linux-kernel - Re: [PATCH V4 0/3] Use mm_struct and switch

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Date:   Fri, 26 Jan 2018 21:16:43 +0000
From:   Matt Fleming <matt@...eblueprint.co.uk>
To:     Sai Praneeth Prakhya <sai.praneeth.prakhya@...el.com>
Cc:     linux-efi@...r.kernel.org, linux-kernel@...r.kernel.org,
        "Lee, Chun-Yi" <jlee@...e.com>, Borislav Petkov <bp@...en8.de>,
        Tony Luck <tony.luck@...el.com>,
        Andy Lutomirski <luto@...nel.org>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Ricardo Neri <ricardo.neri@...el.com>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Ravi Shankar <ravi.v.shankar@...el.com>
Subject: Re: [PATCH V4 0/3] Use mm_struct and switch_mm() instead of manually

On Thu, 18 Jan, at 01:01:04PM, Sai Praneeth Prakhya wrote:
> From: Sai Praneeth <sai.praneeth.prakhya@...el.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@...eblueprint.co.uk>