hard to find a bad
> driver.
>
> This patch reimplements the GART's IOMMU_LEAK feature by using
> DMA_API_DEBUG.
>
> Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>

Yeah, I also had that on my list :-) This feature is indeed unnecessary now.

Acked-by: Joerg Roedel <joerg.roedel@amd.com>

> ---
> arch/x86/Kconfig.debug | 3 +-
> arch/x86/kernel/pci-gart_64.c | 45 +++++++---------------------------------
> 2 files changed, 9 insertions(+), 39 deletions(-)
>
> diff --git a/arch/x86/Kconfig.debug b/arch/x86/Kconfig.debug
> index d8359e7..5865712 100644
> --- a/arch/x86/Kconfig.debug
> +++ b/arch/x86/Kconfig.debug
> @@ -161,8 +161,7 @@ config IOMMU_DEBUG
>
> config IOMMU_LEAK
> bool "IOMMU leak tracing"
> - depends on DEBUG_KERNEL
> - depends on IOMMU_DEBUG
> + depends on IOMMU_DEBUG && DMA_API_DEBUG
> ---help---
> Add a simple leak tracer to the IOMMU code. This is useful when you
> are debugging a buggy device driver that leaks IOMMU mappings.
> diff --git a/arch/x86/kernel/pci-gart_64.c b/arch/x86/kernel/pci-gart_64.c
> index b284b58..1e8920d 100644
> --- a/arch/x86/kernel/pci-gart_64.c
> +++ b/arch/x86/kernel/pci-gart_64.c
> @@ -144,48 +144,21 @@ static void flush_gart(void)
> }
>
> #ifdef CONFIG_IOMMU_LEAK
> -
> -#define SET_LEAK(x) \
> - do { \
> - if (iommu_leak_tab) \
> - iommu_leak_tab[x] = __builtin_return_address(0);\
> - } while (0)
> -
> -#define CLEAR_LEAK(x) \
> - do { \
> - if (iommu_leak_tab) \
> - iommu_leak_tab[x] = NULL; \
> - } while (0)
> -
> /* Debugging aid for drivers that don't free their IOMMU tables */
> -static void **iommu_leak_tab;
> static int leak_trace;
> static int iommu_leak_pages = 20;
>
> static void dump_leak(void)
> {
> - int i;
> static int dump;
>
> - if (dump || !iommu_leak_tab)
> + if (dump)
> return;
> dump = 1;
> - show_stack(NULL, NULL);
>
> - /* Very crude. dump some from the end of the table too */
> - printk(KERN_DEBUG "Dumping %d pages from end of IOMMU:\n",
> - iommu_leak_pages);
> - for (i = 0; i < iommu_leak_pages; i += 2) {
> - printk(KERN_DEBUG "%lu: ", iommu_pages-i);
> - printk_address((unsigned long) iommu_leak_tab[iommu_pages-i],
> - 0);
> - printk(KERN_CONT "%c", (i+1)%2 == 0 ? '\n' : ' ');
> - }
> - printk(KERN_DEBUG "\n");
> + show_stack(NULL, NULL);
> + debug_dma_dump_mappings(NULL);
> }
> -#else
> -# define SET_LEAK(x)
> -# define CLEAR_LEAK(x)
> #endif
>
> static void iommu_full(struct device *dev, size_t size, int dir)
> @@ -248,7 +221,6 @@ static dma_addr_t dma_map_area(struct device *dev, dma_addr_t phys_mem,
>
> for (i = 0; i < npages; i++) {
> iommu_gatt_base[iommu_page + i] = GPTE_ENCODE(phys_mem);
> - SET_LEAK(iommu_page + i);
> phys_mem += PAGE_SIZE;
> }
> return iommu_bus_base + iommu_page*PAGE_SIZE + (phys_mem & ~PAGE_MASK);
> @@ -294,7 +266,6 @@ static void gart_unmap_page(struct device *dev, dma_addr_t dma_addr,
> npages = iommu_num_pages(dma_addr, size, PAGE_SIZE);
> for (i = 0; i < npages; i++) {
> iommu_gatt_base[iommu_page + i] = gart_unmapped_entry;
> - CLEAR_LEAK(iommu_page + i);
> }
> free_iommu(iommu_page, npages);
> }
> @@ -377,7 +348,6 @@ static int __dma_map_cont(struct device *dev, struct scatterlist *start,
> pages = iommu_num_pages(s->offset, s->length, PAGE_SIZE);
> while (pages--) {
> iommu_gatt_base[iommu_page] = GPTE_ENCODE(addr);
> - SET_LEAK(iommu_page);
> addr += PAGE_SIZE;
> iommu_page++;
> }
> @@ -801,11 +771,12 @@ void __init gart_iommu_init(void)
>
> #ifdef CONFIG_IOMMU_LEAK
> if (leak_trace) {
> - iommu_leak_tab = (void *)__get_free_pages(GFP_KERNEL|__GFP_ZERO,
> - get_order(iommu_pages*sizeof(void *)));
> - if (!iommu_leak_tab)
> + int ret;
> +
> + ret = dma_debug_resize_entries(iommu_pages);
> + if (ret)
> printk(KERN_DEBUG
> - "PCI-DMA: Cannot allocate leak trace area\n");
> + "PCI-DMA: Cannot trace all the entries\n");
> }
> #endif
>
> --
> 1.6.0.6
>
>

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