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 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 66601C4450E for ; Wed, 15 Jul 2026 14:31:23 +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=CM9F9th+vhcChYgL9VgHm/M7dqyJr6VAPzlgNcKN7y4=; b=uRKM4xkvdWNP57Xo90Gwww96oD 8//vlxJJvEbwhwDv0dByrlSfB9Fs/nEoWf9DFli4yWiGtVmNhT1dMlo0qFiYRqmIzK5O7C9abHFNC 7han1p2DCr30si330u6hd6jOHl7HoVcL3ZPsTAeuZUpIh0hR1w404mmSjcuzq5pXN6IgaA190IFPw ULC1m2lR9BoavjwDB+kp3yd9OsUrBkop6BNE6LnF3q1JOT7BOr2Mge7aY8lZJmri1P38ue5t3w9kk bnNXOaRqmdkcbCc04JGL9DfSQ0QF1spOyf+jZ/f/rt5GyUirVitscGpBwAkY9dZsgahbRSYmgPAHo Sl1L5VOA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1wk0dn-0000000F9z9-3mSy; Wed, 15 Jul 2026 14:31:15 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1wk0dQ-0000000F9TG-1rnm for linux-arm-kernel@lists.infradead.org; Wed, 15 Jul 2026 14:30:57 +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 7A02B1576; Wed, 15 Jul 2026 07:30:46 -0700 (PDT) Received: from e122027.cambridge.arm.com (e122027.cambridge.arm.com [10.1.25.27]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id CC12D3F7B4; Wed, 15 Jul 2026 07:30:46 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1784125850; bh=UZ1cXeVFfJIYr/MkjIsCfrnNWtsKIftqp2z8gXgFYYo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=o6EnmQZG2h/hdkpXxcWOgUoWhCE801UW7hgVZogcDSyZ1syCIsvkXeBDZIIC6gl// kmESLtaQmhPPAQypvngDvDNXpH+DY+svS3HiQnFE9byeOPWnPXsOtpYZn2G33YuUh8 rK8hSbpRZa+G0TgDCXG35Uc5ZWPjQs0suoZAhOwM= From: Steven Price To: kvm@vger.kernel.org, kvmarm@lists.linux.dev Cc: Steven Price , Catalin Marinas , Marc Zyngier , Will Deacon , James Morse , Oliver Upton , Suzuki K Poulose , Zenghui Yu , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Joey Gouly , Alexandru Elisei , Christoffer Dall , Fuad Tabba , linux-coco@lists.linux.dev, Ganapatrao Kulkarni , Gavin Shan , Shanker Donthineni , Alper Gun , "Aneesh Kumar K . V" , Emi Kisanuki , Vishal Annapurve , WeiLin.Chang@arm.com, Lorenzo Pieralisi Subject: [PATCH v15 24/37] KVM: arm64: CCA: Validate register access for Realm VMs Date: Wed, 15 Jul 2026 15:28:26 +0100 Message-ID: <20260715142841.80544-25-steven.price@arm.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20260715142841.80544-1-steven.price@arm.com> References: <20260715142841.80544-1-steven.price@arm.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260715_073052_687468_FFDF0A7C X-CRM114-Status: GOOD ( 16.10 ) 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 The RMM only allows setting the GPRS (x0-x30) and PC for a realm guest. Check this in kvm_arm_set_reg() so that the VMM can receive a suitable error return if other registers are written to. The RMM makes similar restrictions for reading of the guest's registers (this is *confidential* compute after all), however we don't impose the restriction here. This allows the VMM to read (stale) values from the registers which might be useful to read back the initial values even if the RMM doesn't provide the latest version. For migration of a realm VM, a new interface will be needed so that the VMM can receive an (encrypted) blob of the VM's state. Reviewed-by: Gavin Shan Reviewed-by: Suzuki K Poulose Reviewed-by: Joey Gouly Signed-off-by: Steven Price --- Changes since v5: * Upper GPRS can be set as part of a HOST_CALL return, so fix up the test to allow them. --- arch/arm64/kvm/guest.c | 41 +++++++++++++++++++++++++++++++++++++++++ 1 file changed, 41 insertions(+) diff --git a/arch/arm64/kvm/guest.c b/arch/arm64/kvm/guest.c index b01d6622b872..3e970c4f6214 100644 --- a/arch/arm64/kvm/guest.c +++ b/arch/arm64/kvm/guest.c @@ -73,6 +73,25 @@ static u64 core_reg_offset_from_id(u64 id) return id & ~(KVM_REG_ARCH_MASK | KVM_REG_SIZE_MASK | KVM_REG_ARM_CORE); } +static bool kvm_realm_validate_core_reg(u64 off) +{ + /* + * Note that GPRs can only sometimes be controlled by the VMM. + * For PSCI only X0-X6 are used, higher registers are ignored (restored + * from the REC). + * For HOST_CALL all of X0-X30 are copied to the RsiHostCall structure. + * For emulated MMIO X0 is always used. + * PC can only be set before the realm is activated. + */ + switch (off) { + case KVM_REG_ARM_CORE_REG(regs.regs[0]) ... + KVM_REG_ARM_CORE_REG(regs.regs[30]): + case KVM_REG_ARM_CORE_REG(regs.pc): + return true; + } + return false; +} + static int core_reg_size_from_offset(const struct kvm_vcpu *vcpu, u64 off) { int size; @@ -716,12 +735,34 @@ int kvm_arm_get_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg) return kvm_arm_sys_reg_get_reg(vcpu, reg); } +/* + * The RMI ABI only enables setting some GPRs and PC. The selection of GPRs + * that are available depends on the Realm state and the reason for the last + * exit. All other registers are reset to architectural or otherwise defined + * reset values by the RMM, except for a few configuration fields that + * correspond to Realm parameters. + */ +static bool validate_realm_set_reg(struct kvm_vcpu *vcpu, + const struct kvm_one_reg *reg) +{ + if ((reg->id & KVM_REG_ARM_COPROC_MASK) == KVM_REG_ARM_CORE) { + u64 off = core_reg_offset_from_id(reg->id); + + return kvm_realm_validate_core_reg(off); + } + + return false; +} + int kvm_arm_set_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg) { /* We currently use nothing arch-specific in upper 32 bits */ if ((reg->id & ~KVM_REG_SIZE_MASK) >> 32 != KVM_REG_ARM64 >> 32) return -EINVAL; + if (kvm_is_realm(vcpu->kvm) && !validate_realm_set_reg(vcpu, reg)) + return -EINVAL; + switch (reg->id & KVM_REG_ARM_COPROC_MASK) { case KVM_REG_ARM_CORE: return set_core_reg(vcpu, reg); case KVM_REG_ARM_FW: -- 2.43.0