| 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
| ||
|
Message-ID: <80415a29-14dd-4108-aa02-4b0b5e1f2baf@fujitsu.com>
Date: Thu, 31 Oct 2024 09:33:34 +0000
From: "Zhijian Li (Fujitsu)" <lizhijian@...itsu.com>
To: Huaisheng Ye <huaisheng.ye@...el.com>, "linux-cxl@...r.kernel.org"
<linux-cxl@...r.kernel.org>, "dan.j.williams@...el.com"
<dan.j.williams@...el.com>
CC: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"pei.p.jia@...el.com" <pei.p.jia@...el.com>
Subject: Re: [PATCH] [RFC] cxl/region: Fix region creation for greater than x2
switches
On 27/10/2024 15:57, Huaisheng Ye wrote:
> The cxl_port_setup_targets() algorithm fails to identify valid target list
> ordering in the presence of 4-way and above switches resulting in
> 'cxl create-region' failures of the form:
>
> # cxl create-region -d decoder0.0 -g 1024 -s 2G -t ram -w 8 -m mem4 mem1 mem6 mem3 mem2 mem5 mem7 mem0
> cxl region: create_region: region0: failed to set target7 to mem0
> cxl region: cmd_create_region: created 0 regions
>
> [kernel debug message]
> check_last_peer:1213: cxl region0: pci0000:0c:port1: cannot host mem6:decoder7.0 at 2
> bus_remove_device:574: bus: 'cxl': remove device region0
>
> QEMU can create this failing topology:
>
> ACPI0017:00 [root0]
> |
> HB_0 [port1]
> / \
> RP_0 RP_1
> | |
> USP [port2] USP [port3]
> / / \ \ / / \ \
> DSP DSP DSP DSP DSP DSP DSP DSP
> | | | | | | | |
> mem4 mem6 mem2 mem7 mem1 mem3 mem5 mem0
> Pos: 0 2 4 6 1 3 5 7
Yeah, I tried this topology long long ago, it didn't work. At that time, I thought it
might be just like that. Until recently that I saw this [1] in section
2.13.15.1 Region Spanning 2 HB Root Ports Example Configuration Checks
I once tried to understand why the code used "distance" to determine the order of the target,
but in the end, I still couldn't figure it out (and I still don't understand it now).
IIRC, neither the CXL spec nor this document mentioned the keyword "distance" at all.
[1] https://cdrdv2-public.intel.com/643805/643805_CXL_Memory_Device_SW_Guide_Rev1_1.pdf
Anyway, many thanks.
I tried this patch, it works for me.
Tested-by: Li Zhijian <lizhijian@...itsu.com>
>
> HB: Host Bridge
> RP: Root Port
> USP: Upstream Port
> DSP: Downstream Port
>
> ...with the following command steps:
>
> $ qemu-system-x86_64 -machine q35,cxl=on,accel=tcg \
> -smp cpus=8 \
> -m 8G \
> -hda /home/work/vm-images/centos-stream8-02.qcow2 \
> -object memory-backend-ram,size=4G,id=m0 \
> -object memory-backend-ram,size=4G,id=m1 \
> -object memory-backend-ram,size=2G,id=cxl-mem0 \
> -object memory-backend-ram,size=2G,id=cxl-mem1 \
> -object memory-backend-ram,size=2G,id=cxl-mem2 \
> -object memory-backend-ram,size=2G,id=cxl-mem3 \
> -object memory-backend-ram,size=2G,id=cxl-mem4 \
> -object memory-backend-ram,size=2G,id=cxl-mem5 \
> -object memory-backend-ram,size=2G,id=cxl-mem6 \
> -object memory-backend-ram,size=2G,id=cxl-mem7 \
> -numa node,memdev=m0,cpus=0-3,nodeid=0 \
> -numa node,memdev=m1,cpus=4-7,nodeid=1 \
> -netdev user,id=net0,hostfwd=tcp::2222-:22 \
> -device virtio-net-pci,netdev=net0 \
> -device pxb-cxl,bus_nr=12,bus=pcie.0,id=cxl.1 \
> -device cxl-rp,port=0,bus=cxl.1,id=root_port0,chassis=0,slot=0 \
> -device cxl-rp,port=1,bus=cxl.1,id=root_port1,chassis=0,slot=1 \
