linux-kernel - Re: [RFC 1/1] x86/vmemmap: Add missing update of PML4 table / PML5 table entry

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Message-ID: <25b9d3f5-bfe8-48a9-b11b-819d19cfae1e@intel.com>
Date: Fri, 14 Feb 2025 11:57:50 -0800
From: Dave Hansen <dave.hansen@...el.com>
To: Gwan-gyeong Mun <gwan-gyeong.mun@...el.com>, linux-kernel@...r.kernel.org
Cc: osalvador@...e.de, 42.hyeyoo@...il.com, byungchul@...com,
 dave.hansen@...ux.intel.com, luto@...nel.org, peterz@...radead.org,
 akpm@...ux-foundation.org, max.byungchul.park@...com,
 max.byungchul.park@...il.com
Subject: Re: [RFC 1/1] x86/vmemmap: Add missing update of PML4 table / PML5
 table entry

On 2/14/25 11:51, Gwan-gyeong Mun wrote:
> when performing vmemmap populate, if the entry of the PML4 table/PML5 table
> pointing to the target virtual address has never been updated, a page fault
> occurs when the memset(start) called from the vmemmap_use_new_sub_pmd()
> execution flow.

"Page fault" meaning oops? Or something that we manage to handle and
return from without oopsing?

> This fixes the problem of using the virtual address without updating the
> entry in the PML4 table or PML5 table. But this is a temporary solution to
> prevent page fault problems, and it requires improvement of the routine
> that updates the missing entry in the PML4 table or PML5 table.

Can we please skip past the band-aid and go to the real fix?