linux-kernel - Re: [PATCH v2 04/10] riscv: Implement sv48 support

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Date:   Sun, 3 Oct 2021 20:34:10 -0500
From:   Samuel Holland <samuel@...lland.org>
To:     Alexandre Ghiti <alexandre.ghiti@...onical.com>
Cc:     Jonathan Corbet <corbet@....net>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Zong Li <zong.li@...ive.com>, Anup Patel <anup@...infault.org>,
        Atish Patra <Atish.Patra@....com>,
        Christoph Hellwig <hch@....de>,
        Andrey Ryabinin <ryabinin.a.a@...il.com>,
        Alexander Potapenko <glider@...gle.com>,
        Andrey Konovalov <andreyknvl@...il.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Ard Biesheuvel <ardb@...nel.org>,
        Arnd Bergmann <arnd@...db.de>,
        Kees Cook <keescook@...omium.org>,
        Guo Ren <guoren@...ux.alibaba.com>,
        Heinrich Schuchardt <heinrich.schuchardt@...onical.com>,
        Mayuresh Chitale <mchitale@...tanamicro.com>,
        linux-doc@...r.kernel.org, linux-riscv@...ts.infradead.org,
        linux-kernel@...r.kernel.org, kasan-dev@...glegroups.com,
        linux-efi@...r.kernel.org, linux-arch@...r.kernel.org
Subject: Re: [PATCH v2 04/10] riscv: Implement sv48 support

On 9/29/21 9:51 AM, Alexandre Ghiti wrote:
> By adding a new 4th level of page table, give the possibility to 64bit
> kernel to address 2^48 bytes of virtual address: in practice, that offers
> 128TB of virtual address space to userspace and allows up to 64TB of
> physical memory.
> 
> If the underlying hardware does not support sv48, we will automatically
> fallback to a standard 3-level page table by folding the new PUD level into
> PGDIR level. In order to detect HW capabilities at runtime, we
> use SATP feature that ignores writes with an unsupported mode.
> 
> Signed-off-by: Alexandre Ghiti <alexandre.ghiti@...onical.com>
> ---
>  arch/riscv/Kconfig                      |   4 +-
>  arch/riscv/include/asm/csr.h            |   3 +-
>  arch/riscv/include/asm/fixmap.h         |   1 +
>  arch/riscv/include/asm/kasan.h          |   2 +-
>  arch/riscv/include/asm/page.h           |  10 +
>  arch/riscv/include/asm/pgalloc.h        |  40 ++++
>  arch/riscv/include/asm/pgtable-64.h     | 108 ++++++++++-
>  arch/riscv/include/asm/pgtable.h        |  13 +-
>  arch/riscv/kernel/head.S                |   3 +-
>  arch/riscv/mm/context.c                 |   4 +-
>  arch/riscv/mm/init.c                    | 237 ++++++++++++++++++++----
>  arch/riscv/mm/kasan_init.c              |  91 +++++++--
>  drivers/firmware/efi/libstub/efi-stub.c |   2 +
>  13 files changed, 453 insertions(+), 65 deletions(-)
> 
> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> index 13e9c4298fbc..69c5533955ed 100644
> --- a/arch/riscv/Kconfig
> +++ b/arch/riscv/Kconfig
> @@ -149,7 +149,7 @@ config PAGE_OFFSET
>  	hex
>  	default 0xC0000000 if 32BIT
>  	default 0x80000000 if 64BIT && !MMU
> -	default 0xffffffe000000000 if 64BIT
> +	default 0xffffc00000000000 if 64BIT
>  
>  config ARCH_FLATMEM_ENABLE
>  	def_bool !NUMA
> @@ -197,7 +197,7 @@ config FIX_EARLYCON_MEM
>  
>  config PGTABLE_LEVELS
>  	int
> -	default 3 if 64BIT
> +	default 4 if 64BIT
>  	default 2
>  
>  config LOCKDEP_SUPPORT
> diff --git a/arch/riscv/include/asm/csr.h b/arch/riscv/include/asm/csr.h
> index 87ac65696871..3fdb971c7896 100644
> --- a/arch/riscv/include/asm/csr.h
> +++ b/arch/riscv/include/asm/csr.h
> @@ -40,14 +40,13 @@
>  #ifndef CONFIG_64BIT
>  #define SATP_PPN	_AC(0x003FFFFF, UL)
>  #define SATP_MODE_32	_AC(0x80000000, UL)
> -#define SATP_MODE	SATP_MODE_32
>  #define SATP_ASID_BITS	9
>  #define SATP_ASID_SHIFT	22
>  #define SATP_ASID_MASK	_AC(0x1FF, UL)
>  #else
>  #define SATP_PPN	_AC(0x00000FFFFFFFFFFF, UL)
>  #define SATP_MODE_39	_AC(0x8000000000000000, UL)
> -#define SATP_MODE	SATP_MODE_39
> +#define SATP_MODE_48	_AC(0x9000000000000000, UL)
>  #define SATP_ASID_BITS	16
>  #define SATP_ASID_SHIFT	44
>  #define SATP_ASID_MASK	_AC(0xFFFF, UL)
> diff --git a/arch/riscv/include/asm/fixmap.h b/arch/riscv/include/asm/fixmap.h
> index 54cbf07fb4e9..58a718573ad6 100644
> --- a/arch/riscv/include/asm/fixmap.h
> +++ b/arch/riscv/include/asm/fixmap.h
> @@ -24,6 +24,7 @@ enum fixed_addresses {
>  	FIX_HOLE,
>  	FIX_PTE,
>  	FIX_PMD,
> +	FIX_PUD,
>  	FIX_TEXT_POKE1,
>  	FIX_TEXT_POKE0,
>  	FIX_EARLYCON_MEM_BASE,
> diff --git a/arch/riscv/include/asm/kasan.h b/arch/riscv/include/asm/kasan.h
> index a2b3d9cdbc86..1dcf5fa93aa0 100644
> --- a/arch/riscv/include/asm/kasan.h
> +++ b/arch/riscv/include/asm/kasan.h
> @@ -27,7 +27,7 @@
>   */
>  #define KASAN_SHADOW_SCALE_SHIFT	3
>  
> -#define KASAN_SHADOW_SIZE	(UL(1) << ((CONFIG_VA_BITS - 1) - KASAN_SHADOW_SCALE_SHIFT))
> +#define KASAN_SHADOW_SIZE	(UL(1) << ((VA_BITS - 1) - KASAN_SHADOW_SCALE_SHIFT))

Does this change belong in patch 1, where you remove CONFIG_VA_BITS?

Regards,
Samuel