From: Maxime Ripard <maxime.ripard@free-electrons.com> To: Chen-Yu Tsai <wens@csie.org> Cc: "Nicolas Pitre" <nicolas.pitre@linaro.org>, "Dave Martin" <Dave.Martin@arm.com>, linux-arm-kernel <linux-arm-kernel@lists.infradead.org>, linux-kernel <linux-kernel@vger.kernel.org>, linux-sunxi <linux-sunxi@googlegroups.com>, "Heiko Stübner" <heiko@sntech.de> Subject: Re: [linux-sunxi] Re: [RFC 7/7] ARM: dts: sun9i: Add secure SRAM node used for MCPM SMP hotplug Date: Mon, 25 May 2015 23:24:19 +0200 [thread overview] Message-ID: <20150525212419.GO8557@lukather> (raw) In-Reply-To: <CAGb2v67+F_cnjHXgGwbewPODG=mLMPGaZCzvvLfXL=A3huceew@mail.gmail.com> [-- Attachment #1: Type: text/plain, Size: 3167 bytes --] On Sun, May 24, 2015 at 11:55:22PM +0800, Chen-Yu Tsai wrote: > On Wed, May 20, 2015 at 6:08 PM, Maxime Ripard > <maxime.ripard@free-electrons.com> wrote: > > On Thu, May 14, 2015 at 02:10:11PM +0800, Chen-Yu Tsai wrote: > >> The A80 stores some magic flags in a portion of the secure SRAM. The > >> BROM jumps directly to the software entry point set by the SMP code > >> if the flags are set. This is required for CPU0 hotplugging. > >> > >> Signed-off-by: Chen-Yu Tsai <wens@csie.org> > >> --- > >> arch/arm/boot/dts/sun9i-a80.dtsi | 20 ++++++++++++++++++++ > >> 1 file changed, 20 insertions(+) > >> > >> diff --git a/arch/arm/boot/dts/sun9i-a80.dtsi b/arch/arm/boot/dts/sun9i-a80.dtsi > >> index 1507bd2a88f0..0695215634d4 100644 > >> --- a/arch/arm/boot/dts/sun9i-a80.dtsi > >> +++ b/arch/arm/boot/dts/sun9i-a80.dtsi > >> @@ -366,6 +366,26 @@ > >> */ > >> ranges = <0 0 0 0x20000000>; > >> > >> + sram_b: sram@00020000 { > >> + /* 256 KiB secure SRAM at 0x20000 */ > >> + compatible = "mmio-sram"; > >> + reg = <0x00020000 0x40000>; > >> + > > > > We should probably add a property to that SRAM to tell the driver not > > to access it if we're not booted in secure mode. > > (CC-ing Heiko...) > > That kind of puts architecture (ARM) dependent code into a platform > driver. Furthermore, AFAIK there isn't a safe way to check if we're > in secure mode or not. Checking SCR raises an undefined instruction > exception in non-secure mode. Can the kernel handle that? I really > don't understand this bit well. That's a very good question. I'm pretty sure the kernel can know that, since it actually prints the execution mode, and must be able to know whether it can use the virtualization extensions or not I assume. > > Otherwise, bad things might happen. > > The kernel (or rather the bootloader) boots in secure mode by default, > and we don't have any bootloader support to boot into non-secure mode > ATM. That's not really true. We do have some U-Boot patches, and U-Boot might very well be setup to boot into HYP, even though it doesn't do anything else. And even so, the fact that we have no implementation yet doesn't mean that we won't have one in a few month. So just sweeping it under the carpet doesn't seem to be a very good solution. > Couldn't we have the bootloader mark the SRAM as disabled when > booting into non-secure when we add that support? It actually changes the kernel requirements to be able to boot. Changing that is not an option, especially since it's something that: 1) isn't dynamic in any way, 2) will possibly break the kernel if not done, 3) require synchronisation between the bootloader and the kernel when a new secure SRAM is added to the DT, and require an upgrade of the bootloader, 4) we might not be able to replace the bootloader in the first place. All of these issues make it look like a rather bad solution :/ Maxime -- Maxime Ripard, Free Electrons Embedded Linux, Kernel and Android engineering http://free-electrons.com [-- Attachment #2: Digital signature --] [-- Type: application/pgp-signature, Size: 819 bytes --]
