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Date: Mon, 11 Jan 2021 09:28:48 +0530 From: Anup Patel <anup@...infault.org> To: Atish Patra <atish.patra@....com> Cc: "linux-kernel@...r.kernel.org List" <linux-kernel@...r.kernel.org>, Albert Ou <aou@...s.berkeley.edu>, Anup Patel <anup.patel@....com>, linux-riscv <linux-riscv@...ts.infradead.org>, Palmer Dabbelt <palmer@...belt.com>, Paul Walmsley <paul.walmsley@...ive.com>, Nick Kossifidis <mick@....forth.gr>, Andrew Morton <akpm@...ux-foundation.org>, Ard Biesheuvel <ardb@...nel.org>, Mike Rapoport <rppt@...nel.org> Subject: Re: [PATCH 2/4] RISC-V: Set current memblock limit On Thu, Jan 7, 2021 at 2:57 PM Atish Patra <atish.patra@....com> wrote: > > Currently, linux kernel can not use last 4k bytes of addressable space because > IS_ERR_VALUE macro treats those as an error. This will be an issue for RV32 > as any memblock allocator potentially allocate chunk of memory from the end > of DRAM (2GB) leading bad address error even though the address was technically > valid. > > Fix this issue by limiting the memblock if available memory spans the entire > address space. > > Signed-off-by: Atish Patra <atish.patra@....com> > --- > arch/riscv/mm/init.c | 16 ++++++++++++++-- > 1 file changed, 14 insertions(+), 2 deletions(-) > > diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c > index bf5379135e39..da53902ef0fc 100644 > --- a/arch/riscv/mm/init.c > +++ b/arch/riscv/mm/init.c > @@ -157,9 +157,10 @@ static void __init setup_initrd(void) > void __init setup_bootmem(void) > { > phys_addr_t mem_start = 0; > - phys_addr_t start, end = 0; > + phys_addr_t start, dram_end, end = 0; > phys_addr_t vmlinux_end = __pa_symbol(&_end); > phys_addr_t vmlinux_start = __pa_symbol(&_start); > + phys_addr_t max_mapped_addr = __pa(PHYS_ADDR_MAX); Using PHYS_ADDR_MAX as the max virtual address does not look right. Better use __pa(~(ulong)0) here. Otherwise looks good to me. Reviewed-by: Anup Patel <anup@...infault.org> > u64 i; > > /* Find the memory region containing the kernel */ > @@ -181,7 +182,18 @@ void __init setup_bootmem(void) > /* Reserve from the start of the kernel to the end of the kernel */ > memblock_reserve(vmlinux_start, vmlinux_end - vmlinux_start); > > - max_pfn = PFN_DOWN(memblock_end_of_DRAM()); > + dram_end = memblock_end_of_DRAM(); > + > + /* > + * memblock allocator is not aware of the fact that last 4K bytes of > + * the addressable memory can not be mapped because of IS_ERR_VALUE > + * macro. Make sure that last 4k bytes are not usable by memblock > + * if end of dram is equal to maximum addressable memory. > + */ > + if (max_mapped_addr == (dram_end - 1)) > + memblock_set_current_limit(max_mapped_addr - 4096); > + > + max_pfn = PFN_DOWN(dram_end); > max_low_pfn = max_pfn; > dma32_phys_limit = min(4UL * SZ_1G, (unsigned long)PFN_PHYS(max_low_pfn)); > set_max_mapnr(max_low_pfn); > -- > 2.25.1 > > > _______________________________________________ > linux-riscv mailing list > linux-riscv@...ts.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-riscv Regards, Anup
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