[PATCH] x86/mtrr: Drop workaround for old 32bit CPUs

[PATCH] x86/mtrr: Drop workaround for old 32bit CPUs

[Andrew Cooper]

This logic is dead as Xen is 64bit-only these days.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
---
CC: Jan Beulich <JBeulich@suse.com>
CC: Wei Liu <wl@xen.org>
CC: Roger Pau Monné <roger.pau@citrix.com>
---
 xen/arch/x86/cpu/mtrr/generic.c | 17 -----------------
 1 file changed, 17 deletions(-)

diff --git a/xen/arch/x86/cpu/mtrr/generic.c b/xen/arch/x86/cpu/mtrr/generic.c
index 89634f918f..06fa0c0420 100644
--- a/xen/arch/x86/cpu/mtrr/generic.c
+++ b/xen/arch/x86/cpu/mtrr/generic.c
@@ -570,23 +570,6 @@ int generic_validate_add_page(unsigned long base, unsigned long size, unsigned i
 {
 	unsigned long lbase, last;
 
-	/*  For Intel PPro stepping <= 7, must be 4 MiB aligned 
-	    and not touch 0x70000000->0x7003FFFF */
-	if (is_cpu(INTEL) && boot_cpu_data.x86 == 6 &&
-	    boot_cpu_data.x86_model == 1 &&
-	    boot_cpu_data.x86_mask <= 7) {
-		if (base & ((1 << (22 - PAGE_SHIFT)) - 1)) {
-			printk(KERN_WARNING "mtrr: base(%#lx000) is not 4 MiB aligned\n", base);
-			return -EINVAL;
-		}
-		if (!(base + size < 0x70000 || base > 0x7003F) &&
-		    (type == MTRR_TYPE_WRCOMB
-		     || type == MTRR_TYPE_WRBACK)) {
-			printk(KERN_WARNING "mtrr: writable mtrr between 0x70000000 and 0x7003FFFF may hang the CPU.\n");
-			return -EINVAL;
-		}
-	}
-
 	/*  Check upper bits of base and last are equal and lower bits are 0
 	    for base and 1 for last  */
 	last = base + size - 1;
-- 
2.11.0

Re: [PATCH] x86/mtrr: Drop workaround for old 32bit CPUs

[Roger Pau Monné]

On Wed, Jul 08, 2020 at 11:14:43AM +0100, Andrew Cooper wrote:
> This logic is dead as Xen is 64bit-only these days.
> 
> Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>

Reviewed-by: Roger Pau Monné <roger.pau@citrix.com>

> ---
> CC: Jan Beulich <JBeulich@suse.com>
> CC: Wei Liu <wl@xen.org>
> CC: Roger Pau Monné <roger.pau@citrix.com>
> ---
>  xen/arch/x86/cpu/mtrr/generic.c | 17 -----------------
>  1 file changed, 17 deletions(-)
> 
> diff --git a/xen/arch/x86/cpu/mtrr/generic.c b/xen/arch/x86/cpu/mtrr/generic.c
> index 89634f918f..06fa0c0420 100644
> --- a/xen/arch/x86/cpu/mtrr/generic.c
> +++ b/xen/arch/x86/cpu/mtrr/generic.c
> @@ -570,23 +570,6 @@ int generic_validate_add_page(unsigned long base, unsigned long size, unsigned i
>  {
>  	unsigned long lbase, last;
>  
> -	/*  For Intel PPro stepping <= 7, must be 4 MiB aligned 
> -	    and not touch 0x70000000->0x7003FFFF */
> -	if (is_cpu(INTEL) && boot_cpu_data.x86 == 6 &&
> -	    boot_cpu_data.x86_model == 1 &&
> -	    boot_cpu_data.x86_mask <= 7) {
> -		if (base & ((1 << (22 - PAGE_SHIFT)) - 1)) {
> -			printk(KERN_WARNING "mtrr: base(%#lx000) is not 4 MiB aligned\n", base);
> -			return -EINVAL;
> -		}
> -		if (!(base + size < 0x70000 || base > 0x7003F) &&
> -		    (type == MTRR_TYPE_WRCOMB
> -		     || type == MTRR_TYPE_WRBACK)) {
> -			printk(KERN_WARNING "mtrr: writable mtrr between 0x70000000 and 0x7003FFFF may hang the CPU.\n");
> -			return -EINVAL;
> -		}
> -	}
> -
>  	/*  Check upper bits of base and last are equal and lower bits are 0
>  	    for base and 1 for last  */
>  	last = base + size - 1;

FWIW, you could also initialize last at definition time.

