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 909E7C88E53 for ; Tue, 15 Sep 2026 09:24:57 +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-Type:MIME-Version: References:In-Reply-To:Subject:Cc:To:From:Message-ID:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=2Urobm8pH0RhpZPcqImG2kp6PxgGk+bUshP3+s8LvM4=; b=sTnGcauiL9Q/7ODv2rpoOYO+iO qtIYKBxRkkbenYqe9Zuvcc4rGxq/xJ393tpwZmLqLS/a0EnXCelEoy/+JukWpLDnTTgS74+kJbuLz s2r9qsCxqAxu0Beqk0X4cpZ4GHZ2h5wOhm61ftFvhNg+006IrD6j8ZfN3FzW8qHqeF7wu3d1+Fmts Q5YvfM3GEOCz3+Zq5zUfpQLoxPxoTEJ3AA0iOMn+oz+xfbVN30XBUvMKUhzwC5CW74bCznANvCWuj 2j/tpPVvmtaIzJETrEhXyXtz+8NHus5wZc9bJQ91mKaC6Ja8WW6Hkp4HvHEEu6WTDyhn5g8Md/dyQ +pCivtKg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1x6PPH-00000005m3h-1HBs; Tue, 15 Sep 2026 09:24:51 +0000 Received: from tor.source.kernel.org ([2600:3c04:e001:324:0:1991:8:25]) by bombadil.infradead.org with esmtps (Exim 4.99.1 #2 (Red Hat Linux)) id 1x6PPG-00000005m3J-1olz for linux-arm-kernel@lists.infradead.org; Tue, 15 Sep 2026 09:24:50 +0000 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by tor.source.kernel.org (Postfix) with ESMTP id 7E2B0602BA; Tue, 15 Sep 2026 09:24:49 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 306681F00899; Tue, 15 Sep 2026 09:24:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1789464289; bh=2Urobm8pH0RhpZPcqImG2kp6PxgGk+bUshP3+s8LvM4=; h=Date:From:To:Cc:Subject:In-Reply-To:References; b=fotzjncRuGz2mEZgt940CxB2FO9xn/J3/QtSxglXaZEdeDTLvorADbSxmVIFBJ/Nd gSMhSKygkcppmo1+C+PwBvszwBzd/ZDrvv/6onCVo+ScMsS07VqsOQNx4iGgci5Ur5 abL7CExSFJu624QuWD80PUcMA8DXUtarY10Kg3kUCzlouFZTcIJBGbAsEHQG19NZCO So3DOsPuA34KmevKPUAIS52SVEFtDouroj/RAE+egE618e4Tk5dHhv5RHmh2njtXyU r1db/jf+vUcAJjTNXgKiOWuODpkbHqpRlqvnHTiJQpGoIVmcV2r4zBRuHdXGTmRvHf +ybFCvweHA2mQ== Received: from sofa.misterjones.org ([185.219.108.64] helo=goblin-girl.misterjones.org) by disco-boy.misterjones.org with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.98.2) (envelope-from ) id 1x6PPD-000000091Zg-13i5; Tue, 15 Sep 2026 09:24:47 +0000 Date: Tue, 15 Sep 2026 10:24:46 +0100 Message-ID: <86zexi6f4x.wl-maz@kernel.org> From: Marc Zyngier To: Fuad Tabba Cc: oupton@kernel.org, kvmarm@lists.linux.dev, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, catalin.marinas@arm.com, will@kernel.org, joey.gouly@arm.com, seiden@linux.ibm.com, suzuki.poulose@arm.com, yuzenghui@huawei.com, mark.rutland@arm.com, vdonnefort@google.com, qperret@google.com, tabba@google.com Subject: Re: [PATCH] KVM: arm64: Reject the stage-2 MMU pointer hypercalls under pKVM In-Reply-To: <20260914174521.832575-1-fuad.tabba@linux.dev> References: <20260914174521.832575-1-fuad.tabba@linux.dev> User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI-EPG/1.14.7 (Harue) FLIM-LB/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL-LB/10.8 EasyPG/1.0.0 Emacs/30.1 (aarch64-unknown-linux-gnu) MULE/6.0 (HANACHIRUSATO) MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") Content-Type: text/plain; charset=US-ASCII X-SA-Exim-Connect-IP: 185.219.108.64 X-SA-Exim-Rcpt-To: fuad.tabba@linux.dev, oupton@kernel.org, kvmarm@lists.linux.dev, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, catalin.marinas@arm.com, will@kernel.org, joey.gouly@arm.com, seiden@linux.ibm.com, suzuki.poulose@arm.com, yuzenghui@huawei.com, mark.rutland@arm.com, vdonnefort@google.com, qperret@google.com, tabba@google.com X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false 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 On Mon, 14 Sep 2026 18:45:21 +0100, Fuad Tabba wrote: > > The five hypercalls that take a struct kvm_s2_mmu pointer remain > callable after pKVM finalises, and each dereferences the host pointer > in __load_stage2(). Under pKVM none of them has a valid caller: the > host walks no guest