On Tue, Nov 18, 2025 at 7:36 AM Zhao Liu <[email protected]> wrote: > > APX is enumerated by CPUID.(EAX=0x7, ECX=1).EDX[21]. And this feature > bit also indicates the existence of dedicated CPUID leaf 0x29, called > the Intel APX Advanced Performance Extensions Leaf. > > This new CPUID leaf now is populated with enumerations for a select > set of Intel APX sub-features. > > CPUID.(EAX=0x29, ECX=0) > - EAX > * Maximum Subleaf CPUID.(EAX=0x29, ECX=0).EAX[31:0] = 0 > - EBX > * Reserved CPUID.(EAX=0x29, ECX=0).EBX[31:1] = 0 > * APX_NCI_NDD_NF CPUID.(EAX=0x29, ECX=0).EBX[0:0] = 1, which > enumerates the presence of New Conditional Instructions (NCIs), > explicit New Data Destination (NDD) controls, and explicit Flags > Suppression (NF) controls for select sets of EVEX-encoded Intel > APX instructions (present in EVEX map=4, and EVEX map=2 0x0F38). > - ECX > * Reserved CPUID.(EAX=0x29, ECX=0).ECX[31:0] = 0 > - EDX > * Reserved CPUID.(EAX=0x29, ECX=0).EDX[31:0] = 0 > > Note, APX_NCI_NDD_NF is documented as always enabled for Intel > processors since APX spec (revision v7.0). Now any Intel processor > that enumerates support for APX_F (CPUID.(EAX=0x7, ECX=1).EDX[21]) > will also enumerate support for APX_NCI_NDD_NF.
Please just make the new leaf have constant values based on just APX_F. We'll add the optional NCI/NDD/NF support if needed, i.e. never. :) Paolo
