On Wed, 02 Mar 2022 07:55:45 +0100
Markus Armbruster <arm...@redhat.com> wrote:
> Jonathan Cameron via <qemu-devel@nongnu.org> writes:
>
> > From: Jonathan Cameron <jonathan.came...@huawei.com>
> >
> > The concept of these is introduced in [1] in terms of the
> > description the CEDT ACPI table. The principal is more general.
> > Unlike once traffic hits the CXL root bridges, the host system
> > memory address routing is implementation defined and effectively
> > static once observable by standard / generic system software.
> > Each CXL Fixed Memory Windows (CFMW) is a region of PA space
> > which has fixed system dependent routing configured so that
> > accesses can be routed to the CXL devices below a set of target
> > root bridges. The accesses may be interleaved across multiple
> > root bridges.
> >
> > For QEMU we could have fully specified these regions in terms
> > of a base PA + size, but as the absolute address does not matter
> > it is simpler to let individual platforms place the memory regions.
> >
> > ExampleS:
> > -cxl-fixed-memory-window targets=cxl.0,size=128G
> > -cxl-fixed-memory-window targets=cxl.1,size=128G
> > -cxl-fixed-memory-window
> > targets=cxl0,targets=cxl.1,size=256G,interleave-granularity=2k
> >
> > Specifies
> > * 2x 128G regions not interleaved across root bridges, one for each of
> > the root bridges with ids cxl.0 and cxl.1
> > * 256G region interleaved across root bridges with ids cxl.0 and cxl.1
> > with a 2k interleave granularity.
> >
> > When system software enumerates the devices below a given root bridge
> > it can then decide which CFMW to use. If non interleave is desired
> > (or possible) it can use the appropriate CFMW for the root bridge in
> > question. If there are suitable devices to interleave across the
> > two root bridges then it may use the 3rd CFMS.
> >
> > A number of other designs were considered but the following constraints
> > made it hard to adapt existing QEMU approaches to this particular problem.
> > 1) The size must be known before a specific architecture / board brings
> > up it's PA memory map. We need to set up an appropriate region.
> > 2) Using links to the host bridges provides a clean command line interface
> > but these links cannot be established until command line devices have
> > been added.
> >
> > Hence the two step process used here of first establishing the size,
> > interleave-ways and granularity + caching the ids of the host bridges
> > and then, once available finding the actual host bridges so they can
> > be used later to support interleave decoding.
> >
> > [1] CXL 2.0 ECN: CEDT CFMWS & QTG DSM (computeexpresslink.org /
> > specifications)
> >
> > Signed-off-by: Jonathan Cameron <jonathan.came...@huawei.com>
>
> [...]
>
> > diff --git a/hw/cxl/cxl-host.c b/hw/cxl/cxl-host.c
> > new file mode 100644
> > index 0000000000..9f303e6d8e
> > --- /dev/null
> > +++ b/hw/cxl/cxl-host.c
>
> [...]
>
> > +QemuOptsList qemu_cxl_fixed_window_opts = {
> > + .name = "cxl-fixed-memory-window",
> > + .implied_opt_name = "type",
> > + .head = QTAILQ_HEAD_INITIALIZER(qemu_cxl_fixed_window_opts.head),
> > + .desc = { { 0 } }
> > +};
> > +
>
> [...]
>
> > +static int parse_cxl_fixed_memory_window(void *opaque, QemuOpts *opts,
> > + Error **errp)
> > +{
> > + CXLFixedMemoryWindowOptions *object = NULL;
> > + MachineState *ms = MACHINE(opaque);
> > + Error *err = NULL;
> > + Visitor *v = opts_visitor_new(opts);
> > +
> > + visit_type_CXLFixedMemoryWindowOptions(v, NULL, &object, errp);
> > + visit_free(v);
> > + if (!object) {
> > + return -1;
> > + }
> > +
> > + set_cxl_fixed_memory_window_options(ms, object, &err);
> > +
> > + qapi_free_CXLFixedMemoryWindowOptions(object);
> > + if (err) {
> > + error_propagate(errp, err);
> > + return -1;
> > + }
> > +
> > + return 0;
> > +}
> > +
> > +void parse_cxl_fixed_memory_window_opts(MachineState *ms)
> > +{
> > + qemu_opts_foreach(qemu_find_opts("cxl-fixed-memory-window"),
> > + parse_cxl_fixed_memory_window, ms, &error_fatal);
> > +}
>
> [...]
>
> > diff --git a/qapi/machine.json b/qapi/machine.json
> > index 42fc68403d..0998a9128d 100644
> > --- a/qapi/machine.json
> > +++ b/qapi/machine.json
> > @@ -504,6 +504,21 @@
> > 'dst': 'uint16',
> > 'val': 'uint8' }}
> >
> > +##
> > +# @CXLFixedMemoryWindowOptions:
> > +#
> > +# Create a CXL Fixed Memory Window (for OptsVisitor)
> > +#
> > +# @targets: Target root bridge IDs
>
> Missing: @size, @targets.
>
> > +#
> > +# Since X.X //fixme
>
> Well, "fix me, please".
