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SubjectRe: [PATCH] x86: fix gart iommu using for amd 64 bit system
FUJITA Tomonori wrote:
> On Sat, 21 Nov 2009 20:24:52 -0800
> Yinghai Lu <yinghai@kernel.org> wrote:
>
>> amd 64 systems that
>> 1. do not have AGP
>> 2. do not have IOMMU
>> 3. mem > 4g
>> 4. BIOS do not allocate correct gart in NB.
>> will leave them to use SWIOTLB forcely.
>
> Sorry, I forgot about this GART workaround.
>
>
>> Index: linux-2.6/arch/x86/kernel/pci-dma.c
>> ===================================================================
>> --- linux-2.6.orig/arch/x86/kernel/pci-dma.c
>> +++ linux-2.6/arch/x86/kernel/pci-dma.c
>> @@ -124,11 +124,12 @@ void __init pci_iommu_alloc(void)
>> /* free the range so iommu could get some range less than 4G */
>> dma32_free_bootmem();
>> #endif
>> + if (!swiotlb_force)
>> + gart_iommu_hole_init();
>> +
>> if (pci_swiotlb_init())
>> return;
>>
>> - gart_iommu_hole_init();
>> -
>> detect_calgary();
>>
>> detect_intel_iommu();
>
> I prefer to detect all the IOMMU drivers in a consistent way;
> detecting only GART before swioltb doesn't look nice.
>
> As we did before, we could detect all the IOMMU driver before
> swiotlb. However, I think that it's better to simply change
> pci_swiotlb_init() not to steal the preallocate GART workaround memory.
>
> btw, initializing swiotlb before IOMMU detection is useful to GART
> too? If GART can't allocate the workaround memory, then the kernel
> panic now. We can use swiotlb instead in that case?
>
> =
> From: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
> Subject: [PATCH] x86: stop swiotlb stealing the GART workaround memory
>
> swiotlb wrongly uses the GART workaround memory (for bad BIOS) that
> dma32_reserv_bootmem allocates. We need to initialize swiotlb before
> dma32_free_bootmem().
>
> Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
> ---
> arch/x86/kernel/pci-dma.c | 6 +++++-
> 1 files changed, 5 insertions(+), 1 deletions(-)
>
> diff --git a/arch/x86/kernel/pci-dma.c b/arch/x86/kernel/pci-dma.c
> index afcc58b..26fe2cd 100644
> --- a/arch/x86/kernel/pci-dma.c
> +++ b/arch/x86/kernel/pci-dma.c
> @@ -120,11 +120,15 @@ static void __init dma32_free_bootmem(void)
>
> void __init pci_iommu_alloc(void)
> {
> + int use_swiotlb;
> +
> + use_swiotlb = pci_swiotlb_init();
> +
> #ifdef CONFIG_X86_64
> /* free the range so iommu could get some range less than 4G */
> dma32_free_bootmem();
> #endif
> - if (pci_swiotlb_init())
> + if (use_swiotlb)
> return;
>
> gart_iommu_hole_init();

pci_swiotlb_init need be called after dma32_free_bootmem
otherwise it could fail for system with lots of memory and numa=off

so dma32_free_bootmem will work for gart_iommu_hole_init and pci_swiotlb_init..
make sure they can get RAM < 4g.

also in gart_iommu_hole_init we need check swiotlb and !valid_agp...
- } else if (!valid_agp) {
+ } else if (swiotlb && !valid_agp) {

otherwise the the workaround will be skipped...

YH


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