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Thu, 23 Sep 2021 13:02:22 +0000 Received: from mail.kernel.org ([198.145.29.99]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1mTOMi-00BW6T-Kn for linux-arm-kernel@lists.infradead.org; Thu, 23 Sep 2021 13:02:18 +0000 Received: by mail.kernel.org (Postfix) with ESMTPSA id 2252560F0F; Thu, 23 Sep 2021 13:02:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1632402136; bh=Zkh2489hCo6Fofm1UetCFN/RtntSEUCNZ4fEl6U6ues=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=eQMEP8bc4WCVUmN1L9mTrYo4BJreRtNnXdQXrW7pStqyn7p7q3i1+VTML4eyOFVuK F1dO7AXm6UEoNaXldIAm6TJwk2x8MM4CWn4dBXvHu7Qz9YAL20R+v3//hAUXOnrz2y JgBZ6BUJ7GkBIElz00avFPLWSQtS+U/Cr9EATwa6bNCgUgubpl0DoH/mcpqsZ05GaV +pSk6tdppBv5XwzjHGqSjQrGMe5+TFhTAaUiV3Q9hpDiq1CbN6ouHAVARV8L9uUK7O T9DAj8GS1FznhXjGmLhQcYwq8ubb6ibLXRLkDLWl6b1vp4voVD9FGU4lwAQrQ9QvTb jg0AAFiREdVYQ== Date: Thu, 23 Sep 2021 14:02:11 +0100 From: Will Deacon To: Marc Zyngier Cc: linux-arm-kernel@lists.infradead.org, Quentin Perret , Catalin Marinas , Alexandru Elisei , Suzuki K Poulose , kvmarm@lists.cs.columbia.edu Subject: Re: [PATCH 5/5] KVM: arm64: Disable privileged hypercalls after pKVM finalisation Message-ID: <20210923130211.GB15934@willie-the-truck> References: <20210923112256.15767-1-will@kernel.org> <20210923112256.15767-6-will@kernel.org> <87zgs3tpqi.wl-maz@kernel.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <87zgs3tpqi.wl-maz@kernel.org> User-Agent: Mutt/1.10.1 (2018-07-13) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210923_060216_786004_8B68B54A X-CRM114-Status: GOOD ( 28.86 ) 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: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Thu, Sep 23, 2021 at 01:56:21PM +0100, Marc Zyngier wrote: > On Thu, 23 Sep 2021 12:22:56 +0100, > Will Deacon wrote: > > > > After pKVM has been 'finalised' using the __pkvm_prot_finalize hypercall, > > the calling CPU will have a Stage-2 translation enabled to prevent access > > to memory pages owned by EL2. > > > > Although this forms a significant part of the process to deprivilege the > > host kernel, we also need to ensure that the hypercall interface is > > reduced so that the EL2 code cannot, for example, be re-initialised using > > a new set of vectors. > > > > Re-order the hypercalls so that only a suffix remains available after > > finalisation of pKVM. > > > > Cc: Marc Zyngier > > Cc: Quentin Perret > > Signed-off-by: Will Deacon > > --- > > arch/arm64/include/asm/kvm_asm.h | 43 ++++++++++++++++-------------- > > arch/arm64/kvm/hyp/nvhe/hyp-main.c | 26 +++++++++++------- > > 2 files changed, 39 insertions(+), 30 deletions(-) > > > > diff --git a/arch/arm64/include/asm/kvm_asm.h b/arch/arm64/include/asm/kvm_asm.h > > index e86045ac43ba..68630fd382c5 