Christophe Leroy's on August 27, 2019 4:13 pm: > > > Le 27/08/2019 à 05:30, Nicholas Piggin a écrit : >> There is support for the kernel to execute the 'sc 0' instruction and >> make a system call to itself. This is a relic that is unused in the >> tree, therefore untested. It's also highly questionable for modules to >> be doing this. > > I like it. > > I dropped support for that in PPC32 when I added fast-path syscalls.
Good, then we'll match again. >> - beq 2f /* if from kernel mode */ >> #ifdef CONFIG_PPC_FSL_BOOK3E >> START_BTB_FLUSH_SECTION >> BTB_FLUSH(r10) >> END_BTB_FLUSH_SECTION >> #endif >> ACCOUNT_CPU_USER_ENTRY(r13, r10, r11) >> -2: std r2,GPR2(r1) Btw. there is a hunk which restores this optimisation but it leaked into a later patch, I'll move it back here. >> @@ -122,14 +118,13 @@ END_BTB_FLUSH_SECTION >> >> #if defined(CONFIG_VIRT_CPU_ACCOUNTING_NATIVE) && >> defined(CONFIG_PPC_SPLPAR) >> BEGIN_FW_FTR_SECTION >> - beq 33f >> - /* if from user, see if there are any DTL entries to process */ >> + /* see if there are any DTL entries to process */ >> ld r10,PACALPPACAPTR(r13) /* get ptr to VPA */ >> ld r11,PACA_DTL_RIDX(r13) /* get log read index */ >> addi r10,r10,LPPACA_DTLIDX >> LDX_BE r10,0,r10 /* get log write index */ >> - cmpd cr1,r11,r10 >> - beq+ cr1,33f >> + cmpd r11,r10 >> + beq+ 33f > > Any need to do this change ? Why not keep it as is ? We don't need to keep cr0 alive with the MSR_PR compare, so I prefer to keep the cr usage more compact, and I prefer to have cr0 for short lived results and others for long running ones as a rule. Thanks, Nick
