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Message-ID: <569DF590.6030105@huawei.com>
Date: Tue, 19 Jan 2016 16:36:32 +0800
From: Shannon Zhao <zhaoshenglong@...wei.com>
To: Stefano Stabellini <stefano.stabellini@...citrix.com>
CC: <linux-arm-kernel@...ts.infradead.org>,
<ard.biesheuvel@...aro.org>, <stefano.stabellini@...rix.com>,
<david.vrabel@...rix.com>, <mark.rutland@....com>,
<devicetree@...r.kernel.org>, <linux-efi@...r.kernel.org>,
<catalin.marinas@....com>, <will.deacon@....com>,
<linux-kernel@...r.kernel.org>, <xen-devel@...ts.xen.org>,
<julien.grall@...rix.com>, <shannon.zhao@...aro.org>,
<peter.huangpeng@...wei.com>
Subject: Re: [Xen-devel] [PATCH v2 10/16] ARM: XEN: Move xen_early_init()
before efi_init()
On 2016/1/18 22:59, Stefano Stabellini wrote:
> On Fri, 15 Jan 2016, Shannon Zhao wrote:
>> From: Shannon Zhao <shannon.zhao@...aro.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@...aro.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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