[PATCH 0/2] xen: re-enable booting as Xen PVH guest

[PATCH 0/2] xen: re-enable booting as Xen PVH guest

[Juergen Gross]

The Xen PVH boot protocol passes vital information to the kernel via
a start_info block. One of the data transferred is the physical address
of the RSDP table.

Unfortunately PVH support in the kernel didn't use that passed address
for RSDP, but relied on the legacy mechanism searching for the RSDP in
low memory. After a recent change in Xen putting the RSDP to a higher
address booting as PVH guest is now failing.

This small series repairs that by passing the RSDP address from the
start_info block to ACPI handling.

Juergen Gross (2):
  x86/acpi: add retrieval function for rsdp address
  xen: add acpi_arch_get_root_pointer() for pvh guests

 arch/x86/xen/enlighten_pvh.c | 15 ++++++++++++---
 drivers/acpi/osl.c           | 10 +++++++++-
 include/linux/acpi.h         |  2 ++
 3 files changed, 23 insertions(+), 4 deletions(-)

-- 
2.13.6

[PATCH 1/2] x86/acpi: add retrieval function for rsdp address

[Juergen Gross]

Add a function to get the address of the RSDP table. Per default use a
__weak annotated function being a nop.

Cc: <stable@vger.kernel.org> # 4.11
Signed-off-by: Juergen Gross <jgross@suse.com>
---
 drivers/acpi/osl.c   | 10 +++++++++-
 include/linux/acpi.h |  2 ++
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/drivers/acpi/osl.c b/drivers/acpi/osl.c
index 3bb46cb24a99..2b77db914752 100644
--- a/drivers/acpi/osl.c
+++ b/drivers/acpi/osl.c
@@ -178,6 +178,11 @@ void acpi_os_vprintf(const char *fmt, va_list args)
 #endif
 }
 
+__weak acpi_physical_address acpi_arch_get_root_pointer(void)
+{
+	return 0;
+}
+
 #ifdef CONFIG_KEXEC
 static unsigned long acpi_rsdp;
 static int __init setup_acpi_rsdp(char *arg)
@@ -189,12 +194,15 @@ early_param("acpi_rsdp", setup_acpi_rsdp);
 
 acpi_physical_address __init acpi_os_get_root_pointer(void)
 {
-	acpi_physical_address pa = 0;
+	acpi_physical_address pa;
 
 #ifdef CONFIG_KEXEC
 	if (acpi_rsdp)
 		return acpi_rsdp;
 #endif
+	pa = acpi_arch_get_root_pointer();
+	if (pa)
+		return pa;
 
 	if (efi_enabled(EFI_CONFIG_TABLES)) {
 		if (efi.acpi20 != EFI_INVALID_TABLE_ADDR)
diff --git a/include/linux/acpi.h b/include/linux/acpi.h
index dc1ebfeeb5ec..aa603cc5ad30 100644
--- a/include/linux/acpi.h
+++ b/include/linux/acpi.h
@@ -1266,4 +1266,6 @@ static inline int lpit_read_residency_count_address(u64 *address)
 }
 #endif
 
+acpi_physical_address acpi_arch_get_root_pointer(void);
+
 #endif	/*_LINUX_ACPI_H*/
-- 
2.13.6

[PATCH 1/2] x86/acpi: add retrieval function for rsdp address

[Juergen Gross]

Add a function to get the address of the RSDP table. Per default use a
__weak annotated function being a nop.

Cc: <stable@vger.kernel.org> # 4.11
Signed-off-by: Juergen Gross <jgross@suse.com>
---
 drivers/acpi/osl.c   | 10 +++++++++-
 include/linux/acpi.h |  2 ++
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/drivers/acpi/osl.c b/drivers/acpi/osl.c
index 3bb46cb24a99..2b77db914752 100644
--- a/drivers/acpi/osl.c
+++ b/drivers/acpi/osl.c
@@ -178,6 +178,11 @@ void acpi_os_vprintf(const char *fmt, va_list args)
 #endif
 }
 
+__weak acpi_physical_address acpi_arch_get_root_pointer(void)
+{
+	return 0;
+}
+
 #ifdef CONFIG_KEXEC
 static unsigned long acpi_rsdp;
 static int __init setup_acpi_rsdp(char *arg)
@@ -189,12 +194,15 @@ early_param("acpi_rsdp", setup_acpi_rsdp);
 
 acpi_physical_address __init acpi_os_get_root_pointer(void)
 {
-	acpi_physical_address pa = 0;
+	acpi_physical_address pa;
 
 #ifdef CONFIG_KEXEC
 	if (acpi_rsdp)
 		return acpi_rsdp;
 #endif
+	pa = acpi_arch_get_root_pointer();
+	if (pa)
+		return pa;
 
 	if (efi_enabled(EFI_CONFIG_TABLES)) {
 		if (efi.acpi20 != EFI_INVALID_TABLE_ADDR)
diff --git a/include/linux/acpi.h b/include/linux/acpi.h
index dc1ebfeeb5ec..aa603cc5ad30 100644
--- a/include/linux/acpi.h
+++ b/include/linux/acpi.h
@@ -1266,4 +1266,6 @@ static inline int lpit_read_residency_count_address(u64 *address)
 }
 #endif
 
+acpi_physical_address acpi_arch_get_root_pointer(void);
+
 #endif	/*_LINUX_ACPI_H*/
-- 
2.13.6


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[PATCH 2/2] xen: add acpi_arch_get_root_pointer() for pvh guests

[Juergen Gross]

Add acpi_arch_get_root_pointer() for Xen PVH guests to communicate
the address of the RSDP table given to the kernel via Xen start info.

