From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753891AbdGCJvc (ORCPT ); Mon, 3 Jul 2017 05:51:32 -0400 Received: from mail-wm0-f45.google.com ([74.125.82.45]:35750 "EHLO mail-wm0-f45.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753548AbdGCJva (ORCPT ); Mon, 3 Jul 2017 05:51:30 -0400 Date: Mon, 3 Jul 2017 11:51:26 +0200 From: Christoffer Dall To: Andrew Jones Cc: Jintack Lim , Christoffer Dall , Marc Zyngier , Paolo Bonzini , Radim =?utf-8?B?S3LEjW3DocWZ?= , linux@armlinux.org.uk, Catalin Marinas , Will Deacon , vladimir.murzin@arm.com, Suzuki K Poulose , mark.rutland@arm.com, james.morse@arm.com, lorenzo.pieralisi@arm.com, kevin.brodsky@arm.com, wcohen@redhat.com, shankerd@codeaurora.org, geoff@infradead.org, Andre Przywara , Eric Auger , anna-maria@linutronix.de, Shih-Wei Li , arm-mail-list , kvmarm@lists.cs.columbia.edu, KVM General , lkml - Kernel Mailing List Subject: Re: [RFC 21/55] KVM: arm64: Forward HVC instruction to the guest hypervisor Message-ID: <20170703095126.GH4066@cbox> References: <1483943091-1364-1-git-send-email-jintack@cs.columbia.edu> <1483943091-1364-22-git-send-email-jintack@cs.columbia.edu> <20170222114758.GM26976@cbox> <20170703090850.GG4066@cbox> <20170703093156.m3ds2orbjcyooaag@kamzik.brq.redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170703093156.m3ds2orbjcyooaag@kamzik.brq.redhat.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jul 03, 2017 at 11:31:56AM +0200, Andrew Jones wrote: > On Mon, Jul 03, 2017 at 11:08:50AM +0200, Christoffer Dall wrote: > > On Mon, Jun 26, 2017 at 11:21:25AM -0400, Jintack Lim wrote: > > > On Wed, Feb 22, 2017 at 6:47 AM, Christoffer Dall wrote: > > > > On Mon, Jan 09, 2017 at 01:24:17AM -0500, Jintack Lim wrote: > > > >> Forward exceptions due to hvc instruction to the guest hypervisor. > > > >> > > > >> Signed-off-by: Jintack Lim > > > >> --- > > > >> arch/arm64/include/asm/kvm_nested.h | 5 +++++ > > > >> arch/arm64/kvm/Makefile | 1 + > > > >> arch/arm64/kvm/handle_exit.c | 11 +++++++++++ > > > >> arch/arm64/kvm/handle_exit_nested.c | 27 +++++++++++++++++++++++++++ > > > >> 4 files changed, 44 insertions(+) > > > >> create mode 100644 arch/arm64/include/asm/kvm_nested.h > > > >> create mode 100644 arch/arm64/kvm/handle_exit_nested.c > > > >> > > > >> diff --git a/arch/arm64/include/asm/kvm_nested.h b/arch/arm64/include/asm/kvm_nested.h > > > >> new file mode 100644 > > > >> index 0000000..620b4d3 > > > >> --- /dev/null > > > >> +++ b/arch/arm64/include/asm/kvm_nested.h > > > >> @@ -0,0 +1,5 @@ > > > >> +#ifndef __ARM64_KVM_NESTED_H__ > > > >> +#define __ARM64_KVM_NESTED_H__ > > > >> + > > > >> +int handle_hvc_nested(struct kvm_vcpu *vcpu); > > > >> +#endif > > > >> diff --git a/arch/arm64/kvm/Makefile b/arch/arm64/kvm/Makefile > > > >> index b342bdd..9c35e9a 100644 > > > >> --- a/arch/arm64/kvm/Makefile > > > >> +++ b/arch/arm64/kvm/Makefile > > > >> @@ -35,4 +35,5 @@ kvm-$(CONFIG_KVM_ARM_HOST) += $(KVM)/irqchip.o > > > >> kvm-$(CONFIG_KVM_ARM_HOST) += $(KVM)/arm/arch_timer.o > > > >> kvm-$(CONFIG_KVM_ARM_PMU) += $(KVM)/arm/pmu.o > > > >> > > > >> +kvm-$(CONFIG_KVM_ARM_NESTED_HYP) += handle_exit_nested.o > > > >> kvm-$(CONFIG_KVM_ARM_NESTED_HYP) += emulate-nested.o > > > >> diff --git a/arch/arm64/kvm/handle_exit.c b/arch/arm64/kvm/handle_exit.c > > > >> index a891684..208be16 100644 > > > >> --- a/arch/arm64/kvm/handle_exit.c > > > >> +++ b/arch/arm64/kvm/handle_exit.c > > > >> @@ -29,6 +29,10 @@ > > > >> #include > > > >> #include > > > >> > > > >> +#ifdef CONFIG_KVM_ARM_NESTED_HYP > > > >> +#include > > > >> +#endif > > > >> + > > > >> #define CREATE_TRACE_POINTS > > > >> #include "trace.h" > > > >> > > > >> @@ -42,6 +46,13 @@ static int handle_hvc(struct kvm_vcpu *vcpu, struct kvm_run *run) > > > >> kvm_vcpu_hvc_get_imm(vcpu)); > > > >> vcpu->stat.hvc_exit_stat++; > > > >> > > > >> +#ifdef