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Message-ID: <20151007194544.GA24348@l.oracle.com> Date: Wed, 7 Oct 2015 15:45:44 -0400 From: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com> To: Christian Melki <christian.melki@...ata.com> Cc: joro@...tes.org, linux-kernel@...r.kernel.org Subject: Re: Fwd: SWIOTLB on 32-bit PAE On Mon, Oct 05, 2015 at 05:31:33PM +0200, Christian Melki wrote: > Yes. Operator error indeed. > > Thanks for asking. Included is the same patch with the SoB. I've stuck it at https://git.kernel.org/cgit/linux/kernel/git/konrad/swiotlb.git/ #stable/for-linus-4.3 Will send it out tomorrow if there are no #linux-next issues. > > On 10/05/2015 04:21 PM, Konrad Rzeszutek Wilk wrote: > >On Mon, Oct 05, 2015 at 12:44:55PM +0200, Christian Melki wrote: > >>Joerg, > >> > >>I already sent the patch for Kconfig change to the list. > >>But I discovered something even more disturbing which I mailed Konrad about. > >>With the change my machine does not hang any more, but instead corrupts data > >>which is written. The data however is readable on the machine which > >>corrupted it, unreadable on the other machine without the patch. I don't > >>understand what is going on. I have never encountered "selective" file > >>corruption of fs on different machines. The fs itself checks out cleanly > >>with badblock control (ext4). I fail to understand what is happening. > > > >And I believe this ended up being an operator error? > > > >With the patch you sent, you didn't include your SoB > >(Signed-off-By). I would like to include your patch but I cannot > >with your SoB. It is matter of reading to Documentation/SubmittingPatches > >and just consenting to the Certificate in there. > > > >If you are uncomfortable with that - that is OK, I can make this > >patch myself (a one liner :-)) but I figured it owuld be nice > >for you to have all the credit. > >> > >>Regards, > >>Christian > >> > >>-------- Forwarded Message -------- > >>Subject: SWIOTLB on 32-bit PAE > >>Date: Mon, 5 Oct 2015 10:31:39 +0200 > >>From: Christian Melki <christian.melki@...ata.com> > >>To: linux-kernel@...r.kernel.org > >>CC: konrad.wilk@...cle.com > >> > >>Hi, > >> > >>I discovered that my 32-bit PAE 4.2.0 kernel (no IOMMU code) would hang > >>when writing to my USB disk. The kernel spews million(-ish messages per > >>sec) to syslog, effectively "hanging" userspace with my kernel. > >> > >>Oct 2 14:33:06 voodoochild kernel: [ 223.287447] nommu_map_sg: > >>overflow 25dcac000+1024 of device mask ffffffff > >>Oct 2 14:33:06 voodoochild kernel: [ 223.287448] nommu_map_sg: > >>overflow 25dcac000+1024 of device mask ffffffff > >>Oct 2 14:33:06 voodoochild kernel: [ 223.287449] nommu_map_sg: > >>overflow 25dcac000+1024 of device mask ffffffff > >>... etc ... > >> > >>In my kernel config I noticed that SWIOTLB was not on. It seems SWIOTLB > >>is provided for 64-bit and 32-bit with IOMMU/AGPGART code. But if I > >>compiled the kernel with PAE and no IOMMU and no other GART code, I > >>would not get SWIOTLB. I'd like to think that SWIOTLB should be selected > >>for 32-bit PAE as default. > >> > >>I have attached a oneliner patch which does that. > >>The patch works for me. The issue where the kernel more or less runs > >>endless bashing of (nommu_?)map_sg when failing is another problem I > >>guess. I expected the kernel/drivers to have some more graceful > >>handling, but I know to little about this area to have a proper opinion. > >> > >>Regards, > >>Christian > >> > >> > >> > > > >>diff -urN linux-4.2.orig/arch/x86/Kconfig linux-4.2/arch/x86/Kconfig > >>--- linux-4.2.orig/arch/x86/Kconfig 2015-10-05 08:56:58.933313678 +0200 > >>+++ linux-4.2/arch/x86/Kconfig 2015-10-05 09:00:00.916306025 +0200 > >>@@ -1282,6 +1282,7 @@ > >> config X86_PAE > >> bool "PAE (Physical Address Extension) Support" > >> depends on X86_32 && !HIGHMEM4G > >>+ select SWIOTLB > >> ---help--- > >> PAE is required for NX support, and furthermore enables > >> larger swapspace support for non-overcommit purposes. It > >> > > > > diff -urN linux-4.2.orig/arch/x86/Kconfig linux-4.2/arch/x86/Kconfig > --- linux-4.2.orig/arch/x86/Kconfig 2015-10-05 08:56:58.933313678 +0200 > +++ linux-4.2/arch/x86/Kconfig 2015-10-05 09:00:00.916306025 +0200 > @@ -1282,6 +1282,7 @@ > config X86_PAE > bool "PAE (Physical Address Extension) Support" > depends on X86_32 && !HIGHMEM4G > + select SWIOTLB > ---help--- > PAE is required for NX support, and furthermore enables > larger swapspace support for non-overcommit purposes. It > > Signed-off-by: Christian Melki <christian.melki@...ata.com> -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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