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: <d3c5417d5aaf0b02fb67d834f457f21529296615.camel@intel.com>
Date: Wed, 6 Aug 2025 06:53:25 +0000
From: "Huang, Kai" <kai.huang@...el.com>
To: "tglx@...utronix.de" <tglx@...utronix.de>, "peterz@...radead.org"
	<peterz@...radead.org>, "mingo@...hat.com" <mingo@...hat.com>, "Hansen, Dave"
	<dave.hansen@...el.com>, "thomas.lendacky@....com" <thomas.lendacky@....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 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.