linux-kernel - Re: [PATCH] x86/EISA: Use memremap() to probe for the EISA BIOS signature

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Message-ID: <pmskepgrtwhs5owjr4ok3i32655jyrkbmja7mew357occwlumx@hpd2mqndpkey>
Date: Wed, 28 Aug 2024 10:13:34 +0300
From: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To: Christoph Hellwig <hch@...radead.org>
Cc: "Maciej W. Rozycki" <macro@...am.me.uk>, 
	Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>, 
	Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org, Boris Ostrovsky <boris.ostrovsky@...cle.com>, 
	"H. Peter Anvin" <hpa@...or.com>, Rick Edgecombe <rick.p.edgecombe@...el.com>, 
	Isaku Yamahata <isaku.yamahata@...el.com>, Kevin Loughlin <kevinloughlin@...gle.com>, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86/EISA: Use memremap() to probe for the EISA BIOS
 signature

On Tue, Aug 27, 2024 at 11:14:45PM -0700, Christoph Hellwig wrote:
> On Sat, Aug 24, 2024 at 11:17:10PM +0100, Maciej W. Rozycki wrote:
> > -	void __iomem *p;
> > +	void *p;
> >  
> >  	if ((xen_pv_domain() && !xen_initial_domain()) || cc_platform_has(CC_ATTR_GUEST_SEV_SNP))
> >  		return 0;
> >  
> > -	p = ioremap(0x0FFFD9, 4);
> > +	p = memremap(0x0FFFD9, 4, MEMREMAP_WB);
> >  	if (p && readl(p) == 'E' + ('I' << 8) + ('S' << 16) + ('A' << 24))
> >  		EISA_bus = 1;
> 
> readl requires and __iomem pointer.  If this is just a memory region you
> can and should directly dereference the address instead.
> 
> Note that sparse will complain about the above as well.
 
See v2:

https://lore.kernel.org/all/alpine.DEB.2.21.2408261015270.30766@angie.orcam.me.uk


-- 
  Kiryl Shutsemau / Kirill A. Shutemov