This makes the kernel boot again in PVH mode after on recent Xen the
RSDP was moved to higher addresses. So up to that change it was pure
luck that the legacy method to locate the RSDP was working when
running as PVH mode.

Cc: <stable@vger.kernel.org> # 4.11
Signed-off-by: Juergen Gross <jgross@suse.com>
---
 arch/x86/xen/enlighten_pvh.c | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/arch/x86/xen/enlighten_pvh.c b/arch/x86/xen/enlighten_pvh.c
index 436c4f003e17..9a5c3a7fe673 100644
--- a/arch/x86/xen/enlighten_pvh.c
+++ b/arch/x86/xen/enlighten_pvh.c
@@ -16,15 +16,24 @@
 /*
  * PVH variables.
  *
- * xen_pvh and pvh_bootparams need to live in data segment since they
- * are used after startup_{32|64}, which clear .bss, are invoked.
+ * xen_pvh, pvh_bootparams and pvh_start_info need to live in data segment
+ * since they are used after startup_{32|64}, which clear .bss, are invoked.
  */
 bool xen_pvh __attribute__((section(".data"))) = 0;
 struct boot_params pvh_bootparams __attribute__((section(".data")));
+struct hvm_start_info pvh_start_info __attribute__((section(".data")));
 
-struct hvm_start_info pvh_start_info;
 unsigned int pvh_start_info_sz = sizeof(pvh_start_info);
 
+acpi_physical_address acpi_arch_get_root_pointer(void)
+{
+	if (xen_pvh)
+		return pvh_start_info.rsdp_paddr;
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(acpi_arch_get_root_pointer);
+
 static void __init init_pvh_bootparams(void)
 {
 	struct xen_memory_map memmap;
-- 
2.13.6

[PATCH 2/2] xen: add acpi_arch_get_root_pointer() for pvh guests

[Juergen Gross]

Add acpi_arch_get_root_pointer() for Xen PVH guests to communicate
the address of the RSDP table given to the kernel via Xen start info.

This makes the kernel boot again in PVH mode after on recent Xen the
RSDP was moved to higher addresses. So up to that change it was pure
luck that the legacy method to locate the RSDP was working when
running as PVH mode.

Cc: <stable@vger.kernel.org> # 4.11
Signed-off-by: Juergen Gross <jgross@suse.com>
---
 arch/x86/xen/enlighten_pvh.c | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/arch/x86/xen/enlighten_pvh.c b/arch/x86/xen/enlighten_pvh.c
index 436c4f003e17..9a5c3a7fe673 100644
--- a/arch/x86/xen/enlighten_pvh.c
+++ b/arch/x86/xen/enlighten_pvh.c
@@ -16,15 +16,24 @@
 /*
  * PVH variables.
  *
- * xen_pvh and pvh_bootparams need to live in data segment since they
- * are used after startup_{32|64}, which clear .bss, are invoked.
+ * xen_pvh, pvh_bootparams and pvh_start_info need to live in data segment
+ * since they are used after startup_{32|64}, which clear .bss, are invoked.
  */
 bool xen_pvh __attribute__((section(".data"))) = 0;
 struct boot_params pvh_bootparams __attribute__((section(".data")));
+struct hvm_start_info pvh_start_info __attribute__((section(".data")));
 
-struct hvm_start_info pvh_start_info;
 unsigned int pvh_start_info_sz = sizeof(pvh_start_info);
 
+acpi_physical_address acpi_arch_get_root_pointer(void)
+{
+	if (xen_pvh)
+		return pvh_start_info.rsdp_paddr;
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(acpi_arch_get_root_pointer);
+
 static void __init init_pvh_bootparams(void)
 {
 	struct xen_memory_map memmap;
-- 
2.13.6


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Re: [PATCH 2/2] xen: add acpi_arch_get_root_pointer() for pvh guests

[Greg KH]

