From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1) server-digest SHA256) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A14A260A2625 for ; Fri, 23 Oct 2026 07:02:47 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=lists.infradead.org header.i=@lists.infradead.org header.a=rsa-sha256 header.s=bombadil.20210309 header.b=ADl+XOcW; dkim=pass (1024-bit key, unprotected) header.d=linux.dev header.i=@linux.dev header.a=rsa-sha256 header.s=key1 header.b=VIIyaJ0S 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-Unsubscribe-Post: List-Owner; bh=IthMuZ/X3+pBoLoIufpj4zbJGn8A/2aYhe0XUm0DWMM=; b=ADl+XOcWsk/OwY uI/idKk8PFaFENd4IIFwPGtbgn14Yod8fSPKvJtHRkgWI0JciS1j03R/nBvFAYB9858REitQuyjoi wxDREkztHSpcMu7Cnk10COm0o/eUn/JEcgqBqBoQ9OUMpTk9cPHjj90NZky6j04149nSvEjDrYVmc J0nkuwrDyyKL/YRa5irH0sBb95qB8YAeLfcZ8/A0dkmyeGsp8hASk/HqD5IEGe/p5HKV41zPmkUaw 6OYgS3LrdoBU4pUbOJBezkc+I8O83djTP3Tdvh5SytdD9W9bHKPTZY2/Lk0bgo059SXMQWiaA0Hjq wJY85KEJYQpafGnXdytA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.100.1 #2 (Red Hat Linux)) id 1xK9HP-0000000FfsS-0M88; Fri, 23 Oct 2026 07:01:31 +0000 Received: from out-64.mta1.migadu.com ([2001:41d0:203:375::40] helo=mta1.migadu.com) by bombadil.infradead.org with esmtps (Exim 4.100.1 #2 (Red Hat Linux)) id 1xK9HE-0000000Ffni-0G81 for linux-arm-kernel@lists.infradead.org; Fri, 23 Oct 2026 07:01:22 +0000 X-Envelope-To: linux-arm-kernel@lists.infradead.org DKIM-Signature: a=rsa-sha256; bh=bc/l25RHGTThA1qU58knnGQTtBxP0XgtC5Ldu46NdMg=; c=simple/simple; d=linux.dev; h=from:to:subject:date:message-id:mime-version:content-type; s=key1; t=1792738877; v=1; x=1793343677; b=VIIyaJ0Sw52+V97m1HKFMIqSa8yNktq8sfhmwLCLfRwHTvhwV0dPleik4OXIPg2DcDAfVuTs yVRIUsm/0QDbsndkPZ8u3CEHzlCuhbWSoLIFMxsl3QiNzNSTJBfnt8tWlqqrFHZzL9tRocntdjZ bLk6ry6z00cJbZ/RFAUTs7Mo= X-Envelope-To: linux-arm-kernel@lists.infradead.org Received: by smtp.migadu.com with ESMTPS id c1557c2947e98bd9; Fri, 23 Oct 2026 07:01:16 +0000 X-Mizu-Trace-ID: c1557c2947e98bd9 X-Migadu-Flow: FLOW_OUT From: Fuad Tabba To: Marc Zyngier , Oliver Upton , kvmarm@lists.linux.dev, linux-arm-kernel@lists.infradead.org Cc: Joey Gouly , Suzuki K Poulose , Zenghui Yu , Steffen Eiden , Catalin Marinas , Will Deacon , Mark Rutland , Yicong Yang , Zhou Wang , Arnd Bergmann , Fuad Tabba , kvm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH 1/2] KVM: arm64: Hide FEAT_LS64_ACCDATA from guests Date: Fri, 23 Oct 2026 08:01:09 +0100 Message-ID: <20261023070110.1833446-2-fuad.tabba@linux.dev> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20261023070110.1833446-1-fuad.tabba@linux.dev> References: <20261023070110.1833446-1-fuad.tabba@linux.dev> X-Archived-By: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20261023_000121_443644_2232369D X-CRM114-Status: GOOD ( 14.01 ) X-Spam-Score: -2.1 (--) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" X-Spam-Status: No, score=-19.2 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=4.0.1 