From patchwork Fri Oct 4 11:07:13 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Joey Gouly X-Patchwork-Id: 13822187 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 0C69ECFA76A for ; Fri, 4 Oct 2024 11:16:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: MIME-Version:References:In-Reply-To:Message-Id:Date:Subject:Cc:To:From: Reply-To:Content-Type:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=IcNyAb+XLG1qlbok6YAZILIuzkXBgiBC3CGyD7LkYYk=; b=YBkUqHawoRbsbLrQoygNOZK7pw EuDxNmmOEuwLelnlK5PwbYGnaw0qlqmj1OC+4TOEoP6M9SPq6xoj9g3yyYeJHWKYx1mBXjyKxTbqc AHKwu9jrtoD3q6l7ZJOTeGp3n2WwOhXf4pu51jsa5YgR70YlA+RM7YlmeqATABAMqsc7FIOpvh7+W GPbIQiSuDOqFMGBOMZetwFsMOlXPSrKra/sZ39UlQX8c9bEEWHgnsQtl892TofY2khm9Z3DAU3fO4 CQLecXwToRc8OCk4Ds/3yR3S7MwXdwP2ZUZmowSPSslG4XIjWZIMxLUDdu+6lqyAqtjTO7DCfP/51 0X5BDdoA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98 #2 (Red Hat Linux)) id 1swgIJ-0000000C3lp-3lpF; Fri, 04 Oct 2024 11:16:23 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.98 #2 (Red Hat Linux)) id 1swg9l-0000000C15L-3ok2 for linux-arm-kernel@lists.infradead.org; Fri, 04 Oct 2024 11:07:35 +0000 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 10AA01063; Fri, 4 Oct 2024 04:08:03 -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 E3A723F640; Fri, 4 Oct 2024 04:07:31 -0700 (PDT) From: Joey Gouly To: linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev Cc: anshuman.khandual@arm.com, james.morse@arm.com, joey.gouly@arm.com, Marc Zyngier , Oliver Upton , Suzuki K Poulose , Zenghui Yu , Jing Zhang , Shameerali Kolothum Thodi , Catalin Marinas , Will Deacon Subject: [PATCH v4 6/7] KVM: arm64: Disable MPAM visibility by default and ignore VMM writes Date: Fri, 4 Oct 2024 12:07:13 +0100 Message-Id: <20241004110714.2051604-7-joey.gouly@arm.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20241004110714.2051604-1-joey.gouly@arm.com> References: <20241004110714.2051604-1-joey.gouly@arm.com> MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20241004_040734_070618_7576A648 X-CRM114-Status: GOOD ( 17.23 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org From: James Morse commit 011e5f5bf529f ("arm64/cpufeature: Add remaining feature bits in ID_AA64PFR0 register") exposed the MPAM field of AA64PFR0_EL1 to guests, but didn't add trap handling. A previous patch supplied the missing trap handling. Existing VMs that have the MPAM field of ID_AA64PFR0_EL1 set need to be migratable, but there is little point enabling the MPAM CPU interface on new VMs until there is something a guest can do with it. Clear the MPAM field from the guest's ID_AA64PFR0_EL1 and on hardware that supports MPAM, politely ignore the VMMs attempts to set this bit. Guests exposed to this bug have the sanitised value of the MPAM field, so only the correct value needs to be ignored. This means the field can continue to be used to block migration to incompatible hardware (between MPAM=1 and MPAM=5), and the VMM can't rely on the field being ignored. Signed-off-by: James Morse Signed-off-by: Joey Gouly --- arch/arm64/kvm/sys_regs.c | 53 ++++++++++++++++++++++++++++++++++++--- 1 file changed, 50 insertions(+), 3 deletions(-) diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c index 1fd08f12f2bb..f0c55d3907d9 100644 --- a/arch/arm64/kvm/sys_regs.c +++ b/arch/arm64/kvm/sys_regs.c @@ -1723,6 +1723,23 @@ static u64 read_sanitised_id_aa64pfr0_el1(struct kvm_vcpu *vcpu, val &= ~ID_AA64PFR0_EL1_AMU_MASK; + /* + * MPAM is disabled by default as KVM also needs a set of PARTID to + * program the MPAMVPMx_EL2 PARTID remapping registers with. But some + * older kernels let the guest see the ID bit. + */ + val &= ~ID_AA64PFR0_EL1_MPAM_MASK; + + return val; +} + +static u64 read_sanitised_id_aa64pfr1_el1(struct kvm_vcpu *vcpu, + const struct sys_reg_desc *rd) +{ + u64 val = read_sanitised_ftr_reg(SYS_ID_AA64PFR1_EL1); + + val &= ~ID_AA64PFR1_EL1_MPAM_frac_MASK; + return val; } @@ -1834,9 +1851,38 @@ static int set_id_dfr0_el1(struct kvm_vcpu *vcpu, } static int set_id_aa64pfr0_el1(struct kvm_vcpu *vcpu, - const struct sys_reg_desc *rd, u64 val) + const struct sys_reg_desc *rd, u64 user_val) { - return set_id_reg(vcpu, rd, val); + u64 hw_val = read_sanitised_ftr_reg(SYS_ID_AA64PFR0_EL1); + u64 mpam_mask = ID_AA64PFR0_EL1_MPAM_MASK; + + /* + * Commit 011e5f5bf529f ("arm64/cpufeature: Add remaining feature bits + * in ID_AA64PFR0 register") exposed the MPAM field of AA64PFR0_EL1 to + * guests, but didn't add trap handling. KVM doesn't support MPAM and + * always returns an UNDEF for these registers. The guest must see 0 + * for this field. + * + * But KVM must also accept values from user-space that were provided + * by KVM. On CPUs that support MPAM, permit user-space to write + * the sanitizied value to ID_AA64PFR0_EL1.MPAM, but ignore this field. + */ + if ((hw_val & mpam_mask) == (user_val & mpam_mask)) + user_val &= ~ID_AA64PFR0_EL1_MPAM_MASK; + + return set_id_reg(vcpu, rd, user_val); +} + +static int set_id_aa64pfr1_el1(struct kvm_vcpu *vcpu, + const struct sys_reg_desc *rd, u64 user_val) +{ + u64 hw_val = read_sanitised_ftr_reg(SYS_ID_AA64PFR1_EL1); + u64 mpam_mask = ID_AA64PFR1_EL1_MPAM_frac_MASK; + + if ((hw_val & mpam_mask) == (user_val & mpam_mask)) + user_val &= ~ID_AA64PFR1_EL1_MPAM_frac_MASK; + + return set_id_reg(vcpu, rd, user_val); } /* @@ -2390,7 +2436,8 @@ static const struct sys_reg_desc sys_reg_descs[] = { ID_AA64PFR0_EL1_RAS | ID_AA64PFR0_EL1_AdvSIMD | ID_AA64PFR0_EL1_FP)), - ID_SANITISED(ID_AA64PFR1_EL1), + ID_FILTERED(ID_AA64PFR1_EL1, id_aa64pfr1_el1, + ~ID_AA64PFR1_EL1_MPAM_frac), ID_WRITABLE(ID_AA64PFR2_EL1, ID_AA64PFR2_EL1_FPMR), ID_UNALLOCATED(4,3), ID_WRITABLE(ID_AA64ZFR0_EL1, ~ID_AA64ZFR0_EL1_RES0),