From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 8D5C039D6F2; Mon, 10 Aug 2026 08:52:39 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786351960; cv=none; b=aAbu5S6amjdu6rePACsLaZt72kSa0B3Y85WJIgYK6tzhT5i7c4CeW7P9uGkDXVpnjVExyqjXzh5KpkXkSv/6CqR31TAefvkX9elEHarTg11upWLcMZ259mSa3wY+jQLEFs0e9NjuSEICKDESYt1o14C2ucrOmuGaslzZ9pFWaQU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786351960; c=relaxed/simple; bh=mgI1A5xxMUA4gh1TXWJ/YIU1vpgad5CqsEcXQSz6G6o=; h=Date:Message-ID:From:To:Cc:Subject:In-Reply-To:References: MIME-Version:Content-Type; b=gH3G30+kDXRlf6JdLpYNXw2gcErkaQjvvOD3CF4hNS4DelrwRc3IC25Ech5+WFiGWQdoz2BFwgX1bRz4Me8d3JqoGt/qQY1cOW2CI02W3RcUSIoD+XEHqq5B/PSn2JHNYYcmF+6Joyq3g/xOSILltLR2SXZD4eiakly+hdqVBDg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=CHxySg7v; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="CHxySg7v" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2F12D1F000E9; Mon, 10 Aug 2026 08:52:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1786351959; bh=pq+u/KHK9r+MSQrkQ4op9UevKKFwZbJcBlJBfLPWaJo=; h=Date:From:To:Cc:Subject:In-Reply-To:References; b=CHxySg7vub9y9D0F0caT3xQMuh9IfRYQQ4jnur3KdmHS41+KPOZob+xb8LkVwrYpz 3QQu/LNAAl8LztgatnYVVVAvEpbQYnA30f74Aq4mJ8G1/YZNlGSE1C6ddOWR2qlwJh XjVxsmeh8jBfDtGMwprj84CXEJS577x8+4Jv23t/qDoWBcpJ1Yymr9itNseF7DMuxj 149QD0pHNjFE/LxizeN7noSN+zqCyQ7soWpDGwcvIF1QJH1M3qAaU3mufeVpPUr8+M 4F4wkd8IiEXanyD0RZoMhsVWwfjzleC8eDI+bNBxnOjJqCTGo0CxTZRSbRuOFpjRxX T3unaLHs3I1xQ== 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 1wtLkK-0000000E1LL-3X8j; Mon, 10 Aug 2026 08:52:36 +0000 Date: Mon, 10 Aug 2026 09:52:36 +0100 Message-ID: <86qzk69x2j.wl-maz@kernel.org> From: Marc Zyngier To: Karl Mehltretter Cc: Oliver Upton , kvmarm@lists.linux.dev, Fuad Tabba , Joey Gouly , Steffen Eiden , Suzuki K Poulose , Zenghui Yu , Catalin Marinas , Will Deacon , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] KVM: arm64: Fix AArch32 DBGBXVR handling In-Reply-To: <20260810005616.13227-1-kmehltretter@gmail.com> References: <20260810005616.13227-1-kmehltretter@gmail.com> 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) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: 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: kmehltretter@gmail.com, oupton@kernel.org, kvmarm@lists.linux.dev, tabba@google.com, joey.gouly@arm.com, seiden@linux.ibm.com, suzuki.poulose@arm.com, yuzenghui@huawei.com, catalin.marinas@arm.com, will@kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false On Mon, 10 Aug 2026 01:56:16 +0100, Karl Mehltretter wrote: > > The consolidation of the breakpoint and watchpoint register accessors > switched DBGBXVR from trap_bvr() to trap_dbg_wb_reg(). The latter > selects backing storage with demux_wb_reg(), which only handles Op2 values > 4 through 7. Since DBGBXVR uses Op2 1, an AArch32 guest access hits > KVM_BUG_ON() and marks the VM dead. > > DBGBXVR aliases DBGBVR_EL1[63:32], and its AA32(HI) descriptor > already selects the upper half. Map Op2 1 to dbg_bvr[] alongside Op2 4, > restoring the pre-regression behavior. > > Fixes: 3ce9f3357e9e ("KVM: arm64: Fold DBGxVR/DBGxCR accessors into common set") > Assisted-by: Claude:claude-opus-5 > Signed-off-by: Karl Mehltretter > --- > Tested on a Raspberry Pi 400 with a minimal AArch32 guest. The unpatched > kernel WARNed in demux_wb_reg() and returned -EIO from KVM_RUN. The > patched kernel completed the access without a warning. > > arch/arm64/kvm/sys_regs.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c > index 5d5c579d4579..2862df188155 100644 > --- a/arch/arm64/kvm/sys_regs.c > +++ b/arch/arm64/kvm/sys_regs.c > @@ -889,6 +889,7 @@ static u64 *demux_wb_reg(struct kvm_vcpu *vcpu, const struct sys_reg_desc *rd) > struct kvm_guest_debug_arch *dbg = &vcpu->arch.vcpu_debug_state; > > switch (rd->Op2) { > + case 0b001: > case 0b100: > return &dbg->dbg_bvr[rd->CRm]; > case 0b101: Reviewed-by: Marc Zyngier Cc: stable@vger.kernel.org M. -- Without deviation from the norm, progress is not possible.