Subject: Re: Re: linux-next: Tree for Dec 1 (riscv, crash_core)

From: Baoquan He <[email-masked]>
Date: Mon, 4 Dec 2023 10:10:04 +0800

[email-masked], [email-masked],
	Linux Next Mailing List <[email-masked]>,
	Linux Kernel Mailing List <[email-masked]>,
	linux-riscv <[email-masked]>,
	kexec <[email-masked]>
Bcc: [email-masked]
Subject: Re: linux-next: Tree for Dec 1 (riscv, crash_core)
Reply-To: 
In-Reply-To: <[email-masked]>

On 12/01/23 at 11:53am, Randy Dunlap wrote:
> 
> 
> On 11/30/23 18:37, Stephen Rothwell wrote:
> > Hi all,
> > 
> > Changes since 20231130:
> > 
> 
> on riscv 32-bit or 64-bit, with
> # CONFIG_MMU is not set

Thanks for providing the kernel config to ease reproduction. In the config,
there are:

CONFIG_CRASH_CORE=y
CONFIG_KEXEC_CORE=y
CONFIG_CRASH_DUMP=y
......
# CONFIG_MMU is not set

After investigation, I found this happened after Ignat's patch:
commit 1c7a3fa49ef7 ("kexec: drop dependency on ARCH_SUPPORTS_KEXEC from CRASH_DUMP")

Copy above commit change here for reference, and also risc-v's
ARCH_SUPPORTS_KEXEC depends on MMU:
--------------------------------------------------------
diff --git a/kernel/Kconfig.kexec b/kernel/Kconfig.kexec
index fc38f1ae3a30..946dffa048b7 100644
--- a/kernel/Kconfig.kexec
+++ b/kernel/Kconfig.kexec
@@ -96,7 +96,6 @@ config KEXEC_JUMP
 config CRASH_DUMP
        bool "kernel crash dumps"
        depends on ARCH_SUPPORTS_CRASH_DUMP
-       depends on ARCH_SUPPORTS_KEXEC
        select CRASH_CORE
        select KEXEC_CORE
        help

arch/riscv/Kconfig
---------------------
config ARCH_SUPPORTS_KEXEC
        def_bool MMU

Before Ignat's patch, once CONFIG_MMU is unset, CONFIG_CRASH_DUMP,
CONFIG_KEXEC_CORE, CONFIG_CRASH_CORE are all unset automatically. The
crash_core codes are not compiled. That's why no compiling error is
seen.

After Ignat's patch applied, we can enable CONFIG_CRASH_DUMP,
CONFIG_KEXEC_CORE, CONFIG_CRASH_CORE independently. However, there are
several macro definitions, such as VA_BITS, VMEMMAP_START, VMEMMAP_END,
MODULES_VADDR, MODULES_END are only available when CONFIG_MMU=y.

I made two patches to decouple the kexec/crash code with CONFIG_MMU. Not
sure if risc-v wants that.

Or we can simply add dependency on MMU for ARCH_SUPPORTS_CRASH_DUMP.
Then when CONFIG_MMU=n, CONFIG_CRASH_DUMP, CONFIG_KEXEC_CORE,
CONFIG_CRASH_CORE will be unset too. Please help check which one need be
taken.

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index 24c1799e2ec4..03d290da7262 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -708,6 +708,7 @@ config ARCH_SUPPORTS_KEXEC_PURGATORY
 
 config ARCH_SUPPORTS_CRASH_DUMP
 	def_bool y
+	depends on MMU=y
 
 config ARCH_HAS_GENERIC_CRASHKERNEL_RESERVATION
 	def_bool CRASH_CORE

> 
> In file included from ../arch/riscv/kernel/crash_core.c:3:
> ../arch/riscv/kernel/crash_core.c: In function 'arch_crash_save_vmcoreinfo':
> ../arch/riscv/kernel/crash_core.c:8:27: error: 'VA_BITS' undeclared (first use in this function)
>     8 |         VMCOREINFO_NUMBER(VA_BITS);
>       |                           ^~~~~~~
> ../include/linux/crash_core.h:78:64: note: in definition of macro 'VMCOREINFO_NUMBER'
>    78 |         vmcoreinfo_append_str("NUMBER(%s)=%ld\n", #name, (long)name)
>       |                                                                ^~~~
> ../arch/riscv/kernel/crash_core.c:8:27: note: each undeclared identifier is reported only once for each function it appears in
>     8 |         VMCOREINFO_NUMBER(VA_BITS);
>       |                           ^~~~~~~
> ../include/linux/crash_core.h:78:64: note: in definition of macro 'VMCOREINFO_NUMBER'
>    78 |         vmcoreinfo_append_str("NUMBER(%s)=%ld\n", #name, (long)name)
>       |                                                                ^~~~
> ../arch/riscv/kernel/crash_core.c:12:58: warning: format '%lx' expects argument of type 'long unsigned int', but argument 2 has type 'int' [-Wformat=]
>    12 |         vmcoreinfo_append_str("NUMBER(VMALLOC_START)=0x%lx\n", VMALLOC_START);
>       |                                                        ~~^
>       |                                                          |
>       |                                                          long unsigned int
>       |                                                        %x
> ../arch/riscv/kernel/crash_core.c:14:64: error: 'VMEMMAP_START' undeclared (first use in this function)
>    14 |         vmcoreinfo_append_str("NUMBER(VMEMMAP_START)=0x%lx\n", VMEMMAP_START);
>       |                                                                ^~~~~~~~~~~~~
> ../arch/riscv/kernel/crash_core.c:15:62: error: 'VMEMMAP_END' undeclared (first use in this function); did you mean 'MEMREMAP_ENC'?
>    15 |         vmcoreinfo_append_str("NUMBER(VMEMMAP_END)=0x%lx\n", VMEMMAP_END);
>       |                                                              ^~~~~~~~~~~
>       |                                                              MEMREMAP_ENC
> 
> 64-bit only: 
> 
> ../arch/riscv/kernel/crash_core.c:17:64: error: 'MODULES_VADDR' undeclared (first use in this function)
>    17 |         vmcoreinfo_append_str("NUMBER(MODULES_VADDR)=0x%lx\n", MODULES_VADDR);
>       |                                                                ^~~~~~~~~~~~~
> ../arch/riscv/kernel/crash_core.c:18:62: error: 'MODULES_END' undeclared (first use in this function)
>    18 |         vmcoreinfo_append_str("NUMBER(MODULES_END)=0x%lx\n", MODULES_END);
>       |                                                              ^~~~~~~~~~~
> 
> 
> 
> -- 
> ~Randy
>