Messages in this thread | | | Subject | Re: [RFC PATCH v4 26/28] x86: Allow kexec to be used with SME | From | Tom Lendacky <> | Date | Mon, 6 Mar 2017 11:58:40 -0600 |
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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.
> >> >>> >>> 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, Tom
> > Thanks > Dave >
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