Re: [Qemu RFC 0/7] Early enabling of DCD emulation in Qemu

[address@hidden]

The 05/15/2023 14:00, Jonathan Cameron wrote:
> On Thu, 11 May 2023 17:56:40 +0000
> Fan Ni <fan.ni@samsung.com> wrote:
> 
> > Since the early draft of DCD support in kernel is out
> > (https://lore.kernel.org/linux-cxl/20230417164126.GA1904906@bgt-140510-bm03/T/#t),
> > this patch series provide dcd emulation in qemu so people who are interested
> > can have an early try. It is noted that the patch series may need to be 
> > updated
> > accordingly if the kernel side implementation changes.
> > 
> > To support DCD emulation, the patch series add DCD related mailbox command
> > support (CXL Spec 3.0: 8.2.9.8.9), and extend the cxl type3 memory device
> > with dynamic capacity extent and region representative.
> > To support read/write to the dynamic capacity of the device, a host backend
> > is provided and necessary check mechnism is added to ensure the dynamic
> > capacity accessed is backed with active dc extents.
> > Currently FM related mailbox commands (cxl spec 3.0: 7.6.7.6) is not 
> > supported
> > , but we add two qmp interfaces for adding/releasing dynamic capacity 
> > extents.
> > Also, the support for multiple hosts sharing the same DCD case is missing.
> > 
> > Things we can try with the patch series together with kernel dcd code:
> > 1. Create DC regions to cover the address range of the dynamic capacity
> > regions.
> > 2. Add/release dynamic capacity extents to the device and notify the
> > kernel.
> > 3. Test kernel side code to accept added dc extents and create dax devices,
> > and release dc extents and notify the device
> > 4. Online the memory range backed with dc extents and let application use
> > them.
> > 
> > The patch series is based on Jonathan's local qemu branch:
> > https://gitlab.com/jic23/qemu/-/tree/cxl-2023-02-28
> > 
> > Simple tests peformed with the patch series:
> > 1 Install cxl modules:
> > 
> > modprobe -a cxl_acpi cxl_core cxl_pci cxl_port cxl_mem
> > 
> > 2 Create dc regions:
> > 
> > region=$(cat /sys/bus/cxl/devices/decoder0.0/create_dc_region)
> > echo $region> /sys/bus/cxl/devices/decoder0.0/create_dc_region
> > echo 256 > /sys/bus/cxl/devices/$region/interleave_granularity
> > echo 1 > /sys/bus/cxl/devices/$region/interleave_ways
> > echo "dc" >/sys/bus/cxl/devices/decoder2.0/mode
> > echo 0x10000000 >/sys/bus/cxl/devices/decoder2.0/dpa_size
> > echo 0x10000000 > /sys/bus/cxl/devices/$region/size
> > echo  "decoder2.0" > /sys/bus/cxl/devices/$region/target0
> > echo 1 > /sys/bus/cxl/devices/$region/commit
> > echo $region > /sys/bus/cxl/drivers/cxl_region/bind
> > 
> > /home/fan/cxl/tools-and-scripts# cxl list
> > [
> >   {
> >     "memdevs":[
> >       {
> >         "memdev":"mem0",
> >         "pmem_size":536870912,
> >         "ram_size":0,
> >         "serial":0,
> >         "host":"0000:0d:00.0"
> >       }
> >     ]
> >   },
> >   {
> >     "regions":[
> >       {
> >         "region":"region0",
> >         "resource":45365592064,
> >         "size":268435456,
> >         "interleave_ways":1,
> >         "interleave_granularity":256,
> >         "decode_state":"commit"
> >       }
> >     ]
> >   }
> > ]
> > 
> > 3 Add two dc extents (128MB each) through qmp interface
> > 
> > { "execute": "qmp_capabilities" }
> > 
