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

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

[Ingo Molnar]

* Dan Williams <dan.j.williams@intel.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@linutronix.de>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: "H. Peter Anvin" <hpa@zytor.com>
> Cc: Tony Luck <tony.luck@intel.com>
> Cc: Borislav Petkov <bp@alien8.de>
> Cc: <linux-edac@vger.kernel.org>
> Cc: <x86@kernel.org>
> Signed-off-by: Dan Williams <dan.j.williams@intel.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
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[v6,11/13] x86/mm/pat: Prepare {reserve, free}_memtype() for "decoy" addresses

[Dave Jiang]

On 07/24/2018 12:36 AM, Ingo Molnar wrote:
> 
> * Dan Williams <dan.j.williams@intel.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@linutronix.de>
>> Cc: Ingo Molnar <mingo@redhat.com>
>> Cc: "H. Peter Anvin" <hpa@zytor.com>
>> Cc: Tony Luck <tony.luck@intel.com>
>> Cc: Borislav Petkov <bp@alien8.de>
>> Cc: <linux-edac@vger.kernel.org>
>> Cc: <x86@kernel.org>
>> Signed-off-by: Dan Williams <dan.j.williams@intel.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@lists.01.org
> https://lists.01.org/mailman/listinfo/linux-nvdimm
>
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[v6,11/13] x86/mm/pat: Prepare {reserve, free}_memtype() for "decoy" addresses

[Dan Williams]

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@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: <linux-edac@vger.kernel.org>
Cc: <x86@kernel.org>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
 arch/x86/mm/pat.c |   16 ++++++++++++++++
 1 file changed, 16 insertions(+)


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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;
+}
+
 /*
  * req_type typically has one of the:
  * - _PAGE_CACHE_MODE_WB
@@ -533,6 +544,8 @@ int reserve_memtype(u64 start, u64 end, enum page_cache_mode req_type,
 	int is_range_ram;
 	int err = 0;
 
+	start = sanitize_phys(start);
+	end = sanitize_phys(end);
 	BUG_ON(start >= end); /* end is exclusive */
 
 	if (!pat_enabled()) {
@@ -609,6 +622,9 @@ int free_memtype(u64 start, u64 end)
 	if (!pat_enabled())
 		return 0;
 
+	start = sanitize_phys(start);
+	end = sanitize_phys(end);
+
 	/* Low ISA region is always mapped WB. No need to track */
 	if (x86_platform.is_untracked_pat_range(start, end))
 		return 0;