[PATCH V6 0/4] map GHES memory region according to EFI memory map

[PATCH V6 0/4] map GHES memory region according to EFI memory map

[Jonathan (Zhixiong) Zhang]

From: "Jonathan (Zhixiong) Zhang" <zjzhang@codeaurora.org>

On a platform with APEI (ACPI Platform Error Interface) enabled, firmware
updates a memory region with hardware error record using nocache
attribute. When OS reads the region, since it maps the region with
cacahed attribute even though EFI memory map defines this region as
uncached, OS gets stale data and errorneously reports there is no new
HW error.

When ghes driver maps the memory region, it uses the cache attribute
according to EFI memory map, if EFI memory map feature is enabled
at runtime.

Since both arch/x86 and arch/ia64 implemented architecture agnostic EFI
memory map attribue lookup function efi_memattributes(), the code is
moved from arch/x86 into EFI subsystem and is declared as __weak; archs
other than ia64 should not override the default implementation.

V6:
1. Implemented arch_apei_get_mem_attributes() for arm64 as inline
   function.
2. Rebased to efi-next-14364 of efi/next, pm+acpi-4.2-rc3 of
   linux-pm/master, arm64-upstream-13521 of arm64/master,
   next-20150720 of linux-next/master.
V5:
1. Rebased to next-20150713 of linux-next/master, efi-next-14359 of
   efi/next, pm+acpi-4.2-rc2 of linux-pm/master,
   arm64-fixes-1215 of arm64/master.
2. Added comment for efi_mem_attributes(), explained why it is marked
   as __weak at the function definition site.
V4:
1. Introduced arch_apei_get_mem_attributes() to allow arch specific
   implementation of getting pgprot_t appropriate for a physical
   address.
2. Implemented arch_apei_get_mem_attributes() for x86 and for arm64.

V3:
1. Rebased to v4.1-rc7.
2. Moved efi_mem_attributes() from arch/x86 to drivers/firmware/efi
   and declared it as __weak.
3. Introduced ARCH_APEI_PAGE_KERNEL_UC to allow arch specific page
   protection type for UC.
4. Removed efi_ioremap(). It can not be used for GHES memory region
   mapping purpose since ioremap can not be used in atomic context.

V2:
1. Rebased to v4.1-rc5.
2. Split removal of efi_mem_attributes() and creation of efi_ioremap()
into two patches.

Jonathan (Zhixiong) Zhang (4):
  efi: x86: rearrange efi_mem_attributes()
  x86: acpi: implement arch_apei_get_mem_attributes()
  arm64: apei: implement arch_apei_get_mem_attributes()
  acpi, apei: use appropriate pgprot_t to map GHES memory

 arch/arm64/include/asm/acpi.h | 15 +++++++++++++++
 arch/x86/kernel/acpi/apei.c   | 10 ++++++++++
 arch/x86/platform/efi/efi.c   | 18 ------------------
 drivers/acpi/apei/ghes.c      |  6 ++++--
 drivers/firmware/efi/efi.c    | 31 +++++++++++++++++++++++++++++++
 include/acpi/apei.h           |  1 +
 6 files changed, 61 insertions(+), 20 deletions(-)

-- 
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project

[PATCH V6 2/4] x86: acpi: implement arch_apei_get_mem_attributes()

[Jonathan (Zhixiong) Zhang]

From: "Jonathan (Zhixiong) Zhang" <zjzhang@codeaurora.org>

... to allow arch specific implementation of getting page
protection type associated with a physical address.

If the physical address has memory attributes defined by EFI
memmap as EFI_MEMORY_UC, the page protection type is
PAGE_KENERL_NOCACHE. Otherwise, the page protection type is
PAGE_KERNEL.

Signed-off-by: Jonathan (Zhixiong) Zhang <zjzhang@codeaurora.org>
---
 arch/x86/kernel/acpi/apei.c | 10 ++++++++++
 include/acpi/apei.h         |  1 +
 2 files changed, 11 insertions(+)

diff --git a/arch/x86/kernel/acpi/apei.c b/arch/x86/kernel/acpi/apei.c
index c280df6b2aa2..9c6b3c8d81e4 100644
--- a/arch/x86/kernel/acpi/apei.c
+++ b/arch/x86/kernel/acpi/apei.c
@@ -14,6 +14,8 @@
 
 #include <acpi/apei.h>
 
+#include <linux/efi.h>
+
 #include <asm/mce.h>
 #include <asm/tlbflush.h>
 
@@ -60,3 +62,11 @@ void arch_apei_flush_tlb_one(unsigned long addr)
 {
 	__flush_tlb_one(addr);
 }
+
+pgprot_t arch_apei_get_mem_attribute(phys_addr_t addr)
+{
+	if (efi_mem_attributes(addr) & EFI_MEMORY_UC)
+		return PAGE_KERNEL_NOCACHE;
+
+	return PAGE_KERNEL;
+}
diff --git a/include/acpi/apei.h b/include/acpi/apei.h
index 284801ac7042..64a12ce9880b 100644
--- a/include/acpi/apei.h
+++ b/include/acpi/apei.h
@@ -46,6 +46,7 @@ int erst_clear(u64 record_id);
 int arch_apei_enable_cmcff(struct acpi_hest_header *hest_hdr, void *data);
 void arch_apei_report_mem_error(int sev, struct cper_sec_mem_err *mem_err);
 void arch_apei_flush_tlb_one(unsigned long addr);
+pgprot_t arch_apei_get_mem_attribute(phys_addr_t addr);
 
