From: Sai Praneeth <[email protected]>
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 <[email protected]>
Cc: Lee, Chun-Yi <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Tony Luck <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: Michael S. Tsirkin <[email protected]>
Cc: Ricardo Neri <[email protected]>
Cc: Matt Fleming <[email protected]>
Cc: Ard Biesheuvel <[email protected]>
Cc: Ravi Shankar <[email protected]>
Tested-by: Bhupesh Sharma <[email protected]>
--
2.1.4
On Thu, 18 Jan, at 01:01:04PM, Sai Praneeth Prakhya wrote:
> From: Sai Praneeth <[email protected]>
>
> 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 <[email protected]>
On 26 January 2018 at 21:16, Matt Fleming <[email protected]> wrote:
> On Thu, 18 Jan, at 01:01:04PM, Sai Praneeth Prakhya wrote:
>> From: Sai Praneeth <[email protected]>
>>
>> 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 <[email protected]>
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.
On 29 January 2018 at 10:51, Ard Biesheuvel <[email protected]> wrote:
> On 26 January 2018 at 21:16, Matt Fleming <[email protected]> wrote:
>> On Thu, 18 Jan, at 01:01:04PM, Sai Praneeth Prakhya wrote:
>>> From: Sai Praneeth <[email protected]>
>>>
>>> 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 <[email protected]>
>
> 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.