From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 A7DFB1DE4E0; Sat, 9 Aug 2025 20:19:11 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1754770751; cv=none; b=Yrc4peaBoT9NGXX9/HVPVzNfUhN06mouef5NSuz7keFvkOdrLYmW9bI0F3InxqI/AlmPMahtTxz/nnxFB3lJ7kcspY/PKHYXZRUah3emnCqOBqB3I1aGFN/1GS3/Uc/CNZjgB4mzbQxmXr7EubtzwSuG4nCo1jrjBqjiv6PXnFo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1754770751; c=relaxed/simple; bh=SW26dL28FmmH3dzVI/obdVPmszSNosDs+9XfxxzakzQ=; h=Date:Message-ID:From:To:Cc:Subject:In-Reply-To:References: MIME-Version:Content-Type; b=pYrPslnoVLYCSUY1S68i5N4t/8JudU+8OuKschg/AZ3VMFxkHBgI0asTNBaBFKmC8sjCe/B8MvUn5u19WvCAO5Vv2xvyGwXtX5i1BXcvzcl8J8f7e5soktlE6hxBaXXuwBZ5qq1Doc7JVp6LQSA4F6686rZTTBliSJeWD8lTldY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=CcByh7vf; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="CcByh7vf" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 241E1C4CEE7; Sat, 9 Aug 2025 20:19:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1754770751; bh=SW26dL28FmmH3dzVI/obdVPmszSNosDs+9XfxxzakzQ=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=CcByh7vfH7ONCALgbjVNQCpvhjwAA7uTn+O3ODqhsJA9LgTE/qsGaI2JLKVNVcM2t B5BjOo4gmQyc4h/oPO72HOZ163bomI8buUm12U/awqZ9JXELnS57aTL4vl3QkZZIeb E51hHHz8Y1WyXci6H8//nRqyTxkI1ZVjrDEC//wM89OynCTgLfXWn/oc7TCM4DaYGu ni5UrY3cFyZX15irVvhisfGEFnJnzutiVGz85ji+Y3uq5xH67xzaZk1jFUtKj9P5Y4 uUCKfQCbSHqph/5Nwlm30dtjcEBGAPOacBHjVWVYSK2ppvpaZNOJAyyhklKu7THE7b xdvy2x3pKEiCw== Received: from sofa.misterjones.org ([185.219.108.64] helo=lobster-girl.misterjones.org) by disco-boy.misterjones.org with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.95) (envelope-from ) id 1ukq20-005hxn-No; Sat, 09 Aug 2025 21:19:08 +0100 Date: Sat, 09 Aug 2025 21:19:08 +0100 Message-ID: <874iugtfib.wl-maz@kernel.org> From: Marc Zyngier To: Joey Gouly Cc: kvmarm@lists.linux.dev, linux-arm-kernel@lists.infradead.org, kvm@vger.kernel.org, Suzuki K Poulose , Oliver Upton , Zenghui Yu , Will Deacon , Catalin Marinas , Cornelia Huck Subject: Re: [PATCH v2 4/5] KVM: arm64: Expose FEAT_RASv1p1 in a canonical manner In-Reply-To: <20250807125531.GB2351327@e124191.cambridge.arm.com> References: <20250806165615.1513164-1-maz@kernel.org> <20250806165615.1513164-5-maz@kernel.org> <20250807125531.GB2351327@e124191.cambridge.arm.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: kvm@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: joey.gouly@arm.com, kvmarm@lists.linux.dev, linux-arm-kernel@lists.infradead.org, kvm@vger.kernel.org, suzuki.poulose@arm.com, oliver.upton@linux.dev, yuzenghui@huawei.com, will@kernel.org, catalin.marinas@arm.com, cohuck@redhat.com X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false On Thu, 07 Aug 2025 13:55:31 +0100, Joey Gouly wrote: > > On Wed, Aug 06, 2025 at 05:56:14PM +0100, Marc Zyngier wrote: > > If we have RASv1p1 on the host, advertise it to the guest in the > > "canonical way", by setting ID_AA64PFR0_EL1 to V1P1, rather than > > the convoluted RAS+RAS_frac method. > > > > Note that this also advertises FEAT_DoubleFault, which doesn't > > affect the guest at all, as only EL3 is concerned by this. > > > > Signed-off-by: Marc Zyngier > > --- > > arch/arm64/kvm/sys_regs.c | 12 ++++++++++++ > > 1 file changed, 12 insertions(+) > > > > diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c > > index 1b4114790024e..66e5a733e9628 100644 > > --- a/arch/arm64/kvm/sys_regs.c > > +++ b/arch/arm64/kvm/sys_regs.c > > @@ -1800,6 +1800,18 @@ static u64 sanitise_id_aa64pfr0_el1(const struct kvm_vcpu *vcpu, u64 val) > > if (!vcpu_has_sve(vcpu)) > > val &= ~ID_AA64PFR0_EL1_SVE_MASK; > > > > + /* > > + * Describe RASv1p1 in a canonical way -- ID_AA64PFR1_EL1.RAS_frac > > + * is cleared separately. Note that by advertising RASv1p1 here, we > > Where is it cleared? __kvm_read_sanitised_id_reg() is where I would have > expected to see it: > > case SYS_ID_AA64PFR1_EL1: [...] Ah crap, it is the nested code that we get rid of it, nowhere else. Which means that non-nested VMs have already observed RAS_frac. What a mess. Then RAS_frac must be exposed as writable. The question is whether we want to allow migration between one flavour of RASv1p1 and the other. M. -- Jazz isn't dead. It just smells funny.