linux-kernel - Re: CXL Boot to Bash - Section 2a (Drivers): CXL Decoder Programming

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: <Z-1HPqufU7MnQ6ii@gourry-fedora-PF4VCD3F>
Date: Wed, 2 Apr 2025 10:18:38 -0400
From: Gregory Price <gourry@...rry.net>
To: "Zhijian Li (Fujitsu)" <lizhijian@...itsu.com>
Cc: "lsf-pc@...ts.linux-foundation.org" <lsf-pc@...ts.linux-foundation.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"linux-cxl@...r.kernel.org" <linux-cxl@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: CXL Boot to Bash - Section 2a (Drivers): CXL Decoder Programming

On Wed, Apr 02, 2025 at 06:45:33AM +0000, Zhijian Li (Fujitsu) wrote:
> Hi Gregory,
> 
> 
> On 07/03/2025 07:56, Gregory Price wrote:
> > What if instead, we had two 256MB endpoints on the same host bridge?
> > 
> > ```
> > CEDT
> >             Subtable Type : 01 [CXL Fixed Memory Window Structure]
> >                  Reserved : 00
> >                    Length : 002C
> >                  Reserved : 00000000
> >       Window base address : 0000000100000000   <- Memory Region
> >               Window size : 0000000020000000   <- 512MB
> > Interleave Members (2^n) : 00                 <- Not interleaved
> > 
> > Memory Map:
> >    [mem 0x0000000100000000-0x0000000120000000] usable  <- SPA
> > 
> > Decoders
> >                              decoder0.0
> >                    range=[0x100000000, 0x120000000]
> >                                  |
> >                              decoder1.0
> >                    range=[0x100000000, 0x120000000]
> >                    /                              \
> >              decoded2.0                        decoder3.0
> >    range=[0x100000000, 0x110000000]   range=[0x110000000, 0x120000000]
> > ```
> 
> It reminds me that during construct_region(), it requires decoder range in the
> switch/host-bridge is exact same with the endpoint decoder. see
> match_switch_decoder_by_range()
> 
> If so, does following decoders make sense?
> 
> 
>   Decoders
>                                decoder0.0
>                      range=[0x100000000, 0x120000000]
>                                    |
>                       +------------+-----------+
>                      /                          \
>                     |      Host-bridge contains  |
>               decoder1.0     2 decoders       decoder1.1
>       range=[0x100000000, 0x110000000]     range=[0x110000000, 0x120000000]
>                      /                              \
>                decoded2.0                        decoder3.0
>      range=[0x100000000, 0x110000000]   range=[0x110000000, 0x120000000]
>

You are correct, i'll update this.