From: Palmer Dabbelt <palmer@sifive.com>
To: Arnd Bergmann <arnd@arndb.de>
Cc: hare@suse.de, dhowells@redhat.com, linux-arch@vger.kernel.org,
linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org,
linux-block@vger.kernel.org, linux-ide@vger.kernel.org,
linux-input@vger.kernel.org, netdev@vger.kernel.org,
linux-wireless@vger.kernel.org, linux-pwm@vger.kernel.org,
linux-rtc@vger.kernel.org, linux-spi@vger.kernel.org,
linux-usb@vger.kernel.org, dri-devel@lists.freedesktop.org,
linux-fbdev@vger.kernel.org, linux-watchdog@vger.kernel.org,
linux-fsdevel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [PATCH 00/16] remove eight obsolete architectures
Date: Tue, 20 Mar 2018 10:11:47 -0700 (PDT) [thread overview]
Message-ID: <mhng-f6731cb9-8394-419d-b14b-c6fcd6c0930d@palmer-si-x1c4> (raw)
In-Reply-To: <CAK8P3a01pfvsdM1mR8raU9dA7p4H-jRJz2Y8-+KEY76W_Mukpg@mail.gmail.com>
On Thu, 15 Mar 2018 03:42:25 PDT (-0700), Arnd Bergmann wrote:
> On Thu, Mar 15, 2018 at 10:59 AM, Hannes Reinecke <hare@suse.de> wrote:
>> On 03/15/2018 10:42 AM, David Howells wrote:
>>> Do we have anything left that still implements NOMMU?
>>>
>> RISC-V ?
>> (evil grin :-)
>
> Is anyone producing a chip that includes enough of the Privileged ISA spec
> to have things like system calls, but not the MMU parts?
>
> I thought at least initially the kernel only supports hardware that has a rather
> complete feature set.
We currently do not have a NOMMU port. As far as I know, everyone who's
currently producing RISC-V hardware with enough memory to run Linux has S mode
with paging support. The ISA allows for S mode without paging but there's no
hardware for that -- if you're going to put a DRAM controller on there then
paging seems pretty cheap. You could run a NOMMU port on a system with S-mode
and paging, but With all the superpage stuff I don't think you'll get an
appreciable performance win for any workload running without an MMU so there's
nothing to justify the work (and incompatibility) of a NOMMU port there.
While I think you could implement a NOMMU port on a machine with only M and U
modes (and therefor no address translation at all), I don't know of any MU-only
machines that have enough memory to run Linux (ours have less than 32KiB). A
SBI-free Linux would be a prerequisite for this, but there's some interest in
that outside of a NOMMU port so it might materialize anyway.
Of course, QEMU could probably be tricked into emulating one of these machines
with little to no effort :)... That said, I doubt we'll see a NOMMU port
materialize without some real hardware as it's a lot of work for a QEMU-only
target.
WARNING: multiple messages have this Message-ID (diff)
From: Palmer Dabbelt <palmer-SpMDHPYPyPbQT0dZR+AlfA@public.gmane.org>
To: Arnd Bergmann <arnd-r2nGTMty4D4@public.gmane.org>
Cc: hare-l3A5Bk7waGM@public.gmane.org,
dhowells-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org,
linux-arch-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
linux-doc-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
linux-block-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
linux-ide-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
linux-input-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
netdev-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
linux-wireless-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
linux-pwm-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
linux-rtc-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
linux-spi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
linux-usb-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
dri-devel-PD4FTy7X32lNgt0PjOBp9y5qC8QIuHrW@public.gmane.org,
linux-fbdev-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
linux-watchdog-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
linux-fsdevel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org
Subject: Re: [PATCH 00/16] remove eight obsolete architectures
Date: Tue, 20 Mar 2018 10:11:47 -0700 (PDT) [thread overview]
Message-ID: <mhng-f6731cb9-8394-419d-b14b-c6fcd6c0930d@palmer-si-x1c4> (raw)
In-Reply-To: <CAK8P3a01pfvsdM1mR8raU9dA7p4H-jRJz2Y8-+KEY76W_Mukpg-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
On Thu, 15 Mar 2018 03:42:25 PDT (-0700), Arnd Bergmann wrote:
> On Thu, Mar 15, 2018 at 10:59 AM, Hannes Reinecke <hare-l3A5Bk7waGM@public.gmane.org> wrote:
>> On 03/15/2018 10:42 AM, David Howells wrote:
>>> Do we have anything left that still implements NOMMU?
>>>
>> RISC-V ?
>> (evil grin :-)
>
> Is anyone producing a chip that includes enough of the Privileged ISA spec
> to have things like system calls, but not the MMU parts?
