linux-kernel - Re: [PATCH v4 07/12] efi: passing kexec necessary efi data via setup

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Date:	Wed, 27 Nov 2013 10:17:47 +0000
From:	Matt Fleming <matt@...sole-pimps.org>
To:	Dave Young <dyoung@...hat.com>
Cc:	linux-kernel@...r.kernel.org, linux-efi@...r.kernel.org,
	x86@...nel.org, mjg59@...f.ucam.org, hpa@...or.com,
	James.Bottomley@...senPartnership.com, vgoyal@...hat.com,
	ebiederm@...ssion.com, horms@...ge.net.au,
	kexec@...ts.infradead.org, bp@...en8.de, greg@...ah.com,
	toshi.kani@...com
Subject: Re: [PATCH v4 07/12] efi: passing kexec necessary efi data via
 setup_data

On Wed, 27 Nov, at 12:52:37PM, Dave Young wrote:
> To make it more readable, I will change them like below:
> 
> p = efi_runtime_map;
> md = efi_setup->map;
> for (i = 0; i < nr_efi_runtime_map; i++) {
> 	[...]
> 	md += 1;
> }
 
Actually, md++ is the canonical way to write this.

> > 
> > > +		efi_map_region_fixed(md);
> > > +		size = md->num_pages << PAGE_SHIFT;
> > > +		end = md->phys_addr + size;
> > > +
> > > +		systab = (u64) (unsigned long) efi_phys.systab;
> > > +		if (md->phys_addr <= systab && systab < end) {
> > > +			systab += md->virt_addr - md->phys_addr;
> > > +			efi.systab =
> > > +				(efi_system_table_t *) (unsigned long) systab;
> > > +		}
> > > +		if (efi_runtime_map) {
> > > +			memcpy(p, md, memmap.desc_size);
> > > +			p += memmap.desc_size;
> > > +		}
> > 
> > Is this if () needed? Is it possible to enter the loop and have
> > 'efi_runtime_map' be NULL?
> 
> Yes, it is needed. if efi_runtime_map kmalloc fails I only print error, do not
> return so kernel can still boot, just kexec on efi will not work that has been
> put in the error message.
 
OK. On second thought, is there any way to turn the above code into a
call to efi_save_runtime_map()? Because you've basically duplicated that
code and I can definitely envisage the two code paths fragmenting over
time, e.g. when someone makes changes to one but not the other.

-- 
Matt Fleming, Intel Open Source Technology Center
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