linux-kernel - Re: [PATCH] x86/ioremap: Map EFI runtime services data as encrypted for SEV

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Message-ID: <20200310124003.GE29372@zn.tnic>
Date:   Tue, 10 Mar 2020 13:40:03 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Tom Lendacky <thomas.lendacky@....com>
Cc:     linux-kernel@...r.kernel.org, x86@...nel.org,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Bruce Rogers <brogers@...e.com>, Joerg Roedel <jroedel@...e.de>
Subject: Re: [PATCH] x86/ioremap: Map EFI runtime services data as encrypted
 for SEV

On Tue, Feb 25, 2020 at 09:42:07AM -0600, Tom Lendacky wrote:
> The dmidecode program fails to properly decode the SMBIOS data supplied
> by OVMF/UEFI when running on an SEV guest. The SMBIOS area, under SEV, is
> encrypted and resides in reserved memory that is marked as EFI runtime
> services data. As a result, when memremap() is attempted for the SMBIOS
> data, it can't be mapped as regular RAM (through try_ram_remap()) and,
> since the address isn't part of the iomem resources list, it isn't mapped
> encrypted through the fallback ioremap().
> 
> Update __ioremap_check_mem() to set the IORES_MAP_ENCRYPTED flag if SEV is
> active and the memory being mapped is part of EFI runtime services data.
> This allows any runtime services data, which has been created encrypted,
> to be mapped encrypted.
> 
> Cc: Bruce Rogers <brogers@...e.com>
> Cc: Joerg Roedel <jroedel@...e.de>
> Signed-off-by: Tom Lendacky <thomas.lendacky@....com>
> ---
>  arch/x86/mm/ioremap.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/arch/x86/mm/ioremap.c b/arch/x86/mm/ioremap.c
> index 44e4beb4239f..382b6ca66820 100644
> --- a/arch/x86/mm/ioremap.c
> +++ b/arch/x86/mm/ioremap.c
> @@ -135,6 +135,13 @@ static void __ioremap_check_mem(resource_size_t addr, unsigned long size,
>  	memset(desc, 0, sizeof(struct ioremap_desc));
>  
>  	walk_mem_res(start, end, desc, __ioremap_collect_map_flags);
> +
> +	/*
> +	 * The EFI runtime services data area is not covered by walk_mem_res(),
> +	 * but must be mapped encrypted when SEV is active.
> +	 */
> +	if (sev_active() && efi_mem_type(addr) == EFI_RUNTIME_SERVICES_DATA)
> +		desc->flags |= IORES_MAP_ENCRYPTED;
>  }

Why isn't this done in __ioremap_check_encrypted() which is exactly for
SEV stuff like that?

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette