| Message ID | 20240108082727.420817-1-zhao1.liu@linux.intel.com (mailing list archive) |
|---|---|
| Headers | show |
| Series | Support smp.clusters for x86 in QEMU | expand |
Hi Zhao, Ran few basic tests on AMD systems. Changes look good. Thanks Babu Tested-by: Babu Moger <babu.moger@amd.com> On 1/8/24 02:27, Zhao Liu wrote: > From: Zhao Liu <zhao1.liu@intel.com> > > Hi list, > > This is the our v7 patch series, rebased on the master branch at the > commit d328fef93ae7 ("Merge tag 'pull-20231230' of > https://gitlab.com/rth7680/qemu into staging"). > > No more change since v6 [1] exclude the comment nit update. > > Welcome your comments! > > > PS: Since v5, we have dropped "x-l2-cache-topo" option and now are > working on porting the original x-l2-cache-topo option to smp [2]. > Just like: > > -smp cpus=4,sockets=2,cores=2,threads=1, \ > l3-cache=socket,l2-cache=core,l1-i-cache=core,l1-d-cache=core > > The cache topology enhancement in this patch set is the preparation for > supporting future user-configurable cache topology (via generic cli > interface). > > > --- > # Introduction > > This series adds the cluster support for x86 PC machine, which allows > x86 can use smp.clusters to configure the module level CPU topology > of x86. > > This series also is the preparation to help x86 to define the more > flexible cache topology, such as having multiple cores share the > same L2 cache at cluster level. (That was what x-l2-cache-topo did, > and we will explore a generic way.) > > About why we don't share L2 cache at cluster and need a configuration > way, pls see section: ## Why not share L2 cache in cluster directly. > > > # Background > > The "clusters" parameter in "smp" is introduced by ARM [3], but x86 > hasn't supported it. > > At present, x86 defaults L2 cache is shared in one core, but this is > not enough. There're some platforms that multiple cores share the > same L2 cache, e.g., Alder Lake-P shares L2 cache for one module of > Atom cores [4], that is, every four Atom cores shares one L2 cache. > Therefore, we need the new CPU topology level (cluster/module). > > Another reason is for hybrid architecture. cluster support not only > provides another level of topology definition in x86, but would also > provide required code change for future our hybrid topology support. > > > # Overview > > ## Introduction of module level for x86 > > "cluster" in smp is the CPU topology level which is between "core" and > die. > > For x86, the "cluster" in smp is corresponding to the module level [4], > which is above the core level. So use the "module" other than "cluster" > in x86 code. > > And please note that x86 already has a cpu topology level also named > "cluster" [5], this level is at the upper level of the package. Here, > the cluster in x86 cpu topology is completely different from the > "clusters" as the smp parameter. After the module level is introduced, > the cluster as the smp parameter will actually refer to the module level > of x86. > > > ## Why not share L2 cache in cluster directly > > Though "clusters" was introduced to help define L2 cache topology > [3], using cluster to define x86's L2 cache topology will cause the > compatibility problem: > > Currently, x86 defaults that the L2 cache is shared in one core, which > actually implies a default setting "cores per L2 cache is 1" and > therefore implicitly defaults to having as many L2 caches as cores. > > For example (i386 PC machine): > -smp 16,sockets=2,dies=2,cores=2,threads=2,maxcpus=16 (*) > > Considering the topology of the L2 cache, this (*) implicitly means "1 > core per L2 cache" and "2 L2 caches per die". > > If we use cluster to configure L2 cache topology with the new default > setting "clusters per L2 cache is 1", the above semantics will change > to "2 cores per cluster" and "1 cluster per L2 cache", that is, "2 > cores per L2 cache". > > So the same command (*) will cause changes in the L2 cache topology, > further affecting the performance of the virtual machine. > > Therefore, x86 should only treat cluster as a cpu topology level and > avoid using it to change L2 cache by default for compatibility. > > > ## module level in CPUID > > Linux kernel (from v6.4, with commit edc0a2b595765 ("x86/topology: Fix > erroneous smp_num_siblings on Intel Hybrid platforms") is able to > handle platforms with Module level enumerated via CPUID.1F. > > Expose the module level in CPUID[0x1F] (for Intel CPUs) if the machine > has more than 1 modules since v3. > > > ## New cache topology info in CPUCacheInfo > > (This is in preparation for users being able to configure cache topology > from the cli later on.) > > Currently, by default, the cache topology is encoded as: > 1. i/d cache is shared in one core. > 2. L2 cache is shared in one core. > 3. L3 cache is shared in one die. > > This default general setting has caused a misunderstanding, that is, the > cache topology is completely equated with a specific cpu topology, such > as the connection between L2 cache and core level, and the connection > between L3 cache and die level. > > In fact, the settings of these topologies depend on the specific > platform and are not static. For example, on Alder Lake-P, every > four Atom cores share the same L2 cache [3]. > > Thus, in this patch set, we explicitly define the corresponding cache > topology for different cpu models and this has two benefits: > 1. Easy to expand to new CPU models in the future, which has different > cache topology. > 2. It can easily support custom cache topology by some command. > > > # Patch description > > patch 1 Fixes about x86 topology and Intel l1 cache topology. > > patch 2-3 Cleanups about topology related CPUID encoding and QEMU > topology variables. > > patch 4-5 Refactor CPUID[0x1F] encoding to prepare to introduce module > level. > > patch 6-12 Add the module as the new CPU topology level in x86, and it > is corresponding to the cluster level in generic code. > > patch 13,14,16 Add cache topology information in cache models. > > patch 15 Update AMD CPUs' cache topology encoding. > > > [1]: https://lore.kernel.org/qemu-devel/20231117075106.432499-1-zhao1.liu@linux.intel.com/ > [2]: https://lists.gnu.org/archive/html/qemu-devel/2023-10/msg01954.html > [3]: https://patchew.org/QEMU/20211228092221.21068-1-wangyanan55@huawei.com/ > [4]: https://www.intel.com/content/www/us/en/products/platforms/details/alder-lake-p.html > [5]: SDM, vol.3, ch.9, 9.9.1 Hierarchical Mapping of Shared Resources. > > Best Regards, > Zhao > --- > Changelog: > > Changes since v6: > * Update the comment when check cluster-id. Since there's no > v8.2, the cluster-id support should at least start from v9.0. > * Rebase on commit d328fef93ae7 ("Merge tag 'pull-20231230' of > https://gitlab.com/rth7680/qemu into staging"). > > Changes since v5: > * The first four patches of v5 [1] have been merged, v6 contains > the remaining patches. > * Reabse on the latest master. > * Update the comment when check cluster-id. Since current QEMU is > v8.2, the cluster-id support should at least start from v8.3. > > Changes since v4: > * Drop the "x-l2-cache-topo" option. (Michael) > * Add A/R/T tags. > > Changes since v3 (main changes): > * Expose module level in CPUID[0x1F]. > * Fix compile warnings. (Babu) > * Fixes cache topology uninitialization bugs for some AMD CPUs. (Babu) > > Changes since v2: > * Add "Tested-by", "Reviewed-by" and "ACKed-by" tags. > * Use newly added wrapped helper to get cores per socket in > qemu_init_vcpu(). > > Changes since v1: > * Reordered patches. (Yanan) > * Deprecated the patch to fix comment of machine_parse_smp_config(). > (Yanan) > * Rename test-x86-cpuid.c to test-x86-topo.c. (Yanan) > * Split the intel's l1 cache topology fix into a new separate patch. > (Yanan) > * Combined module_id and APIC ID for module level support into one > patch. (Yanan) > * Make cache_into_passthrough case of cpuid 0x04 leaf in > * cpu_x86_cpuid() use max_processor_ids_for_cache() and > max_core_ids_in_package() to encode CPUID[4]. (Yanan) > * Add the prefix "CPU_TOPO_LEVEL_*" for CPU topology level names. > (Yanan) > > --- > Zhao Liu (10): > i386/cpu: Fix i/d-cache topology to core level for Intel CPU > i386/cpu: Use APIC ID offset to encode cache topo in CPUID[4] > i386/cpu: Consolidate the use of topo_info in cpu_x86_cpuid() > i386: Split topology types of CPUID[0x1F] from the definitions of > CPUID[0xB] > i386: Decouple CPUID[0x1F] subleaf with specific topology level > i386: Expose module level in CPUID[0x1F] > i386: Add cache topology info in CPUCacheInfo > i386: Use CPUCacheInfo.share_level to encode CPUID[4] > i386: Use offsets get NumSharingCache for CPUID[0x8000001D].EAX[bits > 25:14] > i386: Use CPUCacheInfo.share_level to encode > CPUID[0x8000001D].EAX[bits 25:14] > > Zhuocheng Ding (6): > i386: Introduce module-level cpu topology to CPUX86State > i386: Support modules_per_die in X86CPUTopoInfo > i386: Support module_id in X86CPUTopoIDs > i386/cpu: Introduce cluster-id to X86CPU > tests: Add test case of APIC ID for module level parsing > hw/i386/pc: Support smp.clusters for x86 PC machine > > hw/i386/pc.c | 1 + > hw/i386/x86.c | 49 ++++++- > include/hw/i386/topology.h | 35 ++++- > qemu-options.hx | 10 +- > target/i386/cpu.c | 289 +++++++++++++++++++++++++++++-------- > target/i386/cpu.h | 43 +++++- > target/i386/kvm/kvm.c | 2 +- > tests/unit/test-x86-topo.c | 56 ++++--- > 8 files changed, 379 insertions(+), 106 deletions(-) >
Hi Babu, On Mon, Jan 08, 2024 at 11:46:50AM -0600, Moger, Babu wrote: > Date: Mon, 8 Jan 2024 11:46:50 -0600 > From: "Moger, Babu" <babu.moger@amd.com> > Subject: Re: [PATCH v7 00/16] Support smp.clusters for x86 in QEMU > > Hi Zhao, > > Ran few basic tests on AMD systems. Changes look good. > > Thanks > Babu > > > Tested-by: Babu Moger <babu.moger@amd.com> > Thanks much for your test! Regards, Zhao
From: Zhao Liu <zhao1.liu@intel.com> Hi list, This is the our v7 patch series, rebased on the master branch at the commit d328fef93ae7 ("Merge tag 'pull-20231230' of https://gitlab.com/rth7680/qemu into staging"). No more change since v6 [1] exclude the comment nit update. Welcome your comments! PS: Since v5, we have dropped "x-l2-cache-topo" option and now are working on porting the original x-l2-cache-topo option to smp [2]. Just like: -smp cpus=4,sockets=2,cores=2,threads=1, \ l3-cache=socket,l2-cache=core,l1-i-cache=core,l1-d-cache=core The cache topology enhancement in this patch set is the preparation for supporting future user-configurable cache topology (via generic cli interface). --- # Introduction This series adds the cluster support for x86 PC machine, which allows x86 can use smp.clusters to configure the module level CPU topology of x86. This series also is the preparation to help x86 to define the more flexible cache topology, such as having multiple cores share the same L2 cache at cluster level. (That was what x-l2-cache-topo did, and we will explore a generic way.) About why we don't share L2 cache at cluster and need a configuration way, pls see section: ## Why not share L2 cache in cluster directly. # Background The "clusters" parameter in "smp" is introduced by ARM [3], but x86 hasn't supported it. At present, x86 defaults L2 cache is shared in one core, but this is not enough. There're some platforms that multiple cores share the same L2 cache, e.g., Alder Lake-P shares L2 cache for one module of Atom cores [4], that is, every four Atom cores shares one L2 cache. Therefore, we need the new CPU topology level (cluster/module). Another reason is for hybrid architecture. cluster support not only provides another level of topology definition in x86, but would also provide required code change for future our hybrid topology support. # Overview ## Introduction of module level for x86 "cluster" in smp is the CPU topology level which is between "core" and die. For x86, the "cluster" in smp is corresponding to the module level [4], which is above the core level. So use the "module" other than "cluster" in x86 code. And please note that x86 already has a cpu topology level also named "cluster" [5], this level is at the upper level of the package. Here, the cluster in x86 cpu topology is completely different from the "clusters" as the smp parameter. After the module level is introduced, the cluster as the smp parameter will actually refer to the module level of x86. ## Why not share L2 cache in cluster directly Though "clusters" was introduced to help define L2 cache topology [3], using cluster to define x86's L2 cache topology will cause the compatibility problem: Currently, x86 defaults that the L2 cache is shared in one core, which actually implies a default setting "cores per L2 cache is 1" and therefore implicitly defaults to having as many L2 caches as cores. For example (i386 PC machine): -smp 16,sockets=2,dies=2,cores=2,threads=2,maxcpus=16 (*) Considering the topology of the L2 cache, this (*) implicitly means "1 core per L2 cache" and "2 L2 caches per die". If we use cluster to configure L2 cache topology with the new default setting "clusters per L2 cache is 1", the above semantics will change to "2 cores per cluster" and "1 cluster per L2 cache", that is, "2 cores per L2 cache". So the same command (*) will cause changes in the L2 cache topology, further affecting the performance of the virtual machine. Therefore, x86 should only treat cluster as a cpu topology level and avoid using it to change L2 cache by default for compatibility. ## module level in CPUID Linux kernel (from v6.4, with commit edc0a2b595765 ("x86/topology: Fix erroneous smp_num_siblings on Intel Hybrid platforms") is able to handle platforms with Module level enumerated via CPUID.1F. Expose the module level in CPUID[0x1F] (for Intel CPUs) if the machine has more than 1 modules since v3. ## New cache topology info in CPUCacheInfo (This is in preparation for users being able to configure cache topology from the cli later on.) Currently, by default, the cache topology is encoded as: 1. i/d cache is shared in one core. 2. L2 cache is shared in one core. 3. L3 cache is shared in one die. This default general setting has caused a misunderstanding, that is, the cache topology is completely equated with a specific cpu topology, such as the connection between L2 cache and core level, and the connection between L3 cache and die level. In fact, the settings of these topologies depend on the specific platform and are not static. For example, on Alder Lake-P, every four Atom cores share the same L2 cache [3]. Thus, in this patch set, we explicitly define the corresponding cache topology for different cpu models and this has two benefits: 1. Easy to expand to new CPU models in the future, which has different cache topology. 2. It can easily support custom cache topology by some command. # Patch description patch 1 Fixes about x86 topology and Intel l1 cache topology. patch 2-3 Cleanups about topology related CPUID encoding and QEMU topology variables. patch 4-5 Refactor CPUID[0x1F] encoding to prepare to introduce module level. patch 6-12 Add the module as the new CPU topology level in x86, and it is corresponding to the cluster level in generic code. patch 13,14,16 Add cache topology information in cache models. patch 15 Update AMD CPUs' cache topology encoding. [1]: https://lore.kernel.org/qemu-devel/20231117075106.432499-1-zhao1.liu@linux.intel.com/ [2]: https://lists.gnu.org/archive/html/qemu-devel/2023-10/msg01954.html [3]: https://patchew.org/QEMU/20211228092221.21068-1-wangyanan55@huawei.com/ [4]: https://www.intel.com/content/www/us/en/products/platforms/details/alder-lake-p.html [5]: SDM, vol.3, ch.9, 9.9.1 Hierarchical Mapping of Shared Resources. Best Regards, Zhao --- Changelog: Changes since v6: * Update the comment when check cluster-id. Since there's no v8.2, the cluster-id support should at least start from v9.0. * Rebase on commit d328fef93ae7 ("Merge tag 'pull-20231230' of https://gitlab.com/rth7680/qemu into staging"). Changes since v5: * The first four patches of v5 [1] have been merged, v6 contains the remaining patches. * Reabse on the latest master. * Update the comment when check cluster-id. Since current QEMU is v8.2, the cluster-id support should at least start from v8.3. Changes since v4: * Drop the "x-l2-cache-topo" option. (Michael) * Add A/R/T tags. Changes since v3 (main changes): * Expose module level in CPUID[0x1F]. * Fix compile warnings. (Babu) * Fixes cache topology uninitialization bugs for some AMD CPUs. (Babu) Changes since v2: * Add "Tested-by", "Reviewed-by" and "ACKed-by" tags. * Use newly added wrapped helper to get cores per socket in qemu_init_vcpu(). Changes since v1: * Reordered patches. (Yanan) * Deprecated the patch to fix comment of machine_parse_smp_config(). (Yanan) * Rename test-x86-cpuid.c to test-x86-topo.c. (Yanan) * Split the intel's l1 cache topology fix into a new separate patch. (Yanan) * Combined module_id and APIC ID for module level support into one patch. (Yanan) * Make cache_into_passthrough case of cpuid 0x04 leaf in * cpu_x86_cpuid() use max_processor_ids_for_cache() and max_core_ids_in_package() to encode CPUID[4]. (Yanan) * Add the prefix "CPU_TOPO_LEVEL_*" for CPU topology level names. (Yanan) --- Zhao Liu (10): i386/cpu: Fix i/d-cache topology to core level for Intel CPU i386/cpu: Use APIC ID offset to encode cache topo in CPUID[4] i386/cpu: Consolidate the use of topo_info in cpu_x86_cpuid() i386: Split topology types of CPUID[0x1F] from the definitions of CPUID[0xB] i386: Decouple CPUID[0x1F] subleaf with specific topology level i386: Expose module level in CPUID[0x1F] i386: Add cache topology info in CPUCacheInfo i386: Use CPUCacheInfo.share_level to encode CPUID[4] i386: Use offsets get NumSharingCache for CPUID[0x8000001D].EAX[bits 25:14] i386: Use CPUCacheInfo.share_level to encode CPUID[0x8000001D].EAX[bits 25:14] Zhuocheng Ding (6): i386: Introduce module-level cpu topology to CPUX86State i386: Support modules_per_die in X86CPUTopoInfo i386: Support module_id in X86CPUTopoIDs i386/cpu: Introduce cluster-id to X86CPU tests: Add test case of APIC ID for module level parsing hw/i386/pc: Support smp.clusters for x86 PC machine hw/i386/pc.c | 1 + hw/i386/x86.c | 49 ++++++- include/hw/i386/topology.h | 35 ++++- qemu-options.hx | 10 +- target/i386/cpu.c | 289 +++++++++++++++++++++++++++++-------- target/i386/cpu.h | 43 +++++- target/i386/kvm/kvm.c | 2 +- tests/unit/test-x86-topo.c | 56 ++++--- 8 files changed, 379 insertions(+), 106 deletions(-)