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SubjectRe: [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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