From: Dave Hansen <dave.hansen@intel.com>
To: Sohil Mehta <sohil.mehta@intel.com>,
x86@kernel.org, Dave Hansen <dave.hansen@linux.intel.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>
Cc: Jonathan Corbet <corbet@lwn.net>,
"H . Peter Anvin" <hpa@zytor.com>,
Andy Lutomirski <luto@kernel.org>,
Josh Poimboeuf <jpoimboe@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Ard Biesheuvel <ardb@kernel.org>,
"Kirill A . Shutemov" <kas@kernel.org>, Xin Li <xin@zytor.com>,
David Woodhouse <dwmw@amazon.co.uk>,
Sean Christopherson <seanjc@google.com>,
Rick Edgecombe <rick.p.edgecombe@intel.com>,
Vegard Nossum <vegard.nossum@oracle.com>,
Andrew Cooper <andrew.cooper3@citrix.com>,
Randy Dunlap <rdunlap@infradead.org>,
Geert Uytterhoeven <geert@linux-m68k.org>,
Kees Cook <kees@kernel.org>, Tony Luck <tony.luck@intel.com>,
Alexander Shishkin <alexander.shishkin@linux.intel.com>,
linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-efi@vger.kernel.org
Subject: Re: [PATCH v11 5/9] x86/efi: Disable LASS while mapping the EFI runtime services
Date: Fri, 31 Oct 2025 10:11:40 -0700 [thread overview]
Message-ID: <3e9c4fdd-88a8-4597-9405-d865fb837d95@intel.com> (raw)
In-Reply-To: <20251029210310.1155449-6-sohil.mehta@intel.com>
On 10/29/25 14:03, Sohil Mehta wrote:
> From: Alexander Shishkin <alexander.shishkin@linux.intel.com>
>
> While mapping EFI runtime services, set_virtual_address_map() is called
> at its lower mapping, which LASS prohibits. Wrapping the EFI call with
> lass_disable()/_enable() is not enough, because the AC flag only
> controls data accesses, and not instruction fetches.
>
> Use the big hammer and toggle the CR4.LASS bit to make this work.
One thing that's actually missing here is an explanation on how it's OK
to munge CR bits here. Why are preemption and interrupts not a problem?
A reviewer would have to go off and figure this out on their own.
next prev parent reply other threads:[~2025-10-31 17:11 UTC|newest]
Thread overview: 67+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-10-29 21:03 [PATCH v11 0/9] x86: Enable Linear Address Space Separation support Sohil Mehta
2025-10-29 21:03 ` [PATCH v11 1/9] x86/cpufeatures: Enumerate the LASS feature bits Sohil Mehta
2025-10-31 17:03 ` Dave Hansen
2025-10-29 21:03 ` [PATCH v11 2/9] x86/cpu: Add an LASS dependency on SMAP Sohil Mehta
2025-10-31 17:04 ` Dave Hansen
2025-10-29 21:03 ` [PATCH v11 3/9] x86/asm: Introduce inline memcpy and memset Sohil Mehta
2025-10-31 17:06 ` Dave Hansen
2025-10-29 21:03 ` [PATCH v11 4/9] x86/alternatives: Disable LASS when patching kernel code Sohil Mehta
2025-10-31 17:10 ` Dave Hansen
2025-11-10 18:15 ` Sohil Mehta
2025-11-10 19:09 ` H. Peter Anvin
2025-11-10 19:24 ` Borislav Petkov
2025-11-12 13:56 ` Ard Biesheuvel
2025-11-12 14:51 ` Dave Hansen
2025-11-12 14:57 ` H. Peter Anvin
2025-11-12 15:18 ` Ard Biesheuvel
2025-11-12 15:23 ` H. Peter Anvin
2025-11-12 15:28 ` Ard Biesheuvel
2025-11-12 15:47 ` H. Peter Anvin
2025-11-12 16:18 ` Sohil Mehta
2025-11-12 16:26 ` H. Peter Anvin
2025-11-12 16:29 ` H. Peter Anvin
2025-10-29 21:03 ` [PATCH v11 5/9] x86/efi: Disable LASS while mapping the EFI runtime services Sohil Mehta
2025-10-31 17:11 ` Dave Hansen [this message]
2025-10-31 17:38 ` Andy Lutomirski
2025-10-31 17:41 ` Dave Hansen
2025-10-31 18:03 ` Sohil Mehta
2025-10-31 18:12 ` Dave Hansen
2025-11-07 9:04 ` Peter Zijlstra
2025-11-07 9:22 ` Ard Biesheuvel
2025-11-07 9:27 ` H. Peter Anvin
2025-11-07 9:35 ` Ard Biesheuvel
2025-11-07 9:40 ` Peter Zijlstra
2025-11-07 10:09 ` Ard Biesheuvel
2025-11-07 10:27 ` Peter Zijlstra
2025-11-08 0:48 ` Andy Lutomirski
2025-11-08 16:18 ` H. Peter Anvin
2025-11-08 22:50 ` H. Peter Anvin
2025-11-07 10:10 ` Peter Zijlstra
2025-11-07 10:17 ` Ard Biesheuvel
2025-10-31 19:04 ` Sohil Mehta
2025-11-07 7:36 ` Sohil Mehta
2025-10-31 18:32 ` Sohil Mehta
2025-10-29 21:03 ` [PATCH v11 6/9] x86/kexec: Disable LASS during relocate kernel Sohil Mehta
2025-10-31 17:14 ` Dave Hansen
2025-10-29 21:03 ` [PATCH v11 7/9] x86/traps: Communicate a LASS violation in #GP message Sohil Mehta
2025-10-31 17:16 ` Dave Hansen
2025-10-31 19:59 ` Sohil Mehta
2025-10-31 20:03 ` Andy Lutomirski
2025-10-31 20:56 ` Dave Hansen
2025-10-29 21:03 ` [PATCH v11 8/9] selftests/x86: Update the negative vsyscall tests to expect a #GP Sohil Mehta
2025-10-31 17:20 ` Dave Hansen
2025-10-29 21:03 ` [PATCH v11 9/9] x86/cpu: Enable LASS by default during CPU initialization Sohil Mehta
2025-10-30 8:40 ` H. Peter Anvin
2025-10-30 15:45 ` Andy Lutomirski
2025-10-30 16:44 ` Sohil Mehta
2025-10-30 16:53 ` Andy Lutomirski
2025-10-30 17:24 ` Sohil Mehta
2025-10-30 17:31 ` Andy Lutomirski
2025-10-30 21:13 ` David Laight
2025-10-31 6:41 ` H. Peter Anvin
2025-10-31 16:55 ` Dave Hansen
2025-10-30 16:27 ` Dave Hansen
2025-11-07 8:01 ` H. Peter Anvin
2025-11-07 20:08 ` Sohil Mehta
2025-10-31 17:21 ` Dave Hansen
2025-10-31 20:04 ` Sohil Mehta
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