>
> I thought at least initially the kernel only supports hardware that has a rather
> complete feature set.
We currently do not have a NOMMU port. As far as I know, everyone who's
currently producing RISC-V hardware with enough memory to run Linux has S mode
with paging support. The ISA allows for S mode without paging but there's no
hardware for that -- if you're going to put a DRAM controller on there then
paging seems pretty cheap. You could run a NOMMU port on a system with S-mode
and paging, but With all the superpage stuff I don't think you'll get an
appreciable performance win for any workload running without an MMU so there's
nothing to justify the work (and incompatibility) of a NOMMU port there.
While I think you could implement a NOMMU port on a machine with only M and U
modes (and therefor no address translation at all), I don't know of any MU-only
machines that have enough memory to run Linux (ours have less than 32KiB). A
SBI-free Linux would be a prerequisite for this, but there's some interest in
that outside of a NOMMU port so it might materialize anyway.
Of course, QEMU could probably be tricked into emulating one of these machines
with little to no effort :)... That said, I doubt we'll see a NOMMU port
materialize without some real hardware as it's a lot of work for a QEMU-only
target.
WARNING: multiple messages have this Message-ID (diff)
From: Palmer Dabbelt <palmer@sifive.com>
To: Arnd Bergmann <arnd@arndb.de>
Cc: hare@suse.de, dhowells@redhat.com, linux-arch@vger.kernel.org,
linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org,
linux-block@vger.kernel.org, linux-ide@vger.kernel.org,
linux-input@vger.kernel.org, netdev@vger.kernel.org,
linux-wireless@vger.kernel.org, linux-pwm@vger.kernel.org,
linux-rtc@vger.kernel.org, linux-spi@vger.kernel.org,
linux-usb@vger.kernel.org, dri-devel@lists.freedesktop.org,
linux-fbdev@vger.kernel.org, linux-watchdog@vger.kernel.org,
linux-fsdevel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [PATCH 00/16] remove eight obsolete architectures
Date: Tue, 20 Mar 2018 10:11:47 -0700 (PDT) [thread overview]
Message-ID: <mhng-f6731cb9-8394-419d-b14b-c6fcd6c0930d@palmer-si-x1c4> (raw)
In-Reply-To: <CAK8P3a01pfvsdM1mR8raU9dA7p4H-jRJz2Y8-+KEY76W_Mukpg@mail.gmail.com>
On Thu, 15 Mar 2018 03:42:25 PDT (-0700), Arnd Bergmann wrote:
> On Thu, Mar 15, 2018 at 10:59 AM, Hannes Reinecke <hare@suse.de> wrote:
>> On 03/15/2018 10:42 AM, David Howells wrote:
>>> Do we have anything left that still implements NOMMU?
>>>
>> RISC-V ?
>> (evil grin :-)
>
> Is anyone producing a chip that includes enough of the Privileged ISA spec
> to have things like system calls, but not the MMU parts?
>
> I thought at least initially the kernel only supports hardware that has a rather
> complete feature set.
We currently do not have a NOMMU port. As far as I know, everyone who's
currently producing RISC-V hardware with enough memory to run Linux has S mode
with paging support. The ISA allows for S mode without paging but there's no
hardware for that -- if you're going to put a DRAM controller on there then
paging seems pretty cheap. You could run a NOMMU port on a system with S-mode
and paging, but With all the superpage stuff I don't think you'll get an
appreciable performance win for any workload running without an MMU so there's
nothing to justify the work (and incompatibility) of a NOMMU port there.
While I think you could implement a NOMMU port on a machine with only M and U
modes (and therefor no address translation at all), I don't know of any MU-only
machines that have enough memory to run Linux (ours have less than 32KiB). A
SBI-free Linux would be a prerequisite for this, but there's some interest in
that outside of a NOMMU port so it might materialize anyway.
Of course, QEMU could probably be tricked into emulating one of these machines
with little to no effort :)... That said, I doubt we'll see a NOMMU port
materialize without some real hardware as it's a lot of work for a QEMU-only
target.
