linux-kernel - Re: [PATCH 2/2] arm64/mm: Update create_kpti_ng_temp_pgd() to handle pgtable

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Message-ID: <4289fc02-8e09-4d33-a4a1-0e4b268b008c@redhat.com>
Date: Tue, 19 Aug 2025 09:41:40 +0200
From: David Hildenbrand <david@...hat.com>
To: Chaitanya S Prakash <chaitanyas.prakash@....com>,
 linux-arm-kernel@...ts.infradead.org, linux-mm@...ck.org,
 linux-kernel@...r.kernel.org
Cc: Ryan Roberts <ryan.roberts@....com>,
 Yang Shi <yang@...amperecomputing.com>,
 Catalin Marinas <catalin.marinas@....com>, Will Deacon <will@...nel.org>,
 Kevin Brodsky <kevin.brodsky@....com>,
 Anshuman Khandual <anshuman.khandual@....com>,
 Andrew Morton <akpm@...ux-foundation.org>,
 Zhenhua Huang <quic_zhenhuah@...cinc.com>, Joey Gouly <joey.gouly@....com>
Subject: Re: [PATCH 2/2] arm64/mm: Update create_kpti_ng_temp_pgd() to handle
 pgtable_alloc failure

On 13.08.25 16:56, Chaitanya S Prakash wrote:
> create_kpti_ng_temp_pgd() was created as an alias for void returning
> __create_pgd_mapping_locked() and relied on pgtable_alloc() to BUG_ON()
> if an allocation failure occurred. But as __create_pgd_mapping_locked()
> has been updated as a part of the error propagation patch to return a
> non-void value, update create_kpti_ng_temp_pgd() to act as a wrapper
> around __create_pgd_mapping_locked() and BUG_ON() on ret being a non
> zero value.

If  my memory serves me right, panic() is preferred in such unexpected 
early-boot scenarios (BUG_ON is frowned upon), where you can actually 
print what is going wrong.


Which raises the question: could create_kpti_ng_temp_pgd() be __init? 
__kpti_install_ng_mappings(), the only caller, seems to be.

-- 
Cheers

David / dhildenb