[PATCH V4 0/3] Use mm_struct and switch_mm() instead of manually

[PATCH V4 0/3] Use mm_struct and switch_mm() instead of manually

[Sai Praneeth Prakhya]

From: Sai Praneeth <sai.praneeth.prakhya@intel.com>

Presently, in x86, to invoke any efi function like
efi_set_virtual_address_map() or any efi_runtime_service() the code path
typically involves read_cr3() (save previous pgd), write_cr3()
(write efi_pgd) and calling efi function. Likewise after returning from
efi function the code path typically involves read_cr3() (save efi_pgd),
write_cr3() (write previous pgd). We do this couple of times in efi
subsystem of Linux kernel, instead we can use helper function
efi_switch_mm() to do this. This improves readability and maintainability.
Also, instead of maintaining a separate struct "efi_scratch" to store/restore
efi_pgd, we can use mm_struct to do this.

I have tested this patch set against LUV (Linux UEFI Validation), so I
think I didn't break any existing configurations. I have tested this
patch set for
1. x86_64,
2. x86_32,
3. Mixed mode
with efi=old_map and for kexec kernel. Please let me know if I have
missed any other configurations.

Changes in V2:
1. Resolve mm_dropping() issue by not mm_dropping()/mm_grabbing() any mm,
as we are not losing/creating any references.

Changes in V3:
1. When CPUMASK_OFFSTACK is enabled, switch_mm_irqs_off() sets cpumask
by calling cpumask_set_cpu(). This panics kernel as efi_mm is not
initialized, therefore initialize efi_mm in efi_alloc_page_tables().

Changes in V4:
1. Remove the unintended removal of local_irq_restore(flags) (in 3rd patch).
IRQ flags should be restored after switching to orginal mm.

Note:
This patch set is based on Linus's tree v4.15-rc8

Sai Praneeth (3):
  efi: Use efi_mm in x86 as well as ARM
  x86/efi: Replace efi_pgd with efi_mm.pgd
  x86/efi: Use efi_switch_mm() rather than manually twiddling with %cr3

 arch/x86/include/asm/efi.h           | 29 +++++++++---------
 arch/x86/platform/efi/efi_64.c       | 58 +++++++++++++++++++-----------------
 arch/x86/platform/efi/efi_thunk_64.S |  2 +-
 drivers/firmware/efi/arm-runtime.c   |  9 ------
 drivers/firmware/efi/efi.c           |  9 ++++++
 include/linux/efi.h                  |  2 ++
 6 files changed, 57 insertions(+), 52 deletions(-)

Signed-off-by: Sai Praneeth Prakhya <sai.praneeth.prakhya@intel.com>
Cc: Lee, Chun-Yi <jlee@suse.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Ricardo Neri <ricardo.neri@intel.com>
Cc: Matt Fleming <matt@codeblueprint.co.uk>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Ravi Shankar <ravi.v.shankar@intel.com>
Tested-by: Bhupesh Sharma <bhsharma@redhat.com>

-- 
2.1.4

[PATCH V4 0/3] Use mm_struct and switch_mm() instead of manually

[Sai Praneeth Prakhya]

From: Sai Praneeth <sai.praneeth.prakhya-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>

Presently, in x86, to invoke any efi function like
efi_set_virtual_address_map() or any efi_runtime_service() the code path
typically involves read_cr3() (save previous pgd), write_cr3()
(write efi_pgd) and calling efi function. Likewise after returning from
efi function the code path typically involves read_cr3() (save efi_pgd),
write_cr3() (write previous pgd). We do this couple of times in efi
subsystem of Linux kernel, instead we can use helper function
efi_switch_mm() to do this. This improves readability and maintainability.
Also, instead of maintaining a separate struct "efi_scratch" to store/restore
efi_pgd, we can use mm_struct to do this.

I have tested this patch set against LUV (Linux UEFI Validation), so I
think I didn't break any existing configurations. I have tested this
patch set for
1. x86_64,
2. x86_32,
3. Mixed mode
with efi=old_map and for kexec kernel. Please let me know if I have
missed any other configurations.

Changes in V2:
1. Resolve mm_dropping() issue by not mm_dropping()/mm_grabbing() any mm,
as we are not losing/creating any references.

Changes in V3:
1. When CPUMASK_OFFSTACK is enabled, switch_mm_irqs_off() sets cpumask
by calling cpumask_set_cpu(). This panics kernel as efi_mm is not
initialized, therefore initialize efi_mm in efi_alloc_page_tables().

Changes in V4:
1. Remove the unintended removal of local_irq_restore(flags) (in 3rd patch).
IRQ flags should be restored after switching to orginal mm.

Note:
This patch set is based on Linus's tree v4.15-rc8

Sai Praneeth (3):
  efi: Use efi_mm in x86 as well as ARM
  x86/efi: Replace efi_pgd with efi_mm.pgd
  x86/efi: Use efi_switch_mm() rather than manually twiddling with %cr3

 arch/x86/include/asm/efi.h           | 29 +++++++++---------
 arch/x86/platform/efi/efi_64.c       | 58 +++++++++++++++++++-----------------
 arch/x86/platform/efi/efi_thunk_64.S |  2 +-
 drivers/firmware/efi/arm-runtime.c   |  9 ------
 drivers/firmware/efi/efi.c           |  9 ++++++
 include/linux/efi.h                  |  2 ++
 6 files changed, 57 insertions(+), 52 deletions(-)

Signed-off-by: Sai Praneeth Prakhya <sai.praneeth.prakhya-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
Cc: Lee, Chun-Yi <jlee-IBi9RG/b67k@public.gmane.org>
Cc: Borislav Petkov <bp-Gina5bIWoIWzQB+pC5nmwQ@public.gmane.org>
Cc: Tony Luck <tony.luck-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
Cc: Andy Lutomirski <luto-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
Cc: Michael S. Tsirkin <mst-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
Cc: Ricardo Neri <ricardo.neri-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
Cc: Matt Fleming <matt-mF/unelCI9GS6iBeEJttW/XRex20P6io@public.gmane.org>
Cc: Ard Biesheuvel <ard.biesheuvel-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>
Cc: Ravi Shankar <ravi.v.shankar-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
Tested-by: Bhupesh Sharma <bhsharma-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>

-- 
2.1.4

Re: [PATCH V4 0/3] Use mm_struct and switch_mm() instead of manually

[Matt Fleming]

On Thu, 18 Jan, at 01:01:04PM, Sai Praneeth Prakhya wrote:
> From: Sai Praneeth <sai.praneeth.prakhya@intel.com>
> 
> Presently, in x86, to invoke any efi function like
> efi_set_virtual_address_map() or any efi_runtime_service() the code path
> typically involves read_cr3() (save previous pgd), write_cr3()
> (write efi_pgd) and calling efi function. Likewise after returning from
> efi function the code path typically involves read_cr3() (save efi_pgd),
> write_cr3() (write previous pgd). We do this couple of times in efi
> subsystem of Linux kernel, instead we can use helper function
> efi_switch_mm() to do this. This improves readability and maintainability.
> Also, instead of maintaining a separate struct "efi_scratch" to store/restore
> efi_pgd, we can use mm_struct to do this.
 
FWIW this series looks OK to me.

Reviewed-by: Matt Fleming <matt@codeblueprint.co.uk>

Re: [PATCH V4 0/3] Use mm_struct and switch_mm() instead of manually

[Ard Biesheuvel]

On 26 January 2018 at 21:16, Matt Fleming <matt@codeblueprint.co.uk> wrote:
> On Thu, 18 Jan, at 01:01:04PM, Sai Praneeth Prakhya wrote:
>> From: Sai Praneeth <sai.praneeth.prakhya@intel.com>
>>
>> Presently, in x86, to invoke any efi function like
>> efi_set_virtual_address_map() or any efi_runtime_service() the code path
>> typically involves read_cr3() (save previous pgd), write_cr3()
>> (write efi_pgd) and calling efi function. Likewise after returning from
>> efi function the code path typically involves read_cr3() (save efi_pgd),
>> write_cr3() (write previous pgd). We do this couple of times in efi
>> subsystem of Linux kernel, instead we can use helper function
>> efi_switch_mm() to do this. This improves readability and maintainability.
>> Also, instead of maintaining a separate struct "efi_scratch" to store/restore
>> efi_pgd, we can use mm_struct to do this.
>
> FWIW this series looks OK to me.
>
> Reviewed-by: Matt Fleming <matt@codeblueprint.co.uk>

Thanks Matt

I know the x86 guys have been rather busy lately, so I will give them
some more time to respond. If there are no objections raised, I will
queue it for v4.17 in a couple of weeks.

Re: [PATCH V4 0/3] Use mm_struct and switch_mm() instead of manually

[Ard Biesheuvel]

On 26 January 2018 at 21:16, Matt Fleming <matt-mF/unelCI9GS6iBeEJttW/XRex20P6io@public.gmane.org> wrote:
> On Thu, 18 Jan, at 01:01:04PM, Sai Praneeth Prakhya wrote:
>> From: Sai Praneeth <sai.praneeth.prakhya-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
>>
>> Presently, in x86, to invoke any efi function like
>> efi_set_virtual_address_map() or any efi_runtime_service() the code path
>> typically involves read_cr3() (save previous pgd), write_cr3()
>> (write efi_pgd) and calling efi function. Likewise after returning from
>> efi function the code path typically involves read_cr3() (save efi_pgd),
>> write_cr3() (write previous pgd). We do this couple of times in efi
>> subsystem of Linux kernel, instead we can use helper function
>> efi_switch_mm() to do this. This improves readability and maintainability.
>> Also, instead of maintaining a separate struct "efi_scratch" to store/restore
>> efi_pgd, we can use mm_struct to do this.
>
> FWIW this series looks OK to me.
>
> Reviewed-by: Matt Fleming <matt-mF/unelCI9GS6iBeEJttW/XRex20P6io@public.gmane.org>

Thanks Matt

I know the x86 guys have been rather busy lately, so I will give them
some more time to respond. If there are no objections raised, I will
queue it for v4.17 in a couple of weeks.

Re: [PATCH V4 0/3] Use mm_struct and switch_mm() instead of manually

[Ard Biesheuvel]

On 29 January 2018 at 10:51, Ard Biesheuvel <ard.biesheuvel@linaro.org> wrote:
> On 26 January 2018 at 21:16, Matt Fleming <matt@codeblueprint.co.uk> wrote:
>> On Thu, 18 Jan, at 01:01:04PM, Sai Praneeth Prakhya wrote:
>>> From: Sai Praneeth <sai.praneeth.prakhya@intel.com>
>>>
>>> Presently, in x86, to invoke any efi function like
>>> efi_set_virtual_address_map() or any efi_runtime_service() the code path
>>> typically involves read_cr3() (save previous pgd), write_cr3()
>>> (write efi_pgd) and calling efi function. Likewise after returning from
>>> efi function the code path typically involves read_cr3() (save efi_pgd),
>>> write_cr3() (write previous pgd). We do this couple of times in efi
>>> subsystem of Linux kernel, instead we can use helper function
>>> efi_switch_mm() to do this. This improves readability and maintainability.
>>> Also, instead of maintaining a separate struct "efi_scratch" to store/restore
>>> efi_pgd, we can use mm_struct to do this.
>>
>> FWIW this series looks OK to me.
>>
>> Reviewed-by: Matt Fleming <matt@codeblueprint.co.uk>
>
> Thanks Matt
>
> I know the x86 guys have been rather busy lately, so I will give them
> some more time to respond. If there are no objections raised, I will
> queue it for v4.17 in a couple of weeks.

Queued in linux-efi/next

Thanks all.