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Message-ID: <alpine.DEB.2.22.394.2205311713270.1905099@ubuntu-linux-20-04-desktop>
Date: Tue, 31 May 2022 17:13:45 -0700 (PDT)
From: Stefano Stabellini <sstabellini@...nel.org>
To: Juergen Gross <jgross@...e.com>
cc: xen-devel@...ts.xenproject.org, x86@...nel.org,
linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
Boris Ostrovsky <boris.ostrovsky@...cle.com>,
Stefano Stabellini <sstabellini@...nel.org>,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
Dave Hansen <dave.hansen@...ux.intel.com>,
"H. Peter Anvin" <hpa@...or.com>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Jiri Slaby <jirislaby@...nel.org>,
kernel test robot <lkp@...el.com>
Subject: Re: [PATCH] xen: replace xen_remap() with memremap()
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@...el.com>
> Signed-off-by: Juergen Gross <jgross@...e.com>
Acked-by: Stefano Stabellini <sstabellini@...nel.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
>
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