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Re: [Xen-devel] [PATCH v2 10/16] ARM: XEN: Move xen_early_init() before efi_init()

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  Re: [Xen-devel] [PATCH v2 10/16] ARM: XEN: Move xen_early_init()  before efi_init() Stefano Stabellini <stefano.stabellini@eu.citrix.com> - 2016-01-18 16:10 +0100
    Re: [Xen-devel] [PATCH v2 10/16] ARM: XEN: Move xen_early_init()  before efi_init() Shannon Zhao <zhaoshenglong@huawei.com> - 2016-01-19 09:40 +0100
      Re: [Xen-devel] [PATCH v2 10/16] ARM: XEN: Move xen_early_init()  before efi_init() Stefano Stabellini <stefano.stabellini@eu.citrix.com> - 2016-01-19 13:20 +0100

#1311603 — Re: [Xen-devel] [PATCH v2 10/16] ARM: XEN: Move xen_early_init() before efi_init()

On Fri, 15 Jan 2016, Shannon Zhao wrote:
> From: Shannon Zhao <shannon.zhao@linaro.org>
> 
> Move xen_early_init() before efi_init(), then when calling efi_init()
> could initialize Xen specific UEFI.
> 
> Check if it runs on Xen hypervisor through the flat dts.
> 
> Signed-off-by: Shannon Zhao <shannon.zhao@linaro.org>
> ---
>  arch/arm/xen/enlighten.c  | 56 ++++++++++++++++++++++++++++++++++-------------
>  arch/arm64/kernel/setup.c |  2 +-
>  2 files changed, 42 insertions(+), 16 deletions(-)
> 
> diff --git a/arch/arm/xen/enlighten.c b/arch/arm/xen/enlighten.c
> index 4e78c49..5d0fe68 100644
> --- a/arch/arm/xen/enlighten.c
> +++ b/arch/arm/xen/enlighten.c
> @@ -19,6 +19,7 @@
>  #include <linux/irqreturn.h>
>  #include <linux/module.h>
>  #include <linux/of.h>
> +#include <linux/of_fdt.h>
>  #include <linux/of_irq.h>
>  #include <linux/of_address.h>
>  #include <linux/cpuidle.h>
> @@ -52,8 +53,6 @@ struct xen_memory_region xen_extra_mem[XEN_EXTRA_MEM_MAX_REGIONS] __initdata;
>  
>  static __read_mostly unsigned int xen_events_irq;
>  
> -static __initdata struct device_node *xen_node;
> -
>  int xen_remap_domain_gfn_array(struct vm_area_struct *vma,
>  			       unsigned long addr,
>  			       xen_pfn_t *gfn, int nr,
> @@ -222,6 +221,33 @@ static irqreturn_t xen_arm_callback(int irq, void *arg)
>  	return IRQ_HANDLED;
>  }
>  
> +static __initdata struct {
> +	const char *compat;
> +	const char *prefix;
> +	const char *version;
> +	bool found;
> +} xen_node = {"xen,xen", "xen,xen-", NULL, false};
> +
> +static int __init fdt_find_xen_node(unsigned long node, const char *uname,
> +				    int depth, void *data)
> +{
> +	const void *s = NULL;
> +	int len;
> +
> +	if (depth != 1 || strcmp(uname, "hypervisor") != 0)
> +		return 0;
> +
> +	if (of_flat_dt_is_compatible(node, xen_node.compat))
> +		xen_node.found = true;
> +
> +	s = of_get_flat_dt_prop(node, "compatible", &len);
> +	if (strlen(xen_node.prefix) + 3  < len &&
> +	    !strncmp(xen_node.prefix, s, strlen(xen_node.prefix)))
> +		xen_node.version = s + strlen(xen_node.prefix);
> +
> +	return 0;
> +}
> +
>  /*
>   * see Documentation/devicetree/bindings/arm/xen.txt for the
>   * documentation of the Xen Device Tree format.
> @@ -229,26 +255,18 @@ static irqreturn_t xen_arm_callback(int irq, void *arg)
>  #define GRANT_TABLE_PHYSADDR 0
>  void __init xen_early_init(void)
>  {
> -	int len;
> -	const char *s = NULL;
> -	const char *version = NULL;
> -	const char *xen_prefix = "xen,xen-";
> -
> -	xen_node = of_find_compatible_node(NULL, NULL, "xen,xen");
> -	if (!xen_node) {
> +	of_scan_flat_dt(fdt_find_xen_node, NULL);
> +	if (!xen_node.found) {
>  		pr_debug("No Xen support\n");
>  		return;
>  	}
> -	s = of_get_property(xen_node, "compatible", &len);
> -	if (strlen(xen_prefix) + 3  < len &&
> -			!strncmp(xen_prefix, s, strlen(xen_prefix)))
> -		version = s + strlen(xen_prefix);
> -	if (version == NULL) {
> +
> +	if (xen_node.version == NULL) {
>  		pr_debug("Xen version not found\n");
>  		return;
>  	}

