[PATCH v2 1/2] xen: add late init call in start_xen

[Boyoun Park <boyoun.park@xxxxxxxxxxx>]

Thank you for your reply. I will seriously consider contributing
platform specific drivers. Currently, I make a sample usage by applying this
to a function in start_xen. I think functions in start_xen could be reduced
for readability and understandability.
These patches are just one of my suggestion. So feel free to reject it.

On Sat, 30 Jul 2022, Stefano Stabellini wrote:
> On Fri, 29 Jul 2022, Boyoun Park wrote:
>> I really appreciate all the comments and reviews.
>> I understand that it is hard to add this patch without any usage.
>> 
>> On Fri, 29 Jul 2022, Stefano Stabellini:
>>> On Thu, 28 Jul 2022, Jan Beulich wrote:
>>>> On 28.07.2022 11:22, Boyoun Park wrote:
>>>>> Subject: [PATCH v1] xen: add late init call in start_xen
>>>>> 
>>>>> This patch added late_initcall section in init.data.
>>>>> 
>>>>> The late initcall would be called after initcall
>>>>> 
>>>>> in the start_xen function.
>>>>> 
>>>>> Some initializing works on priority should be run
>>>>> 
>>>>> in do_initcalls and other non-prioritized works
>>>>> 
>>>>> would be run in do_late_initcalls.
>>>>> 
>>>>> To call some functions by late_initcall,
>>>>> 
>>>>> then it is possible by using
>>>>> 
>>>>> __late_initcall(/*Function Name*/);
>>>>> 
>>>>> Signed-off-by: Boyoun Park <boyoun.park@xxxxxxxxxxx>
>>>> 
>>>> So I could imagine this patch to be in a series where a subsequent
>>>> patch then adds an actual use of the new functionality. Without
>>>> that what you're proposing is to add dead code.
>>> 
>>> Yeah, I think it would be cool to have late initcalls but it makes sense
>>> to add them if we have someone that makes use of them.
>> 
>> I totally agree with your comments. Some drivers that I'm developing now and 
>>use this function are specific to my hardware environment.
>> Thus, it seems difficult to arrange them in the near future.
>> I will update patches if I can suggest an actual use.
> 
> I totally understand custom setups and non-upstreamable configurations
> and I have certainly some of them myself.
> 
> However, I just wanted to let you know that we are fine with accepting
> platform specific drivers in Xen where it makes sense, for instance:
> 
> - Renesas IPMMU-VMSA found in R-Car Gen3/Gen4 SoCs (an IOMMU driver)
> xen/drivers/passthrough/arm/ipmmu-vmsa.c
> 
> - Xilinx EEMI firmware interface "mediator" in Xen (power management)
> xen/arch/arm/platforms/xilinx-zynqmp-eemi.c

From: Boyoun Park <boyoun.park@xxxxxxxxxxx>
Date: Tue, 15 Mar 2022 12:57:59 +0900
Subject: [PATCH v2 1/2] xen: add late init call in start_xen

This patch added late_initcall section in init.data.
The late initcall would be called after initcall
in the start_xen function.

Some initializing works on priority should be run
in do_initcalls and other non-prioritized works
would be run in do_late_initcalls.

To call some functions by late_initcall,
then it is possible by using
__late_initcall(/*Function Name*/);

Signed-off-by: Boyoun Park <boyoun.park@xxxxxxxxxxx>
---
 xen/arch/arm/setup.c   | 2 ++
 xen/arch/arm/xen.lds.S | 2 ++
 xen/arch/x86/setup.c   | 2 ++
 xen/arch/x86/xen.lds.S | 2 ++
 xen/common/kernel.c    | 9 ++++++++-
 xen/include/xen/init.h | 3 +++
 6 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/xen/arch/arm/setup.c b/xen/arch/arm/setup.c
index 85ff956..332a207 100644
--- a/xen/arch/arm/setup.c
+++ b/xen/arch/arm/setup.c
@@ -1063,6 +1063,8 @@ void __init start_xen(unsigned long boot_phys_offset,
     /* Hide UART from DOM0 if we're using it */
     serial_endboot();
 
