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 67B5E79C8 for ; Wed, 26 Nov 2025 17:10:15 +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=1764177017; cv=none; b=AUxLycdK9bh5FvwIRyaiTnIFibWJVPc4aQZze+SCrBHZTSm/YBZiTLc+sQmyq9H62ZtgeWBNRyE6kBns4lEFfQ0Qzya9931E+Vbb+NH2xEe7E85RUyG5EEDS9rkGhk6Q6maSTBCYbhXtZU7XTPPbowvZ0xVmCPpncpii3wZmFNI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1764177017; c=relaxed/simple; bh=84KXIXsEPdYPW/hv00MCC50tWgoa2u/e9pMLHA0Eugw=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=lY6/imkDKqA3BK9j0qd4u1Gu9ARLPOFtQHMEaqkDH4teIF5Garnq5SSEIlJFO6iMh6KDlWncFzHF/PSpI7P4qf6D/Qpe38GqYIxAccnAwzEw3f46crAzfSLk70g5XEs5vHB05l/ocanl5X7db3zJ6/ooYY4WknuvYM8Dk63cewM= 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 56BE8168F; Wed, 26 Nov 2025 09:10:07 -0800 (PST) Received: from [10.1.196.46] (e134344.arm.com [10.1.196.46]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id AA9AE3F66E; Wed, 26 Nov 2025 09:10:13 -0800 (PST) Message-ID: <26d62f83-c5e2-4706-84ad-b3dbe313dfd1@arm.com> Date: Wed, 26 Nov 2025 17:10:12 +0000 Precedence: bulk X-Mailing-List: kvmarm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 4/5] KVM: arm64: Report optional ID register traps with a 0x18 syndrome To: Marc Zyngier , kvmarm@lists.linux.dev, kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org Cc: Joey Gouly , Suzuki K Poulose , Oliver Upton , Zenghui Yu References: <20251126155951.1146317-1-maz@kernel.org> <20251126155951.1146317-5-maz@kernel.org> From: Ben Horgan Content-Language: en-US In-Reply-To: <20251126155951.1146317-5-maz@kernel.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Hi Marc, On 11/26/25 15:59, Marc Zyngier wrote: > With FEAT_IDST, unimplemented system registers in the feature ID space > must be reported using EC=0x18 at the closest handling EL, rather than > with an UNDEF. > > Most of these system registers are always implemented thanks to their > dependency on FEAT_AA64, except for a set of (currently) three registers: > GMID_EL1 (depending on MTE2), CCSIDR2_EL1 (depending on FEAT_CCIDX), > and SMIDR_EL1 (depending on SME). > > For these three registers, report their trap as EC=0x18 if they > end-up trapping into KVM and that FEAT_IDST is not implemented in the > guest. Otherwise, just make them UNDEF. Missed it before but there is a stray 'not' in there. You get the EC=0x18 trap if FEAT_IDST is implemented. > > Signed-off-by: Marc Zyngier > --- > arch/arm64/kvm/sys_regs.c | 16 +++++++++++++--- > 1 file changed, 13 insertions(+), 3 deletions(-) The code looks good. Reviewed-by: Ben Horgan Thanks, Ben