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WARNING: multiple messages have this Message-ID (diff)
From: Palmer Dabbelt <palmer@sifive.com>
To: Arnd Bergmann <arnd-r2nGTMty4D4@public.gmane.org>
Cc: hare-l3A5Bk7waGM@public.gmane.org,
dhowells-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org,
linux-arch-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
linux-doc-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
linux-block-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
linux-ide-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
linux-input-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
netdev-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
linux-wireless-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
linux-pwm-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
linux-rtc-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
linux-spi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
linux-usb-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
dri-devel-PD4FTy7X32lNgt0PjOBp9y5qC8QIuHrW@public.gmane.org,
linux-fbdev-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
linux-watchdog-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
linux-fsdevel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org
Subject: Re: [PATCH 00/16] remove eight obsolete architectures
Date: Tue, 20 Mar 2018 17:11:47 +0000 [thread overview]
Message-ID: <mhng-f6731cb9-8394-419d-b14b-c6fcd6c0930d@palmer-si-x1c4> (raw)
In-Reply-To: <CAK8P3a01pfvsdM1mR8raU9dA7p4H-jRJz2Y8-+KEY76W_Mukpg-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
On Thu, 15 Mar 2018 03:42:25 PDT (-0700), Arnd Bergmann wrote:
> On Thu, Mar 15, 2018 at 10:59 AM, Hannes Reinecke <hare@suse.de> wrote:
>> On 03/15/2018 10:42 AM, David Howells wrote:
>>> Do we have anything left that still implements NOMMU?
>>>
>> RISC-V ?
>> (evil grin :-)
>
> Is anyone producing a chip that includes enough of the Privileged ISA spec
> to have things like system calls, but not the MMU parts?
>
> I thought at least initially the kernel only supports hardware that has a rather
> complete feature set.
We currently do not have a NOMMU port. As far as I know, everyone who's
currently producing RISC-V hardware with enough memory to run Linux has S mode
with paging support. The ISA allows for S mode without paging but there's no
hardware for that -- if you're going to put a DRAM controller on there then
paging seems pretty cheap. You could run a NOMMU port on a system with S-mode
and paging, but With all the superpage stuff I don't think you'll get an
appreciable performance win for any workload running without an MMU so there's
nothing to justify the work (and incompatibility) of a NOMMU port there.
While I think you could implement a NOMMU port on a machine with only M and U
modes (and therefor no address translation at all), I don't know of any MU-only
machines that have enough memory to run Linux (ours have less than 32KiB). A
SBI-free Linux would be a prerequisite for this, but there's some interest in
that outside of a NOMMU port so it might materialize anyway.
Of course, QEMU could probably be tricked into emulating one of these machines
with little to no effort :)... That said, I doubt we'll see a NOMMU port
materialize without some real hardware as it's a lot of work for a QEMU-only
target.
next prev parent reply other threads:[~2018-03-20 17:11 UTC|newest]
Thread overview: 98+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-03-14 14:34 [PATCH 00/16] remove eight obsolete architectures Arnd Bergmann
2018-03-14 14:34 ` Arnd Bergmann
2018-03-14 14:34 ` Arnd Bergmann
2018-03-14 14:34 ` Arnd Bergmann
2018-03-14 14:36 ` [PATCH 01/16] mn10300: Remove the architecture Arnd Bergmann
2018-03-14 14:36 ` [PATCH 02/16] arch: remove frv port Arnd Bergmann
2018-03-14 14:36 ` [PATCH 03/16] arch: remove m32r port Arnd Bergmann
2018-03-14 14:36 ` [PATCH 04/16] arch: remove score port Arnd Bergmann
2018-03-14 14:36 ` [PATCH 05/16] arch: remove blackfin port Arnd Bergmann
