From: Russell King - ARM Linux admin <linux@armlinux.org.uk>
To: Arnd Bergmann <arnd@arndb.de>
Cc: afzal mohammed <afzal.mohd.ma@gmail.com>,
Linux ARM <linux-arm-kernel@lists.infradead.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: ARM: static kernel in vmalloc space
Date: Thu, 14 May 2020 17:25:35 +0100 [thread overview]
Message-ID: <20200514162535.GP1551@shell.armlinux.org.uk> (raw)
In-Reply-To: <CAK8P3a2PNZY-9L9+SFDLtrp731ZGo6Nbs-7jY6E2PwWXa0kfKw@mail.gmail.com>
On Thu, May 14, 2020 at 02:41:11PM +0200, Arnd Bergmann wrote:
> On Thu, May 14, 2020 at 1:18 PM afzal mohammed <afzal.mohd.ma@gmail.com> wrote:
> > On Tue, May 12, 2020 at 09:49:59PM +0200, Arnd Bergmann wrote:
> >
> > > Any idea which bit you want to try next?
> >
> > My plan has been to next post patches for the static kernel migration
> > to vmalloc space (currently the code is rigid, taking easy route
> > wherever possible & not of high quality) as that feature has an
> > independent existence & adds value by itself. And then start working
> > on other steps towards VMSPLIT_4G_4G.
> >
> > Now that you mentioned about other things, i will slowly start those
> > as well.
>
> Sounds good.
>
> > > Creating a raw_copy_{from,to}_user()
> > > based on get_user_pages()/kmap_atomic()/memcpy() is probably a good
> > > next thing to do. I think it can be done one page at a time with only
> > > checking for
> > > get_fs(), access_ok(), and page permissions, while get_user()/put_user()
> > > need to handle a few more corner cases.
> >
> > Before starting w/ other things, i would like to align on the high
> > level design,
> >
> > My understanding (mostly based on your comments) as follows,
> > (i currently do not have a firm grip over these things, hope to have
> > it once started w/ the implementation)
> >
> > 1. SoC w/ LPAE
> > 2. TTBR1 (top 256MB) for static kernel, modules, io mappings, vmalloc,
> > kmap, fixmap & vectors
>
> Right, these kind of go together because pre-LPAE cannot do the
> same TTBR1 split, and they more frequently have conflicting
> static mappings.
>
> It's clearly possible to do something very similar for older chips
> (v6 or v7 without LPAE, possibly even v5), it just gets harder
> while providing less benefit.
Forget about doing this for anything without a PIPT cache - or you're
going to end up having to flush the data cache each time you enter or
exit the kernel.
--
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
FTTC broadband for 0.8mile line in suburbia: sync at 10.2Mbps down 587kbps up
next prev parent reply other threads:[~2020-05-14 16:25 UTC|newest]
Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-31 9:32 [PATCH 0/3] Highmem support for 32-bit RISC-V Eric Lin
2020-03-31 9:32 ` [PATCH 1/3] riscv/mm: Add pkmap region and CONFIG_HIGHMEM Eric Lin
2020-03-31 9:32 ` [PATCH 2/3] riscv/mm: Implement kmap() and kmap_atomic() Eric Lin
2020-03-31 9:32 ` [PATCH 3/3] riscv/mm: Add pkmap in print_vm_layout() Eric Lin
2020-04-02 9:31 ` [PATCH 0/3] Highmem support for 32-bit RISC-V Arnd Bergmann
2020-04-08 3:51 ` Alan Kao
2020-04-08 14:40 ` Arnd Bergmann
2020-04-14 15:17 ` afzal mohammed
2020-04-14 19:29 ` Arnd Bergmann
2020-04-15 13:54 ` afzal mohammed
2020-05-03 14:50 ` afzal mohammed
2020-05-03 20:20 ` Arnd Bergmann
2020-05-04 9:10 ` afzal mohammed
2020-05-04 11:27 ` Arnd Bergmann
2020-05-11 14:21 ` ARM: static kernel in vmalloc space (was Re: [PATCH 0/3] Highmem support for 32-bit RISC-V) afzal mohammed
2020-05-11 15:29 ` Arnd Bergmann
2020-05-12 10:47 ` ARM: static kernel in vmalloc space afzal mohammed
2020-05-12 19:49 ` Arnd Bergmann
2020-05-14 11:17 ` afzal mohammed
2020-05-14 12:41 ` Arnd Bergmann
2020-05-14 13:35 ` afzal mohammed
2020-05-14 14:44 ` afzal mohammed
2020-05-14 15:32 ` Arnd Bergmann
2020-05-16 6:06 ` afzal mohammed
2020-05-16 7:35 ` Arnd Bergmann
2020-06-07 12:59 ` ARM: vmsplit 4g/4g afzal mohammed
2020-06-07 16:11 ` Russell King - ARM Linux admin
2020-06-08 11:09 ` afzal mohammed
2020-06-10 10:10 ` Linus Walleij
2020-06-12 10:25 ` afzal mohammed
2020-06-15 9:11 ` Linus Walleij
2020-06-15 10:01 ` afzal mohammed
2020-06-07 19:26 ` Arnd Bergmann
2020-06-08 11:18 ` afzal mohammed
2020-06-08 14:43 ` Arnd Bergmann
2020-06-08 15:17 ` afzal mohammed
2020-06-09 12:15 ` afzal mohammed
2020-06-09 14:22 ` Arnd Bergmann
2020-05-14 16:25 ` Russell King - ARM Linux admin [this message]
2020-05-14 21:12 ` ARM: static kernel in vmalloc space Arnd Bergmann
2020-05-14 23:40 ` Russell King - ARM Linux admin
2020-05-15 15:41 ` Arnd Bergmann
2020-07-30 9:33 ` Linus Walleij
2020-07-30 10:17 ` Arnd Bergmann
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