From: Sohil Mehta <sohil.mehta@intel.com>
To: Ard Biesheuvel <ardb@kernel.org>
Cc: <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>,
"H . Peter Anvin" <hpa@zytor.com>,
Andy Lutomirski <luto@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Kiryl Shutsemau <kas@kernel.org>,
Rick Edgecombe <rick.p.edgecombe@intel.com>,
Andrew Cooper <andrew.cooper3@citrix.com>,
Tony Luck <tony.luck@intel.com>,
"Alexander Shishkin" <alexander.shishkin@linux.intel.com>,
<linux-kernel@vger.kernel.org>, <linux-efi@vger.kernel.org>
Subject: Re: [PATCH 0/3] x86: Extend LASS support to EFI configurations
Date: Fri, 12 Dec 2025 16:17:06 -0800 [thread overview]
Message-ID: <ce3a4c0c-1f18-459e-aba5-9d4582e45859@intel.com> (raw)
In-Reply-To: <CAMj1kXECOBQczcNeqmhfgttz_0545B3m7OgLAk4WE_hOkUbohg@mail.gmail.com>
On 12/4/2025 11:03 AM, Ard Biesheuvel wrote:
>
> efi_check_for_embedded_firmwares() maps EFI_BOOT_SERVICES_DATA regions
> in the kernel region, so bit 63 will be set.
Ah, I missed that efi_check_for_embedded_firmwares() remaps the regions.
>
>> LASS wouldn't care whether there is an actual mapping behind the
>> address. It only relies on the MSB for enforcement. So, any code that
>> relied on accessing boot services memory before efi_free_boot_services()
>> could get affected by LASS.
>>
>
> This only applies to code that accesses boot services memory via a
> mapping in the lower range.
>
Yes, I was referring to usages which use the lower mapping. Though,
efi_check_for_embedded_firmwares() doesn't do that, enabling LASS after
freeing boot services memory is still the right thing to do. In theory,
someone could use the 1:1 mapping.
prev parent reply other threads:[~2025-12-13 0:17 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-12-04 7:21 [PATCH 0/3] x86: Extend LASS support to EFI configurations Sohil Mehta
2025-12-04 7:21 ` [PATCH 1/3] x86/cpu: Defer LASS enabling until userspace comes up Sohil Mehta
2025-12-04 7:21 ` [PATCH 2/3] x86/efi: Make runtime services compatible with LASS Sohil Mehta
2025-12-04 7:21 ` [PATCH 3/3] x86/cpu: Remove LASS restriction on EFI Sohil Mehta
2025-12-04 12:47 ` [PATCH 0/3] x86: Extend LASS support to EFI configurations Ard Biesheuvel
2025-12-04 17:34 ` Sohil Mehta
2025-12-04 19:03 ` Ard Biesheuvel
2025-12-04 19:15 ` H. Peter Anvin
2025-12-04 19:40 ` Ard Biesheuvel
2025-12-04 19:51 ` H. Peter Anvin
2025-12-04 19:58 ` Ard Biesheuvel
2025-12-13 0:21 ` Sohil Mehta
2025-12-13 0:17 ` Sohil Mehta [this message]
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