linux-kernel - Re: [PATCH v6 11/13] x86/mm/pat: Prepare {reserve, free}_memtype() for "decoy" addresses

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Date:   Tue, 24 Jul 2018 08:46:06 -0700
From:   Dave Jiang <dave.jiang@...el.com>
To:     Ingo Molnar <mingo@...nel.org>,
        Dan Williams <dan.j.williams@...el.com>
Cc:     Tony Luck <tony.luck@...el.com>, linux-nvdimm@...ts.01.org,
        x86@...nel.org, linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>, linux-fsdevel@...r.kernel.org,
        Thomas Gleixner <tglx@...utronix.de>, hch@....de,
        linux-edac@...r.kernel.org
Subject: Re: [PATCH v6 11/13] x86/mm/pat: Prepare {reserve, free}_memtype()
 for "decoy" addresses

On 07/24/2018 12:36 AM, Ingo Molnar wrote:
> 
> * Dan Williams <dan.j.williams@...el.com> wrote:
> 
>> In preparation for using set_memory_uc() instead set_memory_np() for
>> isolating poison from speculation, teach the memtype code to sanitize
>> physical addresses vs __PHYSICAL_MASK.
>>
>> The motivation for using set_memory_uc() for this case is to allow
>> ongoing access to persistent memory pages via the pmem-driver +
>> memcpy_mcsafe() until the poison is repaired.
>>
>> Cc: Thomas Gleixner <tglx@...utronix.de>
>> Cc: Ingo Molnar <mingo@...hat.com>
>> Cc: "H. Peter Anvin" <hpa@...or.com>
>> Cc: Tony Luck <tony.luck@...el.com>
>> Cc: Borislav Petkov <bp@...en8.de>
>> Cc: <linux-edac@...r.kernel.org>
>> Cc: <x86@...nel.org>
>> Signed-off-by: Dan Williams <dan.j.williams@...el.com>
>> ---
>>  arch/x86/mm/pat.c |   16 ++++++++++++++++
>>  1 file changed, 16 insertions(+)
>>
>> diff --git a/arch/x86/mm/pat.c b/arch/x86/mm/pat.c
>> index 1555bd7d3449..6788ffa990f8 100644
>> --- a/arch/x86/mm/pat.c
>> +++ b/arch/x86/mm/pat.c
>> @@ -512,6 +512,17 @@ static int free_ram_pages_type(u64 start, u64 end)
>>  	return 0;
>>  }
>>  
>> +static u64 sanitize_phys(u64 address)
>> +{
>> +	/*
>> +	 * When changing the memtype for pages containing poison allow
>> +	 * for a "decoy" virtual address (bit 63 clear) passed to
>> +	 * set_memory_X(). __pa() on a "decoy" address results in a
>> +	 * physical address with it 63 set.
>> +	 */
>> +	return address & __PHYSICAL_MASK;
> 
> s/it/bit

Thanks Ingo! I'll update when I pull in the patch.

> 
> Thanks,
> 
> 	Ingo
> _______________________________________________
> Linux-nvdimm mailing list
> Linux-nvdimm@...ts.01.org
> https://lists.01.org/mailman/listinfo/linux-nvdimm
> 

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