linux-kernel - Re: Question to hv_vtl_real_mode_header in hv

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] [day] [month] [year] [list]

Message-ID: <20240813213628.GA7852@yjiang5-mobl.amr.corp.intel.com>
Date: Tue, 13 Aug 2024 14:36:28 -0700
From: Yunhong Jiang <yunhong.jiang@...ux.intel.com>
To: kys@...rosoft.com, haiyangz@...rosoft.com, wei.liu@...nel.org,
	decui@...rosoft.com
Cc: linux-hyperv@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: Question to hv_vtl_real_mode_header in hv_vtl.c

On Tue, Aug 13, 2024 at 10:28:19AM -0700, Yunhong Jiang wrote:
> Hi, Srinivasan and Dexuan,
> 	I have a question to the hv_vtl_real_mode_header in
> arch/x86//hyperv/hv_vtl.c when addressing one patch review comment.
> 	In hv_vtl_early_init(), the real_mode_header is set to
> hv_vtl_real_mode_header, but there is no setup to the real_mode_header, since
> the realmode_init() is marked x86_init_noop in hv_vtl_init_platform.
> 	How is the real_mode_header(in another word, hv_vtl_real_mode_header)
> used? Is it to meet the access requirement from do_boot_cpu(), so that
> real_mode_header->trampoline_start64 will work, although the start_ip is not
> used?
> 	If it's really to support the do_boot_cpu() requirement, how does the
> non-VTL guest meet the access requirement? The hv_vtl_init_platform() is
> unconditionally called from ms_hyperv_init_platform(), so I assume all hyperv
> guest will have the realmode_init() set as x86_init_noop.

The patch review mentioned above is
https://lore.kernel.org/lkml/87a5ho2q6x.ffs@tglx/ . Can we set real_mode_header
to hv_vtl_real_mode_header in hv_vtl_init_platform(), instead of
hv_vtl_early_init()? I'm not sure if such move is safe, because
hv_vtl_early_init() is invoked only for vtl!=0 guest while
hv_vtl_init_platform() is invoked for all the hyperv guest.

> 
> Thank you
> --jyh
>