I recently upgraded my virtual machines hosting server from Ivy-Bridge Xeons to EPYC 7003 (more specifically, dual 7413) and was surprised to find that my motherboard Supermicro H12DSi-N6 does not support AVIC CPU feature. More specifically, it is not listed in the CPU flags. This means that AVIC cannot be enabled in virtual machines relying on IOMMU, which means increased interrupt handling overhead and latency.
# dmidecode | grep -A3 "Base Board Information"
Base Board Information
Manufacturer: Supermicro
Product Name: H12DSi-N6
Version: 1.02
# lscpu | cat
Architecture: x86_64
CPU op-mode(s): 32-bit, 64-bit
Address sizes: 48 bits physical, 48 bits virtual
Byte Order: Little Endian
CPU(s): 96
On-line CPU(s) list: 0-95
Vendor ID: AuthenticAMD
BIOS Vendor ID: Advanced Micro Devices, Inc.
Model name: AMD EPYC 7413 24-Core Processor
BIOS Model name: AMD EPYC 7413 24-Core Processor
CPU family: 25
Model: 1
Thread(s) per core: 2
Core(s) per socket: 24
Socket(s): 2
Stepping: 1
Frequency boost: enabled
CPU max MHz: 3630.8101
CPU min MHz: 1500.0000
BogoMIPS: 5300.34
Flags: fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 ht syscall nx mmxext fxsr_opt pdpe1gb rdtscp lm constant_tsc rep_good nopl nonstop_tsc cpuid extd_apicid aperfmperf rapl pni pclmulqdq monitor ssse3 fma cx16 pcid sse4_1 sse4_2 movbe popcnt aes xsave avx f16c rdrand lahf_lm cmp_legacy svm extapic cr8_legacy abm sse4a misalignsse 3dnowprefetch osvw ibs skinit wdt tce topoext perfctr_core perfctr_nb bpext perfctr_llc mwaitx cpb cat_l3 cdp_l3 invpcid_single hw_pstate ssbd mba ibrs ibpb stibp vmmcall fsgsbase bmi1 avx2 smep bmi2 invpcid cqm rdt_a rdseed adx smap clflushopt clwb sha_ni xsaveopt xsavec xgetbv1 xsaves cqm_llc cqm_occup_llc cqm_mbm_total cqm_mbm_local clzero irperf xsaveerptr rdpru wbnoinvd amd_ppin arat npt lbrv svm_lock nrip_save tsc_scale vmcb_clean flushbyasid decodeassists pausefilter pfthreshold v_vmsave_vmload vgif v_spec_ctrl umip pku ospke vaes vpclmulqdq rdpid overflow_recov succor smca
Virtualization: AMD-V
L1d cache: 1.5 MiB (48 instances)
L1i cache: 1.5 MiB (48 instances)
L2 cache: 24 MiB (48 instances)
L3 cache: 256 MiB (8 instances)
NUMA node(s): 2
NUMA node0 CPU(s): 0-23,48-71
NUMA node1 CPU(s): 24-47,72-95
Vulnerability Itlb multihit: Not affected
Vulnerability L1tf: Not affected
Vulnerability Mds: Not affected
Vulnerability Meltdown: Not affected
Vulnerability Spec store bypass: Mitigation; Speculative Store Bypass disabled via prctl and seccomp
Vulnerability Spectre v1: Mitigation; usercopy/swapgs barriers and __user pointer sanitization
Vulnerability Spectre v2: Mitigation; Retpolines, IBPB conditional, IBRS_FW, STIBP always-on, RSB filling
Vulnerability Srbds: Not affected
Vulnerability Tsx async abort: Not affected
# lscpu | grep avic
1 #
After I asked Supermicro support, I was told that:
I checked with the team and we do not have AVIC implemented.
This was surprising. Since I also have an Asrock ROMED8-2T I checked this motherboard too, and found that AVIC is not available on this motherboard either (I tested with EPYC 7443P CPU).
I would like to understand what's going on? I have found on https://www.amd.com/system/files/TechDocs/56683-PUB_1.04.pdf that AVIC will not be available if Secure Nested Pages is enabled (errata 1278) but I was very careful to keep this feature disabled in the motherboard BIOS options (it is disabled by default). If I switch my VM-hosting server to a different motherboard e.g. Gigabyte MZ72-HB0 rev 3.0 , will AVIC feature work, or is it something that just does not work on EPYC 7003 CPUs ? And if it works, what motherboard should I use ?
