[PATCH v2 0/2] efi/arm*: wire up ESRT table

[PATCH v2 0/2] efi/arm*: wire up ESRT table

[Ard Biesheuvel]

This v2 is a followup to the series I sent out on Feb 15. These now
apply onto Matt's memmap refactoring work which is intended for inclusion
in v4.9, and the diffstat below reveals that enabling ESRT is now absolutely
trivial. The only things needed are replacing ioremap() with memremap(),
and adding the missing efi_esrt_init() invocation.

I dropped the Tested-by tags, simply because the underlying code is completely
different now. I kept Peter's ack on #1, though.

Ard Biesheuvel (2):
  efi: esrt: use memremap not ioremap to access ESRT table in memory
  efi/arm*: esrt: add missing call to efi_esrt_init()

 drivers/firmware/efi/arm-init.c | 1 +
 drivers/firmware/efi/esrt.c     | 5 +++--
 2 files changed, 4 insertions(+), 2 deletions(-)

-- 
1.9.1

[PATCH v2 1/2] efi: esrt: use memremap not ioremap to access ESRT table in memory

[Ard Biesheuvel]

On ARM and arm64, ioremap() and memremap() are not interchangeable like
on x86, and the use of ioremap() on ordinary RAM is typically flagged
as an error if the memory region being mapped is also covered by the
linear mapping, since that would lead to aliases with conflicting
cacheability attributes.

Since what we are dealing with is not an I/O region with side effects,
using ioremap() here is arguably incorrect anyway, so let's replace
it with memremap() instead.

Acked-by: Peter Jones <pjones@redhat.com>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
---
 drivers/firmware/efi/esrt.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/firmware/efi/esrt.c b/drivers/firmware/efi/esrt.c
index b93cd11f9bcc..14914074f716 100644
--- a/drivers/firmware/efi/esrt.c
+++ b/drivers/firmware/efi/esrt.c
@@ -16,6 +16,7 @@
 #include <linux/device.h>
 #include <linux/efi.h>
 #include <linux/init.h>
+#include <linux/io.h>
 #include <linux/kernel.h>
 #include <linux/kobject.h>
 #include <linux/list.h>
@@ -387,9 +388,9 @@ static int __init esrt_sysfs_init(void)
 	if (!esrt_data || !esrt_data_size)
 		return -ENOSYS;
 
-	esrt = ioremap(esrt_data, esrt_data_size);
+	esrt = memremap(esrt_data, esrt_data_size, MEMREMAP_WB);
 	if (!esrt) {
-		pr_err("ioremap(%pa, %zu) failed.\n", &esrt_data,
+		pr_err("memremap(%pa, %zu) failed.\n", &esrt_data,
 		       esrt_data_size);
 		return -ENOMEM;
 	}
-- 
1.9.1

[PATCH v2 1/2] efi: esrt: use memremap not ioremap to access ESRT table in memory

[Matt Fleming]

On Mon, 11 Jul, at 09:00:45PM, Ard Biesheuvel wrote:
> On ARM and arm64, ioremap() and memremap() are not interchangeable like
> on x86, and the use of ioremap() on ordinary RAM is typically flagged
> as an error if the memory region being mapped is also covered by the
> linear mapping, since that would lead to aliases with conflicting
> cacheability attributes.
> 
> Since what we are dealing with is not an I/O region with side effects,
> using ioremap() here is arguably incorrect anyway, so let's replace
> it with memremap() instead.
> 
> Acked-by: Peter Jones <pjones@redhat.com>
> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> ---
>  drivers/firmware/efi/esrt.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)

Looks sensible, thanks Ard, applied.

[PATCH v2 2/2] efi/arm*: esrt: add missing call to efi_esrt_init()

[Ard Biesheuvel]

ESRT support is built by default for all architectures that define
CONFIG_EFI. However, this support was not wired up yet for ARM/arm64,
since efi_esrt_init() was never called. So add the missing call.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
---
 drivers/firmware/efi/arm-init.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/firmware/efi/arm-init.c b/drivers/firmware/efi/arm-init.c
index 5a2df3fefccc..e0a511d4074f 100644
--- a/drivers/firmware/efi/arm-init.c
+++ b/drivers/firmware/efi/arm-init.c
@@ -247,6 +247,7 @@ void __init efi_init(void)
 
 	reserve_regions();
 	efi_memattr_init();
+	efi_esrt_init();
 	efi_memmap_unmap();
 
 	memblock_reserve(params.mmap & PAGE_MASK,
-- 
1.9.1

[PATCH v2 2/2] efi/arm*: esrt: add missing call to efi_esrt_init()

[Matt Fleming]

On Mon, 11 Jul, at 09:00:46PM, Ard Biesheuvel wrote:
> ESRT support is built by default for all architectures that define
> CONFIG_EFI. However, this support was not wired up yet for ARM/arm64,
> since efi_esrt_init() was never called. So add the missing call.
> 
> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> ---
>  drivers/firmware/efi/arm-init.c | 1 +
>  1 file changed, 1 insertion(+)

Thanks Ard, applied and queued up for v4.9 on top of the EFI memmap
refactoring.

[PATCH v2 0/2] efi: ARM/arm64: wire up ESRT table

[Ard Biesheuvel]

As reported by Tyler, the ESRT support was not wired up yet for ARM or
arm64, hence this series.

Patch #1 replaces ioremap with memremap in the generic ESRT support, since
what we are mapping is not I/O, and this does make a difference on ARM/arm64

Patch #2 adds the missing efi_esrt_init() call, and tweaks some memmap fields
that efi_mem_desc_lookup() expects.

Ard Biesheuvel (2):
  efi: esrt: use memremap not ioremap to access ESRT table in memory
  arm64/efi: esrt: add missing call to efi_esrt_init()

 drivers/firmware/efi/arm-init.c |  3 +++
 drivers/firmware/efi/esrt.c     | 16 ++++++++--------
 2 files changed, 11 insertions(+), 8 deletions(-)

-- 
2.5.0

[PATCH v2 1/2] efi: esrt: use memremap not ioremap to access ESRT table in memory

[Ard Biesheuvel]

On ARM and arm64, ioremap() and memremap() are not interchangeable like
on x86, and the use of ioremap() on ordinary RAM is typically flagged
as an error if the memory region being mapped is also covered by the
linear mapping, since that would lead to aliases with conflicting
cacheability attributes.

Since what we are dealing with is not an I/O region with side effects,
using ioremap() here is arguably incorrect anyway, so let's replace
it with memremap instead. Also add a missing unmap on the success path,
and drop a memblock_remove() call which does not belong here, this far
into the boot sequence.

Cc: Peter Jones <pjones@redhat.com>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
---
 drivers/firmware/efi/esrt.c | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/drivers/firmware/efi/esrt.c b/drivers/firmware/efi/esrt.c
index 22c5285f7705..f096a0a26dbd 100644
--- a/drivers/firmware/efi/esrt.c
+++ b/drivers/firmware/efi/esrt.c
@@ -16,6 +16,7 @@
 #include <linux/device.h>
 #include <linux/efi.h>
 #include <linux/init.h>
+#include <linux/io.h>
 #include <linux/kernel.h>
 #include <linux/kobject.h>
 #include <linux/list.h>
@@ -385,15 +386,15 @@ static void cleanup_entry_list(void)
 static int __init esrt_sysfs_init(void)
 {
 	int error;
-	struct efi_system_resource_table __iomem *ioesrt;
+	struct efi_system_resource_table *memesrt;
 
 	pr_debug("esrt-sysfs: loading.\n");
 	if (!esrt_data || !esrt_data_size)
 		return -ENOSYS;
 
