From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (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 8F5AE1FDE04 for ; Fri, 21 Feb 2025 07:52:20 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.133.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1740124342; cv=none; b=DVzvEaFZUbDCYEEFP7dFmRQG1Q0F90cjuCK5RqoU5+BD0QyWRtO9c1W2+Yp9QlmiZUH8WCGutign6FSdnF36ztqulbgCZc34OQkDrg7j5dsSQnysFbUJrqtUAfDuDogqF9JHo8NkPf8yJSjVAfzoVRYFVW6Kg2OD/M6n3EBMEWc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1740124342; c=relaxed/simple; bh=RjnkR8CLqAhZybuqbBDTZjGpwudzdSm6aoF+/1gHzNI=; h=Date:From:To:cc:Subject:In-Reply-To:Message-ID:References: MIME-Version:Content-Type; b=TN8UZoikGAY44US4GIZrNT/nKZtnGPmLOO+/6b57B11uqfbR4m12i0nKh3Intd4vYBBrI7kOKHAigiot3t3n0oaZQn9rnS8AbOk5bsfkOMvaHxAL1O2Tl9/qvohE0b3nZcLSD/ovG8Kn8X4Z6edeGj4pyjljVI9fREQTXlOkLf4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=bBcAWn9c; arc=none smtp.client-ip=170.10.133.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="bBcAWn9c" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1740124339; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=rOI7Z+k/jw/HwkIzU4wUrpSnIOnbW4yX7Ts578dd7m0=; b=bBcAWn9cGqy4H6qmy4L3R6rfw0RlLDCMFoGh/MIEwdo9cwuNSg1NXIutRdcMiRWVf+WCAR Atij/qMDaZ9tV/S7w4L7MqbKE6sZ62j1fLxM91oZYsBe9nYZplSshRYU3tpSXBpH5vAiu+ pCwZwPvMITK8GkGbE/oZyq7/N2Q+jx4= Received: from mail-wm1-f72.google.com (mail-wm1-f72.google.com [209.85.128.72]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-632-BBCMlurhOlGgJqlFp4ab6g-1; Fri, 21 Feb 2025 02:52:18 -0500 X-MC-Unique: BBCMlurhOlGgJqlFp4ab6g-1 X-Mimecast-MFC-AGG-ID: BBCMlurhOlGgJqlFp4ab6g_1740124337 Received: by mail-wm1-f72.google.com with SMTP id 5b1f17b1804b1-439a0e28cfaso9462225e9.2 for ; Thu, 20 Feb 2025 23:52:18 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1740124337; x=1740729137; h=mime-version:references:message-id:in-reply-to:subject:cc:to:from :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=rOI7Z+k/jw/HwkIzU4wUrpSnIOnbW4yX7Ts578dd7m0=; b=EWst5mfvBh7jGjZOJ4gJ6mZ+aMgl5l1NaMqa3/HucmcvUlyviZcxl+jHrb5ekZ6npD 2SUAemqvMm1HmcJyr1/8apU0+sFSTqXTL99Edr4YcjmdjyVyeeYGhkqyS4wyaAuYX1jm oaFnx5FhpUcHe+OnzTWh1bk2YtSG0pwSFT7bsIfVPvt7MWw2pMtduMVNN07WRZRpukG3 z8lYqn1nVFS1kQLl63ijiS2ecjHEOK35v1gZIx0wDebVvOyUVV0FdLmuHo09wvMUWJyo Aes26eYMWS5YtZtCDXBHbecGvGjS2dBlB+qjGfTLyUl+PGxXJYp46d3Lx99dtKAq2GIG loCg== X-Gm-Message-State: AOJu0YxueVz5urTENFC8PHkJxnCVgJ0UY9k3NwO476lJ/eNDxPjXhZXs qeqseGGXLYpmDgy73VsrbGBDxU+DxMoLqxUzg9HYMrHS2kp8k6oOueRik3+p5xYWcLgyk/CHGgF G6V9gGIgb++n8SPYQMWKjuMON3sqN6aray1xl6G8hVZoAUSGSGMpoYA== X-Gm-Gg: ASbGnctDkLqPPHNuDiRTL46cjzNn0fLsXOBPsuzac9PkkmXJPbe2/44rs/d/Qtt9+dx vwZ4PR13P/jGP31PpBek8S+WfwXieusttg0/sawSqPtidG3jYH2YgFPDzZuwEz51z24hMa443EC YDH9T9pwDghncpc3W7BlmIB0UIyo0NEEK+0rRo9SfOBBDYpbwk7tlAbFx7GIMY2RLvjlTlyX7pC