Re: [PATCH 1/2] x86/efi: Reserve SMBIOS table region when EFI booting

[Andrew Cooper <andrew.cooper3@citrix.com>]

On 02/04/15 09:24, Ross Lagerwall wrote:
> Some EFI firmware implementations may place the SMBIOS table in RAM
> marked as BootServicesData, which Xen does not consider as reserved.
> When dom0 tries to access the SMBIOS, the region is not contained in the
> initial P2M and it crashes with a page fault. To fix this, reserve the
> SMBIOS region.
>
> Also, fix the memcmp check for existence of the SMBIOS and the DMI
> checksum calculation.
>
> Signed-off-by: Ross Lagerwall <ross.lagerwall@citrix.com>

Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>

(Personally, I would either have folded the two patches together, or put
the memcmp() one first, fixing both occurrences.  However, as both of
these are candidates for backports, this probably turns more into a
bikeshed activity.)

> ---
>  xen/arch/x86/dmi_scan.c | 25 +++++++++++++++++++------
>  1 file changed, 19 insertions(+), 6 deletions(-)
>
> diff --git a/xen/arch/x86/dmi_scan.c b/xen/arch/x86/dmi_scan.c
> index 187c01e..ec411e6 100644
> --- a/xen/arch/x86/dmi_scan.c
> +++ b/xen/arch/x86/dmi_scan.c
> @@ -189,6 +189,8 @@ static inline bool_t __init dmi_checksum(const void __iomem *buf,
>  
>  static u32 __initdata efi_dmi_address;
>  static u32 __initdata efi_dmi_size;
> +static u32 __initdata efi_smbios_address;
> +static u32 __initdata efi_smbios_size;
>  static u64 __initdata efi_smbios3_address;
>  static u32 __initdata efi_smbios3_size;
>  
> @@ -209,13 +211,18 @@ void __init dmi_efi_get_table(const void *smbios, const void *smbios3)
>  		return;
>  	}
>  
> -	if (eps && memcmp(eps->anchor, "_SM_", 4) &&
> +	if (eps && memcmp(eps->anchor, "_SM_", 4) == 0 &&
>  	    eps->length >= sizeof(*eps) &&
> -	    dmi_checksum(eps, eps->length) &&
> -	    memcmp(eps->dmi.anchor, "_DMI_", 5) == 0 &&
> -	    dmi_checksum(&eps->dmi, sizeof(eps->dmi))) {
> -		efi_dmi_address = eps->dmi.address;
> -		efi_dmi_size = eps->dmi.size;
> +	    dmi_checksum(eps, eps->length)) {
> +		efi_smbios_address = (u32)(long)smbios;
> +		efi_smbios_size = eps->length;
> +
> +		if ( memcmp(eps->dmi.anchor, "_DMI_", 5) == 0 &&
> +		     dmi_checksum(&eps->dmi,
> +				  eps->length - offsetof(struct smbios_eps, dmi)) ) {
> +			efi_dmi_address = eps->dmi.address;
> +			efi_dmi_size = eps->dmi.size;
> +		}
>  	}
>  }
>  
> @@ -236,6 +243,12 @@ const char *__init dmi_get_table(paddr_t *base, u32 *len)
>  			instance |= 2;
>  			return "DMI";
>  		}
> +		if (efi_smbios_size && !(instance & 4)) {
> +			*base = efi_smbios_address;
> +			*len = efi_smbios_size;
> +			instance |= 4;
> +			return "SMBIOS";
> +		}
>  	} else {
>  		char __iomem *p = maddr_to_virt(0xF0000), *q;
>  		union {