-	ioesrt = ioremap(esrt_data, esrt_data_size);
-	if (!ioesrt) {
-		pr_err("ioremap(%pa, %zu) failed.\n", &esrt_data,
+	memesrt = memremap(esrt_data, esrt_data_size, MEMREMAP_WB);
+	if (!memesrt) {
+		pr_err("memremap(%pa, %zu, MEMREMAP_WB) failed.\n", &esrt_data,
 		       esrt_data_size);
 		return -ENOMEM;
 	}
@@ -401,11 +402,12 @@ static int __init esrt_sysfs_init(void)
 	esrt = kmalloc(esrt_data_size, GFP_KERNEL);
 	if (!esrt) {
 		pr_err("kmalloc failed. (wanted %zu bytes)\n", esrt_data_size);
-		iounmap(ioesrt);
+		memunmap(memesrt);
 		return -ENOMEM;
 	}
 
-	memcpy_fromio(esrt, ioesrt, esrt_data_size);
+	memcpy(esrt, memesrt, esrt_data_size);
+	memunmap(memesrt);
 
 	esrt_kobj = kobject_create_and_add("esrt", efi_kobj);
 	if (!esrt_kobj) {
@@ -432,8 +434,6 @@ static int __init esrt_sysfs_init(void)
 	if (error)
 		goto err_cleanup_list;
 
-	memblock_remove(esrt_data, esrt_data_size);
-
 	pr_debug("esrt-sysfs: loaded.\n");
 
 	return 0;
-- 
2.5.0

[PATCH v2 1/2] efi: esrt: use memremap not ioremap to access ESRT table in memory

[Peter Jones]

On Mon, Feb 15, 2016 at 12:32:32PM +0100, Ard Biesheuvel wrote:
> On ARM and arm64, ioremap() and memremap() are not interchangeable like
> on x86, and the use of ioremap() on ordinary RAM is typically flagged
> as an error if the memory region being mapped is also covered by the
> linear mapping, since that would lead to aliases with conflicting
> cacheability attributes.
> 
> Since what we are dealing with is not an I/O region with side effects,
> using ioremap() here is arguably incorrect anyway, so let's replace
> it with memremap instead. Also add a missing unmap on the success path,
> and drop a memblock_remove() call which does not belong here, this far
> into the boot sequence.
> 
> Cc: Peter Jones <pjones@redhat.com>
> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>

Works on my test box and appears to be correct:

Tested-by: Peter Jones <pjones@redhat.com>
Acked-by: Peter Jones <pjones@redhat.com>

> ---
>  drivers/firmware/efi/esrt.c | 16 ++++++++--------
>  1 file changed, 8 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/firmware/efi/esrt.c b/drivers/firmware/efi/esrt.c
> index 22c5285f7705..f096a0a26dbd 100644
> --- a/drivers/firmware/efi/esrt.c
> +++ b/drivers/firmware/efi/esrt.c
> @@ -16,6 +16,7 @@
>  #include <linux/device.h>
>  #include <linux/efi.h>
>  #include <linux/init.h>
> +#include <linux/io.h>
>  #include <linux/kernel.h>
>  #include <linux/kobject.h>
>  #include <linux/list.h>
> @@ -385,15 +386,15 @@ static void cleanup_entry_list(void)
>  static int __init esrt_sysfs_init(void)
>  {
>  	int error;
> -	struct efi_system_resource_table __iomem *ioesrt;
> +	struct efi_system_resource_table *memesrt;
>  
>  	pr_debug("esrt-sysfs: loading.\n");
>  	if (!esrt_data || !esrt_data_size)
>  		return -ENOSYS;
>  
> -	ioesrt = ioremap(esrt_data, esrt_data_size);
> -	if (!ioesrt) {
> -		pr_err("ioremap(%pa, %zu) failed.\n", &esrt_data,
> +	memesrt = memremap(esrt_data, esrt_data_size, MEMREMAP_WB);
> +	if (!memesrt) {
> +		pr_err("memremap(%pa, %zu, MEMREMAP_WB) failed.\n", &esrt_data,
>  		       esrt_data_size);
>  		return -ENOMEM;
>  	}
> @@ -401,11 +402,12 @@ static int __init esrt_sysfs_init(void)
>  	esrt = kmalloc(esrt_data_size, GFP_KERNEL);
>  	if (!esrt) {
>  		pr_err("kmalloc failed. (wanted %zu bytes)\n", esrt_data_size);
> -		iounmap(ioesrt);
> +		memunmap(memesrt);
>  		return -ENOMEM;
>  	}
>  
> -	memcpy_fromio(esrt, ioesrt, esrt_data_size);
> +	memcpy(esrt, memesrt, esrt_data_size);
> +	memunmap(memesrt);
>  
>  	esrt_kobj = kobject_create_and_add("esrt", efi_kobj);
>  	if (!esrt_kobj) {
> @@ -432,8 +434,6 @@ static int __init esrt_sysfs_init(void)
>  	if (error)
>  		goto err_cleanup_list;
>  
> -	memblock_remove(esrt_data, esrt_data_size);
> -
>  	pr_debug("esrt-sysfs: loaded.\n");
>  
>  	return 0;
> -- 
> 2.5.0
> 

[PATCH v2 1/2] efi: esrt: use memremap not ioremap to access ESRT table in memory

[Baicar, Tyler]

On 2/15/2016 4:32 AM, Ard Biesheuvel wrote:
> On ARM and arm64, ioremap() and memremap() are not interchangeable like
> on x86, and the use of ioremap() on ordinary RAM is typically flagged
> as an error if the memory region being mapped is also covered by the
> linear mapping, since that would lead to aliases with conflicting
> cacheability attributes.
>
> Since what we are dealing with is not an I/O region with side effects,
> using ioremap() here is arguably incorrect anyway, so let's replace
> it with memremap instead. Also add a missing unmap on the success path,
> and drop a memblock_remove() call which does not belong here, this far
> into the boot sequence.
>
> Cc: Peter Jones <pjones@redhat.com>
> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>

Tested-by: Tyler Baicar<tbaicar@codeaurora.org>

> ---
>   drivers/firmware/efi/esrt.c | 16 ++++++++--------
>   1 file changed, 8 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/firmware/efi/esrt.c b/drivers/firmware/efi/esrt.c
> index 22c5285f7705..f096a0a26dbd 100644
> --- a/drivers/firmware/efi/esrt.c
> +++ b/drivers/firmware/efi/esrt.c
> @@ -16,6 +16,7 @@
>   #include <linux/device.h>
>   #include <linux/efi.h>
>   #include <linux/init.h>
> +#include <linux/io.h>
>   #include <linux/kernel.h>
>   #include <linux/kobject.h>
>   #include <linux/list.h>
> @@ -385,15 +386,15 @@ static void cleanup_entry_list(void)
>   static int __init esrt_sysfs_init(void)
>   {
>   	int error;
> -	struct efi_system_resource_table __iomem *ioesrt;
> +	struct efi_system_resource_table *memesrt;
>   
>   	pr_debug("esrt-sysfs: loading.\n");
>   	if (!esrt_data || !esrt_data_size)
>   		return -ENOSYS;
>   
> -	ioesrt = ioremap(esrt_data, esrt_data_size);
> -	if (!ioesrt) {
> -		pr_err("ioremap(%pa, %zu) failed.\n", &esrt_data,
> +	memesrt = memremap(esrt_data, esrt_data_size, MEMREMAP_WB);
> +	if (!memesrt) {
> +		pr_err("memremap(%pa, %zu, MEMREMAP_WB) failed.\n", &esrt_data,
>   		       esrt_data_size);
>   		return -ENOMEM;
>   	}
> @@ -401,11 +402,12 @@ static int __init esrt_sysfs_init(void)
>   	esrt = kmalloc(esrt_data_size, GFP_KERNEL);
>   	if (!esrt) {
>   		pr_err("kmalloc failed. (wanted %zu bytes)\n", esrt_data_size);
> -		iounmap(ioesrt);
> +		memunmap(memesrt);
>   		return -ENOMEM;
>   	}
>   
> -	memcpy_fromio(esrt, ioesrt, esrt_data_size);
> +	memcpy(esrt, memesrt, esrt_data_size);
> +	memunmap(memesrt);
>   
>   	esrt_kobj = kobject_create_and_add("esrt", efi_kobj);
>   	if (!esrt_kobj) {
> @@ -432,8 +434,6 @@ static int __init esrt_sysfs_init(void)
>   	if (error)
>   		goto err_cleanup_list;
>   
> -	memblock_remove(esrt_data, esrt_data_size);
> -
>   	pr_debug("esrt-sysfs: loaded.\n");
>   
>   	return 0;
Thanks,
Tyler