On Thu, Jan 25, 2018 at 11:04:54AM +0100, Juergen Gross wrote:
> Add acpi_arch_get_root_pointer() for Xen PVH guests to communicate
> the address of the RSDP table given to the kernel via Xen start info.
> 
> This makes the kernel boot again in PVH mode after on recent Xen the
> RSDP was moved to higher addresses. So up to that change it was pure
> luck that the legacy method to locate the RSDP was working when
> running as PVH mode.
> 
> Cc: <stable@vger.kernel.org> # 4.11
> Signed-off-by: Juergen Gross <jgross@suse.com>
> ---
>  arch/x86/xen/enlighten_pvh.c | 15 ++++++++++++---
>  1 file changed, 12 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/x86/xen/enlighten_pvh.c b/arch/x86/xen/enlighten_pvh.c
> index 436c4f003e17..9a5c3a7fe673 100644
> --- a/arch/x86/xen/enlighten_pvh.c
> +++ b/arch/x86/xen/enlighten_pvh.c
> @@ -16,15 +16,24 @@
>  /*
>   * PVH variables.
>   *
> - * xen_pvh and pvh_bootparams need to live in data segment since they
> - * are used after startup_{32|64}, which clear .bss, are invoked.
> + * xen_pvh, pvh_bootparams and pvh_start_info need to live in data segment
> + * since they are used after startup_{32|64}, which clear .bss, are invoked.
>   */
>  bool xen_pvh __attribute__((section(".data"))) = 0;
>  struct boot_params pvh_bootparams __attribute__((section(".data")));
> +struct hvm_start_info pvh_start_info __attribute__((section(".data")));
>  
> -struct hvm_start_info pvh_start_info;
>  unsigned int pvh_start_info_sz = sizeof(pvh_start_info);
>  
> +acpi_physical_address acpi_arch_get_root_pointer(void)
> +{
> +	if (xen_pvh)
> +		return pvh_start_info.rsdp_paddr;
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(acpi_arch_get_root_pointer);

Why does this have to be an exported symbol?  Does this code get built
as a module and will the linker somehow go and rewrite the previous call
places with this one if it gets loaded?

thanks,

greg k-h

Re: [PATCH 2/2] xen: add acpi_arch_get_root_pointer() for pvh guests

[Greg KH]

On Thu, Jan 25, 2018 at 11:04:54AM +0100, Juergen Gross wrote:
> Add acpi_arch_get_root_pointer() for Xen PVH guests to communicate
> the address of the RSDP table given to the kernel via Xen start info.
> 
> This makes the kernel boot again in PVH mode after on recent Xen the
> RSDP was moved to higher addresses. So up to that change it was pure
> luck that the legacy method to locate the RSDP was working when
> running as PVH mode.
> 
> Cc: <stable@vger.kernel.org> # 4.11
> Signed-off-by: Juergen Gross <jgross@suse.com>
> ---
>  arch/x86/xen/enlighten_pvh.c | 15 ++++++++++++---
>  1 file changed, 12 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/x86/xen/enlighten_pvh.c b/arch/x86/xen/enlighten_pvh.c
> index 436c4f003e17..9a5c3a7fe673 100644
> --- a/arch/x86/xen/enlighten_pvh.c
> +++ b/arch/x86/xen/enlighten_pvh.c
> @@ -16,15 +16,24 @@
>  /*
>   * PVH variables.
>   *
> - * xen_pvh and pvh_bootparams need to live in data segment since they
> - * are used after startup_{32|64}, which clear .bss, are invoked.
> + * xen_pvh, pvh_bootparams and pvh_start_info need to live in data segment
> + * since they are used after startup_{32|64}, which clear .bss, are invoked.
>   */
>  bool xen_pvh __attribute__((section(".data"))) = 0;
>  struct boot_params pvh_bootparams __attribute__((section(".data")));
> +struct hvm_start_info pvh_start_info __attribute__((section(".data")));
>  
> -struct hvm_start_info pvh_start_info;
>  unsigned int pvh_start_info_sz = sizeof(pvh_start_info);
>  
> +acpi_physical_address acpi_arch_get_root_pointer(void)
> +{
> +	if (xen_pvh)
> +		return pvh_start_info.rsdp_paddr;
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(acpi_arch_get_root_pointer);

Why does this have to be an exported symbol?  Does this code get built
as a module and will the linker somehow go and rewrite the previous call
places with this one if it gets loaded?

thanks,

greg k-h

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Re: [PATCH 2/2] xen: add acpi_arch_get_root_pointer() for pvh guests

[Juergen Gross]