> > { "execute": "cxl-add-dynamic-capacity-event",
> >     "arguments": {
> >              "path": "/machine/peripheral/cxl-pmem0",
> >             "region-id" : 0,
> >              "num-extent": 2,
> >             "dpa":0,
> >             "extent-len": 128
> >     }
> > }
> > 
> > /home/fan/cxl/tools-and-scripts# lsmem
> > RANGE                                  SIZE   STATE REMOVABLE   BLOCK
> > 0x0000000000000000-0x000000007fffffff    2G  online       yes    0-15
> > 0x0000000100000000-0x000000027fffffff    6G  online       yes   32-79
> > 0x0000000a90000000-0x0000000a9fffffff  256M offline           338-339
> > 
> > Memory block size:       128M
> > Total online memory:       8G
> > Total offline memory:    256M
> > 
> > 
> > 4.Online the momory with 'daxctl online-memory dax0.0' to online the memory
> > 
> > /home/fan/cxl/ndctl# ./build/daxctl/daxctl online-memory dax0.0
> > [  230.730553] Fallback order for Node 0: 0 1
> > [  230.730825] Fallback order for Node 1: 1 0
> > [  230.730953] Built 2 zonelists, mobility grouping on.  Total pages: 
> > 2042541
> > [  230.731110] Policy zone: Normal
> > onlined memory for 1 device
> > 
> > root@bgt-140510-bm03:/home/fan/cxl/ndctl# lsmem
> > RANGE                                  SIZE   STATE REMOVABLE BLOCK
> > 0x0000000000000000-0x000000007fffffff    2G  online       yes  0-15
> > 0x0000000100000000-0x000000027fffffff    6G  online       yes 32-79
> > 0x0000000a90000000-0x0000000a97ffffff  128M  online       yes   338
> > 0x0000000a98000000-0x0000000a9fffffff  128M offline             339
> > 
> > Memory block size:       128M
> > Total online memory:     8.1G
> > Total offline memory:    128M
> > 
> > 5 using dc extents as regular memory
> > 
> > /home/fan/cxl/ndctl# numactl --membind=1 ls
> > CONTRIBUTING.md  README.md  clean_config.sh  cscope.out   git-version-gen
> > ndctl              scripts  test.h      version.h.in COPYING                
> >  acpi.h
> > config.h.meson   cxl          make-git-snapshot.sh  ndctl.spec.in  sles     
> > tools
> > Documentation        build      contrib          daxctl       meson.build   
> >         rhel
> > tags        topology.png LICENSES    ccan       cscope.files
> > git-version  meson_options.txt      rpmbuild.sh    test     util
> > 
> > 
> > QEMU command line cxl configuration:
> > 
> > RP1="-object 
> > memory-backend-file,id=cxl-mem1,share=on,mem-path=/tmp/cxltest.raw,size=512M
> >  \
> > -object 
> > memory-backend-file,id=cxl-mem2,share=on,mem-path=/tmp/cxltest2.raw,size=512M
> >  \
> > -object 
> > memory-backend-file,id=cxl-lsa1,share=on,mem-path=/tmp/lsa.raw,size=512M \
> > -device pxb-cxl,bus_nr=12,bus=pcie.0,id=cxl.1 \
> > -device cxl-rp,port=0,bus=cxl.1,id=root_port13,chassis=0,slot=2 \
> > -device 
> > cxl-type3,bus=root_port13,memdev=cxl-mem1,lsa=cxl-lsa1,dc-memdev=cxl-mem2,id=cxl-pmem0,num-dc-regions=1\
> > -M 
> > cxl-fmw.0.targets.0=cxl.1,cxl-fmw.0.size=4G,cxl-fmw.0.interleave-granularity=8k"
> > 
> > 
> > Kernel DCD support used to test the changes
> > 
> > The code is tested with the posted kernel dcd support:
> > https://git.kernel.org/pub/scm/linux/kernel/git/cxl/cxl.git/log/?h=for-6.5/dcd-preview
> > 
> 
> Very nice!  +CC Navneet who may want to comment on the below (and the
> emulation as well)
> 
> I've not had a chance to look at the code on the kernel side yet.

