From: Dave Hansen <dave.hansen@intel.com>
To: Zi Yan <ziy@nvidia.com>, Luiz Capitulino <luizcap@redhat.com>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org,
david@kernel.org, baolin.wang@linux.alibaba.com,
ryan.roberts@arm.com, akpm@linux-foundation.org,
lorenzo.stoakes@oracle.com,
Dave Hansen <dave.hansen@linux.intel.com>,
Thomas Gleixner <tglx@kernel.org>, Ingo Molnar <mingo@redhat.com>,
Borislav Petkov <bp@alien8.de>
Subject: Re: [PATCH v3 10/10] mm: thp: x86: cleanup PSE feature bit usage
Date: Thu, 9 Apr 2026 13:10:27 -0700 [thread overview]
Message-ID: <631bceef-d32b-475f-9d1a-644593aceddc@intel.com> (raw)
In-Reply-To: <F9F90195-D89C-4DBF-BDFC-311A32D00B9D@nvidia.com>
On 4/9/26 08:57, Zi Yan wrote:
> Historically, THP support on x86 checked the PSE feature bit to enable
> THP. On 64-bit, this check is redundant since PSE is always enabled by
> default for compatibility.
What do you mean by "PSE is always enabled by default"?
A hypervisor is completely free to not enumerate PSE support to a guest.
Any kernel can disable PSE with clearcpuid=3 on the command-line. PSE is
also disabled for at least one erratum (which I think includes some
64-bit CPUs).
Here's a snippet in a 64-bit VM of /proc/cpuinfo on a normal boot:
DirectMap4k: 83836 kB
DirectMap2M: 1939456 kB
DirectMap1G: 1048576 kB
and with clearcpuid=3:
DirectMap4k: 3071868 kB
DirectMap2M: 0 kB
Just to show that it's possible.
So perhaps I'm reading into the changelog too much, but this doesn't
quite seem right to me.
next prev parent reply other threads:[~2026-04-09 20:10 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-04-08 20:22 [PATCH v3 00/10] mm: thp: always enable mTHP support Luiz Capitulino
2026-04-08 20:22 ` [PATCH v3 01/10] docs: tmpfs: remove implementation detail reference Luiz Capitulino
2026-04-09 15:11 ` Zi Yan
2026-04-08 20:22 ` [PATCH v3 02/10] mm: introduce pgtable_has_pmd_leaves() Luiz Capitulino
2026-04-09 12:26 ` Lance Yang
2026-04-09 18:22 ` Luiz Capitulino
2026-04-08 20:22 ` [PATCH v3 03/10] drivers: dax: use pgtable_has_pmd_leaves() Luiz Capitulino
2026-04-08 20:22 ` [PATCH v3 04/10] drivers: nvdimm: " Luiz Capitulino
2026-04-09 15:21 ` Zi Yan
2026-04-09 18:51 ` Luiz Capitulino
2026-04-08 20:23 ` [PATCH v3 05/10] mm: debug_vm_pgtable: " Luiz Capitulino
2026-04-09 15:25 ` Zi Yan
2026-04-08 20:23 ` [PATCH v3 06/10] mm: shmem: drop has_transparent_hugepage() usage Luiz Capitulino
2026-04-09 15:26 ` Zi Yan
2026-04-08 20:23 ` [PATCH v3 07/10] treewide: rename has_transparent_hugepage() to arch_has_pmd_leaves() Luiz Capitulino
2026-04-09 15:41 ` Zi Yan
2026-04-09 19:43 ` Luiz Capitulino
2026-04-08 20:23 ` [PATCH v3 08/10] mm: replace thp_disabled_by_hw() with pgtable_has_pmd_leaves() Luiz Capitulino
2026-04-09 15:43 ` Zi Yan
2026-04-08 20:23 ` [PATCH v3 09/10] mm: thp: always enable mTHP support Luiz Capitulino
2026-04-09 15:55 ` Zi Yan
2026-04-09 20:07 ` Luiz Capitulino
2026-04-09 20:10 ` Zi Yan
2026-04-09 21:19 ` Luiz Capitulino
2026-04-08 20:23 ` [PATCH v3 10/10] mm: thp: x86: cleanup PSE feature bit usage Luiz Capitulino
2026-04-09 15:57 ` Zi Yan
2026-04-09 20:10 ` Dave Hansen [this message]
2026-04-09 21:24 ` Luiz Capitulino
2026-04-09 8:29 ` [PATCH v3 00/10] mm: thp: always enable mTHP support Lance Yang
2026-04-09 8:36 ` Lorenzo Stoakes
2026-04-09 18:18 ` Luiz Capitulino
2026-04-09 12:35 ` Lance Yang
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=631bceef-d32b-475f-9d1a-644593aceddc@intel.com \
--to=dave.hansen@intel.com \
--cc=akpm@linux-foundation.org \
--cc=baolin.wang@linux.alibaba.com \
--cc=bp@alien8.de \
--cc=dave.hansen@linux.intel.com \
--cc=david@kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=lorenzo.stoakes@oracle.com \
--cc=luizcap@redhat.com \
--cc=mingo@redhat.com \
--cc=ryan.roberts@arm.com \
--cc=tglx@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