linux-kernel - Re: [PATCH -v2] EFI: Runtime services virtual mapping

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Date:	Tue, 24 Sep 2013 11:43:39 +0200 (CEST)
From:	"Borislav Petkov" <bp@...en8.de>
To:	"Dave Young" <dyoung@...hat.com>
Cc:	"H. Peter Anvin" <hpa@...or.com>, "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

Crap,

I need to send from the web interface since the network here doesn't
somehow let through port 587.

On Tue, September 24, 2013 6:57 am, Dave Young wrote:
> On 09/23/13 at 08:06pm, H. Peter Anvin wrote:
>> Okay... I see two problems.
>>
>> 1. It looks like we subtract the region size after, rather than before,
>> assigning an address.
>>
>> 2. The second region is assigned the same address in the secondary
>> kernel as in the first, implying the size of the first region was
>> somehow set to zero.
>
> I find the reason, efi_reserve_boot_services will reserve the
> BOOT_SERVICE_DATA region
> thus the memmap size is changed to 0, so in 2nd kernel the virtual mapping
> addr after
> the md will be not same as 1st kernel, see below code:
>
> void __init efi_map_region(efi_memory_desc_t *md)
> {
>         unsigned long size = md->num_pages << PAGE_SHIFT;
>
>         efi_va -= size;
>         ^^^^^^^^^^^^^^^

Anyway, yes, this is wrong. We probably want to something like the
following, instead (patch might be whitespace-damaged):

--
diff --git a/arch/x86/platform/efi/efi_64.c b/arch/x86/platform/efi/efi_64.c
index a235dc95d629..ea0ea4fd3dab 100644
--- a/arch/x86/platform/efi/efi_64.c
+++ b/arch/x86/platform/efi/efi_64.c
@@ -85,8 +85,7 @@ void __init efi_map_region(efi_memory_desc_t *md)
 {
 	unsigned long size = md->num_pages << PAGE_SHIFT;

-	efi_va -= size;
-	if (efi_va < EFI_VA_END) {
+	if (efi_va - size < EFI_VA_END) {
 		pr_warning(FW_WARN "VA address range overflow!\n");
 		return;
 	}
@@ -101,6 +100,8 @@ void __init efi_map_region(efi_memory_desc_t *md)
 	/* Do the VA map */
 	__map_region(md, efi_va);
 	md->virt_addr = efi_va;
+
+	efi_va -= size;
 }

 void __iomem *__init efi_ioremap(unsigned long phys_addr, unsigned long
size,

-- 
Regards/Gruss,
Boris.

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