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

[PATCH v2 1/2] efi: esrt: use memremap not ioremap to access ESRT table in memory

[Matt Fleming]

On Mon, 15 Feb, at 12:32:32PM, Ard Biesheuvel wrote:
> On ARM and arm64, ioremap() and memremap() are not interchangeable like
> on x86, and the use of ioremap() on ordinary RAM is typically flagged
> as an error if the memory region being mapped is also covered by the
> linear mapping, since that would lead to aliases with conflicting
> cacheability attributes.
> 
> Since what we are dealing with is not an I/O region with side effects,
> using ioremap() here is arguably incorrect anyway, so let's replace
> it with memremap instead. Also add a missing unmap on the success path,
> and drop a memblock_remove() call which does not belong here, this far
> into the boot sequence.
> 
> Cc: Peter Jones <pjones@redhat.com>
> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> ---
>  drivers/firmware/efi/esrt.c | 16 ++++++++--------
>  1 file changed, 8 insertions(+), 8 deletions(-)
> 

[...]

> @@ -432,8 +434,6 @@ static int __init esrt_sysfs_init(void)
>  	if (error)
>  		goto err_cleanup_list;
>  
> -	memblock_remove(esrt_data, esrt_data_size);
> -
>  	pr_debug("esrt-sysfs: loaded.\n");
>  
>  	return 0;

Shouldn't we be replacing memblock_remove() with free_bootmem_late()?
The original ESRT region is still reserved at this point, so we should
do our best to release it to the page allocator.

[PATCH v2 1/2] efi: esrt: use memremap not ioremap to access ESRT table in memory

[Ard Biesheuvel]

On 18 February 2016 at 11:44, Matt Fleming <matt@codeblueprint.co.uk> wrote:
> On Mon, 15 Feb, at 12:32:32PM, Ard Biesheuvel wrote:
>> On ARM and arm64, ioremap() and memremap() are not interchangeable like
>> on x86, and the use of ioremap() on ordinary RAM is typically flagged
>> as an error if the memory region being mapped is also covered by the
>> linear mapping, since that would lead to aliases with conflicting
>> cacheability attributes.
>>
>> Since what we are dealing with is not an I/O region with side effects,
>> using ioremap() here is arguably incorrect anyway, so let's replace
>> it with memremap instead. Also add a missing unmap on the success path,
>> and drop a memblock_remove() call which does not belong here, this far
>> into the boot sequence.
>>
>> Cc: Peter Jones <pjones@redhat.com>
>> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
>> ---
>>  drivers/firmware/efi/esrt.c | 16 ++++++++--------
>>  1 file changed, 8 insertions(+), 8 deletions(-)
>>
>
> [...]
>
>> @@ -432,8 +434,6 @@ static int __init esrt_sysfs_init(void)
>>       if (error)
>>               goto err_cleanup_list;
>>
>> -     memblock_remove(esrt_data, esrt_data_size);
>> -
>>       pr_debug("esrt-sysfs: loaded.\n");
>>
>>       return 0;
>
> Shouldn't we be replacing memblock_remove() with free_bootmem_late()?
> The original ESRT region is still reserved at this point, so we should
> do our best to release it to the page allocator.

I'd rather we keep it reserved. That way, the config table entry still
points to something valid, which could be useful for kexec(), I think?
At least, that is how I intended to handle config tables on ARM ...

[PATCH v2 1/2] efi: esrt: use memremap not ioremap to access ESRT table in memory

[Matt Fleming]

On Thu, 18 Feb, at 01:16:05PM, Ard Biesheuvel wrote:
> On 18 February 2016 at 11:44, Matt Fleming <matt@codeblueprint.co.uk> wrote:
> > On Mon, 15 Feb, at 12:32:32PM, Ard Biesheuvel wrote:
> >> On ARM and arm64, ioremap() and memremap() are not interchangeable like
> >> on x86, and the use of ioremap() on ordinary RAM is typically flagged
> >> as an error if the memory region being mapped is also covered by the
> >> linear mapping, since that would lead to aliases with conflicting
> >> cacheability attributes.
> >>
> >> Since what we are dealing with is not an I/O region with side effects,
> >> using ioremap() here is arguably incorrect anyway, so let's replace
> >> it with memremap instead. Also add a missing unmap on the success path,
> >> and drop a memblock_remove() call which does not belong here, this far
> >> into the boot sequence.
> >>
> >> Cc: Peter Jones <pjones@redhat.com>
> >> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> >> ---
> >>  drivers/firmware/efi/esrt.c | 16 ++++++++--------
> >>  1 file changed, 8 insertions(+), 8 deletions(-)
> >>
> >
> > [...]
> >
> >> @@ -432,8 +434,6 @@ static int __init esrt_sysfs_init(void)
> >>       if (error)
> >>               goto err_cleanup_list;
> >>
> >> -     memblock_remove(esrt_data, esrt_data_size);
> >> -
> >>       pr_debug("esrt-sysfs: loaded.\n");
> >>
> >>       return 0;
> >
> > Shouldn't we be replacing memblock_remove() with free_bootmem_late()?
> > The original ESRT region is still reserved at this point, so we should
> > do our best to release it to the page allocator.
> 
> I'd rather we keep it reserved. That way, the config table entry still
> points to something valid, which could be useful for kexec(), I think?
> At least, that is how I intended to handle config tables on ARM ...

If we're going to reserve it why do we need to copy the data out at
all in esrt_sysfs_init()?

[PATCH v2 1/2] efi: esrt: use memremap not ioremap to access ESRT table in memory

[Ard Biesheuvel]

On 18 February 2016 at 14:28, Matt Fleming <matt@codeblueprint.co.uk> wrote:
> On Thu, 18 Feb, at 01:16:05PM, Ard Biesheuvel wrote:
>> On 18 February 2016 at 11:44, Matt Fleming <matt@codeblueprint.co.uk> wrote:
>> > On Mon, 15 Feb, at 12:32:32PM, Ard Biesheuvel wrote:
>> >> On ARM and arm64, ioremap() and memremap() are not interchangeable like
>> >> on x86, and the use of ioremap() on ordinary RAM is typically flagged
>> >> as an error if the memory region being mapped is also covered by the
>> >> linear mapping, since that would lead to aliases with conflicting
>> >> cacheability attributes.
>> >>
>> >> Since what we are dealing with is not an I/O region with side effects,
>> >> using ioremap() here is arguably incorrect anyway, so let's replace
>> >> it with memremap instead. Also add a missing unmap on the success path,
>> >> and drop a memblock_remove() call which does not belong here, this far
>> >> into the boot sequence.
>> >>
>> >> Cc: Peter Jones <pjones@redhat.com>
>> >> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
>> >> ---
>> >>  drivers/firmware/efi/esrt.c | 16 ++++++++--------
>> >>  1 file changed, 8 insertions(+), 8 deletions(-)
>> >>
>> >
>> > [...]
>> >
>> >> @@ -432,8 +434,6 @@ static int __init esrt_sysfs_init(void)
>> >>       if (error)
>> >>               goto err_cleanup_list;
>> >>
>> >> -     memblock_remove(esrt_data, esrt_data_size);
>> >> -
>> >>       pr_debug("esrt-sysfs: loaded.\n");
>> >>
>> >>       return 0;
>> >
>> > Shouldn't we be replacing memblock_remove() with free_bootmem_late()?
>> > The original ESRT region is still reserved at this point, so we should
>> > do our best to release it to the page allocator.
>>
>> I'd rather we keep it reserved. That way, the config table entry still
>> points to something valid, which could be useful for kexec(), I think?
>> At least, that is how I intended to handle config tables on ARM ...
>
> If we're going to reserve it why do we need to copy the data out at
> all in esrt_sysfs_init()?

