From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id EBCACC433EF for ; Wed, 1 Dec 2021 15:26:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=OSN1ebhw8ocp6Q0Q6KGiSwJxluOPTHWiFERuHPm7CvA=; b=xk700fHUKjkDnv 4UYK0rSjY5Gff1bHaItk/51fFMVjT6ncsWVVGyYz72RIaigk5AJjkTxpl9Umq7hsQJHIm453FBQsi mB5Yi9j6UE6X4kv7zk9R9tzFxFi7R+a3HVl2m6SMuuHjRCHtqnsZImuoE6tRNlpr6azVPbh03twsy SLHajBnn6c4/xRhzGX4bcmC97mOY9xNgO8fu+gKMBhdtWt2+yDE0NllwXsAQscV7s/dL/wXrHbPaJ 5V3jT9sX9Pso6tIX/x2cObCDg6FybvR1oLV13EzsxDtwBdvpqD+JnEEpHVF5OHuFR3gV2mIIF9W53 2XqHkL72bvUOIvtSS0+A==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1msRTa-009Bl0-P5; Wed, 01 Dec 2021 15:24:54 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1msRTX-009Bjq-I7 for linux-arm-kernel@lists.infradead.org; Wed, 01 Dec 2021 15:24:53 +0000 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 697DC143B; Wed, 1 Dec 2021 07:24:48 -0800 (PST) Received: from monolith.localdoman (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id CD2603F766; Wed, 1 Dec 2021 07:24:45 -0800 (PST) Date: Wed, 1 Dec 2021 15:24:35 +0000 From: Alexandru Elisei To: Reiji Watanabe Cc: Marc Zyngier , kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, James Morse , Suzuki K Poulose , Paolo Bonzini , Will Deacon , Andrew Jones , Peng Liang , Peter Shier , Ricardo Koller , Oliver Upton , Jing Zhang , Raghavendra Rao Anata Subject: Re: [RFC PATCH v3 03/29] KVM: arm64: Introduce struct id_reg_info Message-ID: References: <20211117064359.2362060-1-reijiw@google.com> <20211117064359.2362060-4-reijiw@google.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20211117064359.2362060-4-reijiw@google.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20211201_072451_743023_1E84B6F4 X-CRM114-Status: GOOD ( 27.02 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hi Reiji, On Tue, Nov 16, 2021 at 10:43:33PM -0800, Reiji Watanabe wrote: > This patch lays the groundwork to make ID registers writable. > > Introduce struct id_reg_info for an ID register to manage the > register specific control of its value for the guest, and provide set > of functions commonly used for ID registers to make them writable. > > The id_reg_info is used to do register specific initialization, > validation of the ID register and etc. Not all ID registers must > have the id_reg_info. ID registers that don't have the id_reg_info > are handled in a common way that is applied to all ID registers. > > At present, changing an ID register from userspace is allowed only > if the ID register has the id_reg_info, but that will be changed > by the following patches. > > No ID register has the structure yet and the following patches > will add the id_reg_info for some ID registers. > > Signed-off-by: Reiji Watanabe > --- > arch/arm64/include/asm/sysreg.h | 1 + > arch/arm64/kvm/sys_regs.c | 226 ++++++++++++++++++++++++++++++-- > 2 files changed, 218 insertions(+), 9 deletions(-) > > diff --git a/arch/arm64/include/asm/sysreg.h b/arch/arm64/include/asm/sysreg.h > index 16b3f1a1d468..597609f26331 100644 > --- a/arch/arm64/include/asm/sysreg.h > +++ b/arch/arm64/include/asm/sysreg.h > @@ -1197,6 +1197,7 @@ > #define ICH_VTR_TDS_MASK (1 << ICH_VTR_TDS_SHIFT) > > #define ARM64_FEATURE_FIELD_BITS 4 > +#define ARM64_FEATURE_FIELD_MASK ((1ull << ARM64_FEATURE_FIELD_BITS) - 1) > > /* Create a mask for the feature bits of the specified feature. */ > #define ARM64_FEATURE_MASK(x) (GENMASK_ULL(x##_SHIFT + ARM64_FEATURE_FIELD_BITS - 1, x##_SHIFT)) > diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c > index 5608d3410660..1552cd5581b7 100644 > --- a/arch/arm64/kvm/sys_regs.c > +++ b/arch/arm64/kvm/sys_regs.c > @@ -265,6 +265,181 @@ static bool trap_raz_wi(struct kvm_vcpu *vcpu, > return read_zero(vcpu, p); > } > > +/* > + * A value for FCT_LOWER_SAFE must be zero and changing that will affect > + * ftr_check_types of id_reg_info. > + */ > +enum feature_check_type { > + FCT_LOWER_SAFE = 0, > + FCT_HIGHER_SAFE, > + FCT_HIGHER_OR_ZERO_SAFE, > + FCT_EXACT, > + FCT_EXACT_OR_ZERO_SAFE, > + FCT_IGNORE, /* Don't check (any value is fine) */ > +}; > + > +static int arm64_check_feature_one(enum feature_check_type type, int val, > + int limit) > +{ > + bool is_safe = false; > + > + if (val == limit) > + return 0; > + > + switch (type) { > + case FCT_LOWER_SAFE: > + is_safe = (val <= limit); > + break; > + case FCT_HIGHER_OR_ZERO_SAFE: > + if (val == 0) { > + is_safe = true; > + break; > + } > + fallthrough; > + case FCT_HIGHER_SAFE: > + is_safe = (val >= limit); > + break; > + case FCT_EXACT: > + break; > + case FCT_EXACT_OR_ZERO_SAFE: > + is_safe = (val == 0); > + break; > + case FCT_IGNORE: What happens if the a new feature is added and the field has a particular meaning? How are you going to deal with old userspace implementations that use a value here which now is not allowed or it affects the guest? Thanks, Alex _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel