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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 54B8BC6FD1C for ; Fri, 24 Mar 2023 11:40:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229752AbjCXLky (ORCPT ); Fri, 24 Mar 2023 07:40:54 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46214 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229468AbjCXLkx (ORCPT ); Fri, 24 Mar 2023 07:40:53 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D96FF44B4; Fri, 24 Mar 2023 04:40:52 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 7F730B82373; Fri, 24 Mar 2023 11:40:51 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 96249C433EF; Fri, 24 Mar 2023 11:40:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1679658050; bh=H/gG4xxiGHu3PANQDrwb8iNhqg4/9SLJyoyf2hwU5vQ=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=SiPJsKZtYODNVP+k0MB6uHofif2KteWcgogPU19byEjRYeBTpJhc0AcNSfhP37tsl LYSSccsAIelsA6QRm7nmavrC874YuLW0gElNC3rdVJ74X5CHmGebp0VFanZLYkUkXu HC/EMvLDy7Ghx3KKyWFi2b8MeOVjHo/ZsxSEX6ocNaJYe2xC93jDETttOQFadZREXN Z3wdeoW+7N1mvB4zP1HztHpGnLzHE8BcHIdB3PIk/TRmW6ZKSbH5EkKtISqpaMFrV5 wOcQ5+2opo3VWsdqWyc+3yOZdrQoWAImb3ACrvWN2apfJ2GPYPc9NwQmbkA+UascfL wc+eLTNQyX/EQ== Date: Fri, 24 Mar 2023 11:40:46 +0000 From: Mark Brown To: Anshuman Khandual Cc: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, will@kernel.org, catalin.marinas@arm.com, mark.rutland@arm.com, James Clark , Rob Herring , Marc Zyngier , Suzuki Poulose , Peter Zijlstra , Ingo Molnar , Arnaldo Carvalho de Melo , linux-perf-users@vger.kernel.org Subject: Re: [PATCH V9 00/10] arm64/perf: Enable branch stack sampling Message-ID: References: <20230315051444.1683170-1-anshuman.khandual@arm.com> <655ff114-99d2-4612-9167-cc8688f2b6b2@sirena.org.uk> <4d93a3de-c86d-454b-8a43-b24e62ea3be7@sirena.org.uk> <4665d03f-b801-679c-0b52-c426404284b9@arm.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="PeOr3UW4D5MryUYv" Content-Disposition: inline In-Reply-To: <4665d03f-b801-679c-0b52-c426404284b9@arm.com> X-Cookie: Single tasking: Just Say No. Precedence: bulk List-ID: X-Mailing-List: linux-perf-users@vger.kernel.org --PeOr3UW4D5MryUYv Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Fri, Mar 24, 2023 at 08:50:32AM +0530, Anshuman Khandual wrote: > On 3/23/23 18:24, Mark Brown wrote: > > On Thu, Mar 23, 2023 at 09:55:47AM +0530, Anshuman Khandual wrote: > >> By default entire SYS_HFGITR_EL2 is set as cleared during init and tha= t would > >> prevent a guest from using BRBE. > > It should prevent the host as well shouldn't it?=20 > In a EL2 host environment, BRBE is being enabled either in EL2 (kernel/hv= ) or > in EL0 (user space), it never gets enabled on EL1. Moreover BRBIALL/BRBINJ > instructions are always executed while being inside EL2 (kernel/hv). Henc= e how > could these instructions cause trap in EL2 ? Ah, I see - I didn't realise this couldn't run at EL1. > > Yes, looks roughly what I'd expect. > I could send an stand alone patch after your latest series [1], which dis= ables > BRBINJ/BRBIALL instruction trap in EL2 to enable BRBE usage in the guest. Sounds resaonable enough to me. --PeOr3UW4D5MryUYv Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAABCgAdFiEEreZoqmdXGLWf4p/qJNaLcl1Uh9AFAmQdjD4ACgkQJNaLcl1U h9CYxQf/XtDhR1m5Y8l+bIrYp2rDSKduJ4Pa9T6rzZYnk5wbwG7bDG78Q5TJdYMl oWAR04HbTMAshivaOT/UA6KE/6UJCnwgGggQqBRLA4HwSbffPvBb+0363lhssCX0 yY9yQbUAiTNgSm8Pi7CBRhItGZwLvyPeftIGXJNwHghv1V7jsvuzVLfsUJsXxOyY 5jkthhig/aqGol+mbUE7+vunnGAodLl+u0dOyt/lWsrc+ZSj0fQEpK7Hc8JVeQyQ x4cgYHYxZv0O/1avVMGyX2eC8+4grdq9bHECeNpwPbLAQq8SKTkzgk+nxhVzG/Xm wdPn2d5WAQ7DU2u8aLY4dEl+lJzYRQ== =zg2M -----END PGP SIGNATURE----- --PeOr3UW4D5MryUYv--