From: Alex Ghiti <alex@ghiti.fr> To: Geert Uytterhoeven <geert+renesas@glider.be>, Paul Walmsley <paul.walmsley@sifive.com>, Palmer Dabbelt <palmer@dabbelt.com>, Albert Ou <aou@eecs.berkeley.edu> Cc: Damien Le Moal <damien.lemoal@wdc.com>, Arnd Bergmann <arnd@arndb.de>, linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] riscv: Only extend kernel reservation if mapped read-only Date: Thu, 29 Apr 2021 10:09:53 -0400 [thread overview] Message-ID: <605dc5e8-0a41-7458-6037-d6263b0ffd59@ghiti.fr> (raw) In-Reply-To: <1a7660125046b94db9c6a7d62aa0ce88c8cd2f1d.1619617340.git.geert+renesas@glider.be> Hi Geert, Le 4/28/21 à 9:45 AM, Geert Uytterhoeven a écrit : > When the kernel mapping was moved outside of the linear mapping, the > kernel memory reservation was increased, to take into account mapping > granularity. However, this is done unconditionally, regardless of > whether the kernel memory is mapped read-only or not. > > If this extension is not needed, up to 2 MiB may be lost, which has a > big impact on e.g. Canaan K210 (64-bit nommu) platforms with only 8 MiB > of RAM. > > Reclaim the lost memory by only extending the reserved region when > needed, i.e. matching the conditional logic around the call to > protect_kernel_linear_mapping_text_rodata(). > > Fixes: 2bfc6cd81bd17e43 ("riscv: Move kernel mapping outside of linear mapping") > Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be> > --- > Only tested on K210 (SiPeed MAIX BiT): > > -Memory: 5852K/8192K available (1344K kernel code, 147K rwdata, 272K rodata, 106K init, 72K bss, 2340K reserved, 0K cma-reserved) > +Memory: 5948K/8192K available (1344K kernel code, 147K rwdata, 272K rodata, 106K init, 72K bss, 2244K reserved, 0K cma-reserved) > > Yes, I was lucky, as only 96 KiB was lost ;-) > --- > arch/riscv/mm/init.c | 10 ++++++++-- > 1 file changed, 8 insertions(+), 2 deletions(-) > > diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c > index 788eb222deacf994..3439783f26abc488 100644 > --- a/arch/riscv/mm/init.c > +++ b/arch/riscv/mm/init.c > @@ -136,11 +136,17 @@ void __init setup_bootmem(void) > > /* > * Reserve from the start of the kernel to the end of the kernel > - * and make sure we align the reservation on PMD_SIZE since we will > + */ > +#if defined(CONFIG_STRICT_KERNEL_RWX) && defined(CONFIG_64BIT) && \ > + defined(CONFIG_MMU) && !defined(CONFIG_XIP_KERNEL) ARCH_HAS_STRICT_KERNEL_RWX depends on MMU and !XIP_KERNEL so I think you can get rid of those checks. > + /* > + * Make sure we align the reservation on PMD_SIZE since we will > * map the kernel in the linear mapping as read-only: we do not want > * any allocation to happen between _end and the next pmd aligned page. > */ > - memblock_reserve(vmlinux_start, (vmlinux_end - vmlinux_start + PMD_SIZE - 1) & PMD_MASK); > + vmlinux_end = (vmlinux_end + PMD_SIZE - 1) & PMD_MASK; > +#endif > + memblock_reserve(vmlinux_start, vmlinux_end - vmlinux_start); > > /* > * memblock allocator is not aware of the fact that last 4K bytes of > Thanks for fixing this, Alex
WARNING: multiple messages have this Message-ID (diff)
