Messages in this thread | | | Date | Tue, 09 Apr 2013 11:25:27 +0800 | From | Dave Young <> | Subject | Re: [PATCH v3 1/4] x86, kdump: Set crashkernel_low automatically |
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On 04/09/2013 02:37 AM, Yinghai Lu wrote: > On Mon, Apr 8, 2013 at 12:09 AM, Dave Young <dyoung@redhat.com> wrote: >>> We have now modified crashkernel=X to allocate memory beyong 4G (if >>> available) and do not allocate low range for crashkernel if the user >>> does not specify that with crashkernel_low=Y. This causes regression >>> if iommu is not enabled. Without iommu, swiotlb needs to be setup in >>> first 4G and there is no low memory available to second kernel. >> >> Is it possible to reuse the 1st kernel swiotlb region in 2nd capture >> kernel if it's available? > > If the first kernel is using intel iommu, and swiotlb is freed after intel > iommus is enabled in first kernel.
Ok, also it's hard to handle such as 1st kernel iommu=off, 2nd kernel iommu=on etc.
I have another question, under x86_64 consider 1st kernel memory < 4G, is the swiotlb memory still necessary?
> >> >>> >>> Set crashkernel_low automatically if the user does not specify that. >>> >>> For system that does support IOMMU with kdump properly, user could >>> specify crashkernel_low=0 to save that 72M low ram. >> >> How about make swiotlb size tunable in 1st kernel as well such as adding >> a swiotlb_size= to cmdline, if it's set in 1st kernel crashkernel >> reserving code can take it automaticlly. >> > can not understand this.
This maybe out of topic. I means swiotlb size is hardcoded, I'm thinking how about make it configurable via kconfig or boot cmdline.
> > Thanks > > Yinghai >
-- Thanks Dave
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