+    do_late_initcalls();
+
     if ( (rc = xsm_set_system_active()) != 0 )
         panic("xsm: unable to switch to SYSTEM_ACTIVE privilege: %d\n", rc);
 
diff --git a/xen/arch/arm/xen.lds.S b/xen/arch/arm/xen.lds.S
index 1e986e2..215e2c3 100644
--- a/xen/arch/arm/xen.lds.S
+++ b/xen/arch/arm/xen.lds.S
@@ -163,6 +163,8 @@ SECTIONS
        __presmp_initcall_end = .;
        *(.initcall1.init)
        __initcall_end = .;
+       *(.initcalllate.init)
+       __late_initcall_end = .;
 
        . = ALIGN(4);
        __alt_instructions = .;
diff --git a/xen/arch/x86/setup.c b/xen/arch/x86/setup.c
index f08b07b..5dc6654 100644
--- a/xen/arch/x86/setup.c
+++ b/xen/arch/x86/setup.c
@@ -1952,6 +1952,8 @@ void __init noreturn __start_xen(unsigned long mbi_p)
 
     setup_io_bitmap(dom0);
 
+    do_late_initcalls();
+
     if ( bsp_delay_spec_ctrl )
     {
         info->spec_ctrl_flags &= ~SCF_use_shadow;
diff --git a/xen/arch/x86/xen.lds.S b/xen/arch/x86/xen.lds.S
index 8930e14..c90c7b0 100644
--- a/xen/arch/x86/xen.lds.S
+++ b/xen/arch/x86/xen.lds.S
@@ -250,6 +250,8 @@ SECTIONS
        __presmp_initcall_end = .;
        *(.initcall1.init)
        __initcall_end = .;
+       *(.initcalllate.init)
+       __late_initcall_end = .;
 
        *(.init.data)
        *(.init.data.rel)
diff --git a/xen/common/kernel.c b/xen/common/kernel.c
index f8134d3..5a3d037 100644
--- a/xen/common/kernel.c
+++ b/xen/common/kernel.c
@@ -369,7 +369,7 @@ void add_taint(unsigned int flag)
 }
 
 extern const initcall_t __initcall_start[], __presmp_initcall_end[],
-    __initcall_end[];
+    __initcall_end[], __late_initcall_end[];
 
 void __init do_presmp_initcalls(void)
 {
@@ -385,6 +385,13 @@ void __init do_initcalls(void)
         (*call)();
 }
 
+void __init do_late_initcalls(void)
+{
+    const initcall_t *call;
+    for ( call = __initcall_end; call < __late_initcall_end; call++ )
+        (*call)();
+}
+
 #ifdef CONFIG_HYPFS
 static unsigned int __read_mostly major_version;
 static unsigned int __read_mostly minor_version;
diff --git a/xen/include/xen/init.h b/xen/include/xen/init.h
index 0af0e23..48210ee 100644
--- a/xen/include/xen/init.h
+++ b/xen/include/xen/init.h
@@ -68,11 +68,14 @@ typedef void (*exitcall_t)(void);
     const static initcall_t __initcall_##fn __init_call("presmp") = fn
 #define __initcall(fn) \
     const static initcall_t __initcall_##fn __init_call("1") = fn
+#define __late_initcall(fn) \
+    const static initcall_t __initcall_##fn __init_call("late") = fn
 #define __exitcall(fn) \
     static exitcall_t __exitcall_##fn __exit_call = fn
 
 void do_presmp_initcalls(void);
 void do_initcalls(void);
+void do_late_initcalls(void);
 
 #endif /* __ASSEMBLY__ */
 
-- 
2.7.4

Boyoun Park

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