On 25/01/18 11:37, Greg KH wrote:
> On Thu, Jan 25, 2018 at 11:04:54AM +0100, Juergen Gross wrote:
>> Add acpi_arch_get_root_pointer() for Xen PVH guests to communicate
>> the address of the RSDP table given to the kernel via Xen start info.
>>
>> This makes the kernel boot again in PVH mode after on recent Xen the
>> RSDP was moved to higher addresses. So up to that change it was pure
>> luck that the legacy method to locate the RSDP was working when
>> running as PVH mode.
>>
>> Cc: <stable@vger.kernel.org> # 4.11
>> Signed-off-by: Juergen Gross <jgross@suse.com>
>> ---
>>  arch/x86/xen/enlighten_pvh.c | 15 ++++++++++++---
>>  1 file changed, 12 insertions(+), 3 deletions(-)
>>
>> diff --git a/arch/x86/xen/enlighten_pvh.c b/arch/x86/xen/enlighten_pvh.c
>> index 436c4f003e17..9a5c3a7fe673 100644
>> --- a/arch/x86/xen/enlighten_pvh.c
>> +++ b/arch/x86/xen/enlighten_pvh.c
>> @@ -16,15 +16,24 @@
>>  /*
>>   * PVH variables.
>>   *
>> - * xen_pvh and pvh_bootparams need to live in data segment since they
>> - * are used after startup_{32|64}, which clear .bss, are invoked.
>> + * xen_pvh, pvh_bootparams and pvh_start_info need to live in data segment
>> + * since they are used after startup_{32|64}, which clear .bss, are invoked.
>>   */
>>  bool xen_pvh __attribute__((section(".data"))) = 0;
>>  struct boot_params pvh_bootparams __attribute__((section(".data")));
>> +struct hvm_start_info pvh_start_info __attribute__((section(".data")));
>>  
>> -struct hvm_start_info pvh_start_info;
>>  unsigned int pvh_start_info_sz = sizeof(pvh_start_info);
>>  
>> +acpi_physical_address acpi_arch_get_root_pointer(void)
>> +{
>> +	if (xen_pvh)
>> +		return pvh_start_info.rsdp_paddr;
>> +
>> +	return 0;
>> +}
>> +EXPORT_SYMBOL_GPL(acpi_arch_get_root_pointer);
> 
> Why does this have to be an exported symbol?  Does this code get built
> as a module and will the linker somehow go and rewrite the previous call
> places with this one if it gets loaded?

With being called by drivers/acpi/... I just wanted to make sure it is
working properly even in case the acpi code is built as a module.


Juergen

Re: [PATCH 2/2] xen: add acpi_arch_get_root_pointer() for pvh guests

[Juergen Gross]

On 25/01/18 11:37, Greg KH wrote:
> On Thu, Jan 25, 2018 at 11:04:54AM +0100, Juergen Gross wrote:
>> Add acpi_arch_get_root_pointer() for Xen PVH guests to communicate
>> the address of the RSDP table given to the kernel via Xen start info.
>>
>> This makes the kernel boot again in PVH mode after on recent Xen the
>> RSDP was moved to higher addresses. So up to that change it was pure
>> luck that the legacy method to locate the RSDP was working when
>> running as PVH mode.
>>
>> Cc: <stable@vger.kernel.org> # 4.11
>> Signed-off-by: Juergen Gross <jgross@suse.com>
>> ---
>>  arch/x86/xen/enlighten_pvh.c | 15 ++++++++++++---
>>  1 file changed, 12 insertions(+), 3 deletions(-)
>>
>> diff --git a/arch/x86/xen/enlighten_pvh.c b/arch/x86/xen/enlighten_pvh.c
>> index 436c4f003e17..9a5c3a7fe673 100644
>> --- a/arch/x86/xen/enlighten_pvh.c
>> +++ b/arch/x86/xen/enlighten_pvh.c
>> @@ -16,15 +16,24 @@
>>  /*
>>   * PVH variables.
>>   *
>> - * xen_pvh and pvh_bootparams need to live in data segment since they
>> - * are used after startup_{32|64}, which clear .bss, are invoked.
>> + * xen_pvh, pvh_bootparams and pvh_start_info need to live in data segment
>> + * since they are used after startup_{32|64}, which clear .bss, are invoked.
>>   */
>>  bool xen_pvh __attribute__((section(".data"))) = 0;
>>  struct boot_params pvh_bootparams __attribute__((section(".data")));
>> +struct hvm_start_info pvh_start_info __attribute__((section(".data")));
>>  
>> -struct hvm_start_info pvh_start_info;
>>  unsigned int pvh_start_info_sz = sizeof(pvh_start_info);
>>  
>> +acpi_physical_address acpi_arch_get_root_pointer(void)
>> +{
>> +	if (xen_pvh)
>> +		return pvh_start_info.rsdp_paddr;
>> +
>> +	return 0;
>> +}
>> +EXPORT_SYMBOL_GPL(acpi_arch_get_root_pointer);
> 
> Why does this have to be an exported symbol?  Does this code get built
> as a module and will the linker somehow go and rewrite the previous call
> places with this one if it gets loaded?

With being called by drivers/acpi/... I just wanted to make sure it is
working properly even in case the acpi code is built as a module.


Juergen

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Re: [PATCH 2/2] xen: add acpi_arch_get_root_pointer() for pvh guests

[Greg KH]