WARNING: multiple messages have this Message-ID (diff)
From: maxime.ripard@free-electrons.com (Maxime Ripard) To: linux-arm-kernel@lists.infradead.org Subject: [linux-sunxi] Re: [RFC 7/7] ARM: dts: sun9i: Add secure SRAM node used for MCPM SMP hotplug Date: Mon, 25 May 2015 23:24:19 +0200 [thread overview] Message-ID: <20150525212419.GO8557@lukather> (raw) In-Reply-To: <CAGb2v67+F_cnjHXgGwbewPODG=mLMPGaZCzvvLfXL=A3huceew@mail.gmail.com> On Sun, May 24, 2015 at 11:55:22PM +0800, Chen-Yu Tsai wrote: > On Wed, May 20, 2015 at 6:08 PM, Maxime Ripard > <maxime.ripard@free-electrons.com> wrote: > > On Thu, May 14, 2015 at 02:10:11PM +0800, Chen-Yu Tsai wrote: > >> The A80 stores some magic flags in a portion of the secure SRAM. The > >> BROM jumps directly to the software entry point set by the SMP code > >> if the flags are set. This is required for CPU0 hotplugging. > >> > >> Signed-off-by: Chen-Yu Tsai <wens@csie.org> > >> --- > >> arch/arm/boot/dts/sun9i-a80.dtsi | 20 ++++++++++++++++++++ > >> 1 file changed, 20 insertions(+) > >> > >> diff --git a/arch/arm/boot/dts/sun9i-a80.dtsi b/arch/arm/boot/dts/sun9i-a80.dtsi > >> index 1507bd2a88f0..0695215634d4 100644 > >> --- a/arch/arm/boot/dts/sun9i-a80.dtsi > >> +++ b/arch/arm/boot/dts/sun9i-a80.dtsi > >> @@ -366,6 +366,26 @@ > >> */ > >> ranges = <0 0 0 0x20000000>; > >> > >> + sram_b: sram at 00020000 { > >> + /* 256 KiB secure SRAM at 0x20000 */ > >> + compatible = "mmio-sram"; > >> + reg = <0x00020000 0x40000>; > >> + > > > > We should probably add a property to that SRAM to tell the driver not > > to access it if we're not booted in secure mode. > > (CC-ing Heiko...) > > That kind of puts architecture (ARM) dependent code into a platform > driver. Furthermore, AFAIK there isn't a safe way to check if we're > in secure mode or not. Checking SCR raises an undefined instruction > exception in non-secure mode. Can the kernel handle that? I really > don't understand this bit well. That's a very good question. I'm pretty sure the kernel can know that, since it actually prints the execution mode, and must be able to know whether it can use the virtualization extensions or not I assume. > > Otherwise, bad things might happen. > > The kernel (or rather the bootloader) boots in secure mode by default, > and we don't have any bootloader support to boot into non-secure mode > ATM. That's not really true. We do have some U-Boot patches, and U-Boot might very well be setup to boot into HYP, even though it doesn't do anything else. And even so, the fact that we have no implementation yet doesn't mean that we won't have one in a few month. So just sweeping it under the carpet doesn't seem to be a very good solution. > Couldn't we have the bootloader mark the SRAM as disabled when > booting into non-secure when we add that support? It actually changes the kernel requirements to be able to boot. Changing that is not an option, especially since it's something that: 1) isn't dynamic in any way, 2) will possibly break the kernel if not done, 3) require synchronisation between the bootloader and the kernel when a new secure SRAM is added to the DT, and require an upgrade of the bootloader, 4) we might not be able to replace the bootloader in the first place. All of these issues make it look like a rather bad solution :/ Maxime -- Maxime Ripard, Free Electrons Embedded Linux, Kernel and Android engineering http://free-electrons.com -------------- next part -------------- A non-text attachment was scrubbed... Name: signature.asc Type: application/pgp-signature Size: 819 bytes Desc: Digital signature URL: <http://lists.infradead.org/pipermail/linux-arm-kernel/attachments/20150525/4c32b379/attachment.sig>
