linux-kernel - Re: [PATCH v5 1/7] x86/kexec: Consolidate relocate

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <4d761b2d-cdce-1aa7-d138-59dee82e730c@amd.com>
Date: Wed, 6 Aug 2025 08:00:50 -0500
From: Tom Lendacky <thomas.lendacky@....com>
To: "Huang, Kai" <kai.huang@...el.com>,
 "tglx@...utronix.de" <tglx@...utronix.de>,
 "peterz@...radead.org" <peterz@...radead.org>,
 "mingo@...hat.com" <mingo@...hat.com>, "Hansen, Dave"
 <dave.hansen@...el.com>, "bp@...en8.de" <bp@...en8.de>,
 "hpa@...or.com" <hpa@...or.com>
Cc: "ashish.kalra@....com" <ashish.kalra@....com>,
 "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>,
 "seanjc@...gle.com" <seanjc@...gle.com>, "x86@...nel.org" <x86@...nel.org>,
 "kas@...nel.org" <kas@...nel.org>, "Gao, Chao" <chao.gao@...el.com>,
 "Chatre, Reinette" <reinette.chatre@...el.com>,
 "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
 "Williams, Dan J" <dan.j.williams@...el.com>,
 "sagis@...gle.com" <sagis@...gle.com>,
 "pbonzini@...hat.com" <pbonzini@...hat.com>,
 "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
 "dwmw@...zon.co.uk" <dwmw@...zon.co.uk>,
 "Yamahata, Isaku" <isaku.yamahata@...el.com>,
 "nik.borisov@...e.com" <nik.borisov@...e.com>
Subject: Re: [PATCH v5 1/7] x86/kexec: Consolidate relocate_kernel() function
 parameters

On 8/6/25 01:53, Huang, Kai wrote:
> On Tue, 2025-07-29 at 00:28 +1200, Kai Huang wrote:
>> During kexec, the kernel jumps to the new kernel in relocate_kernel(),
>> which is implemented in assembly and both 32-bit and 64-bit have their
>> own version.
>>
>> Currently, for both 32-bit and 64-bit, the last two parameters of the
>> relocate_kernel() are both 'unsigned int' but actually they only convey
>> a boolean, i.e., one bit information.  The 'unsigned int' has enough
>> space to carry two bits information therefore there's no need to pass
>> the two booleans in two separate 'unsigned int'.
>>
>> Consolidate the last two function parameters of relocate_kernel() into a
>> single 'unsigned int' and pass flags instead.
>>
>> Only consolidate the 64-bit version albeit the similar optimization can
>> be done for the 32-bit version too.  Don't bother changing the 32-bit
>> version while it is working (since assembly code change is required).
>>
>> Signed-off-by: Kai Huang <kai.huang@...el.com>
>> ---
>>
>>  v4 -> v5:
>>   - RELOC_KERNEL_HOST_MEM_ACTIVE -> RELOC_KERNEL_HOST_MEM_ENC_ACTIVE
>>     (Tom)
>>   - Add a comment to explain only RELOC_KERNEL_PRESERVE_CONTEXT is
>>     restored after jumping back from peer kernel for preserved_context
>>     kexec (pointed out by Tom).
>>   - Use testb instead of testq when comparing the flag with R11 to save
>>     3 bytes (Hpa).
>>
>>
> 
> Hi Tom,
> 
> Wondering do you have more comments?  Thanks.

Sorry for the delay, LGTM.

Reviewed-by: Tom Lendacky <thomas.lendacky@....com>