On Thu, Jan 25, 2018 at 11:49:35AM +0100, Juergen Gross wrote:
> On 25/01/18 11:37, Greg KH wrote:
> > On Thu, Jan 25, 2018 at 11:04:54AM +0100, Juergen Gross wrote:
> >> Add acpi_arch_get_root_pointer() for Xen PVH guests to communicate
> >> the address of the RSDP table given to the kernel via Xen start info.
> >>
> >> This makes the kernel boot again in PVH mode after on recent Xen the
> >> RSDP was moved to higher addresses. So up to that change it was pure
> >> luck that the legacy method to locate the RSDP was working when
> >> running as PVH mode.
> >>
> >> Cc: <stable@vger.kernel.org> # 4.11
> >> Signed-off-by: Juergen Gross <jgross@suse.com>
> >> ---
> >>  arch/x86/xen/enlighten_pvh.c | 15 ++++++++++++---
> >>  1 file changed, 12 insertions(+), 3 deletions(-)
> >>
> >> diff --git a/arch/x86/xen/enlighten_pvh.c b/arch/x86/xen/enlighten_pvh.c
> >> index 436c4f003e17..9a5c3a7fe673 100644
> >> --- a/arch/x86/xen/enlighten_pvh.c
> >> +++ b/arch/x86/xen/enlighten_pvh.c
> >> @@ -16,15 +16,24 @@
> >>  /*
> >>   * PVH variables.
> >>   *
> >> - * xen_pvh and pvh_bootparams need to live in data segment since they
> >> - * are used after startup_{32|64}, which clear .bss, are invoked.
> >> + * xen_pvh, pvh_bootparams and pvh_start_info need to live in data segment
> >> + * since they are used after startup_{32|64}, which clear .bss, are invoked.
> >>   */
> >>  bool xen_pvh __attribute__((section(".data"))) = 0;
> >>  struct boot_params pvh_bootparams __attribute__((section(".data")));
> >> +struct hvm_start_info pvh_start_info __attribute__((section(".data")));
> >>  
> >> -struct hvm_start_info pvh_start_info;
> >>  unsigned int pvh_start_info_sz = sizeof(pvh_start_info);
> >>  
> >> +acpi_physical_address acpi_arch_get_root_pointer(void)
> >> +{
> >> +	if (xen_pvh)
> >> +		return pvh_start_info.rsdp_paddr;
> >> +
> >> +	return 0;
> >> +}
> >> +EXPORT_SYMBOL_GPL(acpi_arch_get_root_pointer);
> > 
> > Why does this have to be an exported symbol?  Does this code get built
> > as a module and will the linker somehow go and rewrite the previous call
> > places with this one if it gets loaded?
> 
> With being called by drivers/acpi/... I just wanted to make sure it is
> working properly even in case the acpi code is built as a module.

I didn't think the core ACPI code can be built as a module, have you
tried that?

thanks,

greg k-h

Re: [PATCH 2/2] xen: add acpi_arch_get_root_pointer() for pvh guests

[Greg KH]

On Thu, Jan 25, 2018 at 11:49:35AM +0100, Juergen Gross wrote:
> On 25/01/18 11:37, Greg KH wrote:
> > On Thu, Jan 25, 2018 at 11:04:54AM +0100, Juergen Gross wrote:
> >> Add acpi_arch_get_root_pointer() for Xen PVH guests to communicate
> >> the address of the RSDP table given to the kernel via Xen start info.
> >>
> >> This makes the kernel boot again in PVH mode after on recent Xen the
> >> RSDP was moved to higher addresses. So up to that change it was pure
> >> luck that the legacy method to locate the RSDP was working when
> >> running as PVH mode.
> >>
> >> Cc: <stable@vger.kernel.org> # 4.11
> >> Signed-off-by: Juergen Gross <jgross@suse.com>
> >> ---
> >>  arch/x86/xen/enlighten_pvh.c | 15 ++++++++++++---
> >>  1 file changed, 12 insertions(+), 3 deletions(-)
> >>
> >> diff --git a/arch/x86/xen/enlighten_pvh.c b/arch/x86/xen/enlighten_pvh.c
> >> index 436c4f003e17..9a5c3a7fe673 100644
> >> --- a/arch/x86/xen/enlighten_pvh.c
> >> +++ b/arch/x86/xen/enlighten_pvh.c
> >> @@ -16,15 +16,24 @@
> >>  /*
> >>   * PVH variables.
> >>   *
> >> - * xen_pvh and pvh_bootparams need to live in data segment since they
> >> - * are used after startup_{32|64}, which clear .bss, are invoked.
> >> + * xen_pvh, pvh_bootparams and pvh_start_info need to live in data segment
> >> + * since they are used after startup_{32|64}, which clear .bss, are invoked.
> >>   */
> >>  bool xen_pvh __attribute__((section(".data"))) = 0;
> >>  struct boot_params pvh_bootparams __attribute__((section(".data")));
> >> +struct hvm_start_info pvh_start_info __attribute__((section(".data")));
> >>  
> >> -struct hvm_start_info pvh_start_info;
> >>  unsigned int pvh_start_info_sz = sizeof(pvh_start_info);
> >>  
> >> +acpi_physical_address acpi_arch_get_root_pointer(void)
> >> +{
> >> +	if (xen_pvh)
> >> +		return pvh_start_info.rsdp_paddr;
> >> +
> >> +	return 0;
> >> +}
> >> +EXPORT_SYMBOL_GPL(acpi_arch_get_root_pointer);
> > 
> > Why does this have to be an exported symbol?  Does this code get built
> > as a module and will the linker somehow go and rewrite the previous call
> > places with this one if it gets loaded?
> 
> With being called by drivers/acpi/... I just wanted to make sure it is
> working properly even in case the acpi code is built as a module.