next prev parent reply other threads:[~2015-05-25 21:25 UTC|newest] Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top 2015-05-14 6:10 [RFC 0/7] ARM: sun9i: SMP support with Multi-Cluster Power Management Chen-Yu Tsai 2015-05-14 6:10 ` Chen-Yu Tsai 2015-05-14 6:10 ` [RFC 1/7] ARM: sun9i: Support SMP on A80 with Multi-Cluster Power Management (MCPM) Chen-Yu Tsai 2015-05-14 6:10 ` Chen-Yu Tsai 2015-05-14 6:10 ` [RFC 2/7] ARM: dts: sun9i: Add CCI-400 device nodes for A80 Chen-Yu Tsai 2015-05-14 6:10 ` Chen-Yu Tsai 2015-05-17 14:51 ` Maxime Ripard 2015-05-17 14:51 ` Maxime Ripard 2015-05-19 7:12 ` Chen-Yu Tsai 2015-05-19 7:12 ` Chen-Yu Tsai 2015-05-14 6:10 ` [RFC 3/7] ARM: dts: sun9i: Add CPUCFG device node for A80 dtsi Chen-Yu Tsai 2015-05-14 6:10 ` Chen-Yu Tsai 2015-05-14 6:10 ` [RFC 4/7] ARM: dts: sun9i: Add PRCM device node for the " Chen-Yu Tsai 2015-05-14 6:10 ` Chen-Yu Tsai 2015-05-17 14:54 ` Maxime Ripard 2015-05-17 14:54 ` Maxime Ripard 2015-05-19 3:08 ` Chen-Yu Tsai 2015-05-19 3:08 ` Chen-Yu Tsai 2015-05-14 6:10 ` [RFC 5/7] ARM: sunxi: mcpm: Support CPU/cluster power down and hotplugging for cpu1~7 Chen-Yu Tsai 2015-05-14 6:10 ` Chen-Yu Tsai 2015-05-14 6:10 ` [RFC 6/7] ARM: sunxi: mcpm: Support cpu0 hotplug Chen-Yu Tsai 2015-05-14 6:10 ` Chen-Yu Tsai 2015-05-14 6:10 ` [RFC 7/7] ARM: dts: sun9i: Add secure SRAM node used for MCPM SMP hotplug Chen-Yu Tsai 2015-05-14 6:10 ` Chen-Yu Tsai 2015-05-20 10:08 ` Maxime Ripard 2015-05-20 10:08 ` Maxime Ripard 2015-05-24 15:55 ` [linux-sunxi] " Chen-Yu Tsai 2015-05-24 15:55 ` Chen-Yu Tsai 2015-05-25 21:24 ` Maxime Ripard [this message] 2015-05-25 21:24 ` Maxime Ripard 2015-05-26 16:47 ` Chen-Yu Tsai 2015-05-26 16:47 ` Chen-Yu Tsai 2015-06-11 16:33 ` Maxime Ripard 2015-06-11 16:33 ` Maxime Ripard 2015-05-16 10:08 ` [linux-sunxi] [RFC 0/7] ARM: sun9i: SMP support with Multi-Cluster Power Management Ian Campbell 2015-05-16 10:08 ` Ian Campbell 2015-05-17 14:38 ` Maxime Ripard 2015-05-17 14:38 ` Maxime Ripard 2015-05-18 5:19 ` Nicolas Pitre 2015-05-18 5:19 ` Nicolas Pitre 2015-05-18 9:04 ` Maxime Ripard 2015-05-18 9:04 ` Maxime Ripard 2015-05-19 2:51 ` Chen-Yu Tsai 2015-05-19 2:51 ` Chen-Yu Tsai
Reply instructions: You may reply publicly to this message via plain-text email using any one of the following methods: * Save the following mbox file, import it into your mail client, and reply-to-all from there: mbox Avoid top-posting and favor interleaved quoting: https://en.wikipedia.org/wiki/Posting_style#Interleaved_style * Reply using the --to, --cc, and --in-reply-to switches of git-send-email(1): git send-email \ --in-reply-to=20150525212419.GO8557@lukather \ --to=maxime.ripard@free-electrons.com \ --cc=Dave.Martin@arm.com \ --cc=heiko@sntech.de \ --cc=linux-arm-kernel@lists.infradead.org \ --cc=linux-kernel@vger.kernel.org \ --cc=linux-sunxi@googlegroups.com \ --cc=nicolas.pitre@linaro.org \ --cc=wens@csie.org \ /path/to/YOUR_REPLY https://kernel.org/pub/software/scm/git/docs/git-send-email.html * If your mail client supports setting the In-Reply-To header via mailto: links, try the mailto: linkBe sure your reply has a Subject: header at the top and a blank line before the message body.
This is an external index of several public inboxes, see mirroring instructions on how to clone and mirror all data and code used by this external index.