This is going to access data within the fdt, after it has been
unflattened (by the unflatten_device_tree call). Is that allowed?

If that's not allowed, then you could copy the version string to
xen_node.version, rather than just copying the pointer. Otherwise you
could move the version check entirely within fdt_find_xen_node and
remove the version field from xen_node.


> -	pr_info("Xen %s support found\n", version);
> +	pr_info("Xen %s support found\n", xen_node.version);
>  
>  	xen_domain_type = XEN_HVM_DOMAIN;
>  
> @@ -296,6 +314,14 @@ static int __init xen_guest_init(void)
>  		}
>  #endif
>  	} else {
> +		struct device_node *xen_node;
> +
> +		xen_node = of_find_compatible_node(NULL, NULL, "xen,xen");
> +		if (!xen_node) {
> +			pr_debug("No Xen support\n");
> +			return -ENODEV;
> +		}

It makes sense to move this into a DT specific init function called from
xen_guest_init. Also, given that at this point we know that a Xen node
should be present, it makes sense to return EFAULT on error, instead of
ENODEV. The error message could be changed to something like: "Xen
support was detected before, but it has disappeared" and should be
pr_err.


>  		xen_events_irq = irq_of_parse_and_map(xen_node, 0);
>  	}
>  
> diff --git a/arch/arm64/kernel/setup.c b/arch/arm64/kernel/setup.c
> index 8119479..a4a2878 100644
> --- a/arch/arm64/kernel/setup.c
> +++ b/arch/arm64/kernel/setup.c
> @@ -313,6 +313,7 @@ void __init setup_arch(char **cmdline_p)
>  	 */
>  	local_async_enable();
>  
> +	xen_early_init();
>  	efi_init();
>  	arm64_memblock_init();
>  
> @@ -334,7 +335,6 @@ void __init setup_arch(char **cmdline_p)
>  	} else {
>  		psci_acpi_init();
>  	}
> -	xen_early_init();
>  
>  	cpu_read_bootcpu_ops();
>  	smp_init_cpus();