I didn't think the core ACPI code can be built as a module, have you
tried that?

thanks,

greg k-h

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Re: [PATCH 2/2] xen: add acpi_arch_get_root_pointer() for pvh guests

[Juergen Gross]

On 25/01/18 12:00, Greg KH wrote:
> On Thu, Jan 25, 2018 at 11:49:35AM +0100, Juergen Gross wrote:
>> On 25/01/18 11:37, Greg KH wrote:
>>> On Thu, Jan 25, 2018 at 11:04:54AM +0100, Juergen Gross wrote:
>>>> Add acpi_arch_get_root_pointer() for Xen PVH guests to communicate
>>>> the address of the RSDP table given to the kernel via Xen start info.
>>>>
>>>> This makes the kernel boot again in PVH mode after on recent Xen the
>>>> RSDP was moved to higher addresses. So up to that change it was pure
>>>> luck that the legacy method to locate the RSDP was working when
>>>> running as PVH mode.
>>>>
>>>> Cc: <stable@vger.kernel.org> # 4.11
>>>> Signed-off-by: Juergen Gross <jgross@suse.com>
>>>> ---
>>>>  arch/x86/xen/enlighten_pvh.c | 15 ++++++++++++---
>>>>  1 file changed, 12 insertions(+), 3 deletions(-)
>>>>
>>>> diff --git a/arch/x86/xen/enlighten_pvh.c b/arch/x86/xen/enlighten_pvh.c
>>>> index 436c4f003e17..9a5c3a7fe673 100644
>>>> --- a/arch/x86/xen/enlighten_pvh.c
>>>> +++ b/arch/x86/xen/enlighten_pvh.c
>>>> @@ -16,15 +16,24 @@
>>>>  /*
>>>>   * PVH variables.
>>>>   *
>>>> - * xen_pvh and pvh_bootparams need to live in data segment since they
>>>> - * are used after startup_{32|64}, which clear .bss, are invoked.
>>>> + * xen_pvh, pvh_bootparams and pvh_start_info need to live in data segment
>>>> + * since they are used after startup_{32|64}, which clear .bss, are invoked.
>>>>   */
>>>>  bool xen_pvh __attribute__((section(".data"))) = 0;
>>>>  struct boot_params pvh_bootparams __attribute__((section(".data")));
>>>> +struct hvm_start_info pvh_start_info __attribute__((section(".data")));
>>>>  
>>>> -struct hvm_start_info pvh_start_info;
>>>>  unsigned int pvh_start_info_sz = sizeof(pvh_start_info);
>>>>  
>>>> +acpi_physical_address acpi_arch_get_root_pointer(void)
>>>> +{
>>>> +	if (xen_pvh)
>>>> +		return pvh_start_info.rsdp_paddr;
>>>> +
>>>> +	return 0;
>>>> +}
>>>> +EXPORT_SYMBOL_GPL(acpi_arch_get_root_pointer);
>>>
>>> Why does this have to be an exported symbol?  Does this code get built
>>> as a module and will the linker somehow go and rewrite the previous call
>>> places with this one if it gets loaded?
>>
>> With being called by drivers/acpi/... I just wanted to make sure it is
>> working properly even in case the acpi code is built as a module.
> 
> I didn't think the core ACPI code can be built as a module, have you
> tried that?

No, but as the build wouldn't break whenever this is changed I wanted
to make sure the symbol is found.

If you feel strong about that I can remove the EXPORT_SYMBOL_GPL().


Juergen

Re: [PATCH 2/2] xen: add acpi_arch_get_root_pointer() for pvh guests

[Juergen Gross]

