linux-kernel - Re: [PATCH v4 07/12] x86/mtrr: allocate mtrr

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Message-ID: <ef53ce07-6d7e-efbd-0301-4984297c0f5b@suse.com>
Date:   Mon, 27 Mar 2023 07:44:30 +0200
From:   Juergen Gross <jgross@...e.com>
To:     Borislav Petkov <bp@...en8.de>
Cc:     linux-kernel@...r.kernel.org, x86@...nel.org,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH v4 07/12] x86/mtrr: allocate mtrr_value array dynamically

On 27.03.23 00:05, Borislav Petkov wrote:
> On Mon, Mar 06, 2023 at 05:34:20PM +0100, Juergen Gross wrote:
>> The mtrr_value[] array is a static variable, which is used only in a
>> few configurations. Consuming 6kB is ridiculous for this case,
> 
> Ah, that struct mtrr_value is of size 24 due to that first member
> mtrr_type getting padded even if it is a u8.
> 
>> especially as the array doesn't need to be that large and it can easily
>> be allocated dynamically.
>>
>> Signed-off-by: Juergen Gross <jgross@...e.com>
>> ---
>>   arch/x86/kernel/cpu/mtrr/mtrr.c | 3 ++-
>>   1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/x86/kernel/cpu/mtrr/mtrr.c b/arch/x86/kernel/cpu/mtrr/mtrr.c
>> index 0c83990501f5..50cd2287b6e1 100644
>> --- a/arch/x86/kernel/cpu/mtrr/mtrr.c
>> +++ b/arch/x86/kernel/cpu/mtrr/mtrr.c
>> @@ -581,7 +581,7 @@ struct mtrr_value {
>>   	unsigned long	lsize;
>>   };
>>   
>> -static struct mtrr_value mtrr_value[MTRR_MAX_VAR_RANGES];
>> +static struct mtrr_value *mtrr_value;
>>   
>>   static int mtrr_save(void)
>>   {
>> @@ -750,6 +750,7 @@ static int __init mtrr_init_finialize(void)
>>   	 * TBD: is there any system with such CPU which supports
>>   	 * suspend/resume? If no, we should remove the code.
>>   	 */
>> +	mtrr_value = kcalloc(num_var_ranges, sizeof(*mtrr_value), GFP_KERNEL);
> 
> Pls put that over the comment.
> 
> Also, you need to handle kcalloc() returning an error.

Okay.


Juergen


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