Re: [PATCH] x86/efi: always map first physical page into EFI pagetables

Re: [PATCH] x86/efi: always map first physical page into EFI pagetables

[Jiri Kosina]

[ CCing mailinglists that got eaten by my newly configured mail setup, 
  sorry for that ]

On Wed, 25 Jan 2017, Jiri Kosina wrote:

> From: Jiri Kosina <jkosina@suse.cz>
> 
> Commit 129766708 ("x86/efi: Only map RAM into EFI page tables if in 
> mixed-mode") stopped creating 1:1 mapping for all RAM in case of running 
> in native 64bit mode.
> 
> It turns out though that there are 64bit EFI implementations in the wild 
> (this particular problem has been reported on Lenovo Yoga 710-11IKB) which 
> still make use of first physical page for their own private use (which is 
> what legacy BIOS used to do, but EFI specification doesn't grant any such 
> right to EFI BIOS ... oh well).
> 
> In case there is no mapping for this particular frame in EFI pagetables, 
> as soon as firmware tries to make use of it, triple fault occurs and the 
> system reboots (in case of Yoga 710-11IKB this is very early during boot).
> 
> Fix that by always mapping the first page of physical memory into EFI 
> pagetables.
> 
> Note: just reverting 129766708 is not enough on v4.9-rc1+ to fix the 
> regression on affected hardware, as commit ab72a27da ("x86/efi: 
> Consolidate region mapping logic") later made the first physical frame not 
> to be mapped anyway.
> 
> Fixes: 129766708 ("x86/efi: Only map RAM into EFI page tables if in mixed-mode")
> Cc: stable@kernel.org # v4.8+
> Cc: Waiman Long <waiman.long@hpe.com>
> Cc: Borislav Petkov <bp@suse.de>
> Cc: Laura Abbott <labbott@redhat.com>
> Cc: Vojtech Pavlik <vojtech@ucw.cz>
> Reported-by: Hanka Pavlikova <hanka@ucw.cz>
> Signed-off-by: Jiri Kosina <jkosina@suse.cz>
> ---
> 
> Thanks a lot to Matt for excellent hint how to debug EFI failures
> 
>  arch/x86/platform/efi/efi_64.c | 11 +++++++++++
>  1 file changed, 11 insertions(+)
> 
> diff --git a/arch/x86/platform/efi/efi_64.c b/arch/x86/platform/efi/efi_64.c
> index 319148b..02ae2ab 100644
> --- a/arch/x86/platform/efi/efi_64.c
> +++ b/arch/x86/platform/efi/efi_64.c
> @@ -269,6 +269,17 @@ int __init efi_setup_page_tables(unsigned long pa_memmap, unsigned num_pages)
>  	efi_scratch.use_pgd = true;
>  
>  	/*
> +	 * Certain firmware versions are way too sentimental and still believe
> +	 * they are exclusive and unquestionable owners of first physical page.
> +	 * Create 1:1 mapping for this page to avoid triple faults during early
> +	 * boot with such firmware.
> +	 */
> +	if (kernel_map_pages_in_pgd(pgd, 0x0, 0x0, 1, _PAGE_RW)) {
> +		pr_err("Failed to create 1:1 mapping of first page\n");
> +		return 1;
> +	}
> +
> +	/*
>  	 * When making calls to the firmware everything needs to be 1:1
>  	 * mapped and addressable with 32-bit pointers. Map the kernel
>  	 * text and allocate a new stack because we can't rely on the
> -- 
> Jiri Kosina
> SUSE Labs
> 
> 

-- 
Jiri Kosina
SUSE Labs

Re: [PATCH] x86/efi: always map first physical page into EFI pagetables

[Borislav Petkov]

On Wed, Jan 25, 2017 at 09:31:53PM +0100, Jiri Kosina wrote:
> 
> [ CCing mailinglists that got eaten by my newly configured mail setup, 
>   sorry for that ]
> 
> On Wed, 25 Jan 2017, Jiri Kosina wrote:
> 
> > From: Jiri Kosina <jkosina@suse.cz>
> > 
> > Commit 129766708 ("x86/efi: Only map RAM into EFI page tables if in 
> > mixed-mode") stopped creating 1:1 mapping for all RAM in case of running 
> > in native 64bit mode.
> > 
> > It turns out though that there are 64bit EFI implementations in the wild 
> > (this particular problem has been reported on Lenovo Yoga 710-11IKB) which 
> > still make use of first physical page for their own private use (which is 
> > what legacy BIOS used to do, but EFI specification doesn't grant any such 
> > right to EFI BIOS ... oh well).

And now the same rant for the wider audience:

What is this EFI spec even? Toilet paper? Perhaps not even that.

Geez, can we simply say, firmware people, you f*cked up big time. Now
take all that crap with you to your basement, *think* hard about all the
issues we've had and then reengineer the whole thing from the beginning.
Completely anew. Then come back and we can talk.