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#1312001

On 2016/1/18 22:59, Stefano Stabellini wrote:
> On Fri, 15 Jan 2016, Shannon Zhao wrote:
>> From: Shannon Zhao <shannon.zhao@linaro.org>
>>
>> Move xen_early_init() before efi_init(), then when calling efi_init()
>> could initialize Xen specific UEFI.
>>
>> Check if it runs on Xen hypervisor through the flat dts.
>>
>> Signed-off-by: Shannon Zhao <shannon.zhao@linaro.org>
>> ---
>>  arch/arm/xen/enlighten.c  | 56 ++++++++++++++++++++++++++++++++++-------------
>>  arch/arm64/kernel/setup.c |  2 +-
>>  2 files changed, 42 insertions(+), 16 deletions(-)
>>
>> diff --git a/arch/arm/xen/enlighten.c b/arch/arm/xen/enlighten.c
>> index 4e78c49..5d0fe68 100644
>> --- a/arch/arm/xen/enlighten.c
>> +++ b/arch/arm/xen/enlighten.c
>> @@ -19,6 +19,7 @@
>>  #include <linux/irqreturn.h>
>>  #include <linux/module.h>
>>  #include <linux/of.h>
>> +#include <linux/of_fdt.h>
>>  #include <linux/of_irq.h>
>>  #include <linux/of_address.h>
>>  #include <linux/cpuidle.h>
>> @@ -52,8 +53,6 @@ struct xen_memory_region xen_extra_mem[XEN_EXTRA_MEM_MAX_REGIONS] __initdata;
>>  
>>  static __read_mostly unsigned int xen_events_irq;
>>  
>> -static __initdata struct device_node *xen_node;
>> -
>>  int xen_remap_domain_gfn_array(struct vm_area_struct *vma,
>>  			       unsigned long addr,
>>  			       xen_pfn_t *gfn, int nr,
>> @@ -222,6 +221,33 @@ static irqreturn_t xen_arm_callback(int irq, void *arg)
>>  	return IRQ_HANDLED;
>>  }
>>  
>> +static __initdata struct {
>> +	const char *compat;
>> +	const char *prefix;
>> +	const char *version;
>> +	bool found;
>> +} xen_node = {"xen,xen", "xen,xen-", NULL, false};
>> +
>> +static int __init fdt_find_xen_node(unsigned long node, const char *uname,
>> +				    int depth, void *data)
>> +{
>> +	const void *s = NULL;
>> +	int len;
>> +
>> +	if (depth != 1 || strcmp(uname, "hypervisor") != 0)
>> +		return 0;
>> +
>> +	if (of_flat_dt_is_compatible(node, xen_node.compat))
>> +		xen_node.found = true;
>> +
>> +	s = of_get_flat_dt_prop(node, "compatible", &len);
>> +	if (strlen(xen_node.prefix) + 3  < len &&
>> +	    !strncmp(xen_node.prefix, s, strlen(xen_node.prefix)))
>> +		xen_node.version = s + strlen(xen_node.prefix);
>> +
>> +	return 0;
>> +}
>> +
>>  /*
>>   * see Documentation/devicetree/bindings/arm/xen.txt for the
>>   * documentation of the Xen Device Tree format.
>> @@ -229,26 +255,18 @@ static irqreturn_t xen_arm_callback(int irq, void *arg)
>>  #define GRANT_TABLE_PHYSADDR 0
>>  void __init xen_early_init(void)
>>  {
>> -	int len;
>> -	const char *s = NULL;
>> -	const char *version = NULL;
>> -	const char *xen_prefix = "xen,xen-";
>> -
>> -	xen_node = of_find_compatible_node(NULL, NULL, "xen,xen");
>> -	if (!xen_node) {
>> +	of_scan_flat_dt(fdt_find_xen_node, NULL);
>> +	if (!xen_node.found) {
>>  		pr_debug("No Xen support\n");
>>  		return;
>>  	}
>> -	s = of_get_property(xen_node, "compatible", &len);
>> -	if (strlen(xen_prefix) + 3  < len &&
>> -			!strncmp(xen_prefix, s, strlen(xen_prefix)))
>> -		version = s + strlen(xen_prefix);
>> -	if (version == NULL) {
>> +
>> +	if (xen_node.version == NULL) {
>>  		pr_debug("Xen version not found\n");
>>  		return;
>>  	}
> 
> This is going to access data within the fdt, after it has been
> unflattened (by the unflatten_device_tree call). Is that allowed?
> 
> If that's not allowed, then you could copy the version string to
> xen_node.version, rather than just copying the pointer. Otherwise you
> could move the version check entirely within fdt_find_xen_node and
> remove the version field from xen_node.
> 
A little confused. Since here we move xen_early_init before efi_init and
before unflatten_device_tree as well, at this moment in xen_early_init
the fdt is flattened. The xen_node.version is only set in
fdt_find_xen_node and accessed in xen_early_init.