From: Alex Ghiti <alex@ghiti.fr> To: Geert Uytterhoeven <geert+renesas@glider.be>, Paul Walmsley <paul.walmsley@sifive.com>, Palmer Dabbelt <palmer@dabbelt.com>, Albert Ou <aou@eecs.berkeley.edu> Cc: Damien Le Moal <damien.lemoal@wdc.com>, Arnd Bergmann <arnd@arndb.de>, linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] riscv: Only extend kernel reservation if mapped read-only Date: Thu, 29 Apr 2021 10:09:53 -0400 [thread overview] Message-ID: <605dc5e8-0a41-7458-6037-d6263b0ffd59@ghiti.fr> (raw) In-Reply-To: <1a7660125046b94db9c6a7d62aa0ce88c8cd2f1d.1619617340.git.geert+renesas@glider.be> Hi Geert, Le 4/28/21 à 9:45 AM, Geert Uytterhoeven a écrit : > When the kernel mapping was moved outside of the linear mapping, the > kernel memory reservation was increased, to take into account mapping > granularity. However, this is done unconditionally, regardless of > whether the kernel memory is mapped read-only or not. > > If this extension is not needed, up to 2 MiB may be lost, which has a > big impact on e.g. Canaan K210 (64-bit nommu) platforms with only 8 MiB > of RAM. > > Reclaim the lost memory by only extending the reserved region when > needed, i.e. matching the conditional logic around the call to > protect_kernel_linear_mapping_text_rodata(). > > Fixes: 2bfc6cd81bd17e43 ("riscv: Move kernel mapping outside of linear mapping") > Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be> > --- > Only tested on K210 (SiPeed MAIX BiT): > > -Memory: 5852K/8192K available (1344K kernel code, 147K rwdata, 272K rodata, 106K init, 72K bss, 2340K reserved, 0K cma-reserved) > +Memory: 5948K/8192K available (1344K kernel code, 147K rwdata, 272K rodata, 106K init, 72K bss, 2244K reserved, 0K cma-reserved) > > Yes, I was lucky, as only 96 KiB was lost ;-) > --- > arch/riscv/mm/init.c | 10 ++++++++-- > 1 file changed, 8 insertions(+), 2 deletions(-) > > diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c > index 788eb222deacf994..3439783f26abc488 100644 > --- a/arch/riscv/mm/init.c > +++ b/arch/riscv/mm/init.c > @@ -136,11 +136,17 @@ void __init setup_bootmem(void) > > /* > * Reserve from the start of the kernel to the end of the kernel > - * and make sure we align the reservation on PMD_SIZE since we will > + */ > +#if defined(CONFIG_STRICT_KERNEL_RWX) && defined(CONFIG_64BIT) && \ > + defined(CONFIG_MMU) && !defined(CONFIG_XIP_KERNEL) ARCH_HAS_STRICT_KERNEL_RWX depends on MMU and !XIP_KERNEL so I think you can get rid of those checks. > + /* > + * Make sure we align the reservation on PMD_SIZE since we will > * map the kernel in the linear mapping as read-only: we do not want > * any allocation to happen between _end and the next pmd aligned page. > */ > - memblock_reserve(vmlinux_start, (vmlinux_end - vmlinux_start + PMD_SIZE - 1) & PMD_MASK); > + vmlinux_end = (vmlinux_end + PMD_SIZE - 1) & PMD_MASK; > +#endif > + memblock_reserve(vmlinux_start, vmlinux_end - vmlinux_start); > > /* > * memblock allocator is not aware of the fact that last 4K bytes of > Thanks for fixing this, Alex _______________________________________________ linux-riscv mailing list linux-riscv@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-riscv
next prev parent reply other threads:[~2021-04-29 14:10 UTC|newest] Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-04-28 13:45 [PATCH] riscv: Only extend kernel reservation if mapped read-only Geert Uytterhoeven 2021-04-28 13:45 ` Geert Uytterhoeven 2021-04-29 14:09 ` Alex Ghiti [this message] 2021-04-29 14:09 ` Alex Ghiti 2021-04-29 14:41 ` Geert Uytterhoeven 2021-04-29 14:41 ` Geert Uytterhoeven
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