Messages in this thread | | | Date | Fri, 11 Jun 2021 14:36:22 -0700 | From | Pawan Gupta <> | Subject | Re: [PATCH 3/4] x86/tsx: Clear CPUID bits when TSX always force aborts |
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On 11.06.2021 12:03, Borislav Petkov wrote: >On Wed, Jun 09, 2021 at 02:13:38PM -0700, Pawan Gupta wrote: >> @@ -114,6 +127,26 @@ void __init tsx_init(void) >> tsx_ctrl_state = TSX_CTRL_ENABLE; >> } >> >> + /* >> + * Hardware will always abort a TSX transaction if both CPUID bits >> + * RTM_ALWAYS_ABORT and TSX_FORCE_ABORT are enumerated. In this case it >> + * is better not to enumerate CPUID.RTM and CPUID.HLE bits. Clear them >> + * here. >> + */ >> + if (boot_cpu_has(X86_FEATURE_RTM_ALWAYS_ABORT) && >> + boot_cpu_has(X86_FEATURE_TSX_FORCE_ABORT)) { >> + tsx_ctrl_state = TSX_CTRL_RTM_ALWAYS_ABORT; >> + tsx_clear_cpuid(); >> + setup_clear_cpu_cap(X86_FEATURE_RTM); >> + setup_clear_cpu_cap(X86_FEATURE_HLE); >> + return; >> + } > >Why isn't this happening as the first thing on entry in that tsx_init() >function? IOW, there's no point to noodle through cmdline options etc if >the hardware will always abort transactions.
Because the next patch is adding tsx=fake cmdline, for that this code needs to be executed after cmdline parsing. I wanted to avoid the churn to move this code between patches.
But, I see your comment for 4/4 i.e. tsx=fake may not be needed. It was added after an internal test failure.
tsx=fake is really for a corner case and if that patch goes away it would make sense to move the code in question here before cmdline parsing.
Thanks, Pawan
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