From mboxrd@z Thu Jan 1 00:00:00 1970 From: Pavel Fedin Subject: RE: [GIT PULL 3/6] KVM: arm: use GIC support unconditionally Date: Wed, 21 Oct 2015 17:50:02 +0300 Message-ID: <01c601d10c0f$c4e17e10$4ea47a30$@samsung.com> References: <1445357947-6022-1-git-send-email-christoffer.dall@linaro.org> <1445357947-6022-4-git-send-email-christoffer.dall@linaro.org> <672714208.55851501.1445370665940.JavaMail.zimbra@zmail13.collab.prod.int.phx2.redhat.com> <9140096.cYCnE2rDUr@wuerfel> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Return-path: In-reply-to: <9140096.cYCnE2rDUr@wuerfel> Content-language: ru Sender: kvm-owner@vger.kernel.org To: 'Arnd Bergmann' , 'Paolo Bonzini' Cc: kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, christoffer.dall@linaro.org, marc.zyngier@arm.com List-Id: kvmarm@lists.cs.columbia.edu Hello! > The only platform I can think of that uses ARMv7ve without actually having > a GIC is BCM2836 (Raspberry Pi 2). Can we actually run KVM on a platform > like that? We can, with two limitations: 1. GIC has to be emulated in software. I have recently fixed support for this. The only problem here would be that KVM currently refuses to initialize if there's no vGIC, but it is easy to fix, i posted patches for this too. 2. We cannot emulate CP15 timer, because accessing virtual timer registers cannot be trapped to HYP. However, it is possible to trap physical timer access, but a small KVM API extension is needed for this. Currently it is possible to run qemu vexpress model in this mode, because it has another, memory-mapped timer. It is only necessary to either remove CP15 timer from guest device tree, or disable support in guest .config. Kind regards, Pavel Fedin Expert Engineer Samsung Electronics Research center Russia From mboxrd@z Thu Jan 1 00:00:00 1970 From: p.fedin@samsung.com (Pavel Fedin) Date: Wed, 21 Oct 2015 17:50:02 +0300 Subject: [GIT PULL 3/6] KVM: arm: use GIC support unconditionally In-Reply-To: <9140096.cYCnE2rDUr@wuerfel> References: <1445357947-6022-1-git-send-email-christoffer.dall@linaro.org> <1445357947-6022-4-git-send-email-christoffer.dall@linaro.org> <672714208.55851501.1445370665940.JavaMail.zimbra@zmail13.collab.prod.int.phx2.redhat.com> <9140096.cYCnE2rDUr@wuerfel> Message-ID: <01c601d10c0f$c4e17e10$4ea47a30$@samsung.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org Hello! > The only platform I can think of that uses ARMv7ve without actually having > a GIC is BCM2836 (Raspberry Pi 2). Can we actually run KVM on a platform > like that? We can, with two limitations: 1. GIC has to be emulated in software. I have recently fixed support for this. The only problem here would be that KVM currently refuses to initialize if there's no vGIC, but it is easy to fix, i posted patches for this too. 2. We cannot emulate CP15 timer, because accessing virtual timer registers cannot be trapped to HYP. However, it is possible to trap physical timer access, but a small KVM API extension is needed for this. Currently it is possible to run qemu vexpress model in this mode, because it has another, memory-mapped timer. It is only necessary to either remove CP15 timer from guest device tree, or disable support in guest .config. Kind regards, Pavel Fedin Expert Engineer Samsung Electronics Research center Russia