From mboxrd@z Thu Jan 1 00:00:00 1970 From: marc.zyngier@arm.com (Marc Zyngier) Date: Thu, 15 Dec 2016 11:46:41 +0000 Subject: [PATCH 1/2] ARM: hyp-stub: improve ABI In-Reply-To: <20161215113539.GK14217@n2100.armlinux.org.uk> References: <20161213113044.GC19985@leverpostej> <72f93940-cf87-fd91-90f2-760b7ff050fb@arm.com> <20161215113539.GK14217@n2100.armlinux.org.uk> Message-ID: <06fca797-da5d-f7f2-eecb-9b1b33b7e83f@arm.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On 15/12/16 11:35, Russell King - ARM Linux wrote: > On Thu, Dec 15, 2016 at 11:18:48AM +0000, Marc Zyngier wrote: >> On 14/12/16 10:46, Russell King wrote: >>> @@ -231,10 +244,14 @@ ENDPROC(__hyp_stub_do_trap) >>> * initialisation entry point. >>> */ >>> ENTRY(__hyp_get_vectors) >>> - mov r0, #-1 >>> + mov r0, #HVC_GET_VECTORS >> >> This breaks the KVM implementation of __hyp_get_vectors, easily fixed >> with the following patchlet: > > Right, so what Mark said is wrong: > > "The hyp-stub is part of the kernel image, and the API is private to > that particular image, so we can change things -- there's no ABI to > worry about." I think Mark is right. The API *is* private to the kernel, and KVM being the only in-kernel hypervisor on ARM, this is not an ABI. It is an unfortunate bug that no symbolic constant was used to highlight the two implementations of the same functionality, but I don't think that makes anything wrong in what Mark said here. > So no, I'm going with my original patch (which TI has tested) which is > the minimal change, and if we _then_ want to rework the HYP mode > interfaces, that's the time to do the other changes when more people > (such as KVM folk) are paying attention and we can come to a cross- > hypervisor agreement on what the interface should be. Given that there is a single in-kernel hypervisor, I can't really see who we're going to agree anything with... Thanks, M. -- Jazz is not dead. It just smells funny...