From: Dave Hansen <dave.hansen@intel.com>
To: Borislav Petkov <bp@alien8.de>,
Ryusuke Konishi <konishi.ryusuke@gmail.com>
Cc: Andrew Cooper <andrew.cooper3@citrix.com>,
Andrew Morton <akpm@linux-foundation.org>,
Marco Elver <elver@google.com>,
LKML <linux-kernel@vger.kernel.org>,
Alexander Potapenko <glider@google.com>,
Dmitry Vyukov <dvyukov@google.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>,
Dave Hansen <dave.hansen@linux.intel.com>,
X86 ML <x86@kernel.org>, "H. Peter Anvin" <hpa@zytor.com>,
Jann Horn <jannh@google.com>,
kasan-dev@googlegroups.com
Subject: Re: [REGRESSION] x86_32 boot hang in 6.19-rc7 caused by b505f1944535 ("x86/kfence: avoid writing L1TF-vulnerable PTEs")
Date: Mon, 26 Jan 2026 12:25:22 -0800 [thread overview]
Message-ID: <64b91595-1305-4b64-bcce-a6913f76ade0@intel.com> (raw)
In-Reply-To: <20260126195431.GDaXfGd9cSwoH2O52r@fat_crate.local>
On 1/26/26 11:54, Borislav Petkov wrote:
> [ 0.173437] rcu: srcu_init: Setting srcu_struct sizes based on contention.
> [ 0.175172] ------------[ cut here ]------------
> [ 0.176066] kernel BUG at arch/x86/mm/physaddr.c:70!
Take a look at kfence_init_pool_early(). It's riddled with __pa() which
calls down to __phys_addr() => slow_virt_to_phys().
The plain !present PTE is fine, but the inverted one trips up
slow_virt_to_phys(), I bet. The slow_virt_to_phys() only gets called on
when highmem is enabled (not when the memory is highmem) which is why
this is blowing up on 32-bit only.
The easiest hack/fix would be to just turn off kfence on 32-bit. I guess
the better fix would be to make kfence do its __pa() before it mucks
with the PTEs. The other option would be to either comprehend or ignore
those inverted PTEs.
Ugh.
next prev parent reply other threads:[~2026-01-26 20:25 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-01-06 18:04 [PATCH] x86/kfence: Avoid writing L1TF-vulnerable PTEs Andrew Cooper
2026-01-07 11:31 ` Alexander Potapenko
2026-01-07 12:01 ` Andrew Cooper
2026-01-07 23:17 ` Andrew Morton
2026-01-26 19:07 ` [REGRESSION] x86_32 boot hang in 6.19-rc7 caused by b505f1944535 ("x86/kfence: avoid writing L1TF-vulnerable PTEs") Ryusuke Konishi
2026-01-26 19:39 ` Andrew Cooper
2026-01-26 19:52 ` Ryusuke Konishi
2026-01-26 19:54 ` Borislav Petkov
2026-01-26 20:22 ` Andrew Cooper
2026-01-26 20:41 ` Ryusuke Konishi
2026-01-26 20:43 ` Andrew Cooper
2026-01-26 20:25 ` Dave Hansen [this message]
2026-01-26 20:24 ` Andrew Morton
2026-01-26 20:36 ` Dave Hansen
2026-01-26 21:06 ` [PATCH] x86/kfence: Fix booting on 32bit non-PAE systems Andrew Cooper
2026-01-26 21:08 ` Andrew Cooper
2026-01-26 21:10 ` [PATCH v2] " Andrew Cooper
2026-01-26 21:24 ` Andrew Morton
2026-01-26 21:56 ` Borislav Petkov
2026-01-26 22:01 ` Andrew Cooper
2026-01-26 22:09 ` Borislav Petkov
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