On Tuesday 26 November 2013 09:13 AM, Catalin Marinas wrote: > On Mon, Nov 25, 2013 at 07:44:08PM +0000, Santosh Shilimkar wrote: >> On Monday 25 November 2013 12:28 PM, Catalin Marinas wrote: >>> On Mon, Nov 25, 2013 at 04:59:16PM +0000, Santosh Shilimkar wrote: >>>> What I am saying is the platforms like OMAP5 already support PM in >>>> mainline kernel and we can't break that for KVM. Boot-loaders >>>> would be thrashed after boot so you need something which runs >>>> in Kernel or along with Kernel to have equivalent of hyp >>>> switching. >>>> >>>> Am not challenging the agreed direction but we need to solve the >>>> PM problem as well before making "all CPU runs boot-loader for >>>> HYP kernels" as a must have. At least its is a change in boot >>>> strategy from existing kernels. >>> >>> Of course I recommend PSCI which covers both hotplug and suspend ;), but >>> I guess it's not the case for OMAP5. Since OMAP has its own secondary >>> booting protocol and CPU hotplug re-entry, can you not just use >>> different entry point when the primary CPU was initially started in Hyp >>> mode (e.g. omap5_hyp_secondary_startup)? >>> >> How will that solve the guest secondary boot failure case when using >> the same kernel binary for guest-boot ? Even for primary CPU which >> will be suspended it needs to resume already in HYP mode and its not >> going to go through boot-loader. So the low power code needs to have >> HYP switch code so that CPU resumes in HYP mode. > > Is it late to rewrite the OMAP5 firmware? > Well its ROM'ed unfortunately so no choice. OMAP5 ROM did implement a secure API which lets you enter into HYP mode and thats the only thing can be used. > What I meant is that you have the same kernel binary but with two sets > of entry points, or maybe a single set of entry points and some global > variable that you set during cold boot if the primary CPU is entered in > Hyp mode. So you change the boot loader to switch to Hyp before it > starts the kernel and leave the additional switching to be done by the > secondary entry points (or PM code) based on the variable you set during > cold boot. But I would recommend rewriting the firmware. > >> I will look at PSCI more closely and see what can be done here. > > PSCI has a different secondary start-up and hotplug/suspend protocol and > CPUs wake up in Hyp if available. But this requires changing your > firmware, PSCI is not a kernel-only thing. Do you need to support both > older and newer kernels with the OMAP5 firmware (and possibly same DT)? > Hmmm.. So thats rules out PSCI for OMAP5 then. Keystone actually has nice way to deal with the problem since the boot-monitor code can be patched up and hence I had no trouble implementing the "CPU starts in HYP mode" requirement on it. Regards, Santosh -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
