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 E5553CA5FA2 for ; Mon, 28 Sep 2026 17:05:20 +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=yoXTXqPzTE35yeLLUFkb8ceBe47d/S/Yap+eGL4p4bI=; b=2zzqG/hq4SUp0fbg5+FD/qjEHw HxTjPr0vakn6LAcSU6m2zc/TbWeCZLmKwTQIA1DsBdBPaY0q8w0DiXJ+7BIeiJ4Vu6sqRS+bQK58t flsRmZs9A9oYVC0dPlRE3tGsSZMEAJW2U6FIia0Xp2YIr8yBaSVBsOtSV9zM/XhGCnLZaZhmt6Hrw ucHnr8gPENCZQ/gA232vG0RTTE5sw15PwCtCcfCLx7QuRRpXRvubJeXvR0Imw+epOrkK4CoOvJTaF lPmCqQmHF6vdUbLo1A2RpFRE/3PwuNeN2+DyhJOagvLf82sZ3jrhYNjEshUfHBc06QbxX5O8Grlj1 BSS00bdw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1xBEmv-000000016ii-3WfV; Mon, 28 Sep 2026 17:05:13 +0000 Received: from tor.source.kernel.org ([172.105.4.254]) by bombadil.infradead.org with esmtps (Exim 4.99.1 #2 (Red Hat Linux)) id 1xBEmu-000000016iT-0f8N for linux-arm-kernel@lists.infradead.org; Mon, 28 Sep 2026 17:05:12 +0000 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by tor.source.kernel.org (Postfix) with ESMTP id 521E9600CB; Mon, 28 Sep 2026 17:05:11 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id C955C1F00893; Mon, 28 Sep 2026 17:05:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1790615111; bh=yoXTXqPzTE35yeLLUFkb8ceBe47d/S/Yap+eGL4p4bI=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=QdQwx718ik84L+Mq45KEayXLdVMUAcnmUhtWIQfGQXGH9vNemnBJYzTv7sICCtRE+ 39+4B+n3qedPT1V8sl+2ygYB09kLPI75LxEkCv+ptk3g6uZl3mI84+2geK26zblJVE dU3VPa+mYT9RQGE2FWVdw4TEfsCGJJTAjLV9ro+gbqN5ctgqWbX0iNcdk7KDcxbZTS 9OSzG3RytUq0zqCEU4v7C/uqLpG35ZMCaMpPw3ZhQXrShg9Xi0z7w/ReikxlR0bMJF +xQJVbH2q5IZtgeGlH69O9wfIiwUTppVz0/Msyj/Uyt34iWlg7pBcpkIunSyMvzIR/ 2wBtg1LjB0MIA== Date: Mon, 28 Sep 2026 10:05:09 -0700 From: Oliver Upton To: Fuad Tabba Cc: Marc Zyngier , kvmarm@lists.linux.dev, linux-arm-kernel@lists.infradead.org, Joey Gouly , Suzuki K Poulose , Zenghui Yu , Steffen Eiden , Catalin Marinas , Will Deacon , Mark Rutland , Quentin Perret , Vincent Donnefort , Wei-Lin Chang , Fuad Tabba , linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 1/4] KVM: arm64: Don't WARN on an unsupported TLBI OS from vEL1 Message-ID: References: <20260928064643.3265087-1-fuad.tabba@linux.dev> <20260928064643.3265087-2-fuad.tabba@linux.dev> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260928064643.3265087-2-fuad.tabba@linux.dev> 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 Fuad, On Mon, Sep 28, 2026 at 07:46:40AM +0100, Fuad Tabba wrote: > KVM hides TLBI OS from a guest whose ID registers don't advertise it by > trapping the instructions: through the fine-grained traps on a CPU with > FGT, and through HCR_EL2.TTLBOS on one with FEAT_EVT2. With FGT, > triage_sysreg_trap() makes a trapped TLBI OS UNDEFINED. Without it, the > instruction reaches handle_tlbi_el1(), which assumes an EL1 TLBI only > traps from a guest at vEL2 and WARNs before checking whether the guest > supports it. The guest still gets its UNDEF after the WARN. A VMM can > trigger the WARN by hiding TLBI OS and having the guest execute one. So the FGUs don't actually require any hardware support, they're just a representation of our UNDEF emulation that can be applied even on non-FGT. That's actually the way we had them wired before the whole config.c rewrite. Can you look into reinstating the FGUs? Thanks, Oliver