From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 3096C2517B9; Wed, 1 Oct 2025 15:19:25 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1759331966; cv=none; b=eTGGrfvuPEhhoA6CqEZV32pP2q1UkdlDkAOZFM8JGWLoOk5/hx/9wAfASvpGpmQa9c0GJmI+B6j0wGTaquKqn4DjNErDQvprRDmOG5caYgzyHsi0qtwX0ZSPci7Q1WKnp+1NK1v/zJH5CnP35K2V35Z0mCncNe70NlXf1FW2h2w= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1759331966; c=relaxed/simple; bh=AuwwvpeSpDso60zCvsa1OUltjVmGQt8y3NeOBslXwNk=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=btEcg6jRvrPO/Z0Mg4bHrmiF8dqxbKVHEBTOdldmuWmkbAMBLVJ4d82ywhNVHUst4GewEmYl4DaqZBiMp2AslhlFQF5udPg0DGYV1SWs2H1Y/hGwJFYnJS/TkcwNPryOJ7zStG9xY0i/lLa2CswXlmq75QKNdJxdS3JIeBgMx7s= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 7DB241424; Wed, 1 Oct 2025 08:19:16 -0700 (PDT) Received: from [10.57.0.204] (unknown [10.57.0.204]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id C5E213F59E; Wed, 1 Oct 2025 08:19:18 -0700 (PDT) Message-ID: <765f8a3e-2bdd-4352-ba89-99ce3dbc6e4c@arm.com> Date: Wed, 1 Oct 2025 16:19:16 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v10 08/43] kvm: arm64: Don't expose debug capabilities for realm guests To: Marc Zyngier Cc: kvm@vger.kernel.org, kvmarm@lists.linux.dev, Suzuki K Poulose , Catalin Marinas , Will Deacon , James Morse , Oliver Upton , Zenghui Yu , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Joey Gouly , Alexandru Elisei , Christoffer Dall , Fuad Tabba , linux-coco@lists.linux.dev, Ganapatrao Kulkarni , Gavin Shan , Shanker Donthineni , Alper Gun , "Aneesh Kumar K . V" , Emi Kisanuki , Vishal Annapurve References: <20250820145606.180644-1-steven.price@arm.com> <20250820145606.180644-9-steven.price@arm.com> <86ikgyzrzj.wl-maz@kernel.org> From: Steven Price Content-Language: en-GB In-Reply-To: <86ikgyzrzj.wl-maz@kernel.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 01/10/2025 14:11, Marc Zyngier wrote: > On Wed, 20 Aug 2025 15:55:28 +0100, > Steven Price wrote: >> >> From: Suzuki K Poulose >> >> RMM v1.0 provides no mechanism for the host to perform debug operations >> on the guest. So don't expose KVM_CAP_SET_GUEST_DEBUG and report 0 >> breakpoints and 0 watch points. > > What is the guest seeing for the same things? The number of breakpoints/watchpoints is configured using the usual architectural register ID_AA64DFR0_EL1. So the VMM can configure the guest as it pleases to be able to debug itself. Obviously CCA is about the host not seeing into the guest so debugging the guest is generally not permitted. RMM v1.1 should provide some mechanisms for the host to debug a realm - but this would also change the attestation measurement so needs buy in from the guest's attestation flow. I don't think the RMM API for that is finalised yet, and I certainly don't have any Linux patches. Thanks, Steve