linux-kernel - Re: [PATCH v7 1/4] RISC-V: mm: Restrict address space for sv39,sv48,sv57

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Message-ID: <ZMLhrFfoerPIxRL7@ghost>
Date:   Thu, 27 Jul 2023 17:29:16 -0400
From:   Charlie Jenkins <charlie@...osinc.com>
To:     Conor Dooley <conor@...nel.org>
Cc:     linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
        paul.walmsley@...ive.com, palmer@...osinc.com,
        aou@...s.berkeley.edu, anup@...infault.org,
        konstantin@...uxfoundation.org, linux-doc@...r.kernel.org,
        linux-kselftest@...r.kernel.org, linux-mm@...ck.org,
        mick@....forth.gr, jrtc27@...c27.com, rdunlap@...radead.org,
        alexghiti@...osinc.com
Subject: Re: [PATCH v7 1/4] RISC-V: mm: Restrict address space for
 sv39,sv48,sv57

On Thu, Jul 27, 2023 at 01:33:41PM +0100, Conor Dooley wrote:
> Hey Charlie,
> 
> On Wed, Jul 26, 2023 at 09:45:55AM -0700, Charlie Jenkins wrote:
> > Make sv48 the default address space for mmap as some applications
> > currently depend on this assumption. A hint address passed to mmap will
> > cause the largest address space that fits entirely into the hint to be
> > used. If the hint is less than or equal to 1<<38, an sv39 address will
> > be used. An exception is that if the hint address is 0, then a sv48
> > address will be used. After an address space is completely full, the next
> > smallest address space will be used.
> > 
> > Signed-off-by: Charlie Jenkins <charlie@...osinc.com>
> > ---
> >  arch/riscv/include/asm/elf.h       |  2 +-
> >  arch/riscv/include/asm/pgtable.h   | 13 ++++++++-
> >  arch/riscv/include/asm/processor.h | 47 +++++++++++++++++++++++++-----
> >  3 files changed, 53 insertions(+), 9 deletions(-)
> > 
> > diff --git a/arch/riscv/include/asm/elf.h b/arch/riscv/include/asm/elf.h
> > index c24280774caf..5d3368d5585c 100644
> > --- a/arch/riscv/include/asm/elf.h
> > +++ b/arch/riscv/include/asm/elf.h
> > @@ -49,7 +49,7 @@ extern bool compat_elf_check_arch(Elf32_Ehdr *hdr);
> >   * the loader.  We need to make sure that it is out of the way of the program
> >   * that it will "exec", and that there is sufficient room for the brk.
> >   */
> > -#define ELF_ET_DYN_BASE		((TASK_SIZE / 3) * 2)
> > +#define ELF_ET_DYN_BASE		((DEFAULT_MAP_WINDOW / 3) * 2)
> >  
> >  #ifdef CONFIG_64BIT
> >  #ifdef CONFIG_COMPAT
> > diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h
> > index 75970ee2bda2..530f6a171a2b 100644
> > --- a/arch/riscv/include/asm/pgtable.h
> > +++ b/arch/riscv/include/asm/pgtable.h
> > @@ -63,12 +63,23 @@
> >   * position vmemmap directly below the VMALLOC region.
> >   */
> >  #ifdef CONFIG_64BIT
> > +#define VA_BITS_SV39 39
> > +#define VA_BITS_SV48 48
> > +#define VA_BITS_SV57 57
> > +
> > +#define VA_USER_SV39 (UL(1) << (VA_BITS_SV39 - 1))
> > +#define VA_USER_SV48 (UL(1) << (VA_BITS_SV48 - 1))
> > +#define VA_USER_SV57 (UL(1) << (VA_BITS_SV57 - 1))
> > +
> >  #define VA_BITS		(pgtable_l5_enabled ? \
> > -				57 : (pgtable_l4_enabled ? 48 : 39))
> > +				VA_BITS_SV57 : (pgtable_l4_enabled ? VA_BITS_SV48 : VA_BITS_SV39))
> >  #else
> >  #define VA_BITS		32
> >  #endif
> 
> Please, at the very least, build test things for rv32 if you are going
> to change things in mm:
> io_uring/io_uring.c:3457:20: error: use of undeclared identifier 'VA_BITS_SV39'
> io_uring/io_uring.c:3457:20: error: use of undeclared identifier 'VA_BITS_SV39'
> io_uring/io_uring.c:3457:20: error: use of undeclared identifier 'VA_BITS_SV39'
> io_uring/io_uring.c:3457:20: error: use of undeclared identifier 'VA_BITS_SV39'
> io_uring/io_uring.c:3457:20: error: use of undeclared identifier 'VA_BITS_SV39'
> io_uring/io_uring.c:3457:20: error: use of undeclared identifier 'VA_BITS_SV39'
> mm/util.c:441:19: error: use of undeclared identifier 'VA_BITS_SV39'
> mm/util.c:441:19: error: use of undeclared identifier 'VA_BITS_SV39'
> mm/util.c:441:19: error: use of undeclared identifier 'VA_BITS_SV39'
> mm/util.c:441:19: error: use of undeclared identifier 'VA_BITS_SV39'
> mm/util.c:441:19: error: use of undeclared identifier 'VA_BITS_SV39'
> mm/util.c:441:19: error: use of undeclared identifier 'VA_BITS_SV39'
> mm/mmap.c:1770:20: error: use of undeclared identifier 'VA_BITS_SV39'
> mm/mmap.c:1770:20: error: use of undeclared identifier 'VA_BITS_SV39'
> mm/mmap.c:1770:20: error: use of undeclared identifier 'VA_BITS_SV39'
> mm/mmap.c:1770:20: error: use of undeclared identifier 'VA_BITS_SV39'
> mm/mmap.c:1770:20: error: use of undeclared identifier 'VA_BITS_SV39'
> mm/mmap.c:1770:20: error: use of undeclared identifier 'VA_BITS_SV39'
> 
> Thanks,
> Conor.
Thanks for that catch, I sent out a new patch to fix that up. There were
also some problems with 32-bit compat support that I resolved.