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 153BCC9EC76 for ; Mon, 12 Jan 2026 11:26:40 +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=ghPiZ7OelwcaW8u+RLbWed6YYuVAFqTuBWiYtNO6WZ4=; b=HxNIrfW+bnCoi61BQJ/RI8J6Rc pxmTUYLyQJRSY5Kvl9Q2Ip2w7o2+mLfDzkfPncBCzLDL1qg7VVBxhUbHCZpjRNGY9O20t1TY5pNtt PjgdhyeWVjOXPyPSP0t1AnGN/SBQoLVeYh9DKaAQ5zC7rMuydLatAF9v/nTLfFV/Lj5Tss7GbGe3s mU54AJa51Tr4nr33hO+rRS+E3MQRck9ifa/BpVSLS3dyEGzjWt4pYTn19v7IuCXXVKjIldCK8AP4I afySjXK9AUu1Uiz+B83o4UvkwooPNY4YUaoKsQT763GVH0WdajSTq6lg96AdLqsQLj4rB6BOYWqAT 6396VTQA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1vfG47-00000005Fjv-3ESS; Mon, 12 Jan 2026 11:26:31 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1vfG44-00000005FjA-3GLb for linux-arm-kernel@lists.infradead.org; Mon, 12 Jan 2026 11:26:30 +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 3C562497; Mon, 12 Jan 2026 03:26:19 -0800 (PST) Received: from raptor (usa-sjc-mx-foss1.foss.arm.com [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id D0FE63F694; Mon, 12 Jan 2026 03:26:23 -0800 (PST) Date: Mon, 12 Jan 2026 11:26:20 +0000 From: Alexandru Elisei To: James Clark Cc: mark.rutland@arm.com, james.morse@arm.com, maz@kernel.org, oliver.upton@linux.dev, joey.gouly@arm.com, suzuki.poulose@arm.com, yuzenghui@huawei.com, will@kernel.org, catalin.marinas@arm.com, linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev Subject: Re: [RFC PATCH v6 03/35] KVM: arm64: Add CONFIG_KVM_ARM_SPE Kconfig option Message-ID: References: <20251114160717.163230-1-alexandru.elisei@arm.com> <20251114160717.163230-4-alexandru.elisei@arm.com> <1aaffbcd-ba0c-4371-80d7-ce59ac7f13a9@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1aaffbcd-ba0c-4371-80d7-ce59ac7f13a9@linaro.org> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260112_032628_883060_9E94E1A3 X-CRM114-Status: GOOD ( 26.93 ) 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 Hi James, On Fri, Jan 09, 2026 at 04:29:50PM +0000, James Clark wrote: > > > On 14/11/2025 4:06 pm, Alexandru Elisei wrote: > > Add a new configuration option that will be used for KVM SPE emulation. > > CONFIG_KVM_ARM_SPE depends on the SPE driver being builtin because: > > > > 1. The SPE driver maintains a cpumask of physical CPUs that support SPE, > > and that will be used by KVM to emulate SPE on heterogeneous systems. > > > > 2. KVM will rely on the SPE driver enabling the SPE interrupt at the GIC > > level. > > > > Signed-off-by: Alexandru Elisei > > --- > > arch/arm64/kvm/Kconfig | 8 ++++++++ > > 1 file changed, 8 insertions(+) > > > > diff --git a/arch/arm64/kvm/Kconfig b/arch/arm64/kvm/Kconfig > > index 4f803fd1c99a..31388b5b2655 100644 > > --- a/arch/arm64/kvm/Kconfig > > +++ b/arch/arm64/kvm/Kconfig > > @@ -83,4 +83,12 @@ config PTDUMP_STAGE2_DEBUGFS > > If in doubt, say N. > > +config KVM_ARM_SPE > > + bool > > + depends on KVM && ARM_SPE_PMU=y > > I think the most common configuration is module, so requiring built-in isn't > great. If there's any way of avoiding it, even if it costs a little bit of > pain, it would be good for adoption. I'm not sure how that could be done. You need the buffer maintenance interrupt to do a VM exit so KVM can inject the virtual interrupt back into the guest, otherwise there's a possibility of a large blackout window when the buffer is full. The code also relies on the SPE driver to probe all the SPUs in the system. > > It was basically the first thing I got stuck on trying to get it to work. Or > if it really can't be done, maybe some kind of debug message to say why > enabling failed. When you search for the symbol in menuconfig you get a list of the symbols it depends on. Thanks, Alex