linux-kernel - Re: [PATCH v3 1/4] RISC-V: Fix compilation without RISCV_ISA

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Message-ID: <5869751.lOV4Wx5bFT@phil>
Date:   Wed, 19 Oct 2022 14:30:50 +0200
From:   Heiko Stuebner <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,
        Andrew Jones <ajones@...tanamicro.com>,
        kernel test robot <lkp@...el.com>,
        Anup Patel <apatel@...tanamicro.com>,
        Conor Dooley <conor.dooley@...rochip.com>
Subject: Re: [PATCH v3 1/4] RISC-V: Fix compilation without RISCV_ISA_ZICBOM

Hi Anup,

Am Mittwoch, 19. Oktober 2022, 14:16:19 CEST schrieb Anup Patel:
> From: Andrew Jones <ajones@...tanamicro.com>
> 
> riscv_cbom_block_size and riscv_init_cbom_blocksize() should always
> be available and riscv_init_cbom_blocksize() should always be
> invoked, even when compiling without RISCV_ISA_ZICBOM enabled. This
> is because disabling RISCV_ISA_ZICBOM means "don't use zicbom
> instructions in the kernel" not "pretend there isn't zicbom, even
> when there is". When zicbom is available, whether the kernel enables
> its use with RISCV_ISA_ZICBOM or not, KVM will offer it to guests.
> Ensure we can build KVM and that the block size is initialized even
> when compiling without RISCV_ISA_ZICBOM.

either I'm way very low on coffee or something is strange here :-) .

I can fully grasp the need to init the cbom blocksize for guests, even when
the main kernel isn't using it, but below in the patch itself it is still:

+#ifdef CONFIG_RISCV_ISA_ZICBOM
+void riscv_init_cbom_blocksize(void)
+{
[...]

so the init_cbom_blocksize function is still inside a RISCV_ISA_ZICBOM
ifdef?


Heiko


> 
> Fixes: 8f7e001e0325 ("RISC-V: Clean up the Zicbom block size probing")
> Reported-by: kernel test robot <lkp@...el.com>
> Signed-off-by: Andrew Jones <ajones@...tanamicro.com>
> Signed-off-by: Anup Patel <apatel@...tanamicro.com>
> Reviewed-by: Conor Dooley <conor.dooley@...rochip.com>
> ---
>  arch/riscv/mm/cacheflush.c      | 41 +++++++++++++++++++++++++++++++++
>  arch/riscv/mm/dma-noncoherent.c | 41 ---------------------------------
>  2 files changed, 41 insertions(+), 41 deletions(-)
> 
> diff --git a/arch/riscv/mm/cacheflush.c b/arch/riscv/mm/cacheflush.c
> index 6cb7d96ad9c7..f318b2553612 100644
> --- a/arch/riscv/mm/cacheflush.c
> +++ b/arch/riscv/mm/cacheflush.c
> @@ -3,6 +3,8 @@
>   * Copyright (C) 2017 SiFive
>   */
>  
> +#include <linux/of.h>
> +#include <linux/of_device.h>
>  #include <asm/cacheflush.h>
>  
>  #ifdef CONFIG_SMP
> @@ -86,3 +88,42 @@ void flush_icache_pte(pte_t pte)
>  		flush_icache_all();
>  }
>  #endif /* CONFIG_MMU */
> +
> +unsigned int riscv_cbom_block_size;
> +EXPORT_SYMBOL_GPL(riscv_cbom_block_size);
> +
> +#ifdef CONFIG_RISCV_ISA_ZICBOM
> +void riscv_init_cbom_blocksize(void)
> +{
> +	struct device_node *node;
> +	unsigned long cbom_hartid;
> +	u32 val, probed_block_size;
> +	int ret;
> +
> +	probed_block_size = 0;
> +	for_each_of_cpu_node(node) {
> +		unsigned long hartid;
> +
> +		ret = riscv_of_processor_hartid(node, &hartid);
> +		if (ret)
> +			continue;
> +
> +		/* set block-size for cbom extension if available */
> +		ret = of_property_read_u32(node, "riscv,cbom-block-size", &val);
> +		if (ret)
> +			continue;
> +
> +		if (!probed_block_size) {
> +			probed_block_size = val;
> +			cbom_hartid = hartid;
> +		} else {
> +			if (probed_block_size != val)
> +				pr_warn("cbom-block-size mismatched between harts %lu and %lu\n",
> +					cbom_hartid, hartid);
> +		}
> +	}
> +
> +	if (probed_block_size)
> +		riscv_cbom_block_size = probed_block_size;
> +}
> +#endif
> diff --git a/arch/riscv/mm/dma-noncoherent.c b/arch/riscv/mm/dma-noncoherent.c
> index b0add983530a..d919efab6eba 100644
> --- a/arch/riscv/mm/dma-noncoherent.c
> +++ b/arch/riscv/mm/dma-noncoherent.c
> @@ -8,13 +8,8 @@
>  #include <linux/dma-direct.h>
>  #include <linux/dma-map-ops.h>
>  #include <linux/mm.h>
> -#include <linux/of.h>
> -#include <linux/of_device.h>
>  #include <asm/cacheflush.h>
>  
> -unsigned int riscv_cbom_block_size;
> -EXPORT_SYMBOL_GPL(riscv_cbom_block_size);
> -
>  static bool noncoherent_supported;
>  
>  void arch_sync_dma_for_device(phys_addr_t paddr, size_t size,
> @@ -77,42 +72,6 @@ void arch_setup_dma_ops(struct device *dev, u64 dma_base, u64 size,
>  	dev->dma_coherent = coherent;
>  }
>  
> -#ifdef CONFIG_RISCV_ISA_ZICBOM
> -void riscv_init_cbom_blocksize(void)
> -{
> -	struct device_node *node;
> -	unsigned long cbom_hartid;
> -	u32 val, probed_block_size;
> -	int ret;
> -
> -	probed_block_size = 0;
> -	for_each_of_cpu_node(node) {
> -		unsigned long hartid;
> -
> -		ret = riscv_of_processor_hartid(node, &hartid);
> -		if (ret)
> -			continue;
> -
> -		/* set block-size for cbom extension if available */
> -		ret = of_property_read_u32(node, "riscv,cbom-block-size", &val);
> -		if (ret)
> -			continue;
> -
> -		if (!probed_block_size) {
> -			probed_block_size = val;
> -			cbom_hartid = hartid;
> -		} else {
> -			if (probed_block_size != val)
> -				pr_warn("cbom-block-size mismatched between harts %lu and %lu\n",
> -					cbom_hartid, hartid);
> -		}
> -	}
> -
> -	if (probed_block_size)
> -		riscv_cbom_block_size = probed_block_size;
> -}
> -#endif
> -
>  void riscv_noncoherent_supported(void)
>  {
>  	WARN(!riscv_cbom_block_size,
>