From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dave Young Subject: Re: [PATCH 12/12] EFI: Runtime services virtual mapping Date: Wed, 30 Oct 2013 17:32:27 +0800 Message-ID: <20131030093227.GA5791@dhcp-16-126.nay.redhat.com> References: <1379602494-26684-1-git-send-email-bp@alien8.de> <20131008164551.GB16793@pd.tnic> <20131008164831.GD16793@pd.tnic> <20131029064720.GA16009@dhcp-16-126.nay.redhat.com> <20131029094033.GA10972@pd.tnic> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20131029094033.GA10972-fF5Pk5pvG8Y@public.gmane.org> Sender: linux-efi-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Borislav Petkov Cc: X86 ML , LKML , Borislav Petkov , Matt Fleming , Matthew Garrett , "H. Peter Anvin" , James Bottomley , Vivek Goyal , linux-efi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, fwts-devel-nLRlyDuq1AZFpShjVBNYrg@public.gmane.org List-Id: linux-efi@vger.kernel.org On 10/29/13 at 10:40am, Borislav Petkov wrote: > On Tue, Oct 29, 2013 at 02:47:20PM +0800, Dave Young wrote: > > Boris, could you update the comment? it says below: update that memory > > descriptor with the virtual address obtained from ioremap(). > > > > Logiclly your patch should update it, then my patch update it again > > with the case of mapping to fixed address for kexec. > > Thanks for catching this, I ended up doing the following: > > /* > * This function will switch the EFI runtime services to virtual mode. > * Essentially, we look through the EFI memmap and map every region that > * has the runtime attribute bit set in its memory descriptor into the > * ->trampoline_pgd page table using a top-down VA allocation scheme. > * > * The old method which used to update that memory descriptor with the > * virtual address obtained from ioremap() is still supported when the > * kernel is booted with efi=old_map on its command line. Same old > * method enabled the runtime services to be called without having to > * thunk back into physical mode for every invocation. > * > * The new method does a pagetable switch in a preemption-safe manner > * so that we're in a different address space when calling a runtime > * function. For function arguments passing we do copy the PGDs of the > * kernel page table into ->trampoline_pgd prior to each call. > */ Boris, thanks for update, it's very elaborate, I have still wonder if 32 bit case should be mentioned as well. Waiting for you next version of the patch series. I will redo my patches based on that. Thanks Dave