From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tom Lendacky Subject: Re: [RFC PATCH v4 26/28] x86: Allow kexec to be used with SME Date: Mon, 6 Mar 2017 12:04:28 -0600 Message-ID: <87ecaf44-b5a0-61c6-30b1-a798cc535983@amd.com> References: <20170216154158.19244.66630.stgit@tlendack-t1.amdoffice.net> <20170216154755.19244.51276.stgit@tlendack-t1.amdoffice.net> <20170217155756.GJ30272@char.us.ORACLE.com> <20170301092536.GB8353@dhcp-128-65.nay.redhat.com> <998eb58b-eefd-3093-093f-9ae25ddda472@amd.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <998eb58b-eefd-3093-093f-9ae25ddda472-5C7GfCeVMHo@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: iommu-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org Errors-To: iommu-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org To: Dave Young Cc: linux-efi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Brijesh Singh , Toshimitsu Kani , =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= , Matt Fleming , x86-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org, linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org, Alexander Potapenko , "H. Peter Anvin" , Larry Woodman , linux-arch-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, kvm-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Jonathan Corbet , linux-doc-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, kasan-dev-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org, Ingo Molnar , Andrey Ryabinin , Rik van Riel , Arnd Bergmann , Borislav Petkov , Andy Lutomirski , Thomas Gleixner , Dmitry Vyukov , kexec-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org, "Michael S. Tsirkin" List-Id: linux-efi@vger.kernel.org +kexec-list On 3/6/2017 11:58 AM, 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. > >> >>> >>>> >>>> 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 >>