Re: [patch] x86/efi: use GFP_ATOMIC under spin_lock

[Ingo Molnar <mingo-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>]

* Dan Carpenter <dan.carpenter-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org> wrote:

> In phys_efi_get_time() we call efi_call_phys_prelog() with a spin_lock
> so this allocation should be atomic.
> 
> Fixes: b8f2c21db390 ('efi, x86: Pass a proper identity mapping in efi_call_phys_prelog')
> Signed-off-by: Dan Carpenter <dan.carpenter-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org>
> 
> diff --git a/arch/x86/platform/efi/efi_64.c b/arch/x86/platform/efi/efi_64.c
> index 0c2a234fef1e..f5adcadb381b 100644
> --- a/arch/x86/platform/efi/efi_64.c
> +++ b/arch/x86/platform/efi/efi_64.c
> @@ -90,7 +90,7 @@ void __init efi_call_phys_prelog(void)
>  	local_irq_save(efi_flags);
>  
>  	n_pgds = DIV_ROUND_UP((max_pfn << PAGE_SHIFT), PGDIR_SIZE);
> -	save_pgd = kmalloc(n_pgds * sizeof(pgd_t), GFP_KERNEL);
> +	save_pgd = kmalloc(n_pgds * sizeof(pgd_t), GFP_ATOMIC);
>  
>  	for (pgd = 0; pgd < n_pgds; pgd++) {
>  		save_pgd[pgd] = *pgd_offset_k(pgd * PGDIR_SIZE);

The allocation there, if it happens within a spinlocked path, is 
probably a layering violation - and GFP_ATOMIC is at best a 
workaround.

Thanks,

	Ingo