From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andre Przywara Date: Fri, 26 Apr 2013 15:24:10 +0200 Subject: [U-Boot] [RFC PATCH 0/6] ARMv7: Add HYP mode switching support In-Reply-To: References: <1366982099-22360-1-git-send-email-andre.przywara@linaro.org> Message-ID: <517A7FFA.2010000@linaro.org> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: u-boot@lists.denx.de On 04/26/2013 03:18 PM, Peter Maydell wrote: > On 26 April 2013 14:14, Andre Przywara wrote: >> ARM CPUs with the virtualization extension have a new mode called >> HYP mode, which allows hypervisors to safely control and monitor >> guests. The current hypervisor (KVM and Xen) implementations >> require the kernel to be entered in that HYP mode. >> >> This patch series introduces a new U-Boot command called "hypmode" >> which can be used at any time at the U-Boot command prompt to >> switch the CPU into HYP mode - ideally this would be done before >> starting the kernel. > > The obvious question here is "why do we need a new command?". > The kernel booting specification says "boot the kernel in > Hyp mode" so we should just always do that for booting Linux, > surely? Because it avoids regressions. I kind of feel uneasy to do a lot of tinkering with secure state and the GIC unconditionally, especially if enabled on many boards with virt-capable CPUs. As written in question 2) later in that mail, I can also live with a command to _dis_able the HYP mode switching in case it causes problems. Regards, Andre.