X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 Since commit 58ce78667a641 ("arm64: Add support for FEAT_{LS64, LS64_V}"), a guest sees the host's ID_AA64ISAR1_EL1.LS64, but KVM only enables the FEAT_LS64 and FEAT_LS64_V instructions in HCRX_EL2. On a host with FEAT_LS64_ACCDATA, a guest's ST64BV0 therefore traps and hits the WARN_ON_ONCE() in handle_other(). ACCDATA_EL1 isn't trapped or context-switched either, so every guest on that CPU shares it. Rather than support FEAT_LS64_ACCDATA, which requires ACCDATA_EL1 to be context-switched, cap the field at LS64_V. The guest's ACCDATA_EL1 accesses then UNDEF. This hides FEAT_LS64WB too, as it implies FEAT_LS64_ACCDATA. A VM saved on an older kernel can carry any level up to the host's, so keep accepting those from the VMM, capped the same way. One saved at LS64_ACCDATA or above restores at LS64_V. Fixes: 58ce78667a641 ("arm64: Add support for FEAT_{LS64, LS64_V}") Cc: stable@vger.kernel.org Signed-off-by: Fuad Tabba --- arch/arm64/kvm/sys_regs.c | 28 ++++++++++++++++++++++++---- 1 file changed, 24 insertions(+), 4 deletions(-) diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c index 44aae52c473d7..7801166991b12 100644 --- a/arch/arm64/kvm/sys_regs.c +++ b/arch/arm64/kvm/sys_regs.c @@ -1958,6 +1958,9 @@ static u64 __kvm_read_sanitised_id_reg(const struct kvm_vcpu *vcpu, ID_AA64ISAR1_EL1_API | ID_AA64ISAR1_EL1_GPA | ID_AA64ISAR1_EL1_GPI); + + /* ACCDATA_EL1 isn't context-switched, so no FEAT_LS64_ACCDATA */ + val = ID_REG_LIMIT_FIELD_ENUM(val, ID_AA64ISAR1_EL1, LS64, LS64_V); break; case SYS_ID_AA64ISAR2_EL1: if (!vcpu_has_ptrauth(vcpu)) @@ -2403,6 +2406,22 @@ static int set_id_aa64pfr2_el1(struct kvm_vcpu *vcpu, return set_id_reg(vcpu, rd, user_val); } +static int set_id_aa64isar1_el1(struct kvm_vcpu *vcpu, + const struct sys_reg_desc *rd, u64 user_val) +{ + u64 hw_val = read_sanitised_ftr_reg(SYS_ID_AA64ISAR1_EL1); + u64 ls64_mask = ID_AA64ISAR1_EL1_LS64_MASK; + + /* + * Older kernels let userspace set LS64 up to the host's level, so + * keep accepting those values, capped at LS64_V. + */ + if ((user_val & ls64_mask) <= (hw_val & ls64_mask)) + user_val = ID_REG_LIMIT_FIELD_ENUM(user_val, ID_AA64ISAR1_EL1, LS64, LS64_V); + + return set_id_reg(vcpu, rd, user_val); +} + /* * Allow userspace to de-feature a stage-2 translation granule but prevent it * from claiming the impossible. @@ -3428,10 +3447,11 @@ static const struct sys_reg_desc sys_reg_descs[] = { /* CRm=6 */ ID_WRITABLE(ID_AA64ISAR0_EL1, ~ID_AA64ISAR0_EL1_RES0), - ID_WRITABLE(ID_AA64ISAR1_EL1, ~(ID_AA64ISAR1_EL1_GPI | - ID_AA64ISAR1_EL1_GPA | - ID_AA64ISAR1_EL1_API | - ID_AA64ISAR1_EL1_APA)), + ID_FILTERED(ID_AA64ISAR1_EL1, id_aa64isar1_el1, + ~(ID_AA64ISAR1_EL1_GPI | + ID_AA64ISAR1_EL1_GPA | + ID_AA64ISAR1_EL1_API | + ID_AA64ISAR1_EL1_APA)), ID_WRITABLE(ID_AA64ISAR2_EL1, ~(ID_AA64ISAR2_EL1_RES0 | ID_AA64ISAR2_EL1_APA3 | ID_AA64ISAR2_EL1_GPA3)), -- 2.47.3