Re: [PATCH v5 1/4] riscv: Move kernel mapping to vmalloc zone

2020-07-24 Thread Arnd Bergmann
On Wed, Jul 22, 2020 at 11:06 PM Atish Patra wrote: > > On Wed, Jul 22, 2020 at 1:23 PM Arnd Bergmann wrote: > > > > I just noticed that rv32 allows 2GB of lowmem rather than just the usual > > 768MB or 1GB, at the expense of addressable user memory. This seems > > like an unusual choice, but I

Re: [PATCH v5 1/4] riscv: Move kernel mapping to vmalloc zone

2020-07-23 Thread Benjamin Herrenschmidt
On Thu, 2020-07-23 at 01:21 -0400, Alex Ghiti wrote: > > works fine with huge pages, what is your problem there ? You rely on > > punching small-page size holes in there ? > > > > ARCH_HAS_STRICT_KERNEL_RWX prevents the use of a hugepage for the kernel > mapping in the direct mapping as it sets

Re: [PATCH v5 1/4] riscv: Move kernel mapping to vmalloc zone

2020-07-22 Thread Alex Ghiti
Le 7/21/20 à 7:36 PM, Palmer Dabbelt a écrit : On Tue, 21 Jul 2020 16:11:02 PDT (-0700), b...@kernel.crashing.org wrote: On Tue, 2020-07-21 at 14:36 -0400, Alex Ghiti wrote: > > I guess I don't understand why this is necessary at all. > > Specifically: why > > can't we just relocate the

Re: [PATCH v5 1/4] riscv: Move kernel mapping to vmalloc zone

2020-07-22 Thread Alex Ghiti
Hi Palmer, Le 7/21/20 à 3:05 PM, Palmer Dabbelt a écrit : On Tue, 21 Jul 2020 11:36:10 PDT (-0700), a...@ghiti.fr wrote: Let's try to make progress here: I add linux-mm in CC to get feedback on this patch as it blocks sv48 support too. Sorry for being slow here.  I haven't replied because I

Re: [PATCH v5 1/4] riscv: Move kernel mapping to vmalloc zone

2020-07-22 Thread Alex Ghiti
Hi Benjamin, Le 7/21/20 à 7:11 PM, Benjamin Herrenschmidt a écrit : On Tue, 2020-07-21 at 14:36 -0400, Alex Ghiti wrote: I guess I don't understand why this is necessary at all. Specifically: why can't we just relocate the kernel within the linear map? That would let the bootloader put the

Re: [PATCH v5 1/4] riscv: Move kernel mapping to vmalloc zone

2020-07-22 Thread Atish Patra
On Wed, Jul 22, 2020 at 1:23 PM Arnd Bergmann wrote: > > On Wed, Jul 22, 2020 at 9:52 PM Palmer Dabbelt wrote: > > On Wed, 22 Jul 2020 02:43:50 PDT (-0700), Arnd Bergmann wrote: > > > On Tue, Jul 21, 2020 at 9:06 PM Palmer Dabbelt wrote: > > > The eventual goal is to have a split of 3840MB for

Re: [PATCH v5 1/4] riscv: Move kernel mapping to vmalloc zone

2020-07-22 Thread Arnd Bergmann
On Wed, Jul 22, 2020 at 9:52 PM Palmer Dabbelt wrote: > On Wed, 22 Jul 2020 02:43:50 PDT (-0700), Arnd Bergmann wrote: > > On Tue, Jul 21, 2020 at 9:06 PM Palmer Dabbelt wrote: > > The eventual goal is to have a split of 3840MB for either user or linear map > > plus and 256MB for vmalloc,

Re: [PATCH v5 1/4] riscv: Move kernel mapping to vmalloc zone

2020-07-22 Thread Palmer Dabbelt
On Wed, 22 Jul 2020 02:43:50 PDT (-0700), Arnd Bergmann wrote: On Tue, Jul 21, 2020 at 9:06 PM Palmer Dabbelt wrote: On Tue, 21 Jul 2020 11:36:10 PDT (-0700), a...@ghiti.fr wrote: > Let's try to make progress here: I add linux-mm in CC to get feedback on > this patch as it blocks sv48 support

Re: [PATCH v5 1/4] riscv: Move kernel mapping to vmalloc zone

2020-07-22 Thread Arnd Bergmann
On Tue, Jul 21, 2020 at 9:06 PM Palmer Dabbelt wrote: > > On Tue, 21 Jul 2020 11:36:10 PDT (-0700), a...@ghiti.fr wrote: > > Let's try to make progress here: I add linux-mm in CC to get feedback on > > this patch as it blocks sv48 support too. > > Sorry for being slow here. I haven't replied

Re: [PATCH v5 1/4] riscv: Move kernel mapping to vmalloc zone

2020-07-21 Thread Palmer Dabbelt
On Tue, 21 Jul 2020 21:50:42 PDT (-0700), m...@ellerman.id.au wrote: Benjamin Herrenschmidt writes: On Tue, 2020-07-21 at 16:48 -0700, Palmer Dabbelt wrote: > Why ? Branch distance limits ? You can't use trampolines ? Nothing fundamental, it's just that we don't have a large code model in

Re: [PATCH v5 1/4] riscv: Move kernel mapping to vmalloc zone

2020-07-21 Thread Michael Ellerman
Benjamin Herrenschmidt writes: > On Tue, 2020-07-21 at 16:48 -0700, Palmer Dabbelt wrote: >> > Why ? Branch distance limits ? You can't use trampolines ? >> >> Nothing fundamental, it's just that we don't have a large code model in the C >> compiler. As a result all the global symbols are

Re: [PATCH v5 1/4] riscv: Move kernel mapping to vmalloc zone

2020-07-21 Thread Benjamin Herrenschmidt
On Tue, 2020-07-21 at 16:48 -0700, Palmer Dabbelt wrote: > > Why ? Branch distance limits ? You can't use trampolines ? > > Nothing fundamental, it's just that we don't have a large code model in the C > compiler. As a result all the global symbols are resolved as 32-bit > PC-relative accesses.