There's a reason I don't want to deal with that major stinking pile of
crap called firmware but somehow I always get sucked back in.

-- 
Regards/Gruss,
    Boris.

SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg)
-- 

Re: [PATCH] x86/efi: always map first physical page into EFI pagetables

[Matt Fleming]

On Wed, 25 Jan, at 09:31:53PM, Jiri Kosina wrote:
> 
> [ CCing mailinglists that got eaten by my newly configured mail setup, 
>   sorry for that ]
> 
> On Wed, 25 Jan 2017, Jiri Kosina wrote:
> 
> > From: Jiri Kosina <jkosina@suse.cz>
> > 
> > Commit 129766708 ("x86/efi: Only map RAM into EFI page tables if in 
> > mixed-mode") stopped creating 1:1 mapping for all RAM in case of running 
> > in native 64bit mode.
> > 
> > It turns out though that there are 64bit EFI implementations in the wild 
> > (this particular problem has been reported on Lenovo Yoga 710-11IKB) which 
> > still make use of first physical page for their own private use (which is 
> > what legacy BIOS used to do, but EFI specification doesn't grant any such 
> > right to EFI BIOS ... oh well).
> > 
> > In case there is no mapping for this particular frame in EFI pagetables, 
> > as soon as firmware tries to make use of it, triple fault occurs and the 
> > system reboots (in case of Yoga 710-11IKB this is very early during boot).
> > 

The thing missing from this paragraph is that the EFI memmap entry
type for this page is EFI_CONVENTIONAL_MEMORY on these Lenovo Yoga's,
i.e. the firmware is telling the kernel that the first page is "free
memory" but will write to it anyway.

> > Fix that by always mapping the first page of physical memory into EFI 
> > pagetables.
> > 
> > Note: just reverting 129766708 is not enough on v4.9-rc1+ to fix the 
> > regression on affected hardware, as commit ab72a27da ("x86/efi: 
> > Consolidate region mapping logic") later made the first physical frame not 
> > to be mapped anyway.
> > 
> > Fixes: 129766708 ("x86/efi: Only map RAM into EFI page tables if in mixed-mode")
> > Cc: stable@kernel.org # v4.8+
> > Cc: Waiman Long <waiman.long@hpe.com>
> > Cc: Borislav Petkov <bp@suse.de>
> > Cc: Laura Abbott <labbott@redhat.com>
> > Cc: Vojtech Pavlik <vojtech@ucw.cz>
> > Reported-by: Hanka Pavlikova <hanka@ucw.cz>
> > Signed-off-by: Jiri Kosina <jkosina@suse.cz>
> > ---
> > 
> > Thanks a lot to Matt for excellent hint how to debug EFI failures
> > 
> >  arch/x86/platform/efi/efi_64.c | 11 +++++++++++
> >  1 file changed, 11 insertions(+)
> > 
> > diff --git a/arch/x86/platform/efi/efi_64.c b/arch/x86/platform/efi/efi_64.c
> > index 319148b..02ae2ab 100644
> > --- a/arch/x86/platform/efi/efi_64.c
> > +++ b/arch/x86/platform/efi/efi_64.c
> > @@ -269,6 +269,17 @@ int __init efi_setup_page_tables(unsigned long pa_memmap, unsigned num_pages)
> >  	efi_scratch.use_pgd = true;
> >  
> >  	/*
> > +	 * Certain firmware versions are way too sentimental and still believe
> > +	 * they are exclusive and unquestionable owners of first physical page.
> > +	 * Create 1:1 mapping for this page to avoid triple faults during early
> > +	 * boot with such firmware.
> > +	 */
> > +	if (kernel_map_pages_in_pgd(pgd, 0x0, 0x0, 1, _PAGE_RW)) {
> > +		pr_err("Failed to create 1:1 mapping of first page\n");
> > +		return 1;
> > +	}
> > +
> > +	/*
> >  	 * When making calls to the firmware everything needs to be 1:1
> >  	 * mapped and addressable with 32-bit pointers. Map the kernel
> >  	 * text and allocate a new stack because we can't rely on the

Could you update the comment above to include two additional points:

  1) We've seen machines that mark the first page as
     EFI_CONVENTIONAL_MEMORY but the firmware will write to it
     during SetVirtualAddressMap() nevertheless.

  2) trim_bios_range() takes care of actually reserving the first page
     and making it unavailable to the memory allocators.

[PATCH v2] x86/efi: always map first physical page into EFI pagetables

[Jiri Kosina]

From: Jiri Kosina <jkosina@suse.cz>

Commit 129766708 ("x86/efi: Only map RAM into EFI page tables if in 
mixed-mode") stopped creating 1:1 mapping for all RAM in case of running 
in native 64bit mode.

It turns out though that there are 64bit EFI implementations in the wild 
(this particular problem has been reported on Lenovo Yoga 710-11IKB) which 
still make use of first physical page for their own private use even 
though they explicitly mark it EFI_CONVENTIONAL_MEMORY in the memory map.

