linux-kernel - Re: [PATCH] intel-rng workarounds

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Date:	Wed, 3 Jan 2007 11:09:25 +0100
From:	Michael Buesch <mb@...sch.de>
To:	"Jan Beulich" <jbeulich@...ell.com>
Cc:	jgarzik@...ox.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] intel-rng workarounds

On Wednesday 03 January 2007 10:18, Jan Beulich wrote:
> Add a load option to intel-rng to allow skipping the FWH detection,
> necessary in case the BIOS has locked read-only the firmware hub space.
> Also prevent any attempt to write to firmware space if it cannot be
> write enabled (apparently caused hangs on some systems not having an
> FWH and thus also not having a respective RNG).
> 
> Signed-off-by: Jan Beulich <jbeulich@...ell.com>
> 
> --- linux-2.6.20-rc3/drivers/char/hw_random/intel-rng.c	2006-11-29 22:57:37.000000000 +0100
> +++ 2.6.20-rc3-intel-rng-skip-fhw-detect/drivers/char/hw_random/intel-rng.c	2006-11-29 09:09:21.000000000 +0100
> @@ -143,6 +143,8 @@ static const struct pci_device_id pci_tb
>  };
>  MODULE_DEVICE_TABLE(pci, pci_tbl);
>  
> +static __initdata int no_fwh_detect;
> +module_param(no_fwh_detect, int, 0);

I'd say we need some parameter description saying that
-1 == always skip and 1 == skip if R/O.
Otherwise this is quite confusing.

>  static inline u8 hwstatus_get(void __iomem *mem)
>  {
> @@ -240,6 +242,11 @@ static int __init mod_init(void)
>  	if (!dev)
>  		goto out; /* Device not found. */
>  
> +	if (no_fwh_detect < 0) {
> +		pci_dev_put(dev);
> +		goto fwh_done;
> +	}
> +
>  	/* Check for Intel 82802 */
>  	if (dev->device < 0x2640) {
>  		fwh_dec_en1_off = FWH_DEC_EN1_REG_OLD;
> @@ -252,6 +259,23 @@ static int __init mod_init(void)
>  	pci_read_config_byte(dev, fwh_dec_en1_off, &fwh_dec_en1_val);
>  	pci_read_config_byte(dev, bios_cntl_off, &bios_cntl_val);
>  
> +	if ((bios_cntl_val &
> +	     (BIOS_CNTL_LOCK_ENABLE_MASK|BIOS_CNTL_WRITE_ENABLE_MASK))
> +	    == BIOS_CNTL_LOCK_ENABLE_MASK) {
> +		static __initdata /*const*/ char warning[] =
> +			KERN_WARNING PFX "Firmware space is locked read-only. If you can't or\n"
> +			KERN_WARNING PFX "don't want to disable this in firmware setup, and if\n"
> +			KERN_WARNING PFX "you are certain that your system has a functional\n"
> +			KERN_WARNING PFX "RNG, try using the 'no_fwh_detect' option.\n";
> +
> +		pci_dev_put(dev);
> +		if (no_fwh_detect)
> +			goto fwh_done;
> +		printk(warning);
> +		err = -EBUSY;
> +		goto out;
> +	}
> +
>  	mem = ioremap_nocache(INTEL_FWH_ADDR, INTEL_FWH_ADDR_LEN);
>  	if (mem == NULL) {
>  		pci_dev_put(dev);
> @@ -280,8 +304,7 @@ static int __init mod_init(void)
>  		pci_write_config_byte(dev,
>  		                      fwh_dec_en1_off,
>  		                      fwh_dec_en1_val | FWH_F8_EN_MASK);
> -	if (!(bios_cntl_val &
> -	      (BIOS_CNTL_LOCK_ENABLE_MASK|BIOS_CNTL_WRITE_ENABLE_MASK)))
> +	if (!(bios_cntl_val & BIOS_CNTL_WRITE_ENABLE_MASK))
>  		pci_write_config_byte(dev,
>  		                      bios_cntl_off,
>  		                      bios_cntl_val | BIOS_CNTL_WRITE_ENABLE_MASK);
> @@ -315,6 +338,8 @@ static int __init mod_init(void)
>  		goto out;
>  	}
>  
> +fwh_done:
> +
>  	err = -ENOMEM;
>  	mem = ioremap(INTEL_RNG_ADDR, INTEL_RNG_ADDR_LEN);
>  	if (!mem)
> 
> 
> 
> 

-- 
Greetings Michael.
-
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