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Date: Mon, 19 Aug 2019 10:19:01 +0530 From: Anup Patel <anup@...infault.org> To: Christoph Hellwig <hch@...radead.org> Cc: Anup Patel <Anup.Patel@....com>, Palmer Dabbelt <palmer@...ive.com>, Paul Walmsley <paul.walmsley@...ive.com>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, Atish Patra <Atish.Patra@....com>, Alistair Francis <Alistair.Francis@....com>, "linux-riscv@...ts.infradead.org" <linux-riscv@...ts.infradead.org> Subject: Re: [PATCH] RISC-V: Fix FIXMAP area corruption on RV32 systems On Sun, Aug 18, 2019 at 11:49 PM Christoph Hellwig <hch@...radead.org> wrote: > > > +#define FIXADDR_TOP (VMALLOC_START) > > Nit: no need for the braces, the definitions below don't use it > either. Sure, I will update and send v2 soon. > > > +#ifdef CONFIG_64BIT > > +#define FIXADDR_SIZE PMD_SIZE > > +#else > > +#define FIXADDR_SIZE PGDIR_SIZE > > +#endif > > +#define FIXADDR_START (FIXADDR_TOP - FIXADDR_SIZE) > > + > > /* > > - * Task size is 0x4000000000 for RV64 or 0xb800000 for RV32. > > + * Task size is 0x4000000000 for RV64 or 0x9fc00000 for RV32. > > * Note that PGDIR_SIZE must evenly divide TASK_SIZE. > > */ > > #ifdef CONFIG_64BIT > > #define TASK_SIZE (PGDIR_SIZE * PTRS_PER_PGD / 2) > > #else > > -#define TASK_SIZE VMALLOC_START > > +#define TASK_SIZE FIXADDR_START > > #endif > > Mentioning the addresses is a little weird. IMHO this would be > a much nicer place to explain the high-level memory layout, including > maybe a little ASCII art. Also we could have one #ifdef CONFIG_64BIT > for both related values. Last but not least instead of saying that > something should be dividable it would be nice to have a BUILD_BUG_ON > to enforce it. > > Either way we are late in the cycle, so I guess this is ok for now: > > Reviewed-by: Christoph Hellwig <hch@....de> > > But I'd love to see this area improved a little further as it is full > of mine fields. I agree with you. We also have Sparsemem and KASAN patches which touch virtual memory layout so it's important to have virtual memory layout documented clearly. I can add the required documentation as separate patch. I think the best place to add ASCII art would be asm/pgtable.h where all virtual memory related defines are placed. Suggestions?? Regards, Anup
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