linux-kernel - Re: [PATCH -tip] x86: fix iommu=soft boot option

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Date:	Tue, 01 Dec 2009 22:57:37 -0800
From:	Yinghai Lu <yinghai@...nel.org>
To:	FUJITA Tomonori <fujita.tomonori@....ntt.co.jp>
CC:	mingo@...e.hu, linux-kernel@...r.kernel.org
Subject: Re: [PATCH -tip] x86: fix iommu=soft boot option

FUJITA Tomonori wrote:
> On Mon, 30 Nov 2009 23:42:00 -0800
> Yinghai Lu <yinghai@...nel.org> wrote:
> 
>> FUJITA Tomonori wrote:
>>> On Thu, 26 Nov 2009 23:45:33 -0800
>>> Yinghai Lu <yinghai@...nel.org> wrote:
>>>
>>>>>> when AMD64 mem > 4g, no AGP, BIOS set all gart iommu on all nodes size to 32M, and enable bit are set.
>>>>> I have such machine (with sane BIOS).
>>>>>
>>>>> But if BIOS is broken, early_gart_iommu_check() disables GART_EN bit
>>>>> (bits 0)?
>>>> not for 32M small size.
>>>>
>>>> that function only clear that bit when different nodes have different setting.
>>>>
>>>>>> 1. iommu=soft, will go through POINT A and POINT B
>>>>> Not always. if aperture_valid() is true, it doesn't go POINT A. My
>>>>> GART machine doesn't go.
>>>> maybe your bios set GART iommu set to 64M?
>>> Yeah, my machine has sane BIOS.
>>>
>>>
>>>>>> 2. no "iommu=soft", will go through POINT A and POINT C
>>>>> As I said, it's not true about POINT A.
>>>> maybe your bios set GART iommu set to 64M?
>>>>
>>>>>> and all will reach POINT X to make sure ENABLE bit is not set.
>>>>> POINT X doesn't look make sure ENABLE bit is not set. It just fixes up
>>>>> (sets) the address and its size.
>>>>                         write_pci_config(bus, slot, 3, AMD64_GARTAPERTURECTL, aper_order << 1);
>>>>
>>>> that bit is that bit 0 of AMD64_GARTAPERTURECTL reg.
>>> Oops, thanks.
>>>
>>> But as I wrote in the previous mail, can you tell me why we need this?
>>> With 2.6.31 my machine uses swiotlb with GART_EN bit enabled.
>>>
>>> My another question is that why can't early_gart_iommu_check()
>>> _always_ disable GART_EN bit?
>> please check
> 
> Thanks.
> 
> As I said, it looks cleaner if early_gart_iommu_check() disables
> GART_EN bit. So this patch looks better but I still have some
> questions.
> 
> 
>> [PATCH] x86: fix gart iommu using for amd 64 bit system -v4
>>
>> after
>> |commit 75f1cdf1dda92cae037ec848ae63690d91913eac
>> |Author: FUJITA Tomonori <fujita.tomonori@....ntt.co.jp>
>> |Date:   Tue Nov 10 19:46:20 2009 +0900
>> |
>> |    x86: Handle HW IOMMU initialization failure gracefully
>> |    
>> |    If HW IOMMU initialization fails (Intel VT-d often does this,
>> |    typically due to BIOS bugs), we fall back to nommu. It doesn't
>> |    work for the majority since nowadays we have more than 4GB
>> |    memory so we must use swiotlb instead of nommu.
>> ...
>>
>> 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.
> 
> As I asked earlier, can you tell me what dma ops such system is
> supposed to use?

gart_dma_ops
 
> 
>> also in pci_iommu_alloc()
>> pci_swiotlb_init is stealing the preallocate range that is for
>> gart_iommu_hole workaround.
>>
>> so restore the sequence...
>>
>> will get back
>> [    0.000000] Your BIOS doesn't leave a aperture memory hole
>> [    0.000000] Please enable the IOMMU option in the BIOS setup
>> [    0.000000] This costs you 64 MB of RAM
>> [    0.000000] Mapping aperture over 65536 KB of RAM @ 20000000
>> ...
>> [   12.702822] calling  pci_iommu_init+0x0/0x31 @ 1
>> [   12.708728] PCI-DMA: Disabling AGP.
>> [   12.712812] PCI-DMA: aperture base @ 20000000 size 65536 KB
>> [   12.718384] PCI-DMA: using GART IOMMU.
>> [   12.722139] PCI-DMA: Reserving 64MB of IOMMU area in the AGP aperture
>> [   12.736944] initcall pci_iommu_init+0x0/0x31 returned 0 after 28802 usecs
>>
>> -v2: call shutdown when no agp is there
> 
> Is this change related with my above patchset?

looks like one bug that is exposed by
commit 338bac527ed0e35b4cb50390972f15d3cbce92ca
Author: FUJITA Tomonori <fujita.tomonori@....ntt.co.jp>
Date:   Tue Oct 27 16:34:44 2009 +0900

    x86: Use x86_platform for iommu_shutdown
    
    This patch cleans up pci_iommu_shutdown() a bit to use
    x86_platform (similar to how IA64 initializes an IOMMU driver).
    
    This adds iommu_shutdown() to x86_platform to avoid calling
    every IOMMUs' shutdown functions in pci_iommu_shutdown() in
    order. The IOMMU shutdown functions are platform specific (we
    don't have multiple different IOMMU hardware) so the current way
    is pointless.
    
    An IOMMU driver sets x86_platform.iommu_shutdown to the shutdown
    function if necessary.
    
    Signed-off-by: FUJITA Tomonori <fujita.tomonori@....ntt.co.jp>
    Cc: joerg.roedel@....com
    LKML-Reference: <20091027163358F.fujita.tomonori@....ntt.co.jp>
    Signed-off-by: Ingo Molnar <mingo@...e.hu>

diff --git a/arch/x86/kernel/pci-gart_64.c b/arch/x86/kernel/pci-gart_64.c
index a7f1b64..a9bcdf7 100644
--- a/arch/x86/kernel/pci-gart_64.c
+++ b/arch/x86/kernel/pci-gart_64.c
@@ -39,6 +39,7 @@
 #include <asm/swiotlb.h>
 #include <asm/dma.h>
 #include <asm/k8.h>
+#include <asm/x86_init.h>
 
 static unsigned long iommu_bus_base;   /* GART remapping area (physical) */
 static unsigned long iommu_size;       /* size of remapping area bytes */
@@ -688,12 +689,12 @@ static struct dma_map_ops gart_dma_ops = {
        .free_coherent                  = gart_free_coherent,
 };
 
-void gart_iommu_shutdown(void)
+static void gart_iommu_shutdown(void)
 {
        struct pci_dev *dev;
        int i;
 
-       if (no_agp && (dma_ops != &gart_dma_ops))
+       if (no_agp)
                return;
 
        for (i = 0; i < num_k8_northbridges; i++) {
@@ -838,6 +839,7 @@ void __init gart_iommu_init(void)
 
        flush_gart();
        dma_ops = &gart_dma_ops;
+       x86_platform.iommu_shutdown = gart_iommu_shutdown;
 }
 
 void __init gart_parse_options(char *p)

on system without agp, the gart should be shutdown during system shutdown. so make next kexeced kernel happy.

> 
> 
>> -v3: add check_store to restore state for swiotlb
>>      separate pci_swiotlb_detect and pci_swiotlb_init from FUJITA
>> -v4: disable translating in early_gart_iommu_check according to FUJITA
> 
> Why can't we always disable translation in early_gart_iommu_check? We
> really need search_agp_bridge() in early_gart_iommu_check()?

just don't want to messed them up.

YH
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