linux-kernel - RE: ERST: how to avoid a dynamic memory allocation in panic case

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Date:	Wed, 23 Jan 2013 00:44:19 +0000
From:	Seiji Aguchi <seiji.aguchi@....com>
To:	Huang Ying <ying.huang@...el.com>
CC:	"rjw@...k.pl" <rjw@...k.pl>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
	"H. Peter Anvin (hpa@...or.com)" <hpa@...or.com>,
	"robert.moore@...el.com" <robert.moore@...el.com>,
	"trenn@...e.de" <trenn@...e.de>,
	"myron.stowe@...hat.com" <myron.stowe@...hat.com>
Subject: RE: ERST: how to avoid a dynamic memory allocation in panic case



> > <snip>
> > @@ -918,10 +918,7 @@ acpi_os_read_memory(acpi_physical_address phys_addr, u64 *value, u32 width)
> >  	virt_addr = acpi_map_vaddr_lookup(phys_addr, size);
> >  	if (!virt_addr) {
> >  		rcu_read_unlock();
> > -		virt_addr = acpi_os_ioremap(phys_addr, size);
> > -		if (!virt_addr)
> > -			return AE_BAD_ADDRESS;
> > -		unmap = true;
> > +		return AE_BAD_ADDRESS;
> 
> No.  We can not do that.  Because some users rely on acpi_os_read_memory to do ioremap for them.

Thank you for giving me the information.

> The correct fixing should be pre-map the io-memory that may be accessed in erst code patch with acpi_map().

I will take a look at the code.

Seiji