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Code

x86/EISA: Use memremap() to probe for the EISA BIOS signature

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The area at the 0x0FFFD9 physical location in the PC memory space is
regular memory, traditionally ROM BIOS and more recently a copy of BIOS
code and data in RAM, write-protected.

Therefore use memremap() to get access to it rather than ioremap(),
avoiding issues in virtualization scenarios and complementing changes such
as commit f7750a7956 ("x86, mpparse, x86/acpi, x86/PCI, x86/dmi, SFI: Use
memremap() for RAM mappings") or commit 5997efb967 ("x86/boot: Use
memremap() to map the MPF and MPC data").

Reported-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Maciej W. Rozycki <macro@orcam.me.uk>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/alpine.DEB.2.21.2408242025210.30766@angie.orcam.me.uk
Closes: https://lore.kernel.org/r/20240822095122.736522-1-kirill.shutemov@linux.intel.com
This commit is contained in:
Maciej W. Rozycki 2024-08-24 23:17:10 +01:00 committed by Thomas Gleixner
parent 741fc1d788
commit 80a4da0564
1 changed files with 3 additions and 3 deletions
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6
arch/x86/kernel/eisa.c
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@ -11,15 +11,15 @@
static __init int eisa_bus_probe(void) static __init int eisa_bus_probe(void)
{ {
void __iomem *p; void *p;
if ((xen_pv_domain() && !xen_initial_domain()) || cc_platform_has(CC_ATTR_GUEST_SEV_SNP)) if ((xen_pv_domain() && !xen_initial_domain()) || cc_platform_has(CC_ATTR_GUEST_SEV_SNP))
return 0; return 0;
p = ioremap(0x0FFFD9, 4); p = memremap(0x0FFFD9, 4, MEMREMAP_WB);
if (p && readl(p) == 'E' + ('I' << 8) + ('S' << 16) + ('A' << 24)) if (p && readl(p) == 'E' + ('I' << 8) + ('S' << 16) + ('A' << 24))
EISA_bus = 1; EISA_bus = 1;
iounmap(p); memunmap(p);
return 0; return 0;
} }
subsys_initcall(eisa_bus_probe); subsys_initcall(eisa_bus_probe);