2018-03-14 16:51 ` [PATCH] scripts/checkstack.pl: remove blackfin support Tobias Klauser
2018-03-14 17:04 ` Arnd Bergmann
2018-03-15 22:24 ` [PATCH 05/16] arch: remove blackfin port Bryan Wu
2018-03-14 14:36 ` [PATCH 06/16] arch: remove tile port Arnd Bergmann
2018-03-16 1:23 ` Chris Metcalf
2018-03-16 8:12 ` Arnd Bergmann
2018-03-14 14:36 ` [PATCH 07/16] CRIS: Drop support for the CRIS port Arnd Bergmann
2018-03-14 14:39 ` [PATCH 10/16] mm: remove obsolete alloc_remap() Arnd Bergmann
2018-03-14 14:50 ` Pavel Tatashin
2018-03-14 14:56 ` Arnd Bergmann
2018-03-14 14:59 ` Pavel Tatashin
2018-03-14 14:43 ` [PATCH 11/16] treewide: simplify Kconfig dependencies for removed archs Arnd Bergmann
2018-03-14 14:43 ` Arnd Bergmann
2018-03-14 14:43 ` [11/16] " Arnd Bergmann
2018-03-14 14:43 ` [PATCH 11/16] " Arnd Bergmann
2018-03-14 14:43 ` [PATCH 12/16] asm-generic: siginfo: remove obsolete #ifdefs Arnd Bergmann
2018-03-14 16:38 ` Eric W. Biederman
2018-03-14 20:31 ` Dominik Brodowski
2018-03-14 20:40 ` Arnd Bergmann
2018-03-14 20:45 ` Dominik Brodowski
2018-03-15 10:06 ` Eric W. Biederman
2018-03-15 10:48 ` Arnd Bergmann
2018-03-15 11:37 ` Eric W. Biederman
2018-03-15 12:50 ` Arnd Bergmann
2018-03-15 18:07 ` Eric W. Biederman
2018-03-15 12:54 ` [PATCH 11/16] treewide: simplify Kconfig dependencies for removed archs Kalle Valo
2018-03-15 12:54 ` Kalle Valo
2018-03-15 12:54 ` [11/16] " Kalle Valo
2018-03-15 12:54 ` [PATCH 11/16] " Kalle Valo
2018-03-15 12:54 ` Kalle Valo
2018-03-19 23:06 ` Alexandre Belloni
2018-03-19 23:06 ` Alexandre Belloni
2018-03-19 23:06 ` [11/16] " Alexandre Belloni
2018-03-14 14:51 ` [PATCH 13/16] Documentation: arch-support: remove obsolete architectures Arnd Bergmann
2018-03-14 14:52 ` [PATCH 15/16] recordmcount.pl: drop blackin and tile support Arnd Bergmann
2018-03-15 20:42 ` Steven Rostedt
2018-03-14 14:53 ` [PATCH 16/16] ktest: remove obsolete architectures Arnd Bergmann
2018-03-15 20:46 ` Steven Rostedt
2018-03-14 20:38 ` [PATCH 14/16] asm-generic: clean up asm/unistd.h Arnd Bergmann
2018-03-15 9:42 ` [PATCH 00/16] remove eight obsolete architectures David Howells
2018-03-15 9:42 ` David Howells
2018-03-15 9:42 ` David Howells
2018-03-15 9:42 ` David Howells
2018-03-15 9:48 ` Geert Uytterhoeven
2018-03-15 9:48 ` Geert Uytterhoeven
2018-03-15 9:48 ` Geert Uytterhoeven
2018-03-15 9:48 ` Geert Uytterhoeven
2018-03-15 16:56 ` rfc: remove print_vma_addr ? (was Re: [PATCH 00/16] remove eight obsolete architectures) Joe Perches
2018-03-15 16:56 ` Joe Perches
2018-03-15 16:56 ` Joe Perches
2018-03-15 16:56 ` Joe Perches
2018-03-15 16:56 ` Joe Perches
2018-03-15 16:56 ` Joe Perches
2018-03-15 17:08 ` Matthew Wilcox
2018-03-15 17:08 ` Matthew Wilcox
2018-03-15 17:08 ` Matthew Wilcox
2018-03-15 17:08 ` Matthew Wilcox
2018-03-15 17:08 ` Matthew Wilcox
2018-03-15 17:08 ` Matthew Wilcox
2018-03-15 17:13 ` Joe Perches
2018-03-15 17:13 ` Joe Perches
2018-03-15 17:13 ` Joe Perches
2018-03-15 17:13 ` Joe Perches
2018-03-15 17:13 ` Joe Perches
2018-03-15 17:13 ` Joe Perches
2018-03-15 9:56 ` [PATCH 00/16] remove eight obsolete architectures Arnd Bergmann
2018-03-15 9:56 ` Arnd Bergmann
2018-03-15 9:56 ` Arnd Bergmann
2018-03-15 9:56 ` Arnd Bergmann
2018-03-16 4:50 ` afzal mohammed
2018-03-16 4:50 ` afzal mohammed
2018-03-16 4:50 ` afzal mohammed
2018-03-15 9:59 ` Hannes Reinecke
2018-03-15 9:59 ` Hannes Reinecke
2018-03-15 9:59 ` Hannes Reinecke
2018-03-15 9:59 ` Hannes Reinecke
2018-03-15 9:59 ` Hannes Reinecke
2018-03-15 10:42 ` Arnd Bergmann
2018-03-15 10:42 ` Arnd Bergmann
2018-03-15 10:42 ` Arnd Bergmann
2018-03-15 10:42 ` Arnd Bergmann
2018-03-15 14:17 ` Christoph Hellwig
2018-03-15 14:17 ` Christoph Hellwig
2018-03-15 14:17 ` Christoph Hellwig
2018-03-15 14:17 ` Christoph Hellwig
2018-03-20 17:11 ` Palmer Dabbelt [this message]
2018-03-20 17:11 ` Palmer Dabbelt
2018-03-20 17:11 ` Palmer Dabbelt
2018-03-20 17:11 ` Palmer Dabbelt
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