> -device cxl-upstream,bus=root_port0,id=us0 \
> -device cxl-downstream,port=0,bus=us0,id=swport0,chassis=0,slot=4 \
> -device cxl-type3,bus=swport0,volatile-memdev=cxl-mem0,id=cxl-vmem0 \
> -device cxl-downstream,port=1,bus=us0,id=swport1,chassis=0,slot=5 \
> -device cxl-type3,bus=swport1,volatile-memdev=cxl-mem1,id=cxl-vmem1 \
> -device cxl-downstream,port=2,bus=us0,id=swport2,chassis=0,slot=6 \
> -device cxl-type3,bus=swport2,volatile-memdev=cxl-mem2,id=cxl-vmem2 \
> -device cxl-downstream,port=3,bus=us0,id=swport3,chassis=0,slot=7 \
> -device cxl-type3,bus=swport3,volatile-memdev=cxl-mem3,id=cxl-vmem3 \
> -device cxl-upstream,bus=root_port1,id=us1 \
> -device cxl-downstream,port=4,bus=us1,id=swport4,chassis=0,slot=8 \
> -device cxl-type3,bus=swport4,volatile-memdev=cxl-mem4,id=cxl-vmem4 \
> -device cxl-downstream,port=5,bus=us1,id=swport5,chassis=0,slot=9 \
> -device cxl-type3,bus=swport5,volatile-memdev=cxl-mem5,id=cxl-vmem5 \
> -device cxl-downstream,port=6,bus=us1,id=swport6,chassis=0,slot=10 \
> -device cxl-type3,bus=swport6,volatile-memdev=cxl-mem6,id=cxl-vmem6 \
> -device cxl-downstream,port=7,bus=us1,id=swport7,chassis=0,slot=11 \
> -device cxl-type3,bus=swport7,volatile-memdev=cxl-mem7,id=cxl-vmem7 \
> -M cxl-fmw.0.targets.0=cxl.1,cxl-fmw.0.size=32G &
>
> In Guest OS:
> # cxl create-region -d decoder0.0 -g 1024 -s 2G -t ram -w 8 -m mem4 mem1 mem6 mem3 mem2 mem5 mem7 mem0
>
> Fix the method to calculate @distance by iterativeley multiplying the number of targets per switch port. This also follows the algorithm recommended here [1].
>
> Fixes: 27b3f8d13830 ("cxl/region: Program target lists")
> Link: http://lore.kernel.org/6538824b52349_7258329466@dwillia2-xfh.jf.intel.com.notmuch [1]
> Signed-off-by: Huaisheng Ye <huaisheng.ye@...el.com>
>
> ---
> drivers/cxl/core/region.c | 19 ++++++++++++-------
> 1 file changed, 12 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
> index e701e4b04032..9e226a293f45 100644
> --- a/drivers/cxl/core/region.c
> +++ b/drivers/cxl/core/region.c
> @@ -1288,6 +1288,7 @@ static int cxl_port_setup_targets(struct cxl_port *port,
> struct cxl_region_params *p = &cxlr->params;
> struct cxl_decoder *cxld = cxl_rr->decoder;
> struct cxl_switch_decoder *cxlsd;
> + struct cxl_port *iter = port;
> u16 eig, peig;
> u8 eiw, peiw;
>
> @@ -1304,16 +1305,20 @@ static int cxl_port_setup_targets(struct cxl_port *port,
>
> cxlsd = to_cxl_switch_decoder(&cxld->dev);
> if (cxl_rr->nr_targets_set) {
> - int i, distance;
> + int i, distance = 1;
> + struct cxl_region_ref *cxl_rr_iter;
>
> /*
> - * Passthrough decoders impose no distance requirements between
> - * peers
> + * Get distance from the number of distinct targets in region's
> + * interest and the ancestral nr_targets.
> */
> - if (cxl_rr->nr_targets == 1)
> - distance = 0;
> - else
> - distance = p->nr_targets / cxl_rr->nr_targets;
> + do {
> + cxl_rr_iter = cxl_rr_load(iter, cxlr);
> + distance *= cxl_rr_iter->nr_targets;
> + iter = to_cxl_port(iter->dev.parent);
> + } while (!is_cxl_root(iter));
> + distance *= cxlrd->cxlsd.cxld.interleave_ways;
> +
> for (i = 0; i < cxl_rr->nr_targets_set; i++)
> if (ep->dport == cxlsd->target[i]) {
> rc = check_last_peer(cxled, ep, cxl_rr,
Powered by blists - more mailing lists