On 25/01/18 12:00, Greg KH wrote:
> On Thu, Jan 25, 2018 at 11:49:35AM +0100, Juergen Gross wrote:
>> On 25/01/18 11:37, Greg KH wrote:
>>> On Thu, Jan 25, 2018 at 11:04:54AM +0100, Juergen Gross wrote:
>>>> Add acpi_arch_get_root_pointer() for Xen PVH guests to communicate
>>>> the address of the RSDP table given to the kernel via Xen start info.
>>>>
>>>> This makes the kernel boot again in PVH mode after on recent Xen the
>>>> RSDP was moved to higher addresses. So up to that change it was pure
>>>> luck that the legacy method to locate the RSDP was working when
>>>> running as PVH mode.
>>>>
>>>> Cc: <stable@vger.kernel.org> # 4.11
>>>> Signed-off-by: Juergen Gross <jgross@suse.com>
>>>> ---
>>>>  arch/x86/xen/enlighten_pvh.c | 15 ++++++++++++---
>>>>  1 file changed, 12 insertions(+), 3 deletions(-)
>>>>
>>>> diff --git a/arch/x86/xen/enlighten_pvh.c b/arch/x86/xen/enlighten_pvh.c
>>>> index 436c4f003e17..9a5c3a7fe673 100644
>>>> --- a/arch/x86/xen/enlighten_pvh.c
>>>> +++ b/arch/x86/xen/enlighten_pvh.c
>>>> @@ -16,15 +16,24 @@
>>>>  /*
>>>>   * PVH variables.
>>>>   *
>>>> - * xen_pvh and pvh_bootparams need to live in data segment since they
>>>> - * are used after startup_{32|64}, which clear .bss, are invoked.
>>>> + * xen_pvh, pvh_bootparams and pvh_start_info need to live in data segment
>>>> + * since they are used after startup_{32|64}, which clear .bss, are invoked.
>>>>   */
>>>>  bool xen_pvh __attribute__((section(".data"))) = 0;
>>>>  struct boot_params pvh_bootparams __attribute__((section(".data")));
>>>> +struct hvm_start_info pvh_start_info __attribute__((section(".data")));
>>>>  
>>>> -struct hvm_start_info pvh_start_info;
>>>>  unsigned int pvh_start_info_sz = sizeof(pvh_start_info);
>>>>  
>>>> +acpi_physical_address acpi_arch_get_root_pointer(void)
>>>> +{
>>>> +	if (xen_pvh)
>>>> +		return pvh_start_info.rsdp_paddr;
>>>> +
>>>> +	return 0;
>>>> +}
>>>> +EXPORT_SYMBOL_GPL(acpi_arch_get_root_pointer);
>>>
>>> Why does this have to be an exported symbol?  Does this code get built
>>> as a module and will the linker somehow go and rewrite the previous call
>>> places with this one if it gets loaded?
>>
>> With being called by drivers/acpi/... I just wanted to make sure it is
>> working properly even in case the acpi code is built as a module.
> 
> I didn't think the core ACPI code can be built as a module, have you
> tried that?

No, but as the build wouldn't break whenever this is changed I wanted
to make sure the symbol is found.

If you feel strong about that I can remove the EXPORT_SYMBOL_GPL().


Juergen

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Re: [PATCH 2/2] xen: add acpi_arch_get_root_pointer() for pvh guests

[Greg KH]

On Thu, Jan 25, 2018 at 01:06:26PM +0100, Juergen Gross wrote:
> On 25/01/18 12:00, Greg KH wrote:
> > On Thu, Jan 25, 2018 at 11:49:35AM +0100, Juergen Gross wrote:
> >> On 25/01/18 11:37, Greg KH wrote:
> >>> On Thu, Jan 25, 2018 at 11:04:54AM +0100, Juergen Gross wrote:
> >>>> Add acpi_arch_get_root_pointer() for Xen PVH guests to communicate
> >>>> the address of the RSDP table given to the kernel via Xen start info.
> >>>>
> >>>> This makes the kernel boot again in PVH mode after on recent Xen the
> >>>> RSDP was moved to higher addresses. So up to that change it was pure
> >>>> luck that the legacy method to locate the RSDP was working when
> >>>> running as PVH mode.
> >>>>
> >>>> Cc: <stable@vger.kernel.org> # 4.11
> >>>> Signed-off-by: Juergen Gross <jgross@suse.com>
> >>>> ---
> >>>>  arch/x86/xen/enlighten_pvh.c | 15 ++++++++++++---
> >>>>  1 file changed, 12 insertions(+), 3 deletions(-)
> >>>>
> >>>> diff --git a/arch/x86/xen/enlighten_pvh.c b/arch/x86/xen/enlighten_pvh.c
> >>>> index 436c4f003e17..9a5c3a7fe673 100644
> >>>> --- a/arch/x86/xen/enlighten_pvh.c
> >>>> +++ b/arch/x86/xen/enlighten_pvh.c
> >>>> @@ -16,15 +16,24 @@
> >>>>  /*
> >>>>   * PVH variables.
> >>>>   *
> >>>> - * xen_pvh and pvh_bootparams need to live in data segment since they
> >>>> - * are used after startup_{32|64}, which clear .bss, are invoked.
> >>>> + * xen_pvh, pvh_bootparams and pvh_start_info need to live in data segment
> >>>> + * since they are used after startup_{32|64}, which clear .bss, are invoked.
> >>>>   */
> >>>>  bool xen_pvh __attribute__((section(".data"))) = 0;
> >>>>  struct boot_params pvh_bootparams __attribute__((section(".data")));
> >>>> +struct hvm_start_info pvh_start_info __attribute__((section(".data")));
> >>>>  
> >>>> -struct hvm_start_info pvh_start_info;
> >>>>  unsigned int pvh_start_info_sz = sizeof(pvh_start_info);
> >>>>  
> >>>> +acpi_physical_address acpi_arch_get_root_pointer(void)
> >>>> +{
> >>>> +	if (xen_pvh)
> >>>> +		return pvh_start_info.rsdp_paddr;
> >>>> +
> >>>> +	return 0;
> >>>> +}
> >>>> +EXPORT_SYMBOL_GPL(acpi_arch_get_root_pointer);
> >>>
> >>> Why does this have to be an exported symbol?  Does this code get built
> >>> as a module and will the linker somehow go and rewrite the previous call
> >>> places with this one if it gets loaded?
> >>
> >> With being called by drivers/acpi/... I just wanted to make sure it is
> >> working properly even in case the acpi code is built as a module.
> > 
> > I didn't think the core ACPI code can be built as a module, have you
> > tried that?
> 
> No, but as the build wouldn't break whenever this is changed I wanted
> to make sure the symbol is found.
> 
> If you feel strong about that I can remove the EXPORT_SYMBOL_GPL().

