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

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Date:   Wed, 11 Mar 2020 10:04:47 +0100
From:   Joerg Roedel <jroedel@...e.de>
To:     Borislav Petkov <bp@...en8.de>
Cc:     Tom Lendacky <thomas.lendacky@....com>,
        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>
Subject: Re: [PATCH] x86/ioremap: Map EFI runtime services data as encrypted
 for SEV

Hi,

On Tue, Mar 10, 2020 at 06:47:31PM +0100, Borislav Petkov wrote:
> Ok, here's what I have. @joro, I know it is trivially different from the
> version you tested but I'd appreciate it if you ran it again, just to be
> sure.

Looks good and ested it, works fine.

Reviewed-by: Joerg Roedel <jroedel@...e.de>
Tested-by: Joerg Roedel <jroedel@...e.de>

> ---
> >From 244b62ca142c6296361bde953488fc64db31f1bd Mon Sep 17 00:00:00 2001
> From: Tom Lendacky <thomas.lendacky@....com>
> Date: Tue, 10 Mar 2020 18:35:57 +0100
> Subject: [PATCH] x86/ioremap: Map EFI runtime services data as encrypted for
>  SEV
> 
> The dmidecode program fails to properly decode the SMBIOS data supplied
> by OVMF/UEFI when running in 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().
> 
> Add a new __ioremap_check_other() to deal with memory types like
> EFI_RUNTIME_SERVICES_DATA which are not covered by the resource ranges.
> 
> This allows any runtime services data, which has been created encrypted,
> to be mapped encrypted.
> 
>  [ bp: Move functionality to a separate function. ]
> 
> Signed-off-by: Tom Lendacky <thomas.lendacky@....com>
> Signed-off-by: Borislav Petkov <bp@...e.de>
> Cc: <stable@...r.kernel.org> # 5.3
> Link: https://lkml.kernel.org/r/2d9e16eb5b53dc82665c95c6764b7407719df7a0.1582645327.git.thomas.lendacky@amd.com
> ---
>  arch/x86/mm/ioremap.c | 18 ++++++++++++++++++
>  1 file changed, 18 insertions(+)
> 
> diff --git a/arch/x86/mm/ioremap.c b/arch/x86/mm/ioremap.c
> index 44e4beb4239f..935a91e1fd77 100644
> --- a/arch/x86/mm/ioremap.c
> +++ b/arch/x86/mm/ioremap.c
> @@ -106,6 +106,19 @@ static unsigned int __ioremap_check_encrypted(struct resource *res)
>  	return 0;
>  }
>  
> +/*
> + * The EFI runtime services data area is not covered by walk_mem_res(), but must
> + * be mapped encrypted when SEV is active.
> + */
> +static void __ioremap_check_other(resource_size_t addr, struct ioremap_desc *desc)
> +{
> +	if (!sev_active())
> +		return;
> +
> +	if (efi_mem_type(addr) == EFI_RUNTIME_SERVICES_DATA)
> +		desc->flags |= IORES_MAP_ENCRYPTED;
> +}
> +
>  static int __ioremap_collect_map_flags(struct resource *res, void *arg)
>  {
>  	struct ioremap_desc *desc = arg;
> @@ -124,6 +137,9 @@ static int __ioremap_collect_map_flags(struct resource *res, void *arg)
>   * To avoid multiple resource walks, this function walks resources marked as
>   * IORESOURCE_MEM and IORESOURCE_BUSY and looking for system RAM and/or a
>   * resource described not as IORES_DESC_NONE (e.g. IORES_DESC_ACPI_TABLES).
> + *
> + * After that, deal with misc other ranges in __ioremap_check_other() which do
> + * not fall into the above category.
>   */
>  static void __ioremap_check_mem(resource_size_t addr, unsigned long size,
>  				struct ioremap_desc *desc)
> @@ -135,6 +151,8 @@ 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);
> +
> +	__ioremap_check_other(addr, desc);
>  }
>  
>  /*
> -- 
> 2.21.0
> 
> -- 
> Regards/Gruss,
>     Boris.
> 
> https://people.kernel.org/tglx/notes-about-netiquette