 #endif
 #endif
-- 
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project

[PATCH V6 4/4] acpi, apei: use appropriate pgprot_t to map GHES memory

[Jonathan (Zhixiong) Zhang]

From: "Jonathan (Zhixiong) Zhang" <zjzhang@codeaurora.org>

With ACPI APEI firmware first handling, generic hardware error
record is updated by firmware in GHES memory region. When firmware
updated GHES memory region with uncached access attribute, Linux
reads stale data from cache.

GHES memory region should be mapped with page protection type
according to what is returned from arch_apei_get_mem_attribute(),
instead of always with PAGE_KERNEL (eg. cached attribute).

Signed-off-by: Jonathan (Zhixiong) Zhang <zjzhang@codeaurora.org>
---
 drivers/acpi/apei/ghes.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/acpi/apei/ghes.c b/drivers/acpi/apei/ghes.c
index b979b5dbe5bc..98609b404dae 100644
--- a/drivers/acpi/apei/ghes.c
+++ b/drivers/acpi/apei/ghes.c
@@ -173,8 +173,10 @@ static void __iomem *ghes_ioremap_pfn_irq(u64 pfn)
 	unsigned long vaddr;
 
 	vaddr = (unsigned long)GHES_IOREMAP_IRQ_PAGE(ghes_ioremap_area->addr);
-	ioremap_page_range(vaddr, vaddr + PAGE_SIZE,
-			   pfn << PAGE_SHIFT, PAGE_KERNEL);
+	ioremap_page_range(vaddr,
+			   vaddr + PAGE_SIZE,
+			   pfn << PAGE_SHIFT,
+			   arch_apei_get_mem_attribute(pfn << PAGE_SHIFT));
 
 	return (void __iomem *)vaddr;
 }
-- 
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project

Re: [PATCH V6 2/4] x86: acpi: implement arch_apei_get_mem_attributes()

[Matt Fleming]

On Mon, 20 Jul, at 05:32:37PM, Jonathan (Zhixiong) Zhang wrote:
> From: "Jonathan (Zhixiong) Zhang" <zjzhang@codeaurora.org>
> 
> ... to allow arch specific implementation of getting page
> protection type associated with a physical address.
> 
> If the physical address has memory attributes defined by EFI
> memmap as EFI_MEMORY_UC, the page protection type is
> PAGE_KENERL_NOCACHE. Otherwise, the page protection type is
> PAGE_KERNEL.
> 
> Signed-off-by: Jonathan (Zhixiong) Zhang <zjzhang@codeaurora.org>
> ---
>  arch/x86/kernel/acpi/apei.c | 10 ++++++++++
>  include/acpi/apei.h         |  1 +
>  2 files changed, 11 insertions(+)
> 
> diff --git a/arch/x86/kernel/acpi/apei.c b/arch/x86/kernel/acpi/apei.c
> index c280df6b2aa2..9c6b3c8d81e4 100644
> --- a/arch/x86/kernel/acpi/apei.c
> +++ b/arch/x86/kernel/acpi/apei.c
> @@ -14,6 +14,8 @@
>  
>  #include <acpi/apei.h>
>  
> +#include <linux/efi.h>
> +
>  #include <asm/mce.h>
>  #include <asm/tlbflush.h>
>  
> @@ -60,3 +62,11 @@ void arch_apei_flush_tlb_one(unsigned long addr)
>  {
>  	__flush_tlb_one(addr);
>  }
> +
> +pgprot_t arch_apei_get_mem_attribute(phys_addr_t addr)
> +{
> +	if (efi_mem_attributes(addr) & EFI_MEMORY_UC)
> +		return PAGE_KERNEL_NOCACHE;
> +
> +	return PAGE_KERNEL;
> +}

Like I mentioned before, this is theoretically racey because depending
on when you call arch_apei_get_mem_attribute() during boot, you'll
potentially return a different protection for the *same* memory region.
This is because on x86 we discard the EFI memory map in
efi_free_boot_services(), after which time efi_mem_attributes() will
always return 0.

Now, hitting that race would depend on a number of things but most
importantly it would require the region of RAM containing the Hardware
Error data to have EFI_MEMORY_UC set in the EFI memmap. For x86 I think
it's fair to say that's extremely unlikely given our cache coherency
architecture.