Re: [PATCH v5 1/4] riscv: Move kernel mapping to vmalloc zone

2020-07-21 Thread Palmer Dabbelt
On Tue, 21 Jul 2020 16:12:58 PDT (-0700), b...@kernel.crashing.org wrote: On Tue, 2020-07-21 at 12:05 -0700, Palmer Dabbelt wrote: * We waste vmalloc space on 32-bit systems, where there isn't a lot of it. * On 64-bit systems the VA space around the kernel is precious because it's the only

Re: [PATCH v5 1/4] riscv: Move kernel mapping to vmalloc zone

2020-07-21 Thread Palmer Dabbelt
On Tue, 21 Jul 2020 16:11:02 PDT (-0700), b...@kernel.crashing.org wrote: On Tue, 2020-07-21 at 14:36 -0400, Alex Ghiti wrote: > > I guess I don't understand why this is necessary at all. > > Specifically: why > > can't we just relocate the kernel within the linear map? That would > > let the

Re: [PATCH v5 1/4] riscv: Move kernel mapping to vmalloc zone

2020-07-21 Thread Benjamin Herrenschmidt
On Tue, 2020-07-21 at 12:05 -0700, Palmer Dabbelt wrote: > > * We waste vmalloc space on 32-bit systems, where there isn't a lot of it. > * On 64-bit systems the VA space around the kernel is precious because it's > the > only place we can place text (modules, BPF, whatever). Why ? Branch

Re: [PATCH v5 1/4] riscv: Move kernel mapping to vmalloc zone

2020-07-21 Thread Benjamin Herrenschmidt
On Tue, 2020-07-21 at 14:36 -0400, Alex Ghiti wrote: > > > I guess I don't understand why this is necessary at all. > > > Specifically: why > > > can't we just relocate the kernel within the linear map? That would > > > let the > > > bootloader put the kernel wherever it wants, modulo the

Re: [PATCH v5 1/4] riscv: Move kernel mapping to vmalloc zone

2020-07-21 Thread Palmer Dabbelt
On Tue, 21 Jul 2020 11:36:10 PDT (-0700), a...@ghiti.fr wrote: Let's try to make progress here: I add linux-mm in CC to get feedback on this patch as it blocks sv48 support too. Sorry for being slow here. I haven't replied because I hadn't really fleshed out the design yet, but just so

Re: [PATCH v5 1/4] riscv: Move kernel mapping to vmalloc zone

2020-07-21 Thread Alex Ghiti
Let's try to make progress here: I add linux-mm in CC to get feedback on this patch as it blocks sv48 support too. Alex Le 7/9/20 à 7:11 AM, Alex Ghiti a écrit : Hi Palmer, Le 7/9/20 à 1:05 AM, Palmer Dabbelt a écrit : On Sun, 07 Jun 2020 00:59:46 PDT (-0700), a...@ghiti.fr wrote: This is

Re: [PATCH v5 1/4] riscv: Move kernel mapping to vmalloc zone

2020-07-09 Thread Alex Ghiti
Hi Palmer, Le 7/9/20 à 1:05 AM, Palmer Dabbelt a écrit : On Sun, 07 Jun 2020 00:59:46 PDT (-0700), a...@ghiti.fr wrote: This is a preparatory patch for relocatable kernel. The kernel used to be linked at PAGE_OFFSET address and used to be loaded physically at the beginning of the main memory.

Re: [PATCH v5 1/4] riscv: Move kernel mapping to vmalloc zone

2020-07-09 Thread Zong Li
On Thu, Jul 9, 2020 at 1:05 PM Palmer Dabbelt wrote: > > On Sun, 07 Jun 2020 00:59:46 PDT (-0700), a...@ghiti.fr wrote: > > This is a preparatory patch for relocatable kernel. > > > > The kernel used to be linked at PAGE_OFFSET address and used to be loaded > > physically at the beginning of the

Re: [PATCH v5 1/4] riscv: Move kernel mapping to vmalloc zone

2020-07-08 Thread Palmer Dabbelt
On Sun, 07 Jun 2020 00:59:46 PDT (-0700), a...@ghiti.fr wrote: This is a preparatory patch for relocatable kernel. The kernel used to be linked at PAGE_OFFSET address and used to be loaded physically at the beginning of the main memory. Therefore, we could use the linear mapping for the kernel

Re: [PATCH v5 1/4] riscv: Move kernel mapping to vmalloc zone

2020-06-12 Thread Alex Ghiti
Hi Atish, Le 6/11/20 à 5:34 PM, Atish Patra a écrit : On Sun, Jun 7, 2020 at 1:01 AM Alexandre Ghiti wrote: This is a preparatory patch for relocatable kernel. The kernel used to be linked at PAGE_OFFSET address and used to be loaded physically at the beginning of the main memory. Therefore,

Re: [PATCH v5 1/4] riscv: Move kernel mapping to vmalloc zone

2020-06-11 Thread Atish Patra
On Sun, Jun 7, 2020 at 1:01 AM Alexandre Ghiti wrote: > > This is a preparatory patch for relocatable kernel. > > The kernel used to be linked at PAGE_OFFSET address and used to be loaded > physically at the beginning of the main memory. Therefore, we could use > the linear mapping for the kernel