In case there is no mapping for this particular frame in EFI pagetables, 
as soon as firmware tries to make use of it, triple fault occurs and the 
system reboots (in case of Yoga 710-11IKB this is very early during boot).

Fix that by always mapping the first page of physical memory into EFI 
pagetables. We're on a safe side, as trim_bios_range() will reserve the 
first page and isolate it away from memory allocators anyway.

Note: just reverting 129766708 is not enough on v4.9-rc1+ to fix the 
regression on affected hardware, as commit ab72a27da ("x86/efi: 
Consolidate region mapping logic") later made the first physical frame not 
to be mapped anyway.

Fixes: 129766708 ("x86/efi: Only map RAM into EFI page tables if in mixed-mode")
Cc: stable@kernel.org # v4.8+
Cc: Waiman Long <waiman.long@hpe.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: Laura Abbott <labbott@redhat.com>
Cc: Vojtech Pavlik <vojtech@ucw.cz>
Reported-by: Hanka Pavlikova <hanka@ucw.cz>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
---

v1 -> v2: be more explicit in commit message and in code comments
          regarding the BIOS actually marking the page in its memory
	  map as EFI_CONVENTIONAL_MEMORY

	  add a comment regarding trim_bios_range() isolating away the
	  firstpage from allocators anyway

 arch/x86/platform/efi/efi_64.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/arch/x86/platform/efi/efi_64.c b/arch/x86/platform/efi/efi_64.c
index 319148bd4b05..79c21cac1133 100644
--- a/arch/x86/platform/efi/efi_64.c
+++ b/arch/x86/platform/efi/efi_64.c
@@ -269,6 +269,22 @@ int __init efi_setup_page_tables(unsigned long pa_memmap, unsigned num_pages)
 	efi_scratch.use_pgd = true;
 
 	/*
+	 * Certain firmware versions are way too sentimential and still believe
+	 * they are exclusive and unquestionable owners of first physical page
+	 * even though they explicitly mark it as EFI_CONVENTIONAL_MEMORY
+	 * (but then write-access it later during SetVirtualAddressMap()).
+	 *
+	 * Create 1:1 mapping for this page to avoid triple faults during early
+	 * boot with such firmware. We're on a safe side, as trim_bios_range()
+	 * will reserve the first page and isolate it away from memory
+	 * allocators anyway.
+	 */
+	if (kernel_map_pages_in_pgd(pgd, 0x0, 0x0, 1, _PAGE_RW)) {
+		pr_err("Failed to create 1:1 mapping of first page\n");
+		return 1;
+	}
+
+	/*
 	 * When making calls to the firmware everything needs to be 1:1
 	 * mapped and addressable with 32-bit pointers. Map the kernel
 	 * text and allocate a new stack because we can't rely on the
-- 
Jiri Kosina
SUSE Labs

Re: [PATCH v2] x86/efi: always map first physical page into EFI pagetables

[Matt Fleming]

On Fri, 27 Jan, at 04:39:59PM, Jiri Kosina wrote:
> From: Jiri Kosina <jkosina@suse.cz>
> 
> Commit 129766708 ("x86/efi: Only map RAM into EFI page tables if in 
> mixed-mode") stopped creating 1:1 mapping for all RAM in case of running 
> in native 64bit mode.
> 
> It turns out though that there are 64bit EFI implementations in the wild 
> (this particular problem has been reported on Lenovo Yoga 710-11IKB) which 
> still make use of first physical page for their own private use even 
> though they explicitly mark it EFI_CONVENTIONAL_MEMORY in the memory map.
> 
> In case there is no mapping for this particular frame in EFI pagetables, 
> as soon as firmware tries to make use of it, triple fault occurs and the 
> system reboots (in case of Yoga 710-11IKB this is very early during boot).
> 
> Fix that by always mapping the first page of physical memory into EFI 
> pagetables. We're on a safe side, as trim_bios_range() will reserve the 
> first page and isolate it away from memory allocators anyway.
> 
> Note: just reverting 129766708 is not enough on v4.9-rc1+ to fix the 
> regression on affected hardware, as commit ab72a27da ("x86/efi: 
> Consolidate region mapping logic") later made the first physical frame not 
> to be mapped anyway.
> 
> Fixes: 129766708 ("x86/efi: Only map RAM into EFI page tables if in mixed-mode")
> Cc: stable@kernel.org # v4.8+
> Cc: Waiman Long <waiman.long@hpe.com>
> Cc: Borislav Petkov <bp@suse.de>
> Cc: Laura Abbott <labbott@redhat.com>
> Cc: Vojtech Pavlik <vojtech@ucw.cz>
> Reported-by: Hanka Pavlikova <hanka@ucw.cz>
> Signed-off-by: Jiri Kosina <jkosina@suse.cz>
> ---
 
Thanks Jiri. Queued for v4.10-rc6.