Excellent question. I don't think there is any point to doing that.

[PATCH v2 1/2] efi: esrt: use memremap not ioremap to access ESRT table in memory

[Matt Fleming]

On Thu, 18 Feb, at 02:29:32PM, Ard Biesheuvel wrote:
> On 18 February 2016 at 14:28, Matt Fleming <matt@codeblueprint.co.uk> wrote:
> > On Thu, 18 Feb, at 01:16:05PM, Ard Biesheuvel wrote:
> >> On 18 February 2016 at 11:44, Matt Fleming <matt@codeblueprint.co.uk> wrote:
> >> > On Mon, 15 Feb, at 12:32:32PM, Ard Biesheuvel wrote:
> >> >> On ARM and arm64, ioremap() and memremap() are not interchangeable like
> >> >> on x86, and the use of ioremap() on ordinary RAM is typically flagged
> >> >> as an error if the memory region being mapped is also covered by the
> >> >> linear mapping, since that would lead to aliases with conflicting
> >> >> cacheability attributes.
> >> >>
> >> >> Since what we are dealing with is not an I/O region with side effects,
> >> >> using ioremap() here is arguably incorrect anyway, so let's replace
> >> >> it with memremap instead. Also add a missing unmap on the success path,
> >> >> and drop a memblock_remove() call which does not belong here, this far
> >> >> into the boot sequence.
> >> >>
> >> >> Cc: Peter Jones <pjones@redhat.com>
> >> >> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> >> >> ---
> >> >>  drivers/firmware/efi/esrt.c | 16 ++++++++--------
> >> >>  1 file changed, 8 insertions(+), 8 deletions(-)
> >> >>
> >> >
> >> > [...]
> >> >
> >> >> @@ -432,8 +434,6 @@ static int __init esrt_sysfs_init(void)
> >> >>       if (error)
> >> >>               goto err_cleanup_list;
> >> >>
> >> >> -     memblock_remove(esrt_data, esrt_data_size);
> >> >> -
> >> >>       pr_debug("esrt-sysfs: loaded.\n");
> >> >>
> >> >>       return 0;
> >> >
> >> > Shouldn't we be replacing memblock_remove() with free_bootmem_late()?
> >> > The original ESRT region is still reserved at this point, so we should
> >> > do our best to release it to the page allocator.
> >>
> >> I'd rather we keep it reserved. That way, the config table entry still
> >> points to something valid, which could be useful for kexec(), I think?
> >> At least, that is how I intended to handle config tables on ARM ...
> >
> > If we're going to reserve it why do we need to copy the data out at
> > all in esrt_sysfs_init()?
> 
> Excellent question. I don't think there is any point to doing that.

... Unless the data is contained in an EFI Boot Services region ;-)

Peter?

[PATCH v2 1/2] efi: esrt: use memremap not ioremap to access ESRT table in memory

[Ard Biesheuvel]

On 18 February 2016 at 14:43, Matt Fleming <matt@codeblueprint.co.uk> wrote:
> On Thu, 18 Feb, at 02:29:32PM, Ard Biesheuvel wrote:
>> On 18 February 2016 at 14:28, Matt Fleming <matt@codeblueprint.co.uk> wrote:
>> > On Thu, 18 Feb, at 01:16:05PM, Ard Biesheuvel wrote:
>> >> On 18 February 2016 at 11:44, Matt Fleming <matt@codeblueprint.co.uk> wrote:
>> >> > On Mon, 15 Feb, at 12:32:32PM, Ard Biesheuvel wrote:
>> >> >> On ARM and arm64, ioremap() and memremap() are not interchangeable like
>> >> >> on x86, and the use of ioremap() on ordinary RAM is typically flagged
>> >> >> as an error if the memory region being mapped is also covered by the
>> >> >> linear mapping, since that would lead to aliases with conflicting
>> >> >> cacheability attributes.
>> >> >>
>> >> >> Since what we are dealing with is not an I/O region with side effects,
>> >> >> using ioremap() here is arguably incorrect anyway, so let's replace
>> >> >> it with memremap instead. Also add a missing unmap on the success path,
>> >> >> and drop a memblock_remove() call which does not belong here, this far
>> >> >> into the boot sequence.
>> >> >>
>> >> >> Cc: Peter Jones <pjones@redhat.com>
>> >> >> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
>> >> >> ---
>> >> >>  drivers/firmware/efi/esrt.c | 16 ++++++++--------
>> >> >>  1 file changed, 8 insertions(+), 8 deletions(-)
>> >> >>
>> >> >
>> >> > [...]
>> >> >
>> >> >> @@ -432,8 +434,6 @@ static int __init esrt_sysfs_init(void)
>> >> >>       if (error)
>> >> >>               goto err_cleanup_list;
>> >> >>
>> >> >> -     memblock_remove(esrt_data, esrt_data_size);
>> >> >> -
>> >> >>       pr_debug("esrt-sysfs: loaded.\n");
>> >> >>
>> >> >>       return 0;
>> >> >
>> >> > Shouldn't we be replacing memblock_remove() with free_bootmem_late()?
>> >> > The original ESRT region is still reserved at this point, so we should
>> >> > do our best to release it to the page allocator.
>> >>
>> >> I'd rather we keep it reserved. That way, the config table entry still
>> >> points to something valid, which could be useful for kexec(), I think?
>> >> At least, that is how I intended to handle config tables on ARM ...
>> >
>> > If we're going to reserve it why do we need to copy the data out at
>> > all in esrt_sysfs_init()?
>>
>> Excellent question. I don't think there is any point to doing that.
>
> ... Unless the data is contained in an EFI Boot Services region ;-)
>
> Peter?

Yes, it usually is. Is that a problem?

[PATCH v2 1/2] efi: esrt: use memremap not ioremap to access ESRT table in memory

[Matt Fleming]

On Thu, 18 Feb, at 02:44:02PM, Ard Biesheuvel wrote:
> On 18 February 2016 at 14:43, Matt Fleming <matt@codeblueprint.co.uk> wrote:
> > On Thu, 18 Feb, at 02:29:32PM, Ard Biesheuvel wrote:
> >> On 18 February 2016 at 14:28, Matt Fleming <matt@codeblueprint.co.uk> wrote:
> >> > On Thu, 18 Feb, at 01:16:05PM, Ard Biesheuvel wrote:
> >> >> On 18 February 2016 at 11:44, Matt Fleming <matt@codeblueprint.co.uk> wrote:
> >> >> > On Mon, 15 Feb, at 12:32:32PM, Ard Biesheuvel wrote:
> >> >> >> On ARM and arm64, ioremap() and memremap() are not interchangeable like
> >> >> >> on x86, and the use of ioremap() on ordinary RAM is typically flagged
> >> >> >> as an error if the memory region being mapped is also covered by the
> >> >> >> linear mapping, since that would lead to aliases with conflicting
> >> >> >> cacheability attributes.
> >> >> >>
> >> >> >> Since what we are dealing with is not an I/O region with side effects,
> >> >> >> using ioremap() here is arguably incorrect anyway, so let's replace
> >> >> >> it with memremap instead. Also add a missing unmap on the success path,
> >> >> >> and drop a memblock_remove() call which does not belong here, this far
> >> >> >> into the boot sequence.
> >> >> >>
> >> >> >> Cc: Peter Jones <pjones@redhat.com>
> >> >> >> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> >> >> >> ---
> >> >> >>  drivers/firmware/efi/esrt.c | 16 ++++++++--------
> >> >> >>  1 file changed, 8 insertions(+), 8 deletions(-)
> >> >> >>
> >> >> >
> >> >> > [...]
> >> >> >
> >> >> >> @@ -432,8 +434,6 @@ static int __init esrt_sysfs_init(void)
> >> >> >>       if (error)
> >> >> >>               goto err_cleanup_list;
> >> >> >>
> >> >> >> -     memblock_remove(esrt_data, esrt_data_size);
> >> >> >> -
> >> >> >>       pr_debug("esrt-sysfs: loaded.\n");
> >> >> >>
> >> >> >>       return 0;
> >> >> >
> >> >> > Shouldn't we be replacing memblock_remove() with free_bootmem_late()?
> >> >> > The original ESRT region is still reserved at this point, so we should
> >> >> > do our best to release it to the page allocator.
> >> >>
> >> >> I'd rather we keep it reserved. That way, the config table entry still
> >> >> points to something valid, which could be useful for kexec(), I think?
> >> >> At least, that is how I intended to handle config tables on ARM ...
> >> >
> >> > If we're going to reserve it why do we need to copy the data out at
> >> > all in esrt_sysfs_init()?
> >>
> >> Excellent question. I don't think there is any point to doing that.
> >
> > ... Unless the data is contained in an EFI Boot Services region ;-)
> >
> > Peter?
> 
> Yes, it usually is. Is that a problem?

