From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 1BA4835505E for ; Mon, 12 Jan 2026 11:26:26 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768217190; cv=none; b=Ka/LukIW/GZNr8pZbo3c3mYWoUjAQNnaAAuN8wvFpphp9zGU85WGQIl+mtXo5yUIm41hkxpEJ8tECOYE/vgpib/C9y64BJKVYklu2SQvN58skVMue7aSUtfgWvHuUp9DvRxUFHH61SzLD4RiNoBFZiS8yw1SUKWKRJsiy7WT6oA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768217190; c=relaxed/simple; bh=mxYgczMoZd1gWVT4OVPn8KIQGpCIPfjrsKoSOFWtEgc=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=nPyn0xJsC4qGL96iM/3sY271ytzXQqnBDE3cWh2O62cWDI6RiDYdiCCQcggPrDEH9yRmMe0EhH7h3hy31YeYdT6lZE0Mj+qbj8XW2fGmn1AyfvXluEU1jtg1mghYJ8CQpURe11DIh5Y9KDH0+j1myp9qMOk0ZMtkQbvZR9+zhLg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com 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> Precedence: bulk X-Mailing-List: kvmarm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1aaffbcd-ba0c-4371-80d7-ce59ac7f13a9@linaro.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