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Date: Thu, 26 Nov 2009 23:45:33 -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 Wed, 25 Nov 2009 14:33:27 -0800
> Yinghai Lu <yinghai@...nel.org> wrote:
>
>> in aperture_64.c::gart_iommu_hole_init()
>> printk(KERN_INFO "Checking aperture...\n");
>>
>> if (!fallback_aper_force)
>> agp_aper_base = search_agp_bridge(&agp_aper_order, &valid_agp);
>>
>> fix = 0;
>> node = 0;
>> for (i = 0; i < ARRAY_SIZE(bus_dev_ranges); i++) {
>> int bus;
>> int dev_base, dev_limit;
>>
>> bus = bus_dev_ranges[i].bus;
>> dev_base = bus_dev_ranges[i].dev_base;
>> dev_limit = bus_dev_ranges[i].dev_limit;
>>
>> for (slot = dev_base; slot < dev_limit; slot++) {
>>
>> if (!early_is_k8_nb(read_pci_config(bus, slot, 3, 0x00)))
>> continue;
>>
>> iommu_detected = 1;
>> gart_iommu_aperture = 1;
>>
>> aper_order = (read_pci_config(bus, slot, 3, AMD64_GARTAPERTURECTL) >> 1) & 7;
>> aper_size = (32 * 1024 * 1024) << aper_order;
>> aper_base = read_pci_config(bus, slot, 3, AMD64_GARTAPERTUREBASE) & 0x7fff;
>> aper_base <<= 25;
>>
>> printk(KERN_INFO "Node %d: aperture @ %Lx size %u MB\n",
>> node, aper_base, aper_size >> 20);
>> node++;
>>
>> if (!aperture_valid(aper_base, aper_size, 64<<20)) {
>> if (valid_agp && agp_aper_base &&
>> agp_aper_base == aper_base &&
>> agp_aper_order == aper_order) {
>> /* the same between two setting from NB and agp */
>> if (!no_iommu &&
>> max_pfn > MAX_DMA32_PFN &&
>> !printed_gart_size_msg) {
>> printk(KERN_ERR "you are using iommu with agp, but GART size is less than 64M\n");
>> printk(KERN_ERR "please increase GART size in your BIOS setup\n");
>> printk(KERN_ERR "if BIOS doesn't have that option, contact your HW vendor!\n");
>> printed_gart_size_msg = 1;
>> }
>> } else {
>> POINT A:
>> fix = 1;
>> goto out;
>> }
>> }
>>
>> if ((last_aper_order && aper_order != last_aper_order) ||
>> (last_aper_base && aper_base != last_aper_base)) {
>> fix = 1;
>> goto out;
>> }
>> last_aper_order = aper_order;
>> last_aper_base = aper_base;
>> }
>> }
>>
>> out:
>> if (!fix && !fallback_aper_force) {
>> if (last_aper_base) {
>> unsigned long n = (32 * 1024 * 1024) << last_aper_order;
>>
>> insert_aperture_resource((u32)last_aper_base, n);
>> }
>> return;
>> }
>>
>> if (!fallback_aper_force) {
>> aper_alloc = agp_aper_base;
>> aper_order = agp_aper_order;
>> }
>>
>> if (aper_alloc) {
>> /* Got the aperture from the AGP bridge */
>> } else if (swiotlb && !valid_agp) {
>> POINT: B
>> /* Do nothing */
>> } else if ((!no_iommu && max_pfn > MAX_DMA32_PFN) ||
>> force_iommu ||
>> valid_agp ||
>> fallback_aper_force) {
>> POINT: C
>> printk(KERN_INFO
>> "Your BIOS doesn't leave a aperture memory hole\n");
>> printk(KERN_INFO
>> "Please enable the IOMMU option in the BIOS setup\n");
>> printk(KERN_INFO
>> "This costs you %d MB of RAM\n",
>> 32 << fallback_aper_order);
>>
>> aper_order = fallback_aper_order;
>> aper_alloc = allocate_aperture();
>> if (!aper_alloc) {
>> /*
>> * Could disable AGP and IOMMU here, but it's
>> * probably not worth it. But the later users
>> * cannot deal with bad apertures and turning
>> * on the aperture over memory causes very
>> * strange problems, so it's better to panic
>> * early.
>> */
>> panic("Not enough memory for aperture");
>> }
>> } else {
>> return;
>> }
>>
>> POINT X:
>>
>> /* Fix up the north bridges */
>> for (i = 0; i < ARRAY_SIZE(bus_dev_ranges); i++) {
>> int bus;
>> int dev_base, dev_limit;
>>
>> bus = bus_dev_ranges[i].bus;
>> dev_base = bus_dev_ranges[i].dev_base;
>> dev_limit = bus_dev_ranges[i].dev_limit;
>> for (slot = dev_base; slot < dev_limit; slot++) {
>> if (!early_is_k8_nb(read_pci_config(bus, slot, 3, 0x00)))
>> continue;
>>
>> /* Don't enable translation yet. That is done later.
>> Assume this BIOS didn't initialise the GART so
>> just overwrite all previous bits */
>> write_pci_config(bus, slot, 3, AMD64_GARTAPERTURECTL, aper_order << 1);
>> write_pci_config(bus, slot, 3, AMD64_GARTAPERTUREBASE, aper_alloc >> 25);
>> }
>> }
>>
>> 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?
>
>
>> 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.
YH
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