CONFIG_KVM_ARM_NESTED_HYP > > > >> + ret = handle_hvc_nested(vcpu); > > > >> + if (ret < 0 && ret != -EINVAL) > > > >> + return ret; > > > >> + else if (ret >= 0) > > > >> + return ret; > > > >> +#endif > > > >> ret = kvm_psci_call(vcpu); > > > >> if (ret < 0) { > > > >> kvm_inject_undefined(vcpu); > > > >> diff --git a/arch/arm64/kvm/handle_exit_nested.c b/arch/arm64/kvm/handle_exit_nested.c > > > >> new file mode 100644 > > > >> index 0000000..a6ce23b > > > >> --- /dev/null > > > >> +++ b/arch/arm64/kvm/handle_exit_nested.c > > > >> @@ -0,0 +1,27 @@ > > > >> +/* > > > >> + * Copyright (C) 2016 - Columbia University > > > >> + * Author: Jintack Lim > > > >> + * > > > >> + * This program is free software; you can redistribute it and/or modify > > > >> + * it under the terms of the GNU General Public License version 2 as > > > >> + * published by the Free Software Foundation. > > > >> + * > > > >> + * This program is distributed in the hope that it will be useful, > > > >> + * but WITHOUT ANY WARRANTY; without even the implied warranty of > > > >> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the > > > >> + * GNU General Public License for more details. > > > >> + * > > > >> + * You should have received a copy of the GNU General Public License > > > >> + * along with this program. If not, see . > > > >> + */ > > > >> + > > > >> +#include > > > >> +#include > > > >> + > > > >> +#include > > > >> + > > > >> +/* We forward all hvc instruction to the guest hypervisor. */ > > > >> +int handle_hvc_nested(struct kvm_vcpu *vcpu) > > > >> +{ > > > >> + return kvm_inject_nested_sync(vcpu, kvm_vcpu_get_hsr(vcpu)); > > > >> +} > > > > > > > > I don't understand the logic here or in the caller above. Do we really > > > > forward *all" hvc calls to the guest hypervisor now, so that we no > > > > longer support any hypercalls from the VM? That seems a little rough > > > > and probably requires some more discussions. > > > > > > So I think if we run a VM with the EL2 support, then all hvc calls > > > from the VM should be forwarded to the virtual EL2. > > > > But do we actually check if the guest has EL2 here? It seems you cann > > handle_hvc_nested unconditionally when you have > > OCNFIG_KVM_ARM_NESTED_HYP. I think that's what threw me off when first > > reading your patch. > > > > > > > > I may miss something obvious, so can you (or anyone) come up with some > > > cases that the host hypervisor needs to directly handle hvc from the > > > VM with the EL2 support? > > > > > > > So I'm a little unsure what to say here. On one hand you are absolutely > > correct, that architecturally if we emulated virtual EL2, then all > > hypercalls are handled by the virtual EL2 (even hypercalls from virtual > > EL2 which should become self-hypercalls). > > > > On the other hand, an enlightened guest may want to use hypercalls to > > the hypervisor for some reason, but that would require some numbering > > scheme to separate the two concepts. > > Yes, I've been thinking that a KVM generic vcpu needs to be enlightened, > and to use a hypercall to get the host cpu's errata. If we head down that > road, then even a vcpu emulating EL2 would need to be able to this. > We could use SMC calls here a well, as the "conduit" as I believe the ARM folks are calling it. We just need to agree somewhere (across hypervisors preferably), that when you have virtual EL2, everything is via SMC (even upcalls to a host hypervisor), and otherwise it's via HVC. > > > > Do we currently have support for the guest to use SMC calls for PSCI > > when it has virtual EL2? > > Yup, that's already supported by QEMU and the guest kernel. > Yes, and the KVM support follows this patch in the series as it turns out (but given the time since I looked at this series last, I forgot). Thanks, -Christoffer