On Tue, Apr 6, 2010 at 2:13 PM, Vivek Goyal <vgoyal at redhat.com> wrote: > On Tue, Apr 06, 2010 at 04:39:56PM -0400, Vivek Goyal wrote: >> On Tue, Apr 06, 2010 at 07:51:06PM +0200, Joerg Roedel wrote: >> > On Tue, Apr 06, 2010 at 10:42:57AM -0700, Chris Wright wrote: >> > > * Joerg Roedel (joro at 8bytes.org) wrote: >> > > > On Sun, Apr 04, 2010 at 02:44:36AM -0700, Eric W. Biederman wrote: >> > > > > Joerg Roedel <joro at 8bytes.org> writes: >> > > > > >> > > > > > On Sun, Apr 04, 2010 at 09:24:30AM +0200, Bernhard Walle wrote: >> > > > > >> Am 03.04.10 19:49, schrieb Eric W. Biederman: >> > > > > >> > Not a problem. ?We require a lot of things of the kdump kernel, >> > > > > >> > and it is immediately apparent in a basic sanity test. >> > > > > >> >> > > > > >> Also, in most cases (for example: distribution kernels), the kdump >> > > > > >> kernel nowadays is identical to the running kernel. So, if the running >> > > > > >> kernel has IOMMU support, the kdump kernel also has. >> > > > > > >> > > > > > Yes, I know. But is that a requirement for kexec? >> > > > > >> > > > > For normal kexec no. ?That path is expected to do a clean hardware >> > > > > shutdown. >> > > > > >> > > > > For kexec on panic aka kdump the requirement is that your your crash >> > > > > kernel be able to initialize your hardware from any state it can be >> > > > > put in. >> > > > >> > > > Ok, if you show me where this is documented for everybody then I am >> > > > probably convinced :-) >> > > > We should fixup the gart initialization anyway. >> > > >> > > So, you planning to pull in all 4 patches then? >> > >> > Yes, I will apply them tomorrow and write a fix for the GART issue this >> > may introduce. >> > >> >> Hi Joerg, >> >> Going through the old mail thread, I think the commit you pointed to was >> primarily introduced to solve kexec + GART issue and not necessarily kdump >> issue. >> >> In fact disabling IOMMU patch was introduced by you. >> >> Author: Joerg Roedel <joerg.roedel at amd.com> >> Date: ? Tue Jun 9 17:56:09 2009 +0200 >> >> ? ? x86: disable IOMMUs on kernel crash >> >> ? ? If the IOMMUs are still enabled when the kexec kernel boots access to >> ? ? the disk is not possible. This is bad for tools like kdump or anything >> ? ? else which wants to use PCI devices. >> >> ? ? Signed-off-by: Joerg Roedel <joerg.roedel at amd.com> >> >> I am assuming you introduced this patch because you faced issues with >> amd-iommu and not GART. >> >> So basically GART should have been working with kdump even before you >> introduced disabling iommu patch in kdump path. > > Looking at following commit, we were still not shutting down GART and > fixing issues like second kernel accessing the GART aperture set by first > kernel. > > commit aaf230424204864e2833dcc1da23e2cb0b9f39cd > Author: Yinghai Lu <Yinghai.Lu at Sun.COM> > Date: ? Wed Jan 30 13:33:09 2008 +0100 > > ? ?x86: disable the GART early, 64-bit > > ? ?For K8 system: 4G RAM with memory hole remapping enabled, or more than > ? ?4G RAM installed. > > So I guess it should be fine to not shutdown GART in crashing kernel and > then look at the fresh issues which crop up and figure out how to fix > those. not sure if it is related: for crashing kernel, it could do early_memtest to check if some device are still do dma operation. When I use kexec to start second kernel, if enable the early_memtest in second kernel, it will find some pages RAM are BAD, and it will mark them and not use them. memtest=1 should be good enough. Fresh restart will not report there is any BAD ram in the same system. YH