Yes, we free the Boot Services regions before hitting userspace on
x86, see efi_free_boot_services(). We do this map/copy/unmap trick in
the ACPI BGRT driver for that reason.

The Boot Services regions can be many gigabytes in size, which makes
leaving them alone impractical.

For kexec on x86 we simply discard the BGRT table, which isn't the end
of the world because who really needs access to the BGRT image on
kexec reboot? However, I can see the value of preserving the ESRT.

I guess we've got two options, 1) copy out the chunks of Boot Services
regions we're interested in and rewrite the EFI tables to point at
these new allocations and free/discard all of the original Boot
Services regions or 2) only selectively free the Boot Services
regions.

I've always stayed clear of 2) in case there exists cross-region
references in the data that isn't obvious. I'd like to think that
would never happen, but, you know, dragons lurk here, etc.

Though actually, now I think about it, cross-region references can't
possibly exist because they'd cause issues with the current code.

So maybe the best solution is actually 2), where we preserve the Boot
Services regions if any of the drivers (ESRT, BGRT) request them but
free all the others? 

What are the lifetime rules for Boot Services regions on arm*?

[PATCH v2 1/2] efi: esrt: use memremap not ioremap to access ESRT table in memory

[Ard Biesheuvel]

On 18 February 2016 at 15:15, Matt Fleming <matt@codeblueprint.co.uk> wrote:
> On Thu, 18 Feb, at 02:44:02PM, Ard Biesheuvel wrote:
>> On 18 February 2016 at 14:43, Matt Fleming <matt@codeblueprint.co.uk> wrote:
>> > On Thu, 18 Feb, at 02:29:32PM, Ard Biesheuvel wrote:
>> >> On 18 February 2016 at 14:28, Matt Fleming <matt@codeblueprint.co.uk> wrote:
>> >> > On Thu, 18 Feb, at 01:16:05PM, Ard Biesheuvel wrote:
>> >> >> On 18 February 2016 at 11:44, Matt Fleming <matt@codeblueprint.co.uk> wrote:
>> >> >> > On Mon, 15 Feb, at 12:32:32PM, Ard Biesheuvel wrote:
>> >> >> >> On ARM and arm64, ioremap() and memremap() are not interchangeable like
>> >> >> >> on x86, and the use of ioremap() on ordinary RAM is typically flagged
>> >> >> >> as an error if the memory region being mapped is also covered by the
>> >> >> >> linear mapping, since that would lead to aliases with conflicting
>> >> >> >> cacheability attributes.
>> >> >> >>
>> >> >> >> Since what we are dealing with is not an I/O region with side effects,
>> >> >> >> using ioremap() here is arguably incorrect anyway, so let's replace
>> >> >> >> it with memremap instead. Also add a missing unmap on the success path,
>> >> >> >> and drop a memblock_remove() call which does not belong here, this far
>> >> >> >> into the boot sequence.
>> >> >> >>
>> >> >> >> Cc: Peter Jones <pjones@redhat.com>
>> >> >> >> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
>> >> >> >> ---
>> >> >> >>  drivers/firmware/efi/esrt.c | 16 ++++++++--------
>> >> >> >>  1 file changed, 8 insertions(+), 8 deletions(-)
>> >> >> >>
>> >> >> >
>> >> >> > [...]
>> >> >> >
>> >> >> >> @@ -432,8 +434,6 @@ static int __init esrt_sysfs_init(void)
>> >> >> >>       if (error)
>> >> >> >>               goto err_cleanup_list;
>> >> >> >>
>> >> >> >> -     memblock_remove(esrt_data, esrt_data_size);
>> >> >> >> -
>> >> >> >>       pr_debug("esrt-sysfs: loaded.\n");
>> >> >> >>
>> >> >> >>       return 0;
>> >> >> >
>> >> >> > Shouldn't we be replacing memblock_remove() with free_bootmem_late()?
>> >> >> > The original ESRT region is still reserved at this point, so we should
>> >> >> > do our best to release it to the page allocator.
>> >> >>
>> >> >> I'd rather we keep it reserved. That way, the config table entry still
>> >> >> points to something valid, which could be useful for kexec(), I think?
>> >> >> At least, that is how I intended to handle config tables on ARM ...
>> >> >
>> >> > If we're going to reserve it why do we need to copy the data out at
>> >> > all in esrt_sysfs_init()?
>> >>
>> >> Excellent question. I don't think there is any point to doing that.
>> >
>> > ... Unless the data is contained in an EFI Boot Services region ;-)
>> >
>> > Peter?
>>
>> Yes, it usually is. Is that a problem?
>
> Yes, we free the Boot Services regions before hitting userspace on
> x86, see efi_free_boot_services(). We do this map/copy/unmap trick in
> the ACPI BGRT driver for that reason.
>
> The Boot Services regions can be many gigabytes in size, which makes
> leaving them alone impractical.
>
> For kexec on x86 we simply discard the BGRT table, which isn't the end
> of the world because who really needs access to the BGRT image on
> kexec reboot? However, I can see the value of preserving the ESRT.
>
> I guess we've got two options, 1) copy out the chunks of Boot Services
> regions we're interested in and rewrite the EFI tables to point at
> these new allocations and free/discard all of the original Boot
> Services regions or 2) only selectively free the Boot Services
> regions.
>
> I've always stayed clear of 2) in case there exists cross-region
> references in the data that isn't obvious. I'd like to think that
> would never happen, but, you know, dragons lurk here, etc.
>
> Though actually, now I think about it, cross-region references can't
> possibly exist because they'd cause issues with the current code.
>
> So maybe the best solution is actually 2), where we preserve the Boot
> Services regions if any of the drivers (ESRT, BGRT) request them but
> free all the others?
>
> What are the lifetime rules for Boot Services regions on arm*?

We treat all Boot Services regions like Loader Code/Data or free
regions: it is all recorded in memblock as usable memory, and only the
regions that are explicitly reserved are protected from further
general use.

I am currently looking into the memory attribute table, and the use
case is very similar. It would be very useful from our pov to simply
memblock_reserve() the region right after having called
efi_config_parse_tables(), and actually consume its data when we get
around to it later. The ESRT handling is already split down the middle
in the same way.

[PATCH v2 1/2] efi: esrt: use memremap not ioremap to access ESRT table in memory

[Matt Fleming]

On Thu, 18 Feb, at 03:21:25PM, Ard Biesheuvel wrote:
> 
> We treat all Boot Services regions like Loader Code/Data or free
> regions: it is all recorded in memblock as usable memory, and only the
> regions that are explicitly reserved are protected from further
> general use.
> 
> I am currently looking into the memory attribute table, and the use
> case is very similar. It would be very useful from our pov to simply
> memblock_reserve() the region right after having called
> efi_config_parse_tables(), and actually consume its data when we get
> around to it later. The ESRT handling is already split down the middle
> in the same way.

