On 03/06/17 at 11:58am, Tom Lendacky wrote: > On 3/1/2017 3:25 AM, Dave Young wrote: > > Hi Tom, > > Hi Dave, > > > > > On 02/17/17 at 10:43am, Tom Lendacky wrote: > > > On 2/17/2017 9:57 AM, Konrad Rzeszutek Wilk wrote: > > > > On Thu, Feb 16, 2017 at 09:47:55AM -0600, Tom Lendacky wrote: > > > > > Provide support so that kexec can be used to boot a kernel when SME is > > > > > enabled. > > > > > > > > Is the point of kexec and kdump to ehh, dump memory ? But if the > > > > rest of the memory is encrypted you won't get much, will you? > > > > > > Kexec can be used to reboot a system without going back through BIOS. > > > So you can use kexec without using kdump. > > > > > > For kdump, just taking a quick look, the option to enable memory > > > encryption can be provided on the crash kernel command line and then > > > > Is there a simple way to get the SME status? Probably add some sysfs > > file for this purpose. > > Currently there is not. I can look at adding something, maybe just the > sme_me_mask value, which if non-zero, would indicate SME is active. > > > > > > crash kernel can would be able to copy the memory decrypted if the > > > pagetable is set up properly. It looks like currently ioremap_cache() > > > is used to map the old memory page. That might be able to be changed > > > to a memremap() so that the encryption bit is set in the mapping. That > > > will mean that memory that is not marked encrypted (EFI tables, swiotlb > > > memory, etc) would not be read correctly. > > > > Manage to store info about those ranges which are not encrypted so that > > memremap can handle them? > > I can look into whether something can be done in this area. Any input > you can provide as to what would be the best way/place to store the > range info so kdump can make use of it, would be greatly appreciated. Previously to support efi runtime in kexec, I passed some efi infomation via setup_data, see below userspace kexec-tools commit: e1ffc9e9a0769e1f54185003102e9bec428b84e8, it was what Boris mentioned about the setup_data use case for kexec. Suppose you have successfully tested kexec reboot, so the EFI tables you mentioned should be those area in old mem for copying /proc/vmcore? If only EFI tables and swiotlb maybe not worth to passing those stuff across kexec reboot. I have more idea about this for now.. > > > > > > > > > > > > > > Would it make sense to include some printk to the user if they > > > > are setting up kdump that they won't get anything out of it? > > > > > > Probably a good idea to add something like that. > > > > It will break kdump functionality, it should be fixed instead of > > just adding printk to warn user.. > > I do want kdump to work. I'll investigate further what can be done in > this area. Thanks a lot! Dave
