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 BE2ABC3DA41 for ; Tue, 9 Jul 2024 10:49:31 +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=IYfqDrHVxt0MfKR9lu4zeJI8x3VUzp2VSNri/hjL8rM=; b=RbVsrdG7Neud8P6Y4r1UGclw38 WiIS6utfs6VjWX1EFy0Q7POl+r5aLFKpoxAV7gBmqvjs6/Vv54sITHWBonJi0Tp8ufZwi781RrdR8 4BLQxzV9pWaP47qLpl1a1pg4Y7hoWt67LFFOdAdZQ6NvfbobcN96OQ8gX0OixXqttCVwHv8Wi+/qQ dJektaKVHUpHu0PpW7W5J/Y4WtKS4YE+ZDxLluXY/UJ5O8J3SHtnQf/D8H6IEJmzV6tRbWJxdFNvT 5bocbTKgrfyl5wdKlFGCz8Iy1gW5wgn6YeA1xYjU0X6euEsYjDsq1EmAsYFaOFkRXMmT0gpECOhiI HOveAj5g==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.97.1 #2 (Red Hat Linux)) id 1sR8PN-00000006sUJ-0rT5; Tue, 09 Jul 2024 10:49:17 +0000 Received: from sin.source.kernel.org ([2604:1380:40e1:4800::1]) by bombadil.infradead.org with esmtps (Exim 4.97.1 #2 (Red Hat Linux)) id 1sR8P6-00000006sQa-3Vtk for linux-arm-kernel@lists.infradead.org; Tue, 09 Jul 2024 10:49:02 +0000 Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by sin.source.kernel.org (Postfix) with ESMTP id 0DA6CCE1101; Tue, 9 Jul 2024 10:48:59 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1CBF3C3277B; Tue, 9 Jul 2024 10:48:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1720522138; bh=+0UCCKX9eTmUCtlh6j65FUsSAck/OtEeFegBRXqawoA=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=YH2oSUoS8Mrw383mytbFplGa9CwGgWmEBAuIXD1eNNWw4D8cmmis+Ey6BXCcyhJu4 dSUSlQqkWVZoqbU2ratz0Ul7+lyCNt8lJmeFy+hEl8RgcBWlLTxKHSkr6x7QHTphsi FSpKjRepjzSseN2lHHu+UXddVEyNrKX+oyyOvdT5sSgG23FKJT44aYcNBQ+1kOxtU6 8RG+CQVCSWZpUzpAq3baaIm+lD/O8GT/+BLZLh3rjX8XEdk3tw/Wo+tGOAG8+zdZrS yCZF/uUk165W3pxsBTnS4IU8KwSwKto9ja749I67GhEjcYLGBg/bgNzUq4NMSLOLbD WW7gvGuz4JwiQ== Date: Tue, 9 Jul 2024 11:48:51 +0100 From: Will Deacon To: Steven Price Cc: kvm@vger.kernel.org, kvmarm@lists.linux.dev, Jean-Philippe Brucker , Catalin Marinas , Marc Zyngier , James Morse , Oliver Upton , Suzuki K Poulose , Zenghui Yu , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Joey Gouly , Alexandru Elisei , Christoffer Dall , Fuad Tabba , linux-coco@lists.linux.dev, Ganapatrao Kulkarni Subject: Re: [PATCH v4 02/15] firmware/psci: Add psci_early_test_conduit() Message-ID: <20240709104851.GE12978@willie-the-truck> References: <20240701095505.165383-1-steven.price@arm.com> <20240701095505.165383-3-steven.price@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240701095505.165383-3-steven.price@arm.com> User-Agent: Mutt/1.10.1 (2018-07-13) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240709_034901_250665_7FF00FFC X-CRM114-Status: GOOD ( 23.89 ) 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 On Mon, Jul 01, 2024 at 10:54:52AM +0100, Steven Price wrote: > From: Jean-Philippe Brucker > > Add a function to test early if PSCI is present and what conduit it > uses. Because the PSCI conduit corresponds to the SMCCC one, this will > let the kernel know whether it can use SMC instructions to discuss with > the Realm Management Monitor (RMM), early enough to enable RAM and > serial access when running in a Realm. > > Signed-off-by: Jean-Philippe Brucker > Signed-off-by: Steven Price > --- > v4: New patch > --- > drivers/firmware/psci/psci.c | 25 +++++++++++++++++++++++++ > include/linux/psci.h | 5 +++++ > 2 files changed, 30 insertions(+) > > diff --git a/drivers/firmware/psci/psci.c b/drivers/firmware/psci/psci.c > index d9629ff87861..a40dcaf17822 100644 > --- a/drivers/firmware/psci/psci.c > +++ b/drivers/firmware/psci/psci.c > @@ -13,6 +13,7 @@ > #include > #include > #include > +#include > #include > #include > #include > @@ -767,6 +768,30 @@ int __init psci_dt_init(void) > return ret; > } > > +/* > + * Test early if PSCI is supported, and if its conduit matches @conduit > + */ > +bool __init psci_early_test_conduit(enum arm_smccc_conduit conduit) > +{ > + int len; > + int psci_node; > + const char *method; > + unsigned long dt_root; > + > + /* DT hasn't been unflattened yet, we have to work with the flat blob */ > + dt_root = of_get_flat_dt_root(); > + psci_node = of_get_flat_dt_subnode_by_name(dt_root, "psci"); > + if (psci_node <= 0) > + return false; > + > + method = of_get_flat_dt_prop(psci_node, "method", &len); > + if (!method) > + return false; > + > + return (conduit == SMCCC_CONDUIT_SMC && strncmp(method, "smc", len) == 0) || > + (conduit == SMCCC_CONDUIT_HVC && strncmp(method, "hvc", len) == 0); > +} Hmm, I don't think this is sufficient to check for SMCCC reliably. Instead, I think you need to do something more involved: 1. Check for PSCI in the DT 2. Check that the PSCI major version is >= 1 3. Use PSCI_FEATURES to check that you have SMCCC 4. Use SMCCC_VERSION to find out which version of SMCCC you have That's roughly what the PSCI driver does, so we should avoid duplicating that logic. Will