From: Dave Hansen <dave.hansen@intel.com>
To: Brendan Jackman <jackmanb@google.com>,
Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
Peter Zijlstra <peterz@infradead.org>,
Andrew Morton <akpm@linux-foundation.org>,
David Hildenbrand <david@kernel.org>,
Vlastimil Babka <vbabka@kernel.org>, Wei Xu <weixugc@google.com>,
Johannes Weiner <hannes@cmpxchg.org>, Zi Yan <ziy@nvidia.com>,
Lorenzo Stoakes <ljs@kernel.org>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, x86@kernel.org,
rppt@kernel.org, Sumit Garg <sumit.garg@oss.qualcomm.com>,
derkling@google.com, reijiw@google.com,
Will Deacon <will@kernel.org>,
rientjes@google.com, "Kalyazin, Nikita" <kalyazin@amazon.co.uk>,
patrick.roy@linux.dev, "Itazuri, Takahiro" <itazur@amazon.co.uk>,
Andy Lutomirski <luto@kernel.org>,
David Kaplan <david.kaplan@amd.com>,
Thomas Gleixner <tglx@kernel.org>, Yosry Ahmed <yosry@kernel.org>
Subject: Re: [PATCH v2 01/22] x86/mm: split out preallocate_sub_pgd()
Date: Fri, 20 Mar 2026 12:42:25 -0700 [thread overview]
Message-ID: <554c886f-6678-4208-8566-15aa140f6c4b@intel.com> (raw)
In-Reply-To: <20260320-page_alloc-unmapped-v2-1-28bf1bd54f41@google.com>
On 3/20/26 11:23, Brendan Jackman wrote:
> - /*
> - * The goal here is to allocate all possibly required
> - * hardware page tables pointed to by the top hardware
> - * level.
This comment is pretty important, IMNHO, and you zapped it.
The problem here is that the per-MM carved out space is PGD-sized. You
want to make sure there are page tables allocated for that space. But,
if you say "go allocate a p4d" then that will collapse down to doing
nothing on a 4-level system.
So, this is effectively:
Go allocate a p4d or pud, depending on if it's 4 or 5 level.
Basically, always allocate the level that the hardware PGD
points to.
Could we put a comment to that effect around somewhere, please?
next prev parent reply other threads:[~2026-03-20 19:42 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-03-20 18:23 [PATCH v2 00/22] mm: Add __GFP_UNMAPPED Brendan Jackman
2026-03-20 18:23 ` [PATCH v2 01/22] x86/mm: split out preallocate_sub_pgd() Brendan Jackman
2026-03-20 19:42 ` Dave Hansen [this message]
2026-03-23 11:01 ` Brendan Jackman
2026-03-24 15:27 ` Borislav Petkov
2026-03-25 13:28 ` Brendan Jackman
2026-03-20 18:23 ` [PATCH v2 02/22] x86/mm: Generalize LDT remap into "mm-local region" Brendan Jackman
2026-03-20 19:47 ` Dave Hansen
2026-03-23 12:01 ` Brendan Jackman
2026-03-23 12:57 ` Brendan Jackman
2026-03-25 14:23 ` Brendan Jackman
2026-03-20 18:23 ` [PATCH v2 03/22] x86/tlb: Expose some flush function declarations to modules Brendan Jackman
2026-03-20 18:23 ` [PATCH v2 04/22] mm: Create flags arg for __apply_to_page_range() Brendan Jackman
2026-03-20 18:23 ` [PATCH v2 05/22] mm: Add more flags " Brendan Jackman
2026-03-26 16:14 ` Brendan Jackman
2026-03-20 18:23 ` [PATCH v2 06/22] x86/mm: introduce the mermap Brendan Jackman
2026-03-20 18:23 ` [PATCH v2 07/22] mm: KUnit tests for " Brendan Jackman
2026-03-24 8:00 ` kernel test robot
2026-03-20 18:23 ` [PATCH v2 08/22] mm: introduce for_each_free_list() Brendan Jackman
2026-03-20 18:23 ` [PATCH v2 09/22] mm/page_alloc: don't overload migratetype in find_suitable_fallback() Brendan Jackman
2026-03-20 18:23 ` [PATCH v2 10/22] mm: introduce freetype_t Brendan Jackman
2026-03-20 18:23 ` [PATCH v2 11/22] mm: move migratetype definitions to freetype.h Brendan Jackman
2026-03-20 18:23 ` [PATCH v2 12/22] mm: add definitions for allocating unmapped pages Brendan Jackman
2026-03-20 18:23 ` [PATCH v2 13/22] mm: rejig pageblock mask definitions Brendan Jackman
2026-03-20 18:23 ` [PATCH v2 14/22] mm: encode freetype flags in pageblock flags Brendan Jackman
2026-03-20 18:23 ` [PATCH v2 15/22] mm/page_alloc: remove ifdefs from pindex helpers Brendan Jackman
2026-03-20 18:23 ` [PATCH v2 16/22] mm/page_alloc: separate pcplists by freetype flags Brendan Jackman
2026-03-20 18:23 ` [PATCH v2 17/22] mm/page_alloc: rename ALLOC_NON_BLOCK back to _HARDER Brendan Jackman
2026-03-20 18:23 ` [PATCH v2 18/22] mm/page_alloc: introduce ALLOC_NOBLOCK Brendan Jackman
2026-03-20 18:23 ` [PATCH v2 19/22] mm/page_alloc: implement __GFP_UNMAPPED allocations Brendan Jackman
2026-03-20 18:23 ` [PATCH v2 20/22] mm/page_alloc: implement __GFP_UNMAPPED|__GFP_ZERO allocations Brendan Jackman
2026-03-20 18:23 ` [PATCH v2 21/22] mm: Minimal KUnit tests for some new page_alloc logic Brendan Jackman
2026-03-20 18:23 ` [PATCH v2 22/22] mm/secretmem: Use __GFP_UNMAPPED when available Brendan Jackman
2026-03-31 14:40 ` Brendan Jackman
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=554c886f-6678-4208-8566-15aa140f6c4b@intel.com \
--to=dave.hansen@intel.com \
--cc=akpm@linux-foundation.org \
--cc=bp@alien8.de \
--cc=dave.hansen@linux.intel.com \
--cc=david.kaplan@amd.com \
--cc=david@kernel.org \
--cc=derkling@google.com \
--cc=hannes@cmpxchg.org \
--cc=itazur@amazon.co.uk \
--cc=jackmanb@google.com \
--cc=kalyazin@amazon.co.uk \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=ljs@kernel.org \
--cc=luto@kernel.org \
--cc=patrick.roy@linux.dev \
--cc=peterz@infradead.org \
--cc=reijiw@google.com \
--cc=rientjes@google.com \
--cc=rppt@kernel.org \
--cc=sumit.garg@oss.qualcomm.com \
--cc=tglx@kernel.org \
--cc=vbabka@kernel.org \
--cc=weixugc@google.com \
--cc=will@kernel.org \
--cc=x86@kernel.org \
--cc=yosry@kernel.org \
--cc=ziy@nvidia.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox