On 04/09/2013 02:37 AM, Yinghai Lu wrote: > On Mon, Apr 8, 2013 at 12:09 AM, Dave Young <dyo...@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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/