Re: [PATCH 1/1] x86/platform/hyperv: When on Hyper-v use NULL legacy PIC

[Vivek Goyal]

On Thu, Apr 03, 2014 at 06:16:33PM -0700, K. Y. Srinivasan wrote:
> Use the NULL legacy PIC when on Hyper-V. With this change we can support kexec
> even when booting on EFI firmware. This patch has been tested on both EFI as
> well as non-EFI firmware stacks on Hyper-V.
> 
> This patch is required to support kexec on EFI firmware on Hyper-V. Please
> apply.

Can you give some more details about what's the problem we run into with
kexec on EFI on hyper-V.

Now EFI should be enabled in kexeced kernel. That means
efi_enabled(EFI_BOOT) should be true and that means you would set
legacy_pic to null anyway.

So with this patch, what changed w.r.t kexec on EFI.

Thansk
Vivek

> 
> Signed-off-by: K. Y. Srinivasan <kys@xxxxxxxxxxxxx>
> Cc: <stable@xxxxxxxxxxxxxxx>        [3.13+]
> ---
>  arch/x86/kernel/cpu/mshyperv.c |   10 ++--------
>  1 files changed, 2 insertions(+), 8 deletions(-)
> 
> diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
> index 76f98fe..47359f7 100644
> --- a/arch/x86/kernel/cpu/mshyperv.c
> +++ b/arch/x86/kernel/cpu/mshyperv.c
> @@ -133,14 +133,8 @@ static void __init ms_hyperv_init_platform(void)
>  		printk(KERN_INFO "HyperV: LAPIC Timer Frequency: %#x\n",
>  				lapic_timer_frequency);
>  
> -		/*
> -		 * On Hyper-V, when we are booting off an EFI firmware stack,
> -		 * we do not have many legacy devices including PIC, PIT etc.
> -		 */
> -		if (efi_enabled(EFI_BOOT)) {
> -			printk(KERN_INFO "HyperV: Using null_legacy_pic\n");
> -			legacy_pic = &null_legacy_pic;
> -		}
> +		printk(KERN_INFO "HyperV: Using null_legacy_pic\n");
> +		legacy_pic = &null_legacy_pic;
>  	}
>  #endif
>  
> -- 
> 1.7.4.1
> 
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