Agreed, this would also be useful in general for kexec. I've got a
couple of patches in flight that try to handle the BGRT case in a
different way,

  https://lkml.kernel.org/r/1455723910-16710-2-git-send-email-matt at codeblueprint.co.uk
  https://lkml.kernel.org/r/1455723910-16710-3-git-send-email-matt at codeblueprint.co.uk

Let me instead take a look at how we might be able to preserve only
those Boot Services regions we care out.

[PATCH v2 1/2] efi: esrt: use memremap not ioremap to access ESRT table in memory

[Dave Young]

On 02/18/16 at 03:21pm, Ard Biesheuvel wrote:
> On 18 February 2016 at 15:15, Matt Fleming <matt@codeblueprint.co.uk> wrote:
> > On Thu, 18 Feb, at 02:44:02PM, Ard Biesheuvel wrote:
> >> On 18 February 2016 at 14:43, Matt Fleming <matt@codeblueprint.co.uk> wrote:
> >> > On Thu, 18 Feb, at 02:29:32PM, Ard Biesheuvel wrote:
> >> >> On 18 February 2016 at 14:28, Matt Fleming <matt@codeblueprint.co.uk> wrote:
> >> >> > On Thu, 18 Feb, at 01:16:05PM, Ard Biesheuvel wrote:
> >> >> >> On 18 February 2016 at 11:44, Matt Fleming <matt@codeblueprint.co.uk> wrote:
> >> >> >> > On Mon, 15 Feb, at 12:32:32PM, Ard Biesheuvel wrote:
> >> >> >> >> On ARM and arm64, ioremap() and memremap() are not interchangeable like
> >> >> >> >> on x86, and the use of ioremap() on ordinary RAM is typically flagged
> >> >> >> >> as an error if the memory region being mapped is also covered by the
> >> >> >> >> linear mapping, since that would lead to aliases with conflicting
> >> >> >> >> cacheability attributes.
> >> >> >> >>
> >> >> >> >> Since what we are dealing with is not an I/O region with side effects,
> >> >> >> >> using ioremap() here is arguably incorrect anyway, so let's replace
> >> >> >> >> it with memremap instead. Also add a missing unmap on the success path,
> >> >> >> >> and drop a memblock_remove() call which does not belong here, this far
> >> >> >> >> into the boot sequence.
> >> >> >> >>
> >> >> >> >> Cc: Peter Jones <pjones@redhat.com>
> >> >> >> >> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> >> >> >> >> ---
> >> >> >> >>  drivers/firmware/efi/esrt.c | 16 ++++++++--------
> >> >> >> >>  1 file changed, 8 insertions(+), 8 deletions(-)
> >> >> >> >>
> >> >> >> >
> >> >> >> > [...]
> >> >> >> >
> >> >> >> >> @@ -432,8 +434,6 @@ static int __init esrt_sysfs_init(void)
> >> >> >> >>       if (error)
> >> >> >> >>               goto err_cleanup_list;
> >> >> >> >>
> >> >> >> >> -     memblock_remove(esrt_data, esrt_data_size);
> >> >> >> >> -
> >> >> >> >>       pr_debug("esrt-sysfs: loaded.\n");
> >> >> >> >>
> >> >> >> >>       return 0;
> >> >> >> >
> >> >> >> > Shouldn't we be replacing memblock_remove() with free_bootmem_late()?
> >> >> >> > The original ESRT region is still reserved at this point, so we should
> >> >> >> > do our best to release it to the page allocator.
> >> >> >>
> >> >> >> I'd rather we keep it reserved. That way, the config table entry still
> >> >> >> points to something valid, which could be useful for kexec(), I think?
> >> >> >> At least, that is how I intended to handle config tables on ARM ...
> >> >> >
> >> >> > If we're going to reserve it why do we need to copy the data out at
> >> >> > all in esrt_sysfs_init()?
> >> >>
> >> >> Excellent question. I don't think there is any point to doing that.
> >> >
> >> > ... Unless the data is contained in an EFI Boot Services region ;-)
> >> >
> >> > Peter?
> >>
> >> Yes, it usually is. Is that a problem?
> >
> > Yes, we free the Boot Services regions before hitting userspace on
> > x86, see efi_free_boot_services(). We do this map/copy/unmap trick in
> > the ACPI BGRT driver for that reason.
> >
> > The Boot Services regions can be many gigabytes in size, which makes
> > leaving them alone impractical.
> >
> > For kexec on x86 we simply discard the BGRT table, which isn't the end
> > of the world because who really needs access to the BGRT image on
> > kexec reboot? However, I can see the value of preserving the ESRT.
> >
> > I guess we've got two options, 1) copy out the chunks of Boot Services
> > regions we're interested in and rewrite the EFI tables to point at
> > these new allocations and free/discard all of the original Boot
> > Services regions or 2) only selectively free the Boot Services
> > regions.
> >
> > I've always stayed clear of 2) in case there exists cross-region
> > references in the data that isn't obvious. I'd like to think that
> > would never happen, but, you know, dragons lurk here, etc.
> >
> > Though actually, now I think about it, cross-region references can't
> > possibly exist because they'd cause issues with the current code.
> >
> > So maybe the best solution is actually 2), where we preserve the Boot
> > Services regions if any of the drivers (ESRT, BGRT) request them but
> > free all the others?

It is a good idea so that drivers can add their useful sections to
a list or an array, they can avoid another copy of the memory also.

> >
> > What are the lifetime rules for Boot Services regions on arm*?
> 
> We treat all Boot Services regions like Loader Code/Data or free
> regions: it is all recorded in memblock as usable memory, and only the
> regions that are explicitly reserved are protected from further
> general use.
> 
> I am currently looking into the memory attribute table, and the use
> case is very similar. It would be very useful from our pov to simply
> memblock_reserve() the region right after having called
> efi_config_parse_tables(), and actually consume its data when we get
> around to it later. The ESRT handling is already split down the middle
> in the same way.

A question is how can make a general way for both x86 and arm*.

Maybe change the efi_free_boot_mem to something like efi_clean_boot_mem?
It can first call efi_free_boot_mem, then reserve the ranges to be reserved
again, but it sounds odd though.

Thanks
Dave

[PATCH v2 1/2] efi: esrt: use memremap not ioremap to access ESRT table in memory

[Peter Jones]