> 
>> -	pr_info("Xen %s support found\n", version);
>> +	pr_info("Xen %s support found\n", xen_node.version);
>>  
>>  	xen_domain_type = XEN_HVM_DOMAIN;
>>  
>> @@ -296,6 +314,14 @@ static int __init xen_guest_init(void)
>>  		}
>>  #endif
>>  	} else {
>> +		struct device_node *xen_node;
>> +
>> +		xen_node = of_find_compatible_node(NULL, NULL, "xen,xen");
>> +		if (!xen_node) {
>> +			pr_debug("No Xen support\n");
>> +			return -ENODEV;
>> +		}
> 
> It makes sense to move this into a DT specific init function called from
> xen_guest_init. Also, given that at this point we know that a Xen node
> should be present, it makes sense to return EFAULT on error, instead of
> ENODEV. The error message could be changed to something like: "Xen
> support was detected before, but it has disappeared" and should be
> pr_err.
> 
OK, thanks.
> 
>>  		xen_events_irq = irq_of_parse_and_map(xen_node, 0);
>>  	}
>>  
>> diff --git a/arch/arm64/kernel/setup.c b/arch/arm64/kernel/setup.c
>> index 8119479..a4a2878 100644
>> --- a/arch/arm64/kernel/setup.c
>> +++ b/arch/arm64/kernel/setup.c
>> @@ -313,6 +313,7 @@ void __init setup_arch(char **cmdline_p)
>>  	 */
>>  	local_async_enable();
>>  
>> +	xen_early_init();
>>  	efi_init();
>>  	arm64_memblock_init();
>>  
>> @@ -334,7 +335,6 @@ void __init setup_arch(char **cmdline_p)
>>  	} else {
>>  		psci_acpi_init();
>>  	}
>> -	xen_early_init();
>>  
>>  	cpu_read_bootcpu_ops();
>>  	smp_init_cpus();
> 
> .
> 