100644 > > --- a/arch/arm64/include/asm/kvm_asm.h > > +++ b/arch/arm64/include/asm/kvm_asm.h > > @@ -43,27 +43,30 @@ > > > > #define KVM_HOST_SMCCC_FUNC(name) KVM_HOST_SMCCC_ID(__KVM_HOST_SMCCC_FUNC_##name) > > > > +/* Hypercalls available only prior to pKVM finalisation */ > > #define __KVM_HOST_SMCCC_FUNC___kvm_hyp_init 0 > > -#define __KVM_HOST_SMCCC_FUNC___kvm_vcpu_run 1 > > -#define __KVM_HOST_SMCCC_FUNC___kvm_flush_vm_context 2 > > -#define __KVM_HOST_SMCCC_FUNC___kvm_tlb_flush_vmid_ipa 3 > > -#define __KVM_HOST_SMCCC_FUNC___kvm_tlb_flush_vmid 4 > > -#define __KVM_HOST_SMCCC_FUNC___kvm_flush_cpu_context 5 > > -#define __KVM_HOST_SMCCC_FUNC___kvm_timer_set_cntvoff 6 > > -#define __KVM_HOST_SMCCC_FUNC___kvm_enable_ssbs 7 > > -#define __KVM_HOST_SMCCC_FUNC___vgic_v3_get_gic_config 8 > > -#define __KVM_HOST_SMCCC_FUNC___vgic_v3_read_vmcr 9 > > -#define __KVM_HOST_SMCCC_FUNC___vgic_v3_write_vmcr 10 > > -#define __KVM_HOST_SMCCC_FUNC___vgic_v3_init_lrs 11 > > -#define __KVM_HOST_SMCCC_FUNC___kvm_get_mdcr_el2 12 > > -#define __KVM_HOST_SMCCC_FUNC___vgic_v3_save_aprs 13 > > -#define __KVM_HOST_SMCCC_FUNC___vgic_v3_restore_aprs 14 > > -#define __KVM_HOST_SMCCC_FUNC___pkvm_init 15 > > -#define __KVM_HOST_SMCCC_FUNC___pkvm_host_share_hyp 16 > > -#define __KVM_HOST_SMCCC_FUNC___pkvm_create_private_mapping 17 > > -#define __KVM_HOST_SMCCC_FUNC___pkvm_cpu_set_vector 18 > > -#define __KVM_HOST_SMCCC_FUNC___pkvm_prot_finalize 19 > > -#define __KVM_HOST_SMCCC_FUNC___kvm_adjust_pc 20 > > +#define __KVM_HOST_SMCCC_FUNC___kvm_get_mdcr_el2 1 > > +#define __KVM_HOST_SMCCC_FUNC___pkvm_init 2 > > +#define __KVM_HOST_SMCCC_FUNC___pkvm_create_private_mapping 3 > > +#define __KVM_HOST_SMCCC_FUNC___pkvm_cpu_set_vector 4 > > +#define __KVM_HOST_SMCCC_FUNC___kvm_enable_ssbs 5 > > +#define __KVM_HOST_SMCCC_FUNC___vgic_v3_init_lrs 6 > > +#define __KVM_HOST_SMCCC_FUNC___vgic_v3_get_gic_config 7 > > +#define __KVM_HOST_SMCCC_FUNC___pkvm_prot_finalize 8 > > + > > +/* Hypercalls available after pKVM finalisation */ > > +#define __KVM_HOST_SMCCC_FUNC___pkvm_host_share_hyp 9 > > +#define __KVM_HOST_SMCCC_FUNC___kvm_adjust_pc 10 > > +#define __KVM_HOST_SMCCC_FUNC___kvm_vcpu_run 11 > > +#define __KVM_HOST_SMCCC_FUNC___kvm_flush_vm_context 12 > > +#define __KVM_HOST_SMCCC_FUNC___kvm_tlb_flush_vmid_ipa 13 > > +#define __KVM_HOST_SMCCC_FUNC___kvm_tlb_flush_vmid 14 > > +#define __KVM_HOST_SMCCC_FUNC___kvm_flush_cpu_context 15 > > +#define __KVM_HOST_SMCCC_FUNC___kvm_timer_set_cntvoff 16 > > +#define __KVM_HOST_SMCCC_FUNC___vgic_v3_read_vmcr 17 > > +#define __KVM_HOST_SMCCC_FUNC___vgic_v3_write_vmcr 18 > > +#define __KVM_HOST_SMCCC_FUNC___vgic_v3_save_aprs 19 > > +#define __KVM_HOST_SMCCC_FUNC___vgic_v3_restore_aprs 20 > > > > #ifndef __ASSEMBLY__ > > > > diff --git