Thanks Jonathan for all the comments for the series, will reflect them
in the next version.

Fan

> 
> 
> > commit: f425bc34c600e2a3721d6560202962ec41622815
> > 
> > To make the test work, we have made the following changes to the above 
> > kernel commit:
> > 
> > diff --git a/drivers/cxl/core/mbox.c b/drivers/cxl/core/mbox.c
> > index 5f04bbc18af5..5f421d3c5cef 100644
> > --- a/drivers/cxl/core/mbox.c
> > +++ b/drivers/cxl/core/mbox.c
> > @@ -68,6 +68,7 @@ static struct cxl_mem_command 
> > cxl_mem_commands[CXL_MEM_COMMAND_ID_MAX] = {
> >     CXL_CMD(SCAN_MEDIA, 0x11, 0, 0),
> >     CXL_CMD(GET_SCAN_MEDIA, 0, CXL_VARIABLE_PAYLOAD, 0),
> >     CXL_CMD(GET_DC_EXTENT_LIST, 0x8, CXL_VARIABLE_PAYLOAD, 0),
> > +   CXL_CMD(GET_DC_CONFIG, 0x2, CXL_VARIABLE_PAYLOAD, 0),
> >  };
> >  
> >  /*
> > diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
> > index 291c716abd49..ae10e3cf43a1 100644
> > --- a/drivers/cxl/core/region.c
> > +++ b/drivers/cxl/core/region.c
> > @@ -194,7 +194,7 @@ static int cxl_region_manage_dc(struct cxl_region *cxlr)
> >             }
> >             cxlds->dc_list_gen_num = extent_gen_num;
> >             dev_dbg(cxlds->dev, "No of preallocated extents :%d\n", rc);
> > -           enable_irq(cxlds->cxl_irq[CXL_EVENT_TYPE_DCD]);
> > +           /*enable_irq(cxlds->cxl_irq[CXL_EVENT_TYPE_DCD]);*/
> 
> Some race condition that means we need to enable the DCD event earlier?
> 
> >     }
> >     return 0;
> >  err:
> > @@ -2810,7 +2810,8 @@ int cxl_add_dc_extent(struct cxl_dev_state *cxlds, 
> > struct resource *alloc_dpa_re
> >                             dev_dax->align, memremap_compat_align()))) {
> >             rc = alloc_dev_dax_range(dev_dax, hpa,
> >                                     resource_size(alloc_dpa_res));
> > -           return rc;
> > +           if (rc)
> > +                   return rc;
> 
> No idea on this one as it's in the code I haven't looked at yet!
> 
> >     }
> >  
> >     rc = xa_insert(&cxlr_dc->dax_dev_list, hpa, dev_dax, GFP_KERNEL);
> > diff --git a/drivers/cxl/pci.c b/drivers/cxl/pci.c
> > index 9e45b1056022..653bec203838 100644
> > --- a/drivers/cxl/pci.c
> > +++ b/drivers/cxl/pci.c
> > @@ -659,7 +659,7 @@ static int cxl_event_irqsetup(struct cxl_dev_state 
> > *cxlds)
> >  
> >     /* Driver enables DCD interrupt after creating the dc cxl_region */
> >     rc = cxl_event_req_irq(cxlds, policy.dyncap_settings, 
> > CXL_EVENT_TYPE_DCD,
> > -                                   IRQF_SHARED | IRQF_ONESHOT | 
> > IRQF_NO_AUTOEN);
> > +                                   IRQF_SHARED | IRQF_ONESHOT);
> 
> This will be otherside of the removal of the enable above.
> 
> >     if (rc) {
> >             dev_err(cxlds->dev, "Failed to get interrupt for event dc 
> > log\n");
> >             return rc;
> > diff --git a/include/uapi/linux/cxl_mem.h b/include/uapi/linux/cxl_mem.h
> > index 6ca85861750c..910a48259239 100644
> > --- a/include/uapi/linux/cxl_mem.h
> > +++ b/include/uapi/linux/cxl_mem.h
> > @@ -47,6 +47,7 @@
> >     ___C(SCAN_MEDIA, "Scan Media"),                                   \
> >     ___C(GET_SCAN_MEDIA, "Get Scan Media Results"),                   \
> >     ___C(GET_DC_EXTENT_LIST, "Get dynamic capacity extents"),         \
> > +   ___C(GET_DC_CONFIG, "Get dynamic capacity configuration"),         \
> >     ___C(MAX, "invalid / last command")
> >  
> >  #define ___C(a, b) CXL_MEM_COMMAND_ID_##a
> > 
> > 
> > 
> > Fan Ni (7):
> >   hw/cxl/cxl-mailbox-utils: Add dc_event_log_size field to output
> >     payload of identify memory device command
> >   hw/cxl/cxl-mailbox-utils: Add dynamic capacity region representative
> >     and mailbox command support
> >   hw/mem/cxl_type3: Add a parameter to pass number of DC regions the
> >     device supports in qemu command line
> >   hw/mem/cxl_type3: Add DC extent representative to cxl type3 device
> >   hw/cxl/cxl-mailbox-utils: Add mailbox commands to support add/release
> >     dynamic capacity response
> >   Add qmp interfaces to add/release dynamic capacity extents
> >   hw/mem/cxl_type3: add read/write support to dynamic capacity
> > 
> >  hw/cxl/cxl-mailbox-utils.c  | 389 +++++++++++++++++++++++++++-
> >  hw/mem/cxl_type3.c          | 492 +++++++++++++++++++++++++++++++-----
> >  include/hw/cxl/cxl_device.h |  50 +++-
> >  include/hw/cxl/cxl_events.h |  16 ++
> >  qapi/cxl.json               |  44 ++++
> >  5 files changed, 924 insertions(+), 67 deletions(-)
> > 
> 

-- 
Fan Ni <nifan@outlook.com>