From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-18.2 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6E1A2C4338F for ; Tue, 27 Jul 2021 18:11:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5583960F6C for ; Tue, 27 Jul 2021 18:11:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231901AbhG0SLj (ORCPT ); Tue, 27 Jul 2021 14:11:39 -0400 Received: from mail.kernel.org ([198.145.29.99]:54596 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229453AbhG0SLi (ORCPT ); Tue, 27 Jul 2021 14:11:38 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 6A6686056B; Tue, 27 Jul 2021 18:11:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1627409498; bh=BEDd+h2W4eFzLeu2/Kd2s9Jkn7/PmvBnCgRz19A2CTc=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=ndvRHWn3doV9PuLCYw5aGZyf9RmorsMksOc4AkU0fxy1AGJt5EjCMAk5jZFxQyiGF aURvGsNYuOnNBqaH4DSEPIFluR2Vb7dJpiZwFmr9iLRjiZtkYgdanBNZ+D6T1CHIqC xMxfIg95OFfkw86Q7XCXDRZtvoD/ySkxJXIgLwRvBOWXxBR5i+qDF/jlB3UDkKO1E5 bSRZ0wIZa+EQVL6uNhwLIe9QvhM98PJb9EdckxgWqwyqd0+5ghqKye7tcTyMzyC+ay 7Hua073iRgXf9Y6biPyVihRiG8ULriLeNTeKv4dd1vvgHBRgTy5+XyPARqMopwMtjF UDoPS8AY3SIrA== Date: Tue, 27 Jul 2021 19:11:33 +0100 From: Will Deacon To: Marc Zyngier Cc: linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, qperret@google.com, dbrazdil@google.com, Srivatsa Vaddagiri , Shanker R Donthineni , James Morse , Suzuki K Poulose , Alexandru Elisei , kernel-team@android.com Subject: Re: [PATCH 06/16] KVM: arm64: Force a full unmap on vpcu reinit Message-ID: <20210727181132.GE19173@willie-the-truck> References: <20210715163159.1480168-1-maz@kernel.org> <20210715163159.1480168-7-maz@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210715163159.1480168-7-maz@kernel.org> User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Thu, Jul 15, 2021 at 05:31:49PM +0100, Marc Zyngier wrote: > As we now keep information in the S2PT, we must be careful not > to keep it across a VM reboot, which could otherwise lead to > interesting problems. > > Make sure that the S2 is completely discarded on reset of > a vcpu, and remove the flag that enforces the MMIO check. > > Signed-off-by: Marc Zyngier > --- > arch/arm64/kvm/arm.c | 8 +++++++- > 1 file changed, 7 insertions(+), 1 deletion(-) > > diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c > index 97ab1512c44f..b0d2225190d2 100644 > --- a/arch/arm64/kvm/arm.c > +++ b/arch/arm64/kvm/arm.c > @@ -1096,12 +1096,18 @@ static int kvm_arch_vcpu_ioctl_vcpu_init(struct kvm_vcpu *vcpu, > * ensuring that the data side is always coherent. We still > * need to invalidate the I-cache though, as FWB does *not* > * imply CTR_EL0.DIC. > + * > + * If the MMIO guard was enabled, we pay the price of a full > + * unmap to get back to a sane state (and clear the flag). > */ > if (vcpu->arch.has_run_once) { > - if (!cpus_have_final_cap(ARM64_HAS_STAGE2_FWB)) > + if (!cpus_have_final_cap(ARM64_HAS_STAGE2_FWB) || > + test_bit(KVM_ARCH_FLAG_MMIO_GUARD, &vcpu->kvm->arch.flags)) > stage2_unmap_vm(vcpu->kvm); > else > icache_inval_all_pou(); > + > + clear_bit(KVM_ARCH_FLAG_MMIO_GUARD, &vcpu->kvm->arch.flags); What prevents this racing with another vCPU trying to set the bit? Will