linux-kernel - [PATCH 5.15.y] xen: replace xen

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Message-Id: <2398723b73ddd9923a9bb994364c2c7d3b89d21d.1751446695.git.teddy.astie@vates.tech>
Date: Wed, 02 Jul 2025 09:14:39 +0000
From: "Teddy Astie" <teddy.astie@...es.tech>
To: linux-kernel@...r.kernel.org, xen-devel@...ts.xenproject.org
Cc: "Teddy Astie" <teddy.astie@...es.tech>, "Boris Ostrovsky" <boris.ostrovsky@...cle.com>, "Juergen Gross" <jgross@...e.com>, "Stefano Stabellini" <sstabellini@...nel.org>, "Greg Kroah-Hartman" <gregkh@...uxfoundation.org>, "Sasha Levin" <sashal@...nel.org>, "Jason Andryuk" <jason.andryuk@....com>, stable@...r.kernel.org, "kernel test robot" <lkp@...el.com>
Subject: [PATCH 5.15.y] xen: replace xen_remap() with memremap()

From: Juergen Gross <jgross@...e.com>

[ upstream commit 41925b105e345ebc84cedb64f59d20cb14a62613 ]

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>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@...cle.com>
Acked-by: Stefano Stabellini <sstabellini@...nel.org>
Link: https://lore.kernel.org/r/20220530082634.6339-1-jgross@suse.com
Signed-off-by: Juergen Gross <jgross@...e.com>
Signed-off-by: Teddy Astie <teddy.astie@...es.tech> [backport to 5.15.y]
---
 arch/x86/include/asm/xen/page.h   | 3 ---
 drivers/xen/grant-table.c         | 6 +++---
 drivers/xen/xenbus/xenbus_probe.c | 3 +--
 3 files changed, 4 insertions(+), 8 deletions(-)

diff --git a/arch/x86/include/asm/xen/page.h b/arch/x86/include/asm/xen/page.h
index 1a162e559753..c183b7f9efef 100644
--- a/arch/x86/include/asm/xen/page.h
+++ b/arch/x86/include/asm/xen/page.h
@@ -355,9 +355,6 @@ 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/xen/grant-table.c b/drivers/xen/grant-table.c
index 0a2d24d6ac6f..a10e0741bec5 100644
--- a/drivers/xen/grant-table.c
+++ b/drivers/xen/grant-table.c
@@ -743,7 +743,7 @@ 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);
@@ -751,7 +751,7 @@ 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++)
@@ -770,7 +770,7 @@ 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 2068f83556b7..77ca24611293 100644
--- a/drivers/xen/xenbus/xenbus_probe.c
+++ b/drivers/xen/xenbus/xenbus_probe.c
@@ -982,8 +982,7 @@ 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);
 		break;
 	default:
 		pr_warn("Xenstore state unknown\n");
-- 
2.50.0



Teddy Astie | Vates XCP-ng Developer

XCP-ng & Xen Orchestra - Vates solutions

web: https://vates.tech