On Thu, Feb 18, 2016 at 02:15:44PM +0000, Matt Fleming wrote:
> On Thu, 18 Feb, at 02:44:02PM, Ard Biesheuvel wrote:
> > On 18 February 2016 at 14:43, Matt Fleming <matt@codeblueprint.co.uk> wrote:
> > > On Thu, 18 Feb, at 02:29:32PM, Ard Biesheuvel wrote:
> > >> On 18 February 2016 at 14:28, Matt Fleming <matt@codeblueprint.co.uk> wrote:
> > >> > On Thu, 18 Feb, at 01:16:05PM, Ard Biesheuvel wrote:
> > >> >> On 18 February 2016 at 11:44, Matt Fleming <matt@codeblueprint.co.uk> wrote:
> > >> >> > On Mon, 15 Feb, at 12:32:32PM, Ard Biesheuvel wrote:
> > >> >> >> On ARM and arm64, ioremap() and memremap() are not interchangeable like
> > >> >> >> on x86, and the use of ioremap() on ordinary RAM is typically flagged
> > >> >> >> as an error if the memory region being mapped is also covered by the
> > >> >> >> linear mapping, since that would lead to aliases with conflicting
> > >> >> >> cacheability attributes.
> > >> >> >>
> > >> >> >> Since what we are dealing with is not an I/O region with side effects,
> > >> >> >> using ioremap() here is arguably incorrect anyway, so let's replace
> > >> >> >> it with memremap instead. Also add a missing unmap on the success path,
> > >> >> >> and drop a memblock_remove() call which does not belong here, this far
> > >> >> >> into the boot sequence.
> > >> >> >>
> > >> >> >> Cc: Peter Jones <pjones@redhat.com>
> > >> >> >> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> > >> >> >> ---
> > >> >> >>  drivers/firmware/efi/esrt.c | 16 ++++++++--------
> > >> >> >>  1 file changed, 8 insertions(+), 8 deletions(-)
> > >> >> >>
> > >> >> >
> > >> >> > [...]
> > >> >> >
> > >> >> >> @@ -432,8 +434,6 @@ static int __init esrt_sysfs_init(void)
> > >> >> >>       if (error)
> > >> >> >>               goto err_cleanup_list;
> > >> >> >>
> > >> >> >> -     memblock_remove(esrt_data, esrt_data_size);
> > >> >> >> -
> > >> >> >>       pr_debug("esrt-sysfs: loaded.\n");
> > >> >> >>
> > >> >> >>       return 0;
> > >> >> >
> > >> >> > Shouldn't we be replacing memblock_remove() with free_bootmem_late()?
> > >> >> > The original ESRT region is still reserved at this point, so we should
> > >> >> > do our best to release it to the page allocator.
> > >> >>
> > >> >> I'd rather we keep it reserved. That way, the config table entry still
> > >> >> points to something valid, which could be useful for kexec(), I think?
> > >> >> At least, that is how I intended to handle config tables on ARM ...
> > >> >
> > >> > If we're going to reserve it why do we need to copy the data out at
> > >> > all in esrt_sysfs_init()?
> > >>
> > >> Excellent question. I don't think there is any point to doing that.
> > >
> > > ... Unless the data is contained in an EFI Boot Services region ;-)
> > >
> > > Peter?
> > 
> > Yes, it usually is. Is that a problem?
> 
> Yes, we free the Boot Services regions before hitting userspace on
> x86, see efi_free_boot_services(). We do this map/copy/unmap trick in
> the ACPI BGRT driver for that reason.
> 
> The Boot Services regions can be many gigabytes in size, which makes
> leaving them alone impractical.
> 
> For kexec on x86 we simply discard the BGRT table, which isn't the end
> of the world because who really needs access to the BGRT image on
> kexec reboot? However, I can see the value of preserving the ESRT.
> 
> I guess we've got two options, 1) copy out the chunks of Boot Services
> regions we're interested in and rewrite the EFI tables to point at
> these new allocations and free/discard all of the original Boot
> Services regions or 2) only selectively free the Boot Services
> regions.

I think we've got to copy them out anyway and give a new copy to any
kexec'd kernel.  In 5.6 in the spec, it says of the table data:

  The VendorGuid associated with a given VendorTable pointer defines
  whether or not a particular address reported in the table gets fixed
  up when a call to SetVirtualAddressMap() is made. It is the
  responsibility of the specification defining the VendorTable to
  specify whether to convert the addresses reported in the table.

Of course the ESRT definition doesn't say anything about that, since
it actually says it's in BootServicesData, and so remapping its address
doesn't really make a lot of sense.  Unfortunately the others are
actually *less* well defined.  Here's a list of the tables defined in
the 2.6 spec, and what they say about either their allocation region
or their remap policy:

ACPI20		nada			Physical Address (PA)
ACPI		nada			PA
SAL		nada			PA
SMBIOS		nada			PA
SMBIOS3		nada			PA
MPS		nada			PA
properties	nada			PA
memory attrs	nada			nada
debugimage info	nada			nada
IEIT		nada			nada
ESRT		BootServicesData	nada

So... for the ones specified by physical addresses, we know we can
access them early on, and it probably doesn't matter what allocation
pool they're in, because we're reserving them anyway.  Memory attributes
I would /guess/ have to also be specified by PAs; it's in the very next
subsection of the spec from all the other ones, and I think it just got
omitted from the list.  That leaves the last three.  As an aside, since
these definitions are so very poor, I'm going to put it on my TODO for
USST to clarify and fix these up, as well as to look at systemic fixes
for this problem in the future.

Anyway, the last three.  I think it's safe to assume that they are
mapped to virtual addresses we can read from *before*
SetVirtualAddressMap() and ExitBootServices() are called, especially
since we generally have an identity map before then anyway, but we
really don't know anything at all after that.  We also don't know the
sizes without parsing the tables themselves, which continues to be a
pain in the ass.

> I've always stayed clear of 2) in case there exists cross-region
> references in the data that isn't obvious. I'd like to think that
> would never happen, but, you know, dragons lurk here, etc.
> 
> Though actually, now I think about it, cross-region references can't
> possibly exist because they'd cause issues with the current code.

I would think any single table has to be entirely within the same
region, yes.

> So maybe the best solution is actually 2), where we preserve the Boot
> Services regions if any of the drivers (ESRT, BGRT) request them but
> free all the others? 

Note that BGRT is an ACPI table rather than an EFI Configuration Table,
and as such we actually have bounds for it.  The others are... special.

- Debug Image Info actually has a size.  That's nice of it.  It's also
  the table we've never talked about using.
- ESRT you have to compute the size as your parse it, and it has
  variable length members, so the driver for it needs to figure it out.
- IEIT has a number of entries at the top level, and then each entry has
  a size.  Probably still best to have the driver that's parsing it
  figure the size out.
- the Memory Attributes Table has a number of entries and a size of each
  entry, so you can just multiply.

> What are the lifetime rules for Boot Services regions on arm*?

I'll leave this for Ard and friends.

So the question I have is: would you rather chop up regions and reserve
the space, or allocate a new copy and update the configuration table
(after ExitBootServices()) to point to it?  The latter makes it pretty
easy to do from an API that all these drivers can use, and it makes the
kexec case completely transparent.

Up to you.

-- 
  Peter

[PATCH v2 1/2] efi: esrt: use memremap not ioremap to access ESRT table in memory

[Matt Fleming]

On Thu, 18 Feb, at 02:16:24PM, Peter Jones wrote:
> 
> So the question I have is: would you rather chop up regions and reserve
> the space, or allocate a new copy and update the configuration table
> (after ExitBootServices()) to point to it?  The latter makes it pretty
> easy to do from an API that all these drivers can use, and it makes the
> kexec case completely transparent.
> 
> Up to you.

I think it makes the most sense to chop up the regions we care about
(i.e. the ones we have drivers for) because not only does that save us
the effort of copying out the data on every kexec reboot, it also
prevents us from leaking each copy since we don't free them at the
moment.

Then we just need to maintain a separate list of regions to free in
efi_free_boot_services() or have some other way to distinguish between
them.

Oh, and save_runtime_map() would need updating to save Boot Services
regions too.

[PATCH v2 1/2] efi: esrt: use memremap not ioremap to access ESRT table in memory

[Matt Fleming]

On Fri, 26 Feb, at 02:41:14PM, Matt Fleming wrote:
> On Thu, 18 Feb, at 02:16:24PM, Peter Jones wrote:
> > 
> > So the question I have is: would you rather chop up regions and reserve
> > the space, or allocate a new copy and update the configuration table
> > (after ExitBootServices()) to point to it?  The latter makes it pretty
> > easy to do from an API that all these drivers can use, and it makes the
> > kexec case completely transparent.
> > 
> > Up to you.
> 
> I think it makes the most sense to chop up the regions we care about
> (i.e. the ones we have drivers for) because not only does that save us
> the effort of copying out the data on every kexec reboot, it also
> prevents us from leaking each copy since we don't free them at the
> moment.
> 
> Then we just need to maintain a separate list of regions to free in
> efi_free_boot_services() or have some other way to distinguish between
> them.
> 
> Oh, and save_runtime_map() would need updating to save Boot Services
> regions too.

