From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 32EB856441; Tue, 27 Feb 2024 08:12:21 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1709021542; cv=none; b=ADeiX/HjwT2RYoHUcpfKMUhZIft4Sn+NCvAtwgIde3hq1yV8/GOpiMCJ+pfsM4vE6/NI8SkRokcLlPFHT4G5l55kQGk+OKAZWDNUGnAVL+xB/bwpW/Rtu/jybYc7vdbs0T2b91MRZ5SxOUSaIqnqcBlCL66Y1wPKsIiVnR8wxF0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1709021542; c=relaxed/simple; bh=RzvSoN1d+y+H0+TLwarmN0FFOj8Wb4VWXo/kszcd3Lo=; h=Date:Message-ID:From:To:Cc:Subject:In-Reply-To:References: MIME-Version:Content-Type; b=ERR0qE9X44GSwbrYl75IUJK3wlt7dGFcydPvrgSVTE1CJL104kROq+wG5AGhdpGJQ2SifVmmPrdEzpAno6L056wRhYV1CtQZncZas4iFYUqa+v4eRTurYlQlOd6MQMmIXCJH4nHrX3ltwn+pWXcxJYEmRheLM9z2LJ5OG+Pf9yM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Nm/bGc92; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="Nm/bGc92" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A3456C433F1; Tue, 27 Feb 2024 08:12:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1709021541; bh=RzvSoN1d+y+H0+TLwarmN0FFOj8Wb4VWXo/kszcd3Lo=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=Nm/bGc927EhmL4UobMryUyxB1RwBxVWWUAw7mA/nmxCYTHcfg38j0bzvwh6eugkza 5g3LqJegrd2xgP1RmSoLz+3kwlPJxNYTii3G3VjMdz/4EdXr/Tjnw9hrwzKnKwVvBn GBIsWx+U5N4Bw48gD3uAvJ9oNLxp90NblAluTCMYnt7KSXZxsIHdhNtk4s25I7YXsh NomaEDKCD2Dx0qAObiol8gQ5e5QMOSkhirr7JfqBR7WOjVNA43bb1JCb7RIijomfYN 07Q9/QuPjFIZRvZaD9yEvyvtBpPRT6QbX+OQq0OTWswcq4k8099ICUnY/+FTxSoWo2 qTi6CsOUVNCBg== Received: from ip-185-104-136-29.ptr.icomera.net ([185.104.136.29] helo=wait-a-minute.misterjones.org) by disco-boy.misterjones.org with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.95) (envelope-from ) id 1resZW-007AGt-Jj; Tue, 27 Feb 2024 08:12:18 +0000 Date: Tue, 27 Feb 2024 08:10:48 +0000 Message-ID: <874jdu9vjr.wl-maz@kernel.org> From: Marc Zyngier To: Wei-Lin Chang Cc: oliver.upton@linux.dev, james.morse@arm.com, suzuki.poulose@arm.com, yuzenghui@huawei.com, catalin.marinas@arm.com, will@kernel.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, linux-kernel@vger.kernel.org, sauravsc@amazon.com, eric.auger@redhat.com Subject: Re: [PATCH 1/1] KVM: arm64: Affinity level 3 support In-Reply-To: <20240227022708.795214-1-r09922117@csie.ntu.edu.tw> References: <86frxg3i6u.wl-maz@kernel.org> <20240227022708.795214-1-r09922117@csie.ntu.edu.tw> User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI-EPG/1.14.7 (Harue) FLIM-LB/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL-LB/10.8 EasyPG/1.0.0 Emacs/28.2 (x86_64-pc-linux-gnu) MULE/6.0 (HANACHIRUSATO) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") Content-Type: text/plain; charset=US-ASCII X-SA-Exim-Connect-IP: 185.104.136.29 X-SA-Exim-Rcpt-To: r09922117@csie.ntu.edu.tw, oliver.upton@linux.dev, james.morse@arm.com, suzuki.poulose@arm.com, yuzenghui@huawei.com, catalin.marinas@arm.com, will@kernel.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, linux-kernel@vger.kernel.org, sauravsc@amazon.com, eric.auger@redhat.com X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false On Tue, 27 Feb 2024 02:27:08 +0000, Wei-Lin Chang wrote: > > On Sun, 25 Feb 2024 11:19:05 +0000, > Marc Zyngier wrote: [...] > > I can see multiple problems with this: > > > > - this is the host state, which shouldn't necessarily represent the > > guest state. It should be possible to restore a VM that have a > > different A3V value and still have the same guarantees. There is > > however a small nit around ICV_CTLR_EL1.A3V, which would require > > trapping to emulate the A3V bit. > > > > - this assumes GICv3, which is definitely not universal (we support > > GICv2, for which no such restriction actually exists). > > > > Finally, I don't see VM save/restore being addressed here, and I > > suspect it hasn't been looked at. > > > > Overall, this patch does too many things, and it should be split in > > discrete changes. I also want to see an actual justification for Aff3 > > support. And if we introduce it, it must be fully virtualised > > (independent of the A3V support on the host). > > Hi Marc, > > Really appreciate for the feedback. I think I understand most of your > comments and agree with them. It appears that I don't fully understand > the changes that I am doing with this. Thanks for explaining. I hope this doesn't deter you from working on this feature. I'll happily answer questions and discuss the above points. Thanks, M. -- Without deviation from the norm, progress is not possible.