AMD tau tshaj tawm tsab ntawv tshaj tawm kev txheeb xyuas kev ruaj ntseg ntawm PSF (Predictive Store Forwarding) optimization thev naus laus zis tau siv hauv Zen 3 series processors Txoj kev tshawb no tau lees paub qhov siv tau ntawm Spectre-STL (Spectre-v4) txoj kev tawm tsam, txheeb xyuas thaum lub Tsib Hlis 2018, rau. PSF thev naus laus zis, tab sis hauv kev xyaum, tsis muaj cov qauv qauv uas muaj peev xwm ua rau muaj kev tawm tsam tseem tsis tau pom thiab qhov kev phom sij tag nrho raug ntsuas raws li qhov tsis tseem ceeb.
Cia peb nco qab tias Spectre-v4 (Speculative Store Bypass) nres yog ua raws li cov ntaub ntawv rov qab uas tau nyob hauv lub processor cache tom qab muab pov tseg cov txiaj ntsig ntawm kev ua tiav ntawm kev ua haujlwm thaum ua kev sib hloov sau thiab nyeem cov haujlwm siv qhov chaw nyob tsis ncaj. Thaum kev nyeem ntawv ua raws li kev sau ntawv (piv txwv li, mov [rbx + rcx], 0x0; mov rax, [rdx + rsi]), qhov offset ntawm qhov chaw nyeem ntawv yuav raug paub vim muaj kev ua haujlwm zoo sib xws (nyeem cov haujlwm yog ua tau ntau zaus thiab nyeem tau tuaj yeem ua tau los ntawm cache) thiab tus processor tuaj yeem ua qhov kev nyeem ntawv ua ntej sau yam tsis tau tos rau kev sau cov kev taw qhia offset suav.
Qhov no tso cai rau kev nyeem cov lus qhia kom nkag mus rau tus nqi qub ntawm qee qhov chaw nyob thaum lub khw lag luam tseem tsis tau ua tiav. Yog tias muaj qhov ua yuam kev, kev ua haujlwm tsis ua tiav yuav raug muab pov tseg, tab sis cov cim ntawm nws qhov kev ua tiav yuav nyob twj ywm hauv processor cache thiab tuaj yeem rov qab tau los ntawm ib txoj hauv kev los txiav txim siab cov ntsiab lus ntawm lub cache raws li kev txheeb xyuas kev hloov pauv hauv kev nkag. sijhawm rau cached thiab uncached cov ntaub ntawv.
Ntxiv rau AMD Zen 3 processors, PSF optimizes STLF (Store-To-Load-Forwarding), uas ua haujlwm nyeem ntawv speculatively los ntawm kev kwv yees kev sib raug zoo ntawm kev nyeem ntawv thiab sau ntawv. Thaum siv classic STLF, lub processor ua haujlwm "load" ntawm cov ntaub ntawv xa ncaj qha los ntawm cov lus txib "khoom" yav dhau los, tsis tau tos kom cov txiaj ntsig tau sau rau lub cim xeeb, tab sis nco ntsoov tias cov chaw nyob siv hauv "load" thiab "kho" commands match. PSF optimization ua rau qhov chaw kuaj xyuas qhov xav tau thiab ua haujlwm "load" ua ntej cov ntaub ntawv chaw nyob tau suav yog tias lub khw / thauj khoom khub tswj hwm ib qhov chaw nyob yav dhau los tau raug tua. Yog tias qhov kev twv ua tsis tiav, lub xeev tau rov qab, tab sis cov ntaub ntawv tseem nyob hauv lub cache.
Kev tawm tsam ntawm PSF tsuas yog ua tau nyob rau hauv lub moj khaum ntawm ib theem ntawm cov cai, tsuas yog tsuas yog cov txheej txheem txheej txheem tam sim no thiab raug thaiv los ntawm qhov chaw nyob qhov chaw cais tawm lossis kho vajtse sandbox mechanisms. Hauv qhov no, software sandboxing txoj kev hauv cov txheej txheem tuaj yeem cuam tshuam los ntawm qhov teeb meem. Qhov kev tawm tsam ua rau muaj kev hem thawj rau cov tshuab xws li browsers, code execution virtual machines, thiab JITs uas ua rau cov neeg thib peb code nyob rau hauv ib txheej txheem (qhov kev tawm tsam tuaj yeem tso cai rau tsis ntseeg sandboxed code kom nkag mus rau lwm cov ntaub ntawv txheej txheem).
AMD tau muab ntau txoj hauv kev rau kev ua tiav lossis xaiv tsis siv PSF, tab sis muab qhov kev pheej hmoo tsis txaus ntseeg rau feem ntau cov ntawv thov, tau pom zoo tias qhov kev ua kom zoo no tsis raug cuam tshuam los ntawm lub neej ntawd. Txhawm rau xaiv kev tiv thaiv cov txheej txheem uas cais cov kev ua txhaum cai tsis tsim nyog, nws tau thov kom lov tes taw PSF los ntawm kev teeb tsa "SSBD" thiab "PSFD" MSR cov khoom, suav nrog rau cov xov tooj ntawm tus kheej. Patches tau npaj rau Linux ntsiav nrog kev siv ntawm "psfd" thiab "nopsfd" cov kab lus hais kom tswj tau li cas PSF qhib thiab tawm.
Tau qhov twg los: opennet.ru