-- 
Shannon

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#1312173

On Tue, 19 Jan 2016, Shannon Zhao wrote:
> On 2016/1/18 22:59, Stefano Stabellini wrote:
> > On Fri, 15 Jan 2016, Shannon Zhao wrote:
> >> From: Shannon Zhao <shannon.zhao@linaro.org>
> >>
> >> Move xen_early_init() before efi_init(), then when calling efi_init()
> >> could initialize Xen specific UEFI.
> >>
> >> Check if it runs on Xen hypervisor through the flat dts.
> >>
> >> Signed-off-by: Shannon Zhao <shannon.zhao@linaro.org>
> >> ---
> >>  arch/arm/xen/enlighten.c  | 56 ++++++++++++++++++++++++++++++++++-------------
> >>  arch/arm64/kernel/setup.c |  2 +-
> >>  2 files changed, 42 insertions(+), 16 deletions(-)
> >>
> >> diff --git a/arch/arm/xen/enlighten.c b/arch/arm/xen/enlighten.c
> >> index 4e78c49..5d0fe68 100644
> >> --- a/arch/arm/xen/enlighten.c
> >> +++ b/arch/arm/xen/enlighten.c
> >> @@ -19,6 +19,7 @@
> >>  #include <linux/irqreturn.h>
> >>  #include <linux/module.h>
> >>  #include <linux/of.h>
> >> +#include <linux/of_fdt.h>
> >>  #include <linux/of_irq.h>
> >>  #include <linux/of_address.h>
> >>  #include <linux/cpuidle.h>
> >> @@ -52,8 +53,6 @@ struct xen_memory_region xen_extra_mem[XEN_EXTRA_MEM_MAX_REGIONS] __initdata;
> >>  
> >>  static __read_mostly unsigned int xen_events_irq;
> >>  
> >> -static __initdata struct device_node *xen_node;
> >> -
> >>  int xen_remap_domain_gfn_array(struct vm_area_struct *vma,
> >>  			       unsigned long addr,
> >>  			       xen_pfn_t *gfn, int nr,
> >> @@ -222,6 +221,33 @@ static irqreturn_t xen_arm_callback(int irq, void *arg)
> >>  	return IRQ_HANDLED;
> >>  }
> >>  
> >> +static __initdata struct {
> >> +	const char *compat;
> >> +	const char *prefix;
> >> +	const char *version;
> >> +	bool found;
> >> +} xen_node = {"xen,xen", "xen,xen-", NULL, false};
> >> +
> >> +static int __init fdt_find_xen_node(unsigned long node, const char *uname,
> >> +				    int depth, void *data)
> >> +{
> >> +	const void *s = NULL;
> >> +	int len;
> >> +
> >> +	if (depth != 1 || strcmp(uname, "hypervisor") != 0)
> >> +		return 0;
> >> +
> >> +	if (of_flat_dt_is_compatible(node, xen_node.compat))
> >> +		xen_node.found = true;
> >> +
> >> +	s = of_get_flat_dt_prop(node, "compatible", &len);
> >> +	if (strlen(xen_node.prefix) + 3  < len &&
> >> +	    !strncmp(xen_node.prefix, s, strlen(xen_node.prefix)))
> >> +		xen_node.version = s + strlen(xen_node.prefix);
> >> +
> >> +	return 0;
> >> +}
> >> +
> >>  /*
> >>   * see Documentation/devicetree/bindings/arm/xen.txt for the
> >>   * documentation of the Xen Device Tree format.
> >> @@ -229,26 +255,18 @@ static irqreturn_t xen_arm_callback(int irq, void *arg)
> >>  #define GRANT_TABLE_PHYSADDR 0
> >>  void __init xen_early_init(void)
> >>  {
> >> -	int len;
> >> -	const char *s = NULL;
> >> -	const char *version = NULL;
> >> -	const char *xen_prefix = "xen,xen-";
> >> -
> >> -	xen_node = of_find_compatible_node(NULL, NULL, "xen,xen");
> >> -	if (!xen_node) {
> >> +	of_scan_flat_dt(fdt_find_xen_node, NULL);
> >> +	if (!xen_node.found) {
> >>  		pr_debug("No Xen support\n");
> >>  		return;
> >>  	}
> >> -	s = of_get_property(xen_node, "compatible", &len);
> >> -	if (strlen(xen_prefix) + 3  < len &&
> >> -			!strncmp(xen_prefix, s, strlen(xen_prefix)))
> >> -		version = s + strlen(xen_prefix);
> >> -	if (version == NULL) {
> >> +
> >> +	if (xen_node.version == NULL) {
> >>  		pr_debug("Xen version not found\n");
> >>  		return;
> >>  	}
> > 
> > This is going to access data within the fdt, after it has been
> > unflattened (by the unflatten_device_tree call). Is that allowed?
> > 
> > If that's not allowed, then you could copy the version string to
> > xen_node.version, rather than just copying the pointer. Otherwise you
> > could move the version check entirely within fdt_find_xen_node and
> > remove the version field from xen_node.
> > 
> A little confused. Since here we move xen_early_init before efi_init and
> before unflatten_device_tree as well, at this moment in xen_early_init
> the fdt is flattened. The xen_node.version is only set in
> fdt_find_xen_node and accessed in xen_early_init.

You are right, sorry, I must have been confused. It might be good to
rename the xen_node variable that this patch introduced in xen_guest_init.



> >> -	pr_info("Xen %s support found\n", version);
> >> +	pr_info("Xen %s support found\n", xen_node.version);
> >>  
> >>  	xen_domain_type = XEN_HVM_DOMAIN;
> >>  
> >> @@ -296,6 +314,14 @@ static int __init xen_guest_init(void)
> >>  		}
> >>  #endif
> >>  	} else {
> >> +		struct device_node *xen_node;
> >> +
> >> +		xen_node = of_find_compatible_node(NULL, NULL, "xen,xen");
> >> +		if (!xen_node) {
> >> +			pr_debug("No Xen support\n");
> >> +			return -ENODEV;
> >> +		}
> > 
> > It makes sense to move this into a DT specific init function called from
> > xen_guest_init. Also, given that at this point we know that a Xen node
> > should be present, it makes sense to return EFAULT on error, instead of
> > ENODEV. The error message could be changed to something like: "Xen
> > support was detected before, but it has disappeared" and should be
> > pr_err.
> > 
> OK, thanks.

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