On a Thursday in 2024, Jiri Denemark wrote:
When starting a domain we check whether the guest CPU definition is compatible with the host (i.e., when the host supports all features required both explicitly and by the specified CPU model) as long as check == 'partial', which is the default. We are doing so by checking our definition of the CPU model in the CPU map amending it with explicitly mentioned features and comparing it to features QEMU would enabled when started with -cpu host. But since our CPU model definitions often slightly differ from QEMU we may be checking features which are not actually needed and on the other hand not checking something that is part of the CPU model in QEMU. This patch changes the algorithm for CPU models added in the future (changing it for existing models could cause them to suddenly become incompatible with the host and domains using them would fail to start). The new algorithm uses information we probe from QEMU about features that block each model from being directly usable. If all those features are explicitly disabled in the CPU definition we consider the base model compatible with the host. Then we only need to check that all explicitly required features are supported by QEMU on the host to get the result for the whole CPU definition. After this we only use the model definitions (for newly added models) from CPU map for creating a CPU definition for host-model. Jiri Denemark (9): cpu_x86: Introduce <check> element for CPU models cpu_map: Use compat partial check for all x86 CPU models cpu: Introduce virCPUGetCheckMode qemu: Use g_autoptr in qemuConnectCompareHypervisorCPU qemu: Use virCPUCompare in qemuConnectCompareHypervisorCPU directly qemu: Separate partial CPU check into a function cpu: Introduce virCPUCompareUnusable qemu_capabilities: Introduce virQEMUCapsGetCPUBlockers qemu: Change CPU comparison algorithm for future models src/cpu/cpu.c | 104 ++++++++++++++++++ src/cpu/cpu.h | 17 +++ src/cpu/cpu_x86.c | 67 +++++++++++ src/cpu_map/x86_486.xml | 1 + src/cpu_map/x86_Broadwell-IBRS.xml | 1 + src/cpu_map/x86_Broadwell-noTSX-IBRS.xml | 1 + src/cpu_map/x86_Broadwell-noTSX.xml | 1 + src/cpu_map/x86_Broadwell.xml | 1 + src/cpu_map/x86_Cascadelake-Server-noTSX.xml | 1 + src/cpu_map/x86_Cascadelake-Server.xml | 1 + src/cpu_map/x86_Conroe.xml | 1 + src/cpu_map/x86_Cooperlake.xml | 1 + src/cpu_map/x86_Dhyana.xml | 1 + src/cpu_map/x86_EPYC-Genoa.xml | 1 + src/cpu_map/x86_EPYC-IBPB.xml | 1 + src/cpu_map/x86_EPYC-Milan.xml | 1 + src/cpu_map/x86_EPYC-Rome.xml | 1 + src/cpu_map/x86_EPYC.xml | 1 + src/cpu_map/x86_GraniteRapids.xml | 1 + src/cpu_map/x86_Haswell-IBRS.xml | 1 + src/cpu_map/x86_Haswell-noTSX-IBRS.xml | 1 + src/cpu_map/x86_Haswell-noTSX.xml | 1 + src/cpu_map/x86_Haswell.xml | 1 + src/cpu_map/x86_Icelake-Client-noTSX.xml | 1 + src/cpu_map/x86_Icelake-Client.xml | 1 + src/cpu_map/x86_Icelake-Server-noTSX.xml | 1 + src/cpu_map/x86_Icelake-Server.xml | 1 + src/cpu_map/x86_IvyBridge-IBRS.xml | 1 + src/cpu_map/x86_IvyBridge.xml | 1 + src/cpu_map/x86_Nehalem-IBRS.xml | 1 + src/cpu_map/x86_Nehalem.xml | 1 + src/cpu_map/x86_Opteron_G1.xml | 1 + src/cpu_map/x86_Opteron_G2.xml | 1 + src/cpu_map/x86_Opteron_G3.xml | 1 + src/cpu_map/x86_Opteron_G4.xml | 1 + src/cpu_map/x86_Opteron_G5.xml | 1 + src/cpu_map/x86_Penryn.xml | 1 + src/cpu_map/x86_SandyBridge-IBRS.xml | 1 + src/cpu_map/x86_SandyBridge.xml | 1 + src/cpu_map/x86_SapphireRapids.xml | 1 + src/cpu_map/x86_SierraForest.xml | 1 + src/cpu_map/x86_Skylake-Client-IBRS.xml | 1 + src/cpu_map/x86_Skylake-Client-noTSX-IBRS.xml | 1 + src/cpu_map/x86_Skylake-Client.xml | 1 + src/cpu_map/x86_Skylake-Server-IBRS.xml | 1 + src/cpu_map/x86_Skylake-Server-noTSX-IBRS.xml | 1 + src/cpu_map/x86_Skylake-Server.xml | 1 + src/cpu_map/x86_Snowridge.xml | 1 + src/cpu_map/x86_Westmere-IBRS.xml | 1 + src/cpu_map/x86_Westmere.xml | 1 + src/cpu_map/x86_athlon.xml | 1 + src/cpu_map/x86_core2duo.xml | 1 + src/cpu_map/x86_coreduo.xml | 1 + src/cpu_map/x86_cpu64-rhel5.xml | 1 + src/cpu_map/x86_cpu64-rhel6.xml | 1 + src/cpu_map/x86_kvm32.xml | 1 + src/cpu_map/x86_kvm64.xml | 1 + src/cpu_map/x86_n270.xml | 1 + src/cpu_map/x86_pentium.xml | 1 + src/cpu_map/x86_pentium2.xml | 1 + src/cpu_map/x86_pentium3.xml | 1 + src/cpu_map/x86_pentiumpro.xml | 1 + src/cpu_map/x86_phenom.xml | 1 + src/cpu_map/x86_qemu32.xml | 1 + src/cpu_map/x86_qemu64.xml | 1 + src/libvirt_private.syms | 2 + src/qemu/qemu_capabilities.c | 38 +++++++ src/qemu/qemu_capabilities.h | 4 + src/qemu/qemu_domain.c | 65 +++++++++++ src/qemu/qemu_domain.h | 7 ++ src/qemu/qemu_driver.c | 45 ++++---- src/qemu/qemu_process.c | 7 +- 72 files changed, 390 insertions(+), 28 deletions(-)
Reviewed-by: Ján Tomko <jtomko@xxxxxxxxxx> Jano
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