linux-kernel - Re: [PATCH v2 3/4] RISC-V: Implement arch specific PMEM APIs

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Date:   Thu, 01 Sep 2022 17:38:53 +0200
From:   Heiko Stübner <heiko@...ech.de>
To:     Palmer Dabbelt <palmer@...belt.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Anup Patel <apatel@...tanamicro.com>
Cc:     Atish Patra <atishp@...shpatra.org>,
        Anup Patel <anup@...infault.org>,
        linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Anup Patel <apatel@...tanamicro.com>,
        Mayuresh Chitale <mchitale@...tanamicro.com>
Subject: Re: [PATCH v2 3/4] RISC-V: Implement arch specific PMEM APIs

Hi Anup,

Am Dienstag, 30. August 2022, 06:46:41 CEST schrieb Anup Patel:
> The NVDIMM PMEM driver expects arch specific APIs for cache maintenance
> and if arch does not provide these APIs then NVDIMM PMEM driver will
> always use MEMREMAP_WT to map persistent memory which in-turn maps as
> UC memory type defined by the RISC-V Svpbmt specification.
> 
> Now that the Svpbmt and Zicbom support is available in RISC-V kernel,
> we implement PMEM APIs using ALT_CMO_OP() macros so that the NVDIMM
> PMEM driver can use MEMREMAP_WB to map persistent memory.

Zicbom is detected at runtime, though that kconfig setting changes the
behaviour for the memremap-type at compile-time. So what happens on
systems not using zicbom (or another cmo-variant) ?


Heiko

> Co-developed-by: Mayuresh Chitale <mchitale@...tanamicro.com>
> Signed-off-by: Mayuresh Chitale <mchitale@...tanamicro.com>
> Signed-off-by: Anup Patel <apatel@...tanamicro.com>
> ---
>  arch/riscv/Kconfig     |  1 +
>  arch/riscv/mm/Makefile |  1 +
>  arch/riscv/mm/pmem.c   | 21 +++++++++++++++++++++
>  3 files changed, 23 insertions(+)
>  create mode 100644 arch/riscv/mm/pmem.c
> 
> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> index 0ebd8da388d8..37d6370d29c3 100644
> --- a/arch/riscv/Kconfig
> +++ b/arch/riscv/Kconfig
> @@ -25,6 +25,7 @@ config RISCV
>  	select ARCH_HAS_GIGANTIC_PAGE
>  	select ARCH_HAS_KCOV
>  	select ARCH_HAS_MMIOWB
> +	select ARCH_HAS_PMEM_API
>  	select ARCH_HAS_PTE_SPECIAL
>  	select ARCH_HAS_SET_DIRECT_MAP if MMU
>  	select ARCH_HAS_SET_MEMORY if MMU
> diff --git a/arch/riscv/mm/Makefile b/arch/riscv/mm/Makefile
> index d76aabf4b94d..3b368e547f83 100644
> --- a/arch/riscv/mm/Makefile
> +++ b/arch/riscv/mm/Makefile
> @@ -31,3 +31,4 @@ endif
>  
>  obj-$(CONFIG_DEBUG_VIRTUAL) += physaddr.o
>  obj-$(CONFIG_RISCV_DMA_NONCOHERENT) += dma-noncoherent.o
> +obj-$(CONFIG_ARCH_HAS_PMEM_API) += pmem.o
> diff --git a/arch/riscv/mm/pmem.c b/arch/riscv/mm/pmem.c
> new file mode 100644
> index 000000000000..089df92ae876
> --- /dev/null
> +++ b/arch/riscv/mm/pmem.c
> @@ -0,0 +1,21 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (C) 2022 Ventana Micro Systems Inc.
> + */
> +
> +#include <linux/export.h>
> +#include <linux/libnvdimm.h>
> +
> +#include <asm/cacheflush.h>
> +
> +void arch_wb_cache_pmem(void *addr, size_t size)
> +{
> +	ALT_CMO_OP(clean, addr, size, riscv_cbom_block_size);
> +}
> +EXPORT_SYMBOL_GPL(arch_wb_cache_pmem);
> +
> +void arch_invalidate_pmem(void *addr, size_t size)
> +{
> +	ALT_CMO_OP(inval, addr, size, riscv_cbom_block_size);
> +}
> +EXPORT_SYMBOL_GPL(arch_invalidate_pmem);
>