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Date:   Tue, 31 May 2022 17:13:45 -0700 (PDT)
From:   Stefano Stabellini <sstabellini@kernel.org>
To:     Juergen Gross <jgross@suse.com>
cc:     xen-devel@lists.xenproject.org, x86@kernel.org,
        linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
        Boris Ostrovsky <boris.ostrovsky@oracle.com>,
        Stefano Stabellini <sstabellini@kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        "H. Peter Anvin" <hpa@zytor.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Jiri Slaby <jirislaby@kernel.org>,
        kernel test robot <lkp@intel.com>
Subject: Re: [PATCH] xen: replace xen_remap() with memremap()
In-Reply-To: <20220530082634.6339-1-jgross@suse.com>
Message-ID: <alpine.DEB.2.22.394.2205311713270.1905099@ubuntu-linux-20-04-desktop>
References: <20220530082634.6339-1-jgross@suse.com>
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On Mon, 30 May 2022, Juergen Gross wrote:
> xen_remap() is used to establish mappings for frames not under direct
> control of the kernel: for Xenstore and console ring pages, and for
> grant pages of non-PV guests.
> 
> Today xen_remap() is defined to use ioremap() on x86 (doing uncached
> mappings), and ioremap_cache() on Arm (doing cached mappings).
> 
> Uncached mappings for those use cases are bad for performance, so they
> should be avoided if possible. As all use cases of xen_remap() don't
> require uncached mappings (the mapped area is always physical RAM),
> a mapping using the standard WB cache mode is fine.
> 
> As sparse is flagging some of the xen_remap() use cases to be not
> appropriate for iomem(), as the result is not annotated with the
> __iomem modifier, eliminate xen_remap() completely and replace all
> use cases with memremap() specifying the MEMREMAP_WB caching mode.
> 
> xen_unmap() can be replaced with memunmap().
> 
> Reported-by: kernel test robot <lkp@intel.com>
> Signed-off-by: Juergen Gross <jgross@suse.com>

Acked-by: Stefano Stabellini <sstabellini@kernel.org>


> ---
>  arch/x86/include/asm/xen/page.h   | 3 ---
>  drivers/tty/hvc/hvc_xen.c         | 2 +-
>  drivers/xen/grant-table.c         | 6 +++---
>  drivers/xen/xenbus/xenbus_probe.c | 8 ++++----
>  include/xen/arm/page.h            | 3 ---
>  5 files changed, 8 insertions(+), 14 deletions(-)
> 
> diff --git a/arch/x86/include/asm/xen/page.h b/arch/x86/include/asm/xen/page.h
> index 1fc67df50014..fa9ec20783fa 100644
> --- a/arch/x86/include/asm/xen/page.h
> +++ b/arch/x86/include/asm/xen/page.h
> @@ -347,9 +347,6 @@ unsigned long arbitrary_virt_to_mfn(void *vaddr);
>  void make_lowmem_page_readonly(void *vaddr);
>  void make_lowmem_page_readwrite(void *vaddr);
>  
> -#define xen_remap(cookie, size) ioremap((cookie), (size))
> -#define xen_unmap(cookie) iounmap((cookie))
> -
>  static inline bool xen_arch_need_swiotlb(struct device *dev,
>  					 phys_addr_t phys,
>  					 dma_addr_t dev_addr)
> diff --git a/drivers/tty/hvc/hvc_xen.c b/drivers/tty/hvc/hvc_xen.c
> index ebaf7500f48f..7c23112dc923 100644
> --- a/drivers/tty/hvc/hvc_xen.c
> +++ b/drivers/tty/hvc/hvc_xen.c