I have a very rough draft of patches that implement this strategy on
the 'experiemntal/efi-memmap' branch in the EFI tree if anyone is
curious and wants to take a look. The series will be sent out soon.

I wouldn't necessarily try running them or anything as there's a few
things that I know are broken; ia64 build, EFI mixed mode boot,
probably arm64 regressions.

The upshot of the patch series is that there's a whole lot of code we
can share for manipulating memory maps between all EFI architectures
and by fixing this "reserve boot services regions" in a generic way it
should mean kexec under EFI on arm64 should be fairly trivial to
implement, along with ESRT, etc.

[PATCH v2 1/2] efi: esrt: use memremap not ioremap to access ESRT table in memory

[Matt Fleming]

On Tue, 01 Mar, at 11:30:40PM, Matt Fleming wrote:
> On Fri, 26 Feb, at 02:41:14PM, Matt Fleming wrote:
> > On Thu, 18 Feb, at 02:16:24PM, Peter Jones wrote:
> > > 
> > > So the question I have is: would you rather chop up regions and reserve
> > > the space, or allocate a new copy and update the configuration table
> > > (after ExitBootServices()) to point to it?  The latter makes it pretty
> > > easy to do from an API that all these drivers can use, and it makes the
> > > kexec case completely transparent.
> > > 
> > > Up to you.
> > 
> > I think it makes the most sense to chop up the regions we care about
> > (i.e. the ones we have drivers for) because not only does that save us
> > the effort of copying out the data on every kexec reboot, it also
> > prevents us from leaking each copy since we don't free them at the
> > moment.
> > 
> > Then we just need to maintain a separate list of regions to free in
> > efi_free_boot_services() or have some other way to distinguish between
> > them.
> > 
> > Oh, and save_runtime_map() would need updating to save Boot Services
> > regions too.
> 
> I have a very rough draft of patches that implement this strategy on
> the 'experiemntal/efi-memmap' branch in the EFI tree if anyone is
> curious and wants to take a look. The series will be sent out soon.

Obviously that's supposed to read: experimental/efi-memmap

[PATCH v2 1/2] efi: esrt: use memremap not ioremap to access ESRT table in memory

[Dave Young]

On 03/01/16 at 11:30pm, Matt Fleming wrote:
> On Fri, 26 Feb, at 02:41:14PM, Matt Fleming wrote:
> > On Thu, 18 Feb, at 02:16:24PM, Peter Jones wrote:
> > > 
> > > So the question I have is: would you rather chop up regions and reserve
> > > the space, or allocate a new copy and update the configuration table
> > > (after ExitBootServices()) to point to it?  The latter makes it pretty
> > > easy to do from an API that all these drivers can use, and it makes the
> > > kexec case completely transparent.
> > > 
> > > Up to you.
> > 
> > I think it makes the most sense to chop up the regions we care about
> > (i.e. the ones we have drivers for) because not only does that save us
> > the effort of copying out the data on every kexec reboot, it also
> > prevents us from leaking each copy since we don't free them at the
> > moment.
> > 
> > Then we just need to maintain a separate list of regions to free in
> > efi_free_boot_services() or have some other way to distinguish between
> > them.
> > 
> > Oh, and save_runtime_map() would need updating to save Boot Services
> > regions too.
> 
> I have a very rough draft of patches that implement this strategy on
> the 'experiemntal/efi-memmap' branch in the EFI tree if anyone is
> curious and wants to take a look. The series will be sent out soon.
> 
> I wouldn't necessarily try running them or anything as there's a few
> things that I know are broken; ia64 build, EFI mixed mode boot,
> probably arm64 regressions.
> 
> The upshot of the patch series is that there's a whole lot of code we
> can share for manipulating memory maps between all EFI architectures
> and by fixing this "reserve boot services regions" in a generic way it
> should mean kexec under EFI on arm64 should be fairly trivial to
> implement, along with ESRT, etc.

Matt, thanks. One question is for the acpi patches you sent before, do you
think they are still necessary as a fix for the bgrt problem and coexist
with the "reserve useful boot services" proposal?

Thanks
Dave

[PATCH v2 1/2] efi: esrt: use memremap not ioremap to access ESRT table in memory

[Matt Fleming]

On Wed, 02 Mar, at 09:16:19AM, Dave Young wrote:
> 
> Matt, thanks. One question is for the acpi patches you sent before, do you
> think they are still necessary as a fix for the bgrt problem and coexist
> with the "reserve useful boot services" proposal?

No, the previous ACPI patches I sent can be thrown in the bin if we go
with the approach outlined in this email.

This approach is superior because it allows useful features such as
ESRT and the new memory attributes to be used for kexec boot - the
ACPI patches prevented a crash by disabling BGRT.

[PATCH v2 1/2] efi: esrt: use memremap not ioremap to access ESRT table in memory

[Dave Young]

> I have a very rough draft of patches that implement this strategy on
> the 'experiemntal/efi-memmap' branch in the EFI tree if anyone is
> curious and wants to take a look. The series will be sent out soon.
> 
> I wouldn't necessarily try running them or anything as there's a few
> things that I know are broken; ia64 build, EFI mixed mode boot,
> probably arm64 regressions.

Matt, I tried :). I see a build warning about print phys_addr_t without
%pa anotation and booting with ioremap error messages about slot not found
, and ioremap region leak messages.

Looking forward to your formal posts.

Thanks
Dave

[PATCH v2 1/2] efi: esrt: use memremap not ioremap to access ESRT table in memory

[Ard Biesheuvel]

On 4 March 2016 at 07:25, Dave Young <dyoung@redhat.com> wrote:
>> I have a very rough draft of patches that implement this strategy on
>> the 'experiemntal/efi-memmap' branch in the EFI tree if anyone is
>> curious and wants to take a look. The series will be sent out soon.
>>
>> I wouldn't necessarily try running them or anything as there's a few
>> things that I know are broken; ia64 build, EFI mixed mode boot,
>> probably arm64 regressions.
>
> Matt, I tried :). I see a build warning about print phys_addr_t without
> %pa anotation and booting with ioremap error messages about slot not found
> , and ioremap region leak messages.
>
> Looking forward to your formal posts.
>

So what is the status here? I know Sai is working on x86 support for
the memory attributes table, so it would make sense settle this matter
as well.

[PATCH v2 1/2] efi: esrt: use memremap not ioremap to access ESRT table in memory

[Matt Fleming]

On Wed, 18 May, at 10:36:33AM, Ard Biesheuvel wrote:
> 
> So what is the status here? I know Sai is working on x86 support for
> the memory attributes table, so it would make sense settle this matter
> as well.

This got stuck behind some other work, sorry about that.

Some of this was just merged by Linus (getting rid of the global
memmap and switching everyone over to efi.memmap), a large chunk
remains however.

I should be able to get those patches mailed out once the merge window
closes.

[PATCH v2 1/2] efi: esrt: use memremap not ioremap to access ESRT table in memory

[Ard Biesheuvel]

On 18 May 2016 at 10:53, Matt Fleming <matt@codeblueprint.co.uk> wrote:
> On Wed, 18 May, at 10:36:33AM, Ard Biesheuvel wrote:
>>
>> So what is the status here? I know Sai is working on x86 support for
>> the memory attributes table, so it would make sense settle this matter
>> as well.
>
> This got stuck behind some other work, sorry about that.
>
> Some of this was just merged by Linus (getting rid of the global
> memmap and switching everyone over to efi.memmap), a large chunk
> remains however.
>
> I should be able to get those patches mailed out once the merge window
> closes.

Hi Matt,

Any progress here?

[PATCH v2 1/2] efi: esrt: use memremap not ioremap to access ESRT table in memory

[Matt Fleming]

On Thu, 16 Jun, at 03:47:30PM, Ard Biesheuvel wrote:
> 
> Hi Matt,
> 
> Any progress here?

Expect something to be posted this week.