[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] [PATCH] microcode: Scan the multiboot payloads for cpio format microcode blob. (v3.2)
Changelog: * since v3 posting - Addressed Andrew's comments. * since v2 posting (http://mid.gmane.org/1374165371-24716-1-git-send-email-konrad.wilk@xxxxxxxxxx) - Addressed Jan's comments (I hope all of them) Greetings, <from v1> Please see the following patch which implements a mechanism to scan the initramfs for the format of an microcode files. This is a feature that the Linux kernel has since v3.10 - where it searches in the initramfs for an archive of the microcode blob. The format is documented in the Linux tree and the commit description contains it. The tool to make this work is the initramfs creator. The one tool 'dracut' has support for this via the '--early-microcode' parameter. (See http://news.gmane.org/gmane.linux.kernel.initramfs for dracut 030 announcement)) That, along with this patch, allows the Xen hypervisor to update the microcode during bootup. Please review attached patch. I had also tested just using Linux how well it deals with an initramfs composed of two cpio images. Testing revealed that it worked great even if the kernel did not have the early cpio support build in. David Vrabel pointed out that it b/c: "The kernel unpacks all cpio archives it finds in the initramfs image so the kernel doesn't have to be aware of the way tools have packed the filesystem into different cpio archive." The way to use this is by the 'ucode' parameter. It has now two meanings: [<index>|initrd] Which CANNOT be used together. By default this auto scanning is turned off as Jan pointed out that: "Xen otoh has to be careful not to mis-interpret a blob passed to a non-Linux Dom0 as a CPIO. How good the guarding against this is in the code I'll have to check". The author would like to have this on by default but that can wait till a later time when maintainer is comfortable with this being on by default. </from v1> There is also the question whether the parameter should be 'cpio','initrd' or 'scan'. As in the future the extraction of the payload could be from a different format than the cpio (say a microcode blob with an magic string at the start). The author believes that at that time the logic to scan the mulitboot payloads can be expanded to also scan formats other than cpio format. These patches are also available at: git://xenbits.xen.org/people/konradwilk/xen.git microcode.v3.2 docs/misc/xen-command-line.markdown | 14 ++- xen/arch/x86/microcode.c | 174 ++++++++++++++++++++++++++++++++---- xen/common/Makefile | 2 +- xen/common/earlycpio.c | 151 +++++++++++++++++++++++++++++++ xen/include/xen/earlycpio.h | 14 +++ 5 files changed, 335 insertions(+), 20 deletions(-) Konrad Rzeszutek Wilk (2): microcode: Scan the initramfs payload for microcode blob. microcode: Check whether the microcode is correct. _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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