>
> > +##
> > +{ 'struct': 'CXLFixedMemoryWindowOptions',
> > + 'data': {
> > + 'size': 'size',
> > + '*interleave-granularity': 'size',
> > + 'targets': ['str'] }}
> > +
> > ##
> > # @X86CPURegister32:
> > #
>
> [...]
>
> > diff --git a/qemu-options.hx b/qemu-options.hx
> > index ba3ae6a42a..b4d2cc6f48 100644
> > --- a/qemu-options.hx
> > +++ b/qemu-options.hx
> > @@ -467,6 +467,43 @@ SRST
> > -numa
> > hmat-cache,node-id=1,size=10K,level=1,associativity=direct,policy=write-back,line=8
> > ERST
> >
> > +DEF("cxl-fixed-memory-window", HAS_ARG,
> > QEMU_OPTION_cxl_fixed_memory_window,
> > + "-cxl-fixed-memory-window
> > targets=firsttarget,targets=secondtarget,size=size[,interleave-granularity=granularity]\n",
> > + QEMU_ARCH_ALL)
> > +SRST
> > +``-cxl-fixed-memory-window
> > targets=firsttarget,targets=secondtarget,size=size[,interleave-granularity=granularity]``
> > + Define a CXL Fixed Memory Window (CFMW).
> > +
> > + Described in the CXL 2.0 ECN: CEDT CFMWS & QTG _DSM.
> > +
> > + They are regions of Host Physical Addresses (HPA) on a system which
> > + may be interleaved across one or more CXL host bridges. The system
> > + software will assign particular devices into these windows and
> > + configure the downstream Host-managed Device Memory (HDM) decoders
> > + in root ports, switch ports and devices appropriately to meet the
> > + interleave requirements before enabling the memory devices.
> > +
> > + ``targets=firsttarget`` provides the mapping to CXL host bridges
> > + which may be identified by the id provied in the -device entry.
> > + Multiple entries are needed to specify all the targets when
> > + the fixed memory window represents interleaved memory.
> > +
> > + ``size=size`` sets the size of the CFMW. This must be a multiple of
> > + 256MiB. The region will be aligned to 256MiB but the location is
> > + platform and configuration dependent.
> > +
> > + ``interleave-granularity=granularity`` sets the granularity of
> > + interleave. Default 256KiB. Only 256KiB, 512KiB, 1024KiB, 2048KiB
> > + 4096KiB, 8192KiB and 16384KiB granularities supported.
> > +
> > + Example:
> > +
> > + ::
> > +
> > + -cxl-fixed-memory-window
> > -targets=cxl.0,-targets=cxl.1,size=128G,interleave-granularity=512k
> > +
> > +ERST
> > +
> > DEF("add-fd", HAS_ARG, QEMU_OPTION_add_fd,
> > "-add-fd fd=fd,set=set[,opaque=opaque]\n"
> > " Add 'fd' to fd 'set'\n", QEMU_ARCH_ALL)
> > diff --git a/softmmu/vl.c b/softmmu/vl.c
> > index 5e1b35ba48..f83f158fff 100644
> > --- a/softmmu/vl.c
> > +++ b/softmmu/vl.c
> > @@ -91,6 +91,7 @@
> > #include "qemu/config-file.h"
> > #include "qemu/qemu-options.h"
> > #include "qemu/main-loop.h"
> > +#include "hw/cxl/cxl.h"
> > #ifdef CONFIG_VIRTFS
> > #include "fsdev/qemu-fsdev.h"
> > #endif
> > @@ -2744,6 +2745,7 @@ void qmp_x_exit_preconfig(Error **errp)
> >
> > qemu_init_board();
> > qemu_create_cli_devices();
> > + cxl_fixed_memory_window_link_targets(errp);
> > qemu_machine_creation_done();
> >
> > if (loadvm) {
> > @@ -2805,6 +2807,7 @@ void qemu_init(int argc, char **argv, char **envp)
> > qemu_add_opts(&qemu_msg_opts);
> > qemu_add_opts(&qemu_name_opts);
> > qemu_add_opts(&qemu_numa_opts);
> > + qemu_add_opts(&qemu_cxl_fixed_window_opts);
> > qemu_add_opts(&qemu_icount_opts);
> > qemu_add_opts(&qemu_semihosting_config_opts);
> > qemu_add_opts(&qemu_fw_cfg_opts);
> > @@ -2927,6 +2930,13 @@ void qemu_init(int argc, char **argv, char **envp)
> > exit(1);
> > }
> > break;
> > + case QEMU_OPTION_cxl_fixed_memory_window:
> > + opts =
> > qemu_opts_parse_noisily(qemu_find_opts("cxl-fixed-memory-window"),
> > + optarg, true);
> > + if (!opts) {
> > + exit(1);
> > + }
> > + break;
> > case QEMU_OPTION_display:
> > parse_display(optarg);
> > break;
> > @@ -3764,6 +3774,7 @@ void qemu_init(int argc, char **argv, char **envp)
> >
> > qemu_resolve_machine_memdev();
> > parse_numa_opts(current_machine);
> > + parse_cxl_fixed_memory_window_opts(current_machine);
> >
> > if (vmstate_dump_file) {
> > /* dump and exit */
>
> Have you considered using qobject_input_visitor_new_str() instead of
> QemuOpts?
>
Umm. No. Why might that be a better approach?
Thanks,
Jonathan