Please don't export symbols that do not need to be exported, that's just
a waste.

thanks,

greg k-h

Re: [PATCH 2/2] xen: add acpi_arch_get_root_pointer() for pvh guests

[Greg KH]

On Thu, Jan 25, 2018 at 01:06:26PM +0100, Juergen Gross wrote:
> On 25/01/18 12:00, Greg KH wrote:
> > On Thu, Jan 25, 2018 at 11:49:35AM +0100, Juergen Gross wrote:
> >> On 25/01/18 11:37, Greg KH wrote:
> >>> On Thu, Jan 25, 2018 at 11:04:54AM +0100, Juergen Gross wrote:
> >>>> Add acpi_arch_get_root_pointer() for Xen PVH guests to communicate
> >>>> the address of the RSDP table given to the kernel via Xen start info.
> >>>>
> >>>> This makes the kernel boot again in PVH mode after on recent Xen the
> >>>> RSDP was moved to higher addresses. So up to that change it was pure
> >>>> luck that the legacy method to locate the RSDP was working when
> >>>> running as PVH mode.
> >>>>
> >>>> Cc: <stable@vger.kernel.org> # 4.11
> >>>> Signed-off-by: Juergen Gross <jgross@suse.com>
> >>>> ---
> >>>>  arch/x86/xen/enlighten_pvh.c | 15 ++++++++++++---
> >>>>  1 file changed, 12 insertions(+), 3 deletions(-)
> >>>>
> >>>> diff --git a/arch/x86/xen/enlighten_pvh.c b/arch/x86/xen/enlighten_pvh.c
> >>>> index 436c4f003e17..9a5c3a7fe673 100644
> >>>> --- a/arch/x86/xen/enlighten_pvh.c
> >>>> +++ b/arch/x86/xen/enlighten_pvh.c
> >>>> @@ -16,15 +16,24 @@
> >>>>  /*
> >>>>   * PVH variables.
> >>>>   *
> >>>> - * xen_pvh and pvh_bootparams need to live in data segment since they
> >>>> - * are used after startup_{32|64}, which clear .bss, are invoked.
> >>>> + * xen_pvh, pvh_bootparams and pvh_start_info need to live in data segment
> >>>> + * since they are used after startup_{32|64}, which clear .bss, are invoked.
> >>>>   */
> >>>>  bool xen_pvh __attribute__((section(".data"))) = 0;
> >>>>  struct boot_params pvh_bootparams __attribute__((section(".data")));
> >>>> +struct hvm_start_info pvh_start_info __attribute__((section(".data")));
> >>>>  
> >>>> -struct hvm_start_info pvh_start_info;
> >>>>  unsigned int pvh_start_info_sz = sizeof(pvh_start_info);
> >>>>  
> >>>> +acpi_physical_address acpi_arch_get_root_pointer(void)
> >>>> +{
> >>>> +	if (xen_pvh)
> >>>> +		return pvh_start_info.rsdp_paddr;
> >>>> +
> >>>> +	return 0;
> >>>> +}
> >>>> +EXPORT_SYMBOL_GPL(acpi_arch_get_root_pointer);
> >>>
> >>> Why does this have to be an exported symbol?  Does this code get built
> >>> as a module and will the linker somehow go and rewrite the previous call
> >>> places with this one if it gets loaded?
> >>
> >> With being called by drivers/acpi/... I just wanted to make sure it is
> >> working properly even in case the acpi code is built as a module.
> > 
> > I didn't think the core ACPI code can be built as a module, have you
> > tried that?
> 
> No, but as the build wouldn't break whenever this is changed I wanted
> to make sure the symbol is found.
> 
> If you feel strong about that I can remove the EXPORT_SYMBOL_GPL().

Please don't export symbols that do not need to be exported, that's just
a waste.

thanks,

greg k-h

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[PATCH 0/2] xen: re-enable booting as Xen PVH guest

[Juergen Gross]

The Xen PVH boot protocol passes vital information to the kernel via
a start_info block. One of the data transferred is the physical address
of the RSDP table.

Unfortunately PVH support in the kernel didn't use that passed address
for RSDP, but relied on the legacy mechanism searching for the RSDP in
low memory. After a recent change in Xen putting the RSDP to a higher
address booting as PVH guest is now failing.

This small series repairs that by passing the RSDP address from the
start_info block to ACPI handling.

Juergen Gross (2):
  x86/acpi: add retrieval function for rsdp address
  xen: add acpi_arch_get_root_pointer() for pvh guests

 arch/x86/xen/enlighten_pvh.c | 15 ++++++++++++---
 drivers/acpi/osl.c           | 10 +++++++++-
 include/linux/acpi.h         |  2 ++
 3 files changed, 23 insertions(+), 4 deletions(-)

-- 
2.13.6


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