linux-kernel - Re: [PATCH 2/5 V6] x86/ioremap: strengthen the logic in early_memremap_pgprot

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Date:   Mon, 3 Sep 2018 10:45:12 +0800
From:   Dave Young <dyoung@...hat.com>
To:     Lianbo Jiang <lijiang@...hat.com>
Cc:     linux-kernel@...r.kernel.org, mingo@...hat.com, tglx@...utronix.de,
        hpa@...or.com, ebiederm@...ssion.com, joro@...tes.org,
        thomas.lendacky@....com, kexec@...ts.infradead.org,
        iommu@...ts.linux-foundation.org, bhe@...hat.com
Subject: Re: [PATCH 2/5 V6] x86/ioremap: strengthen the logic in
 early_memremap_pgprot_adjust() to adjust encryption mask

On 08/31/18 at 04:19pm, Lianbo Jiang wrote:
> For kdump kernel, when SME is enabled, the acpi table and dmi table will need
> to be remapped without the memory encryption mask. So we have to strengthen
> the logic in early_memremap_pgprot_adjust(), which makes us have an opportunity
> to adjust the memory encryption mask.
> 
> Signed-off-by: Lianbo Jiang <lijiang@...hat.com>
> ---
>  arch/x86/mm/ioremap.c | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/mm/ioremap.c b/arch/x86/mm/ioremap.c
> index e01e6c695add..f9d9a39955f3 100644
> --- a/arch/x86/mm/ioremap.c
> +++ b/arch/x86/mm/ioremap.c
> @@ -689,8 +689,15 @@ pgprot_t __init early_memremap_pgprot_adjust(resource_size_t phys_addr,
>  	encrypted_prot = true;
>  
>  	if (sme_active()) {
> +                /*
> +                 * In kdump kernel, the acpi table and dmi table will need
> +                 * to be remapped without the memory encryption mask. Here
> +                 * we have to strengthen the logic to adjust the memory
> +                 * encryption mask.

Assume the acpi/dmi tables are identical for both 1st kernel and kdump
kernel, I'm not sure what is the difference, why need special handling
for kdump. Can you add more explanations?

> +                 */
>  		if (early_memremap_is_setup_data(phys_addr, size) ||
> -		    memremap_is_efi_data(phys_addr, size))
> +		    memremap_is_efi_data(phys_addr, size) ||
> +		    is_kdump_kernel())
>  			encrypted_prot = false;
>  	}
>  
> -- 
> 2.17.1
> 

Thanks
Dave