On 04/27/17 at 08:52am, Dave Hansen wrote: > On 04/27/2017 12:25 AM, Dave Young wrote: > > On 04/21/17 at 02:55pm, Dave Hansen wrote: > >> On 04/18/2017 02:22 PM, Tom Lendacky wrote: > >>> Add sysfs support for SME so that user-space utilities (kdump, etc.) can > >>> determine if SME is active. > >>> > >>> A new directory will be created: > >>> /sys/kernel/mm/sme/ > >>> > >>> And two entries within the new directory: > >>> /sys/kernel/mm/sme/active > >>> /sys/kernel/mm/sme/encryption_mask > >> > >> Why do they care, and what will they be doing with this information? > > > > Since kdump will copy old memory but need this to know if the old memory > > was encrypted or not. With this sysfs file we can know the previous SME > > status and pass to kdump kernel as like a kernel param. > > > > Tom, have you got chance to try if it works or not? > > What will the kdump kernel do with it though? We kexec() into that > kernel so the SME keys will all be the same, right? So, will the kdump > kernel be just setting the encryption bit in the PTE so it can copy the > old plaintext out? I assume it is for active -> non active case, the new boot need to know the old memory is encrypted. But I think I did not read all the patches I may miss things. > > Why do we need both 'active' and 'encryption_mask'? How could it be > that the hardware-enumerated 'encryption_mask' changes across a kexec()? Leave this question to Tom.. Thanks Dave