stage-2, its TLB flushes go through the handle-based > __pkvm_tlb_flush_vmid, and kvm_arch_vcpu_load() skips the CPU context > flush. > > Reject all five when protected mode is enabled. > > Reported-by: Sashiko > Closes: https://lore.kernel.org/all/20260914130152.F0D5F1F000FF@smtp.kernel.org/ > Signed-off-by: Fuad Tabba > --- > > Notes: > No in-tree host path reaches these, so no Fixes: tag. > > arch/arm64/kvm/hyp/nvhe/hyp-main.c | 15 +++++++++++++++ > 1 file changed, 15 insertions(+) > > diff --git a/arch/arm64/kvm/hyp/nvhe/hyp-main.c b/arch/arm64/kvm/hyp/nvhe/hyp-main.c > index 9a3b92e626adb..4b0d00e55e2ea 100644 > --- a/arch/arm64/kvm/hyp/nvhe/hyp-main.c > +++ b/arch/arm64/kvm/hyp/nvhe/hyp-main.c > @@ -557,6 +557,9 @@ static void handle___kvm_tlb_flush_vmid_ipa(struct kvm_cpu_context *host_ctxt) > DECLARE_REG(phys_addr_t, ipa, host_ctxt, 2); > DECLARE_REG(int, level, host_ctxt, 3); > > + if (unlikely(is_protected_kvm_enabled())) > + return; > + > __kvm_tlb_flush_vmid_ipa(kern_hyp_va(mmu), ipa, level); > } > > @@ -566,6 +569,9 @@ static void handle___kvm_tlb_flush_vmid_ipa_nsh(struct kvm_cpu_context *host_ctx > DECLARE_REG(phys_addr_t, ipa, host_ctxt, 2); > DECLARE_REG(int, level, host_ctxt, 3); > > + if (unlikely(is_protected_kvm_enabled())) > + return; > + > __kvm_tlb_flush_vmid_ipa_nsh(kern_hyp_va(mmu), ipa, level); > } > > @@ -576,6 +582,9 @@ handle___kvm_tlb_flush_vmid_range(struct kvm_cpu_context *host_ctxt) > DECLARE_REG(phys_addr_t, start, host_ctxt, 2); > DECLARE_REG(unsigned long, pages, host_ctxt, 3); > > + if (unlikely(is_protected_kvm_enabled())) > + return; > + > __kvm_tlb_flush_vmid_range(kern_hyp_va(mmu), start, pages); > } > > @@ -583,6 +592,9 @@ static void handle___kvm_tlb_flush_vmid(struct kvm_cpu_context *host_ctxt) > { > DECLARE_REG(struct kvm_s2_mmu *, mmu, host_ctxt, 1); > > + if (unlikely(is_protected_kvm_enabled())) > + return; > + > __kvm_tlb_flush_vmid(kern_hyp_va(mmu)); > } > > @@ -602,6 +614,9 @@ static void handle___kvm_flush_cpu_context(struct kvm_cpu_context *host_ctxt) > { > DECLARE_REG(struct kvm_s2_mmu *, mmu, host_ctxt, 1); > > + if (unlikely(is_protected_kvm_enabled())) > + return; > + > __kvm_flush_cpu_context(kern_hyp_va(mmu)); > } > Anf why not __kvm_flush_vm_context()? It doesn't take a S2 MMU pointer, but it is still logically wrong to let this being called. And the whole sprinkling of guards like this is just horrible. We already have a filtering mechanism, just make use of it: diff --git a/arch/arm64/include/asm/kvm_asm.h b/arch/arm64/include/asm/kvm_asm.h index bffdeb36da1d2..51bf30b671fe4 100644 --- a/arch/arm64/include/asm/kvm_asm.h +++ b/arch/arm64/include/asm/kvm_asm.h @@ -62,6 +62,11 @@ enum __kvm_host_smccc_func { __KVM_HOST_SMCCC_FUNC___kvm_enable_ssbs, __KVM_HOST_SMCCC_FUNC___vgic_v3_init_lrs, __KVM_HOST_SMCCC_FUNC___vgic_v3_get_gic_config, + __KVM_HOST_SMCCC_FUNC___kvm_flush_vm_context, + __KVM_HOST_SMCCC_FUNC___kvm_tlb_flush_vmid_ipa, + __KVM_HOST_SMCCC_FUNC___kvm_tlb_flush_vmid_ipa_nsh, + __KVM_HOST_SMCCC_FUNC___kvm_tlb_flush_vmid, + __KVM_HOST_SMCCC_FUNC___kvm_tlb_flush_vmid_range, MARKER(__KVM_HOST_SMCCC_FUNC_MIN_PKVM), @@ -70,11 +75,6 @@ enum __kvm_host_smccc_func { /* Hypercalls that are always available and common to [nh]VHE/pKVM. */ __KVM_HOST_SMCCC_FUNC___kvm_adjust_pc, __KVM_HOST_SMCCC_FUNC___kvm_vcpu_run, - __KVM_HOST_SMCCC_FUNC___kvm_flush_vm_context, - __KVM_HOST_SMCCC_FUNC___kvm_tlb_flush_vmid_ipa, - __KVM_HOST_SMCCC_FUNC___kvm_tlb_flush_vmid_ipa_nsh, - __KVM_HOST_SMCCC_FUNC___kvm_tlb_flush_vmid, - __KVM_HOST_SMCCC_FUNC___kvm_tlb_flush_vmid_range, __KVM_HOST_SMCCC_FUNC___kvm_flush_cpu_context, __KVM_HOST_SMCCC_FUNC___kvm_timer_set_cntvoff, __KVM_HOST_SMCCC_FUNC___tracing_load, Thanks, M. -- Without deviation from the norm, progress is not possible.