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[PATCH v2 13/16] ARM: XEN: Set EFI_PARAVIRT if Xen supports EFI

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  [PATCH v2 13/16] ARM: XEN: Set EFI_PARAVIRT if Xen supports EFI Shannon Zhao <zhaoshenglong@huawei.com> - 2016-01-15 08:00 +0100
    Re: [PATCH v2 13/16] ARM: XEN: Set EFI_PARAVIRT if Xen supports EFI Mark Rutland <mark.rutland@arm.com> - 2016-01-18 12:00 +0100

#1309901 — [PATCH v2 13/16] ARM: XEN: Set EFI_PARAVIRT if Xen supports EFI

From: Shannon Zhao <shannon.zhao@linaro.org>

Check if there is "uefi" node in the DT. If so, set EFI_PARAVIRT flag.

Signed-off-by: Shannon Zhao <shannon.zhao@linaro.org>
---
 arch/arm/xen/enlighten.c | 23 +++++++++++++++++++++++
 arch/arm64/kernel/efi.c  |  5 +++++
 2 files changed, 28 insertions(+)

diff --git a/arch/arm/xen/enlighten.c b/arch/arm/xen/enlighten.c
index 5d0fe68..485e117 100644
--- a/arch/arm/xen/enlighten.c
+++ b/arch/arm/xen/enlighten.c
@@ -31,6 +31,7 @@
 #include <linux/timekeeping.h>
 #include <linux/timekeeper_internal.h>
 #include <linux/acpi.h>
+#include <linux/efi.h>
 
 #include <linux/mm.h>
 
@@ -248,6 +249,19 @@ static int __init fdt_find_xen_node(unsigned long node, const char *uname,
 	return 0;
 }
 
+static int __init fdt_find_uefi_node(unsigned long node, const char *uname,
+				     int depth, void *data)
+{
+	bool *found = data;
+
+	if (depth != 2 || strcmp(uname, "uefi") != 0)
+		return 0;
+
+	*found = true;
+
+	return 1;
+}
+
 /*
  * see Documentation/devicetree/bindings/arm/xen.txt for the
  * documentation of the Xen Device Tree format.
@@ -255,6 +269,8 @@ static int __init fdt_find_xen_node(unsigned long node, const char *uname,
 #define GRANT_TABLE_PHYSADDR 0
 void __init xen_early_init(void)
 {
+	bool uefi_found = false;
+
 	of_scan_flat_dt(fdt_find_xen_node, NULL);
 	if (!xen_node.found) {
 		pr_debug("No Xen support\n");
@@ -279,6 +295,13 @@ void __init xen_early_init(void)
 
 	if (!console_set_on_cmdline && !xen_initial_domain())
 		add_preferred_console("hvc", 0, NULL);
+
+	if (IS_ENABLED(CONFIG_XEN_EFI)) {
+		/* Check if Xen support UEFI */
+		of_scan_flat_dt(fdt_find_uefi_node, &uefi_found);
+		if (uefi_found)
+			set_bit(EFI_PARAVIRT, &efi.flags);
+	}
 }
 
 static int __init xen_guest_init(void)
diff --git a/arch/arm64/kernel/efi.c b/arch/arm64/kernel/efi.c
index 4eeb171..16c6b72 100644
--- a/arch/arm64/kernel/efi.c
+++ b/arch/arm64/kernel/efi.c
@@ -288,6 +288,11 @@ static int __init arm64_enable_runtime_services(void)
 		return 0;
 	}
 
