From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 6C1DA1D517A for ; Thu, 17 Oct 2024 10:58:57 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1729162739; cv=none; b=MFuPtrbVRNUKYCfnOzT8XkWQf03wdL4XFqGGCOko+arX9CqdO0pWWEoYQr0wybEsyjDsgWX4WV01cOe/WD60ZjHNd1qBwlbfMHXmvMaGxaFbh9yBrfsc20ePCE+kNxtwXAu4qckQcVZJCYFEzT7+P+EdmUlA9DSnUq37ox2I+KA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1729162739; c=relaxed/simple; bh=K7k0XI6rwQ/GVZ/Jm7ekmwlXhPQS6XYdRHi6pMMyWDw=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=d6EckLuj1hEKT2HKyVdxbRIwfUhAH2QwuDQGtmXPJuubCnp1RLtivL4S9fL7ndVN6yqtrcjYGrwtLWLXVF+T3ChlfIIQwBWX7GoYKyHucnM5tzK2qhJTBYr3/PRXy39hF29y0ds0ESLdgu9naKTSCeEvphK0dF+DsKNSp73z02E= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 74A37FEC; Thu, 17 Oct 2024 03:59:26 -0700 (PDT) Received: from e124191.cambridge.arm.com (e124191.cambridge.arm.com [10.1.197.45]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id BF21B3F528; Thu, 17 Oct 2024 03:58:54 -0700 (PDT) Date: Thu, 17 Oct 2024 11:58:49 +0100 From: Joey Gouly To: Oliver Upton Cc: linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, anshuman.khandual@arm.com, james.morse@arm.com, Marc Zyngier , Suzuki K Poulose , Zenghui Yu , Jing Zhang , Shameerali Kolothum Thodi , Catalin Marinas , Will Deacon Subject: Re: [PATCH v5 4/7] KVM: arm64: Fix missing traps of guest accesses to the MPAM registers Message-ID: <20241017105849.GA122054@e124191.cambridge.arm.com> References: <20241015133923.3910916-1-joey.gouly@arm.com> <20241015133923.3910916-5-joey.gouly@arm.com> Precedence: bulk X-Mailing-List: kvmarm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Wed, Oct 16, 2024 at 05:10:17PM -0700, Oliver Upton wrote: > Hi Joey, > > On Tue, Oct 15, 2024 at 02:39:20PM +0100, Joey Gouly wrote: > > +static inline void __activate_traps_mpam(struct kvm_vcpu *vcpu) > > +{ > > + u64 r = MPAM2_EL2_TRAPMPAM0EL1 | MPAM2_EL2_TRAPMPAM1EL1; > > + > > + if (!cpus_support_mpam()) > > + return; > > + > > + /* trap guest access to MPAMIDR_EL1 */ > > + if (mpam_cpus_have_mpam_hcr()) { > > + write_sysreg_s(MPAMHCR_EL2_TRAP_MPAMIDR_EL1, SYS_MPAMHCR_EL2); > > + } else { > > + /* From v1.1 TIDR can trap MPAMIDR, set it unconditionally */ > > + r |= MPAM2_EL2_TIDR; > > + } > > + > > + write_sysreg_s(r, SYS_MPAM2_EL2); > > +} > > + > > +static inline void __deactivate_traps_mpam(void) > > +{ > > + if (!cpus_support_mpam()) > > + return; > > + > > + write_sysreg_s(0, SYS_MPAM2_EL2); > > + > > + if (mpam_cpus_have_mpam_hcr()) > > + write_sysreg_s(MPAMHCR_HOST_FLAGS, SYS_MPAMHCR_EL2); > > +} > > TBH, I think our trap configuration should *not* be conditioned on > CONFIG_ARM64_MPAM. Otherwise we're silently allowing the guest to change > things under the nose of KVM/host kernel, assuming an unkind firmware > that left the EL2 trap configuration in a permissive state. > > WDYT about detecting the feature && enforcing traps regardless of the Kconfig? I had actually thought about the same thing. I spoke with James and he agrees, so I will look into removing that. I will probably end up removing the Kconfig entirely, it can be added back in later, when actual support for MPAM is added. Thanks, Joey > > -- > Thanks, > Oliver