W8+HFmRcp1eoxDIqbejCf72WLMhXSEVwWchUeWIaCEctPaQvEcMbuePHxVUvMG9ub3z96Y/sdoc YMhoO/Qh5n4JhVUra1rT3nCm0sGgeWccv/dd9F792UCh3HVTGzAiqC/eRt2na1pH X-Received: by 2002:a05:600c:5246:b0:439:9a40:aa09 with SMTP id 5b1f17b1804b1-439ae21d202mr13079595e9.25.1740124337019; Thu, 20 Feb 2025 23:52:17 -0800 (PST) X-Google-Smtp-Source: AGHT+IE6RndQ6ymoZEFzvzfDt+1GKRpaPngpEuFYmDAHqGLJUcufH5YS8MWYZmZqlHO+/W+nddETwA== X-Received: by 2002:a05:600c:5246:b0:439:9a40:aa09 with SMTP id 5b1f17b1804b1-439ae21d202mr13079435e9.25.1740124336660; Thu, 20 Feb 2025 23:52:16 -0800 (PST) Received: from rh (p200300f6af0e4d00dda53016e366575f.dip0.t-ipconnect.de. [2003:f6:af0e:4d00:dda5:3016:e366:575f]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-439b02ce735sm9240925e9.3.2025.02.20.23.52.15 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 20 Feb 2025 23:52:16 -0800 (PST) Date: Fri, 21 Feb 2025 08:52:15 +0100 (CET) From: Sebastian Ott To: Marc Zyngier cc: kvmarm@lists.linux.dev, kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Joey Gouly , Suzuki K Poulose , Oliver Upton , Zenghui Yu , Eric Auger , gankulkarni@os.amperecomputing.com Subject: Re: [PATCH v2 02/14] KVM: arm64: Hide ID_AA64MMFR2_EL1.NV from guest and userspace In-Reply-To: <86r03squ0w.wl-maz@kernel.org> Message-ID: <5f9699c5-ccc8-9339-bfca-1ace8d7f86b6@redhat.com> References: <20250220134907.554085-1-maz@kernel.org> <20250220134907.554085-3-maz@kernel.org> <86r03squ0w.wl-maz@kernel.org> Precedence: bulk X-Mailing-List: kvmarm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: xvSpRdEZ7xOPwe3alW94sFtDM3ixVhWordvR71coiIo_1740124337 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=US-ASCII; format=flowed On Thu, 20 Feb 2025, Marc Zyngier wrote: > On Thu, 20 Feb 2025 17:36:35 +0000, > Sebastian Ott wrote: >> On Thu, 20 Feb 2025, Marc Zyngier wrote: >>> Since our take on FEAT_NV is to only support FEAT_NV2, we should >>> never expose ID_AA64MMFR2_EL1.NV to a guest nor userspace. >>> >>> Make sure we mask this field for good. >>> >>> Signed-off-by: Marc Zyngier >>> --- >>> 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 82430c1e1dd02..9f10dbd26e348 100644 >>> --- a/arch/arm64/kvm/sys_regs.c >>> +++ b/arch/arm64/kvm/sys_regs.c >>> @@ -1627,6 +1627,7 @@ static u64 __kvm_read_sanitised_id_reg(const struct kvm_vcpu *vcpu, >>> break; >>> case SYS_ID_AA64MMFR2_EL1: >>> val &= ~ID_AA64MMFR2_EL1_CCIDX_MASK; >>> + val &= ~ID_AA64MMFR2_EL1_NV; >>> break; >> >> This would cause issues when you update the host kernel while keeping the >> guests register state. Could we allow to write (but ignore) the previously >> valid value? Like it was handled in: >> 6685f5d572c2 KVM: arm64: Disable MPAM visibility by default and ignore VMM writes > > Yeah, this falls into the same "shouldn't have exposed this the first > place" bucket. Annoying. Something like the diff below? Yes, thanks!