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Tue, 5 Sep 2023 02:30:36 +0000 (UTC) Received: from localhost (unknown [10.72.113.126]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 171AD200BAA9; Tue, 5 Sep 2023 02:30:35 +0000 (UTC) Date: Tue, 5 Sep 2023 10:30:32 +0800 From: Baoquan He To: Hari Bathini Subject: Re: [PATCH 1/2] vmcore: allow alternate dump capturing methods to export vmcore without is_kdump_kernel() Message-ID: References: <20230901190438.375678-1-hbathini@linux.ibm.com> <8fcd7ba7-0f27-7bbc-676f-7e13c8bf00d7@linux.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <8fcd7ba7-0f27-7bbc-676f-7e13c8bf00d7@linux.ibm.com> X-Scanned-By: MIMEDefang 3.1 on 10.11.54.6 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linuxppc-dev , Kexec-ml , lkml , Sourabh Jain , Mahesh J Salgaonkar , Dave Young Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On 09/04/23 at 08:04pm, Hari Bathini wrote: > Hi Baoquan, > > Thanks for the review... > > On 03/09/23 9:06 am, Baoquan He wrote: > > Hi Hari, > > > > On 09/02/23 at 12:34am, Hari Bathini wrote: > > > Currently, is_kdump_kernel() returns true when elfcorehdr_addr is set. > > > While elfcorehdr_addr is set for kexec based kernel dump mechanism, > > > alternate dump capturing methods like fadump [1] also set it to export > > > the vmcore. is_kdump_kernel() is used to restrict resources in crash > > > dump capture kernel but such restrictions may not be desirable for > > > fadump. Allow is_kdump_kernel() to be defined differently for such > > > scenarios. With this, is_kdump_kernel() could be false while vmcore > > > is usable. So, introduce is_crashdump_kernel() to return true when > > > elfcorehdr_addr is set and use it for vmcore related checks. > > > > I got what is done in these two patches, but didn't get why they need be > > done. vmcore_unusable()/is_vmcore_usable() are only unitilized in ia64. > > Why do you care if it's is_crashdump_kernel() or is_kdump_kernel()? > > If you want to override the generic is_kdump_kernel() with powerpc's own > > is_kdump_kernel(), your below change is enough to allow you to do that. > > I can't see why is_crashdump_kernel() is needed. Could you explain that > > specifically? > > You mean to just remove is_kdump_kernel() check in is_vmcore_usable() & > vmcore_unusable() functions? Replaced generic is_crashdump_kernel() > function instead, that returns true for any dump capturing method, > irrespective of whether is_kdump_kernel() returns true or false. > For fadump case, is_kdump_kernel() will return false after patch 2/2. OK, I could understand what you want to achieve. You want to make is_kdump_kernel() only return true for kdump, while is_vmcore_usable() returns true for both kdump and fadump. IIUC, can we change as below? It could make code clearer and more straightforward. I don't think adding another is_crashdump_kernel() is a good idea, that would be a torture for non-powerpc people reading code when they need differentiate between kdump and crashdump. diff --git a/include/linux/crash_dump.h b/include/linux/crash_dump.h index 0f3a656293b0..102a8b710b38 100644 --- a/include/linux/crash_dump.h +++ b/include/linux/crash_dump.h @@ -50,6 +50,7 @@ void vmcore_cleanup(void); #define vmcore_elf64_check_arch(x) (elf_check_arch(x) || vmcore_elf_check_arch_cross(x)) #endif +#ifndef is_kdump_active /* * is_kdump_kernel() checks whether this kernel is booting after a panic of * previous kernel or not. This is determined by checking if previous kernel @@ -64,6 +65,14 @@ static inline bool is_kdump_kernel(void) { return elfcorehdr_addr != ELFCORE_ADDR_MAX; } +#endif + +#ifndef is_fadump_active +static inline bool is_fadump_active(void) +{ + return false; +} +#endif /* is_vmcore_usable() checks if the kernel is booting after a panic and * the vmcore region is usable. @@ -75,7 +84,8 @@ static inline bool is_kdump_kernel(void) static inline int is_vmcore_usable(void) { - return is_kdump_kernel() && elfcorehdr_addr != ELFCORE_ADDR_ERR ? 1 : 0; + return (is_kdump_kernel() || is_fadump_active()) + && elfcorehdr_addr != ELFCORE_ADDR_ERR ? 1 : 0; } /* vmcore_unusable() marks the vmcore as unusable, @@ -84,7 +94,7 @@ static inline int is_vmcore_usable(void) static inline void vmcore_unusable(void) { - if (is_kdump_kernel()) + if (is_kdump_kernel() || is_fadump_active()) elfcorehdr_addr = ELFCORE_ADDR_ERR; }