linux-kernel - Re: [PATCHv3 08/11] arm64: Check for selected granule support

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Date:	Thu, 15 Oct 2015 16:02:36 +0100
From:	"Suzuki K. Poulose" <Suzuki.Poulose@....com>
To:	Jeremy Linton <jeremy.linton@....com>,
	Mark Rutland <mark.rutland@....com>
Cc:	linux-arm-kernel@...ts.infradead.org, steve.capper@...aro.org,
	ard.biesheuvel@...aro.org, marc.zyngier@....com,
	catalin.marinas@....com, will.deacon@....com,
	linux-kernel@...r.kernel.org, christoffer.dall@...aro.org
Subject: Re: [PATCHv3 08/11] arm64: Check for selected granule support

On 15/10/15 15:47, Jeremy Linton wrote:
> On 10/15/2015 06:25 AM, Suzuki K. Poulose wrote:
>> +    /*
>> +     * Check to see if the CPU supports the requested pagesize
>> +     */
>> +    asm volatile("mrs %0, ID_AA64MMFR0_EL1" : "=r" (aa64mmfr0_el1));
>> +    aa64mmfr0_el1 >>= ID_AA64MMFR0_TGRAN_SHIFT;
>> +    if ((aa64mmfr0_el1 & 0xf) != ID_AA64MMFR0_TGRAN_SUPPORTED) {
>> +        pr_efi_err(sys_table_arg, PAGE_SIZE_STR" granule not supported by the CPU\n");
>> +        return EFI_UNSUPPORTED;
>> +    }
>
>
> This is definitely an improvement over my original hack job.
>
> I would like to add, that I actually think this should be in a new function
> "check_kernel_compatibility" (or whatever) that is called before handle_kernel_image.
>
> That is because I don't really think it belongs in handle_kernel_image which is
>  focused on relocation.  Plus, if you add another function, you can avoid the
> "Failed to relocate kernel" error that comes out following the granule not supported message.
> Further, checks like this in the future will have a place to live.
>
> Of course you will then need a matching stubbed out function for the normal arm kernel as well.


OK, I will drop it from this series then and can be worked as a separate patch.

Thanks
Suzuki

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