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Date: Wed, 25 Sep 2013 10:36:15 +0800 From: Dave Young <dyoung@...hat.com> To: "H. Peter Anvin" <hpa@...or.com> Cc: Borislav Petkov <bp@...en8.de>, X86 ML <x86@...nel.org>, LKML <linux-kernel@...r.kernel.org>, Borislav Petkov <bp@...e.de>, Matt Fleming <matt@...sole-pimps.org>, Matthew Garrett <mjg59@...f.ucam.org>, James Bottomley <james.bottomley@...senpartnership.com>, Vivek Goyal <vgoyal@...hat.com>, linux-efi@...r.kernel.org Subject: Re: [PATCH -v2] EFI: Runtime services virtual mapping On 09/24/13 at 05:12pm, H. Peter Anvin wrote: > On 09/24/2013 07:56 AM, Borislav Petkov wrote: > > On Tue, September 24, 2013 2:45 pm, Dave Young wrote: > >> Think again about this, how about 1:1 map them from a base address > >> like -64G phy_addr -> (-64G + phy_addr), in this way we can avoid > >> depending on the previous region size. > > > > Right, how we layout the regions is arbitrary as long as we start at > > the same VA and use the same regions, in the same order and of the same > > size... > > > >> For the zero region problem, we can resolve it as a standalone > >> problem. > > > > ... however, we still need to understand why it fails mapping the boot > > services region as some implementations apparently do call boot services > > even after ExitBootServices(). IOW, we need that region mapped in the > > kexec'ed kernel too. > > > > I am starting to think that we really should explicitly pass along the > EFI mappings to the secondary kernel. This will also help if we have to > change the algorithm in a future kernel. The 0 size mem region is still a problem even we pass the previous mapping to 2nd kernel. So will be be enough to 1:1 map on high address and leave the firmware provided memmap not touched, use a copy of memmap in kernel? > > The most logical way to do this is to define a new setup_data type and > pass the entire set of physical-to-virtual mappings that way. > > For example: > > struct efi_mapping { > u64 va; /* Virtual start address */ > u64 pa; /* Physical start address */ > u64 len; /* Length in bytes */ > u64 type; /* Mapping type */ > u64 reserved[3]; /* Reserved, must be zero */ > }; > > Adding some reserved fields seems like a prudent precaution; the map > shouldn't be all that large anyway. > > -hpa > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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