From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=91.218.175.146 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1792738885; b=Jk8G8p6/roftbZRM560YrnDC7pZWGiMvCSWUuwYlyQbiwvdCijnepsfdybLEuvlc/G1I PvAAITV+EHKaf9zuqKM/j7nbMksp1PwvubFmsv8q1jZFWvHcqOqHGSDvRgdm7JVEYd2rW ay1oLZMdIYPoy9V7LXrlfiQ5EnsQvtatNX9Kijsc5dWyTO6Xn2oENFzacWUP9R/TTd2jk PGDoKZkFOIyDcq1SRLGQf5t+J/m73MS9TtgyFeuCP8SYZOFuiFwJKMZ6oq8+pHlh7CqxD 4pTQOYEdTQnlecievV37APxuu/J5pbOnfSIgLEQgV5scZHcY26WhPZ2heP/zkwUWdtA== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1792738885; h=DMARC-Filter:X-Envelope-To:DKIM-Signature:X-Envelope-To:Received: X-Mizu-Trace-ID:X-Migadu-Flow:From:To:Cc:Subject:Date:Message-ID: X-Mailer:In-Reply-To:References:MIME-Version: Content-Transfer-Encoding; bh=IthMuZ/X3+pBoLoIufpj4zbJGn8A/2aYhe0XUm0DWMM=; b=Y8HUrnwi3wt8/ydJfdqgfJW7RA+IfAvvCAoWCqeOZ3IDhzNo9kigk3W+NHzlSk+JzkFt t7SuBerKo3gnrEeKhfNP3EaAwWz7yhddAPHyAVaHhHKSmg54EZc43KBZ2WtGqLRRGG5FK zaKIq5L8VJD+1Bd4S1bRGUrEJ0/3cg11DgW/EXO6uLTSpjsNIv+VZtqFmqjWjyqROZ3JR X05hIA9FFr7WVJPjrV7tf+J1OdDtIbtQzgxaxs8L7JP8rifKsBdPDQZ4oLDn9H0Vi7ulk tAcjTA9w+FJ2rIYJPB+pQCvRcNT78eylBlzPQ90B+6GruC4HpQdyNsSKFwxGawudTqw== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass header.d=linux.dev header.i=@linux.dev header.a=rsa-sha256 header.s=key1 header.b=VIIyaJ0S; arc=none smtp.remote-ip=91.218.175.146 Received: from mta0.migadu.com (out-146.mta0.migadu.com [91.218.175.146]) (using TLSv1.3 with cipher TLS_AES_128_GCM_SHA256 (128/128 bits) key-exchange X25519 server-signature ECDSA (prime256v1) server-digest SHA256) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 2BF87606A322 for ; Fri, 23 Oct 2026 07:01:18 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.2 smtp.subspace.kernel.org 2BF87606A322 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key, unprotected) header.d=linux.dev header.i=@linux.dev header.a=rsa-sha256 header.s=key1 header.b=VIIyaJ0S X-Envelope-To: linux-kernel@vger.kernel.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-kernel@vger.kernel.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-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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