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 47AD1C02198 for ; Wed, 12 Feb 2025 11:13:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=3BRs0MPM6DW7ovKbcQaZPP+NQTME6gKBy5BMI0U2KY4=; b=WI6KPsQ0vv7ZqPnlJyivfisMuo PxjnFBuuqEF7Y/WB9kQN99hzL73ktiy4kU4xnEzhC0ozli4JTLj/axb49DMxbO7hS1TlKArKiwW9/ la9zBfEgRNMiWCmVyyziy2mmfB3Y4STNh+cKBDEANqJoGpJcg9TxTMf3vYAz9dg+mdk1k03JztdcQ tYTwxq0qif3XCU6rAWXmYfObNclrL5HzOWmhNKJtuFWS0YYpfUMsIB6Cqomq2tkyYfB/MppMR/L43 o34IVc/UnQOQLWnMVzGW4ESqB7sj3M1NirLaCk2OjvrG647dJw9ld7imjJnI+1UF+0ol4pEPu4Heb bLkfMHUw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98 #2 (Red Hat Linux)) id 1tiAfw-000000077nj-3q9m; Wed, 12 Feb 2025 11:13:04 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.98 #2 (Red Hat Linux)) id 1tiAe6-000000077Jm-0CSs for linux-arm-kernel@lists.infradead.org; Wed, 12 Feb 2025 11:11:11 +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 1A91C106F; Wed, 12 Feb 2025 03:11:30 -0800 (PST) Received: from J2N7QTR9R3 (usa-sjc-imap-foss1.foss.arm.com [10.121.207.14]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 1436B3F6A8; Wed, 12 Feb 2025 03:11:06 -0800 (PST) Date: Wed, 12 Feb 2025 11:11:04 +0000 From: Mark Rutland To: Mark Brown , Marc Zyngier Cc: linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, linux-kernel@vger.kernel.org, Fuad Tabba , Oliver Upton , James Morse , Suzuki K Poulose , Catalin Marinas , Will Deacon Subject: Re: [PATCH v7] KVM: arm64: Fix confusion in documentation for pKVM SME assert Message-ID: References: <20250212-kvm-arm64-sme-assert-v7-1-0f786db838d3@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250212-kvm-arm64-sme-assert-v7-1-0f786db838d3@kernel.org> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250212_031110_173953_E90DF786 X-CRM114-Status: GOOD ( 29.70 ) 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: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Wed, Feb 12, 2025 at 12:44:57AM +0000, Mark Brown wrote: > As raised in the review comments for the original patch the assert and > comment added in afb91f5f8ad7 ("KVM: arm64: Ensure that SME controls are > disabled in protected mode") are bogus. The comments says that we check > that we do not have SME enabled for a pKVM guest but the assert actually > checks to see if the host has anything set in SVCR which is unrelated to > the guest features or state, regardless of if those guests are protected > or not. This check is also made in the hypervisor, it will refuse to run > a guest if the check fails, so it appears that the assert here is > intended to improve diagnostics. > > Update the comment to reflect the check in the code, and to clarify that > we do actually enforce this in the hypervisor. While we're here also > update to use a WARN_ON_ONCE() to avoid log spam if this triggers. > > Fixes: afb91f5f8ad7 ("KVM: arm64: Ensure that SME controls are disabled in protected mode") > Reviewed-by: Fuad Tabba > Signed-off-by: Mark Brown > --- > This has been sent with v6.10 with only positive review comments after > the first revision, if there is some issue with the change please share > it. > > To: Marc Zyngier > To: Oliver Upton > To: James Morse > To: Suzuki K Poulose > To: Catalin Marinas > To: Will Deacon > To: Fuad Tabba > Cc: Mark Rutland > --- > Changes in v7: > - Reword the comment. > - Link to v6: https://lore.kernel.org/r/20250210-kvm-arm64-sme-assert-v6-1-cc26c46d1b43@kernel.org > > Changes in v6: > - Rebase onto v6.14-rc1. > - Link to v5: https://lore.kernel.org/r/20241210-kvm-arm64-sme-assert-v5-1-995c8dd1025b@kernel.org > > Changes in v5: > - Rebase onto v6.13-rc1. > - Link to v4: https://lore.kernel.org/r/20240930-kvm-arm64-sme-assert-v4-1-3c9df71db688@kernel.org > > Changes in v4: > - Rebase onto v6.12-rc1 > - Link to v3: https://lore.kernel.org/r/20240730-kvm-arm64-sme-assert-v3-1-8699454e5cb8@kernel.org > > Changes in v3: > - Rebase onto v6.11-rc1. > - Link to v2: https://lore.kernel.org/r/20240605-kvm-arm64-sme-assert-v2-1-54391b0032f4@kernel.org > > Changes in v2: > - Commit message tweaks. > - Change the assert to WARN_ON_ONCE(). > - Link to v1: https://lore.kernel.org/r/20240604-kvm-arm64-sme-assert-v1-1-5d98348d00f8@kernel.org > --- > arch/arm64/kvm/fpsimd.c | 11 +++++++---- > 1 file changed, 7 insertions(+), 4 deletions(-) > > diff --git a/arch/arm64/kvm/fpsimd.c b/arch/arm64/kvm/fpsimd.c > index 4d3d1a2eb157047b4b2488e9c4ffaabc6f5a0818..e37e53883c357093ff4455f5afdaec90e662d744 100644 > --- a/arch/arm64/kvm/fpsimd.c > +++ b/arch/arm64/kvm/fpsimd.c > @@ -93,11 +93,14 @@ void kvm_arch_vcpu_load_fp(struct kvm_vcpu *vcpu) > } > > /* > - * If normal guests gain SME support, maintain this behavior for pKVM > - * guests, which don't support SME. > + * Protected and non-protected KVM modes require that > + * SVCR.{SM,ZA} == {0,0} when entering a guest so that no > + * host/guest SME state needs to be saved/restored by hyp code. > + * > + * In protected mode, hyp code will verify this later. > */ > - WARN_ON(is_protected_kvm_enabled() && system_supports_sme() && > - read_sysreg_s(SYS_SVCR)); > + WARN_ON_ONCE(is_protected_kvm_enabled() && system_supports_sme() && > + read_sysreg_s(SYS_SVCR)); As I mentioned on the last round, we can drop the is_protected_kvm_enabled() check, i.e. have: /* * Protected and non-protected KVM modes require that * SVCR.{SM,ZA} == {0,0} when entering a guest so that no * host/guest SME state needs to be saved/restored by hyp code. * * In protected mode, hyp code will verify this later. */ WARN_ON_ONCE(system_supports_sme() && read_sysreg_s(SYS_SVCR)); Either way: Acked-by: Mark Rutland Marc, are you happy to queue this atop the recent fixes from me? Those try to ensure SVCR.{SM,ZA} == {0,0} regardless of whether KVM is in protected mode. Mark.