From: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
To: Andi Kleen <ak@linux.intel.com>
Cc: akataria@vmware.com, Len Brown <lenb@kernel.org>,
the arch/x86 maintainers <x86@kernel.org>,
linux-acpi <linux-acpi@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
Petr Vandrovec <petr@vmware.com>
Subject: Re: [LKML] Re: swiotlb detection should be memory hotplug aware ?
Date: Mon, 15 Mar 2010 20:51:40 -0400 [thread overview]
Message-ID: <20100316005140.GB7622@phenom.dumpdata.com> (raw)
In-Reply-To: <4B9B01F5.3000807@linux.intel.com>
On Fri, Mar 12, 2010 at 07:09:41PM -0800, Andi Kleen wrote:
> , Alok Kataria wrote:
>
> Hi Alok,
>
>> Hi,
>>
>> Looking at the current code swiotlb is initialized for 64bit kernels
>> only when the max_pfn value is greater than 4G (MAX_DMA32_PFN value).
>> So in cases when the initial memory is less than 4GB the kernel boots
>> without enabling swiotlb, when we hotadd memory to such a kernel and go
>> beyond the 4G limit, swiotlb is still disabled. As a result when any
>> 32bit devices start using this newly added memory beyond 4G, the kernel
>> starts spitting error messages like below or in some cases it causes
>> kernel panics.
>
> Yes seems like a real problem.
>
>>
>> 1. Enable swiotlb for all 64bit kernels which have memory hot-add
>> support.
>
> I don't think that's a good idea. It would enable it everywhere on
> distributions which compile with hotadd. Need (2)
>
>> 2. Instead of checking the max_pfn value in pci_swiotlb_detect, check
>> for max_hotpluggable_pfn (or some such) value. Though I don't see such a
>> value readily available. I could parse the SRAT and get hotplug memory
>> information but that will make swiotlb detection logic a little too
>> complex. A quick look around srat_xx.c files and the acpi_memhotplug
>> module didn't find any useful API that could be used directly either.
>> So was wondering if any of you are aware of an easy way to get such
>> information ?
>
> I have a patchkit to revamp the SRAT parsing to store the hotadd information
There is a late mechanism to do kickoff the SWIOTLB. Perhaps the hot-add
could use swiotlb_init_late and start up the SWIOTLB?
> more efficiently (the current way is pretty dumb) I need to repost that.
>
> With that it would be relatively easy to do I think.
>
> -Andi
> --
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next prev parent reply other threads:[~2010-03-16 1:18 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-03-13 2:07 swiotlb detection should be memory hotplug aware ? Alok Kataria
2010-03-13 3:09 ` Andi Kleen
2010-03-15 17:22 ` Alok Kataria
2010-03-16 0:51 ` Konrad Rzeszutek Wilk [this message]
2010-03-16 1:33 ` [LKML] " FUJITA Tomonori
2010-03-16 12:45 ` [LKML] " Konrad Rzeszutek Wilk
2010-03-17 22:48 ` Alok Kataria
2010-07-20 22:14 ` Alok Kataria
2010-07-21 4:58 ` FUJITA Tomonori
2010-07-21 17:13 ` Alok Kataria
2010-07-21 23:44 ` FUJITA Tomonori
2010-07-22 0:03 ` FUJITA Tomonori
2010-07-22 18:34 ` Alok Kataria
2010-07-23 14:22 ` Konrad Rzeszutek Wilk
2010-07-23 14:33 ` Andi Kleen
2010-07-23 14:59 ` Konrad Rzeszutek Wilk
2010-07-23 15:23 ` Andi Kleen
2010-07-28 10:10 ` FUJITA Tomonori
2010-07-28 11:09 ` Andi Kleen
2010-07-28 14:20 ` FUJITA Tomonori
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