From: Alexandre Ghiti <alexandre.ghiti@canonical.com>
To: Jonathan Corbet <corbet@lwn.net>,
Paul Walmsley <paul.walmsley@sifive.com>,
Palmer Dabbelt <palmer@dabbelt.com>,
Albert Ou <aou@eecs.berkeley.edu>, Zong Li <zong.li@sifive.com>,
Anup Patel <anup@brainfault.org>,
Atish Patra <Atish.Patra@wdc.com>, Christoph Hellwig <hch@lst.de>,
Andrey Ryabinin <ryabinin.a.a@gmail.com>,
Alexander Potapenko <glider@google.com>,
Andrey Konovalov <andreyknvl@gmail.com>,
Dmitry Vyukov <dvyukov@google.com>,
Ard Biesheuvel <ardb@kernel.org>, Arnd Bergmann <arnd@arndb.de>,
Kees Cook <keescook@chromium.org>,
Guo Ren <guoren@linux.alibaba.com>,
Heinrich Schuchardt <heinrich.schuchardt@canonical.com>,
Mayuresh Chitale <mchitale@ventanamicro.com>,
linux-doc@vger.kernel.org, linux-riscv@lists.infradead.org,
linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com,
linux-efi@vger.kernel.org, linux-arch@vger.kernel.org
Cc: Alexandre Ghiti <alexandre.ghiti@canonical.com>,
Palmer Dabbelt <palmerdabbelt@google.com>
Subject: [PATCH v2 06/10] riscv: Explicit comment about user virtual address space size
Date: Wed, 29 Sep 2021 16:51:09 +0200 [thread overview]
Message-ID: <20210929145113.1935778-7-alexandre.ghiti@canonical.com> (raw)
In-Reply-To: <20210929145113.1935778-1-alexandre.ghiti@canonical.com>
Define precisely the size of the user accessible virtual space size
for sv32/39/48 mmu types and explain why the whole virtual address
space is split into 2 equal chunks between kernel and user space.
Signed-off-by: Alexandre Ghiti <alexandre.ghiti@canonical.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
Reviewed-by: Palmer Dabbelt <palmerdabbelt@google.com>
---
arch/riscv/include/asm/pgtable.h | 9 +++++++++
1 file changed, 9 insertions(+)
diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h
index 2f92d61237b4..fd37cc45ef2a 100644
--- a/arch/riscv/include/asm/pgtable.h
+++ b/arch/riscv/include/asm/pgtable.h
@@ -664,6 +664,15 @@ static inline pmd_t pmdp_establish(struct vm_area_struct *vma,
/*
* Task size is 0x4000000000 for RV64 or 0x9fc00000 for RV32.
* Note that PGDIR_SIZE must evenly divide TASK_SIZE.
+ * Task size is:
+ * - 0x9fc00000 (~2.5GB) for RV32.
+ * - 0x4000000000 ( 256GB) for RV64 using SV39 mmu
+ * - 0x800000000000 ( 128TB) for RV64 using SV48 mmu
+ *
+ * Note that PGDIR_SIZE must evenly divide TASK_SIZE since "RISC-V
+ * Instruction Set Manual Volume II: Privileged Architecture" states that
+ * "load and store effective addresses, which are 64bits, must have bits
+ * 63–48 all equal to bit 47, or else a page-fault exception will occur."
*/
#ifdef CONFIG_64BIT
#define TASK_SIZE (PGDIR_SIZE * PTRS_PER_PGD / 2)
--
2.30.2
next prev parent reply other threads:[~2021-09-29 14:57 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-29 14:51 [PATCH v2 00/10] Introduce sv48 support without relocatable kernel Alexandre Ghiti
2021-09-29 14:51 ` [PATCH v2 01/10] riscv: Allow to dynamically define VA_BITS Alexandre Ghiti
2021-09-29 14:51 ` [PATCH v2 02/10] riscv: Get rid of MAXPHYSMEM configs Alexandre Ghiti
2021-09-29 14:51 ` [PATCH v2 03/10] asm-generic: Prepare for riscv use of pud_alloc_one and pud_free Alexandre Ghiti
2021-09-29 14:51 ` [PATCH v2 04/10] riscv: Implement sv48 support Alexandre Ghiti
2021-10-04 1:34 ` Samuel Holland
2021-10-04 7:31 ` Alexandre Ghiti
2021-09-29 14:51 ` [PATCH v2 05/10] riscv: Use pgtable_l4_enabled to output mmu_type in cpuinfo Alexandre Ghiti
2021-09-29 14:51 ` Alexandre Ghiti [this message]
2021-09-29 14:51 ` [PATCH v2 07/10] riscv: Improve virtual kernel memory layout dump Alexandre Ghiti
2021-09-29 14:51 ` [PATCH v2 08/10] Documentation: riscv: Add sv48 description to VM layout Alexandre Ghiti
2021-09-29 14:51 ` [PATCH v2 09/10] riscv: Initialize thread pointer before calling C functions Alexandre Ghiti
2021-09-29 14:51 ` [PATCH v2 10/10] riscv: Allow user to downgrade to sv39 when hw supports sv48 Alexandre Ghiti
2021-11-24 23:29 ` [PATCH v2 00/10] Introduce sv48 support without relocatable kernel Heiko Stübner
2021-12-06 10:49 ` Alexandre ghiti
2021-12-06 11:17 ` Heiko Stübner
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