Roger.

Re: [PATCH] x86/mtrr: Drop workaround for old 32bit CPUs

[Andrew Cooper]

On 08/07/2020 11:48, Roger Pau Monné wrote:
> On Wed, Jul 08, 2020 at 11:14:43AM +0100, Andrew Cooper wrote:
>> This logic is dead as Xen is 64bit-only these days.
>>
>> Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
> Reviewed-by: Roger Pau Monné <roger.pau@citrix.com>

Thanks,

>> ---
>> CC: Jan Beulich <JBeulich@suse.com>
>> CC: Wei Liu <wl@xen.org>
>> CC: Roger Pau Monné <roger.pau@citrix.com>
>> ---
>>  xen/arch/x86/cpu/mtrr/generic.c | 17 -----------------
>>  1 file changed, 17 deletions(-)
>>
>> diff --git a/xen/arch/x86/cpu/mtrr/generic.c b/xen/arch/x86/cpu/mtrr/generic.c
>> index 89634f918f..06fa0c0420 100644
>> --- a/xen/arch/x86/cpu/mtrr/generic.c
>> +++ b/xen/arch/x86/cpu/mtrr/generic.c
>> @@ -570,23 +570,6 @@ int generic_validate_add_page(unsigned long base, unsigned long size, unsigned i
>>  {
>>  	unsigned long lbase, last;
>>  
>> -	/*  For Intel PPro stepping <= 7, must be 4 MiB aligned 
>> -	    and not touch 0x70000000->0x7003FFFF */
>> -	if (is_cpu(INTEL) && boot_cpu_data.x86 == 6 &&
>> -	    boot_cpu_data.x86_model == 1 &&
>> -	    boot_cpu_data.x86_mask <= 7) {
>> -		if (base & ((1 << (22 - PAGE_SHIFT)) - 1)) {
>> -			printk(KERN_WARNING "mtrr: base(%#lx000) is not 4 MiB aligned\n", base);
>> -			return -EINVAL;
>> -		}
>> -		if (!(base + size < 0x70000 || base > 0x7003F) &&
>> -		    (type == MTRR_TYPE_WRCOMB
>> -		     || type == MTRR_TYPE_WRBACK)) {
>> -			printk(KERN_WARNING "mtrr: writable mtrr between 0x70000000 and 0x7003FFFF may hang the CPU.\n");
>> -			return -EINVAL;
>> -		}
>> -	}
>> -
>>  	/*  Check upper bits of base and last are equal and lower bits are 0
>>  	    for base and 1 for last  */
>>  	last = base + size - 1;
> FWIW, you could also initialize last at definition time.

I've got some very different cleanup in mind for that code, seeing as it
can be simplified to a single test expression.

~Andrew

Re: [PATCH] x86/mtrr: Drop workaround for old 32bit CPUs

[Roger Pau Monné]

On Wed, Jul 08, 2020 at 11:52:57AM +0100, Andrew Cooper wrote:
> On 08/07/2020 11:48, Roger Pau Monné wrote:
> > On Wed, Jul 08, 2020 at 11:14:43AM +0100, Andrew Cooper wrote:
> >>  	/*  Check upper bits of base and last are equal and lower bits are 0
> >>  	    for base and 1 for last  */
> >>  	last = base + size - 1;
> > FWIW, you could also initialize last at definition time.
> 
> I've got some very different cleanup in mind for that code, seeing as it
> can be simplified to a single test expression.

Oh, I certainly didn't look at it that much :).

Thanks, Roger.

Re: [PATCH] x86/mtrr: Drop workaround for old 32bit CPUs

[Jan Beulich]

On 08.07.2020 12:14, Andrew Cooper wrote:
> This logic is dead as Xen is 64bit-only these days.

Ah, yes, this should have long been gone.

Jan