+	if (efi_enabled(EFI_PARAVIRT)) {
+		pr_info("EFI runtime services access via paravirt.\n");
+		return -1;
+	}
+
 	pr_info("Remapping and enabling EFI services.\n");
 
 	mapsize = memmap.map_end - memmap.map;
-- 
2.0.4

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#1311475

On Fri, Jan 15, 2016 at 02:55:26PM +0800, Shannon Zhao wrote:
> From: Shannon Zhao <shannon.zhao@linaro.org>
> 
> Check if there is "uefi" node in the DT. If so, set EFI_PARAVIRT flag.
> 
> Signed-off-by: Shannon Zhao <shannon.zhao@linaro.org>
> ---
>  arch/arm/xen/enlighten.c | 23 +++++++++++++++++++++++
>  arch/arm64/kernel/efi.c  |  5 +++++
>  2 files changed, 28 insertions(+)
> 
> diff --git a/arch/arm/xen/enlighten.c b/arch/arm/xen/enlighten.c
> index 5d0fe68..485e117 100644
> --- a/arch/arm/xen/enlighten.c
> +++ b/arch/arm/xen/enlighten.c
> @@ -31,6 +31,7 @@
>  #include <linux/timekeeping.h>
>  #include <linux/timekeeper_internal.h>
>  #include <linux/acpi.h>
> +#include <linux/efi.h>
>  
>  #include <linux/mm.h>
>  
> @@ -248,6 +249,19 @@ static int __init fdt_find_xen_node(unsigned long node, const char *uname,
>  	return 0;
>  }
>  
> +static int __init fdt_find_uefi_node(unsigned long node, const char *uname,
> +				     int depth, void *data)
> +{
> +	bool *found = data;
> +
> +	if (depth != 2 || strcmp(uname, "uefi") != 0)
> +		return 0;
> +
> +	*found = true;
> +
> +	return 1;
> +}

I don't like this. What if we had to add a uefi node in the !Xen case
for some reason?

You want to look for /hypervisor/uefi, specifically when the hypervisor
compatible contains "xen,xen".

It would be better to find the "/hypervisor" node, checking for the
compatible string, then walk within that in the Xen-specific init
routine.

> +
>  /*
>   * see Documentation/devicetree/bindings/arm/xen.txt for the
>   * documentation of the Xen Device Tree format.
> @@ -255,6 +269,8 @@ static int __init fdt_find_xen_node(unsigned long node, const char *uname,
>  #define GRANT_TABLE_PHYSADDR 0
>  void __init xen_early_init(void)
>  {
> +	bool uefi_found = false;
> +
>  	of_scan_flat_dt(fdt_find_xen_node, NULL);
>  	if (!xen_node.found) {
>  		pr_debug("No Xen support\n");
> @@ -279,6 +295,13 @@ void __init xen_early_init(void)
>  
>  	if (!console_set_on_cmdline && !xen_initial_domain())
>  		add_preferred_console("hvc", 0, NULL);
> +
> +	if (IS_ENABLED(CONFIG_XEN_EFI)) {
> +		/* Check if Xen support UEFI */
> +		of_scan_flat_dt(fdt_find_uefi_node, &uefi_found);
> +		if (uefi_found)
> +			set_bit(EFI_PARAVIRT, &efi.flags);
> +	}
>  }

This alone is insufficient given that we haven't parsed the rest of the
/hypervisor/uefi properties. Is the kernel resilient such that this
patch alone will not result in a panic?

I think it would be best for this to be in the same patch as the rest of
the hypervisor UEFI property parsing, being unified with that.

Mark.

>  static int __init xen_guest_init(void)
> diff --git a/arch/arm64/kernel/efi.c b/arch/arm64/kernel/efi.c
> index 4eeb171..16c6b72 100644
> --- a/arch/arm64/kernel/efi.c
> +++ b/arch/arm64/kernel/efi.c
> @@ -288,6 +288,11 @@ static int __init arm64_enable_runtime_services(void)
>  		return 0;
>  	}
>  
> +	if (efi_enabled(EFI_PARAVIRT)) {
> +		pr_info("EFI runtime services access via paravirt.\n");
> +		return -1;
> +	}
> +
>  	pr_info("Remapping and enabling EFI services.\n");
>  
>  	mapsize = memmap.map_end - memmap.map;
> -- 
> 2.0.4
> 
> 
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