Also, as Will noted for arm64, this really wants to be static inline.
I'm still hoping the x86/ACPI folks will chime in on this patch.

For x86 we don't need to perform this lookup today for GHES so I would
just always return PAGE_KERNEL but include a comment explaining that
doing anything else is unneeded. Something like this?

---

static inline pgprot_t arch_apei_get_mem_attribute(phys_addr_t addr)
{

	/*
	 * We currently have no way to lookup the EFI memory map
	 * attributes for a region in a consistent way because the memap
	 * is discarded after efi_free_boot_services(). So if you call
	 * efi_mem_attributes() during boot and at runtime you could
	 * theoretically see different attributes.
	 *
	 * Since we've yet to see any x86 platforms that require
	 * anything other than PAGE_KERNEL (some arm64 platforms require
	 * the equivalent of PAGE_KERNEL_NOCACHE), return that until we
	 * know different.
	 */

	return PAGE_KERNEL;
}

-- 
Matt Fleming, Intel Open Source Technology Center

Re: [PATCH V6 2/4] x86: acpi: implement arch_apei_get_mem_attributes()

[Zhang, Jonathan Zhixiong]

Thank you Matt for the great feedback.

On 7/22/2015 5:09 AM, Matt Fleming wrote:
> On Mon, 20 Jul, at 05:32:37PM, Jonathan (Zhixiong) Zhang wrote:
>> From: "Jonathan (Zhixiong) Zhang" <zjzhang-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org>
>>
>> ... to allow arch specific implementation of getting page
>> protection type associated with a physical address.
>>
>> If the physical address has memory attributes defined by EFI
>> memmap as EFI_MEMORY_UC, the page protection type is
>> PAGE_KENERL_NOCACHE. Otherwise, the page protection type is
>> PAGE_KERNEL.
>>
>> Signed-off-by: Jonathan (Zhixiong) Zhang <zjzhang-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org>
>> ---
>>   arch/x86/kernel/acpi/apei.c | 10 ++++++++++
>>   include/acpi/apei.h         |  1 +
>>   2 files changed, 11 insertions(+)
>>
>> diff --git a/arch/x86/kernel/acpi/apei.c b/arch/x86/kernel/acpi/apei.c
>> index c280df6b2aa2..9c6b3c8d81e4 100644
>> --- a/arch/x86/kernel/acpi/apei.c
>> +++ b/arch/x86/kernel/acpi/apei.c
>> @@ -14,6 +14,8 @@
>>
>>   #include <acpi/apei.h>
>>
>> +#include <linux/efi.h>
>> +
>>   #include <asm/mce.h>
>>   #include <asm/tlbflush.h>
>>
>> @@ -60,3 +62,11 @@ void arch_apei_flush_tlb_one(unsigned long addr)
>>   {
>>   	__flush_tlb_one(addr);
>>   }
>> +
>> +pgprot_t arch_apei_get_mem_attribute(phys_addr_t addr)
>> +{
>> +	if (efi_mem_attributes(addr) & EFI_MEMORY_UC)
>> +		return PAGE_KERNEL_NOCACHE;
>> +
>> +	return PAGE_KERNEL;
>> +}
>
> Like I mentioned before, this is theoretically racey because depending
> on when you call arch_apei_get_mem_attribute() during boot, you'll
> potentially return a different protection for the *same* memory region.
> This is because on x86 we discard the EFI memory map in
> efi_free_boot_services(), after which time efi_mem_attributes() will
> always return 0.
>
> Now, hitting that race would depend on a number of things but most
> importantly it would require the region of RAM containing the Hardware
> Error data to have EFI_MEMORY_UC set in the EFI memmap. For x86 I think
> it's fair to say that's extremely unlikely given our cache coherency
> architecture.
>
> Also, as Will noted for arm64, this really wants to be static inline.
Yes, will do.
> I'm still hoping the x86/ACPI folks will chime in on this patch.
Same here.
>
> For x86 we don't need to perform this lookup today for GHES so I would
> just always return PAGE_KERNEL but include a comment explaining that
> doing anything else is unneeded. Something like this?
The analysis and comments added make total sense to me. Will do so in V8
of the patch set after Will's feedback on v7.
>
> ---
>
> static inline pgprot_t arch_apei_get_mem_attribute(phys_addr_t addr)
> {
>
> 	/*
> 	 * We currently have no way to lookup the EFI memory map
> 	 * attributes for a region in a consistent way because the memap
> 	 * is discarded after efi_free_boot_services(). So if you call
> 	 * efi_mem_attributes() during boot and at runtime you could
> 	 * theoretically see different attributes.
> 	 *
> 	 * Since we've yet to see any x86 platforms that require
> 	 * anything other than PAGE_KERNEL (some arm64 platforms require
> 	 * the equivalent of PAGE_KERNEL_NOCACHE), return that until we
> 	 * know different.
> 	 */
>
> 	return PAGE_KERNEL;
> }
>

-- 
Jonathan (Zhixiong) Zhang
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project