> @@ -253,7 +253,7 @@ static int xen_hvm_console_init(void)
>  	if (r < 0 || v == 0)
>  		goto err;
>  	gfn = v;
> -	info->intf = xen_remap(gfn << XEN_PAGE_SHIFT, XEN_PAGE_SIZE);
> +	info->intf = memremap(gfn << XEN_PAGE_SHIFT, XEN_PAGE_SIZE, MEMREMAP_WB);
>  	if (info->intf == NULL)
>  		goto err;
>  	info->vtermno = HVC_COOKIE;
> diff --git a/drivers/xen/grant-table.c b/drivers/xen/grant-table.c
> index 1a1aec0a88a1..2f4f0ed5d8f8 100644
> --- a/drivers/xen/grant-table.c
> +++ b/drivers/xen/grant-table.c
> @@ -632,7 +632,7 @@ int gnttab_setup_auto_xlat_frames(phys_addr_t addr)
>  	if (xen_auto_xlat_grant_frames.count)
>  		return -EINVAL;
>  
> -	vaddr = xen_remap(addr, XEN_PAGE_SIZE * max_nr_gframes);
> +	vaddr = memremap(addr, XEN_PAGE_SIZE * max_nr_gframes, MEMREMAP_WB);
>  	if (vaddr == NULL) {
>  		pr_warn("Failed to ioremap gnttab share frames (addr=%pa)!\n",
>  			&addr);
> @@ -640,7 +640,7 @@ int gnttab_setup_auto_xlat_frames(phys_addr_t addr)
>  	}
>  	pfn = kcalloc(max_nr_gframes, sizeof(pfn[0]), GFP_KERNEL);
>  	if (!pfn) {
> -		xen_unmap(vaddr);
> +		memunmap(vaddr);
>  		return -ENOMEM;
>  	}
>  	for (i = 0; i < max_nr_gframes; i++)
> @@ -659,7 +659,7 @@ void gnttab_free_auto_xlat_frames(void)
>  	if (!xen_auto_xlat_grant_frames.count)
>  		return;
>  	kfree(xen_auto_xlat_grant_frames.pfn);
> -	xen_unmap(xen_auto_xlat_grant_frames.vaddr);
> +	memunmap(xen_auto_xlat_grant_frames.vaddr);
>  
>  	xen_auto_xlat_grant_frames.pfn = NULL;
>  	xen_auto_xlat_grant_frames.count = 0;
> diff --git a/drivers/xen/xenbus/xenbus_probe.c b/drivers/xen/xenbus/xenbus_probe.c
> index d367f2bd2b93..58b732dcbfb8 100644
> --- a/drivers/xen/xenbus/xenbus_probe.c
> +++ b/drivers/xen/xenbus/xenbus_probe.c
> @@ -752,8 +752,8 @@ static void xenbus_probe(void)
>  	xenstored_ready = 1;
>  
>  	if (!xen_store_interface) {
> -		xen_store_interface = xen_remap(xen_store_gfn << XEN_PAGE_SHIFT,
> -						XEN_PAGE_SIZE);
> +		xen_store_interface = memremap(xen_store_gfn << XEN_PAGE_SHIFT,
> +					       XEN_PAGE_SIZE, MEMREMAP_WB);
>  		/*
>  		 * Now it is safe to free the IRQ used for xenstore late
>  		 * initialization. No need to unbind: it is about to be
> @@ -1009,8 +1009,8 @@ static int __init xenbus_init(void)
>  #endif
>  			xen_store_gfn = (unsigned long)v;
>  			xen_store_interface =
> -				xen_remap(xen_store_gfn << XEN_PAGE_SHIFT,
> -					  XEN_PAGE_SIZE);
> +				memremap(xen_store_gfn << XEN_PAGE_SHIFT,
> +					 XEN_PAGE_SIZE, MEMREMAP_WB);
>  			if (xen_store_interface->connection != XENSTORE_CONNECTED)
>  				wait = true;
>  		}
> diff --git a/include/xen/arm/page.h b/include/xen/arm/page.h
> index 7e199c6656b9..e5c84ff28c8b 100644
> --- a/include/xen/arm/page.h
> +++ b/include/xen/arm/page.h
> @@ -109,9 +109,6 @@ static inline bool set_phys_to_machine(unsigned long pfn, unsigned long mfn)
>  	return __set_phys_to_machine(pfn, mfn);
>  }
>  
> -#define xen_remap(cookie, size) ioremap_cache((cookie), (size))
> -#define xen_unmap(cookie) iounmap((cookie))
> -
>  bool xen_arch_need_swiotlb(struct device *dev,
>  			   phys_addr_t phys,
>  			   dma_addr_t dev_addr);
> -- 
> 2.35.3
>