a/arch/arm64/kvm/hyp/nvhe/hyp-main.c b/arch/arm64/kvm/hyp/nvhe/hyp-main.c > > index 2da6aa8da868..4120e34288e1 100644 > > --- a/arch/arm64/kvm/hyp/nvhe/hyp-main.c > > +++ b/arch/arm64/kvm/hyp/nvhe/hyp-main.c > > @@ -165,36 +165,42 @@ typedef void (*hcall_t)(struct kvm_cpu_context *); > > #define HANDLE_FUNC(x) [__KVM_HOST_SMCCC_FUNC_##x] = (hcall_t)handle_##x > > > > static const hcall_t host_hcall[] = { > > - HANDLE_FUNC(__kvm_vcpu_run), > > + /* ___kvm_hyp_init */ > > + HANDLE_FUNC(__kvm_get_mdcr_el2), > > + HANDLE_FUNC(__pkvm_init), > > + HANDLE_FUNC(__pkvm_create_private_mapping), > > + HANDLE_FUNC(__pkvm_cpu_set_vector), > > + HANDLE_FUNC(__kvm_enable_ssbs), > > + HANDLE_FUNC(__vgic_v3_init_lrs), > > + HANDLE_FUNC(__pkvm_prot_finalize), > > + > > + HANDLE_FUNC(__pkvm_host_share_hyp), > > HANDLE_FUNC(__kvm_adjust_pc), > > + HANDLE_FUNC(__kvm_vcpu_run), > > HANDLE_FUNC(__kvm_flush_vm_context), > > HANDLE_FUNC(__kvm_tlb_flush_vmid_ipa), > > HANDLE_FUNC(__kvm_tlb_flush_vmid), > > HANDLE_FUNC(__kvm_flush_cpu_context), > > HANDLE_FUNC(__kvm_timer_set_cntvoff), > > - HANDLE_FUNC(__kvm_enable_ssbs), > > HANDLE_FUNC(__vgic_v3_get_gic_config), > > HANDLE_FUNC(__vgic_v3_read_vmcr), > > HANDLE_FUNC(__vgic_v3_write_vmcr), > > - HANDLE_FUNC(__vgic_v3_init_lrs), > > - HANDLE_FUNC(__kvm_get_mdcr_el2), > > HANDLE_FUNC(__vgic_v3_save_aprs), > > HANDLE_FUNC(__vgic_v3_restore_aprs), > > - HANDLE_FUNC(__pkvm_init), > > - HANDLE_FUNC(__pkvm_cpu_set_vector), > > - HANDLE_FUNC(__pkvm_host_share_hyp), > > - HANDLE_FUNC(__pkvm_create_private_mapping), > > - HANDLE_FUNC(__pkvm_prot_finalize), > > }; > > > > static void handle_host_hcall(struct kvm_cpu_context *host_ctxt) > > { > > DECLARE_REG(unsigned long, id, host_ctxt, 0); > > + unsigned long hcall_min = 0; > > hcall_t hfn; > > > > + if (static_branch_unlikely(&kvm_protected_mode_initialized)) > > + hcall_min = __KVM_HOST_SMCCC_FUNC___pkvm_prot_finalize; > > + > > id -= KVM_HOST_SMCCC_ID(0); > > > > - if (unlikely(id >= ARRAY_SIZE(host_hcall))) > > + if (unlikely(id < hcall_min || id >= ARRAY_SIZE(host_hcall))) > > So I can still issue a pkvm_prot_finalize after finalisation? Seems > odd. As hcall_min has to be inclusive, you probably want it to be set > to __KVM_HOST_SMCCC_FUNC___pkvm_host_share_hyp once protected. Yeah, I ended up addresing that one in the previous patch. The problem is that we need to allow pkvm_prot_finalize to be called on each CPU, so I think we'd end up having an extra "really finalize damnit!" call to be issued _once_ after each CPU is done with the finalisation if we want to lock it down. The approach I took instead is to make pkvm_prot_finalize return -EBUSY if it's called on a CPU where it's already been called. Will _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel