Messages in this thread | | | From | Thomas Gleixner <> | Subject | Re: [PATCH v3 3/5] arch/x86/mm: Refactor cond_ibpb() to support other use cases | Date | Tue, 21 Apr 2020 11:02:54 +0200 |
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"Singh, Balbir" <sblbir@amazon.com> writes: > On Sat, 2020-04-18 at 11:59 +0200, Thomas Gleixner wrote: >> >> "Singh, Balbir" <sblbir@amazon.com> writes: >> > On Fri, 2020-04-17 at 15:07 +0200, Thomas Gleixner wrote: >> > > >> > > Balbir Singh <sblbir@amazon.com> writes: >> > > > >> > > > /* >> > > > - * Use bit 0 to mangle the TIF_SPEC_IB state into the mm pointer >> > > > which is >> > > > - * stored in cpu_tlb_state.last_user_mm_ibpb. >> > > > + * Bits to mangle the TIF_SPEC_IB state into the mm pointer which is >> > > > + * stored in cpu_tlb_state.last_user_mm_spec. >> > > > */ >> > > > #define LAST_USER_MM_IBPB 0x1UL >> > > > +#define LAST_USER_MM_SPEC_MASK (LAST_USER_MM_IBPB) >> > > > >> > > > /* Reinitialize tlbstate. */ >> > > > - this_cpu_write(cpu_tlbstate.last_user_mm_ibpb, >> > > > LAST_USER_MM_IBPB); >> > > > + this_cpu_write(cpu_tlbstate.last_user_mm_spec, >> > > > LAST_USER_MM_IBPB); >> > > >> > > Shouldn't that be LAST_USER_MM_MASK? >> > > >> > >> > No, that crashes the system for SW flushes, because it tries to flush the >> > L1D >> > via the software loop and early enough we don't have the l1d_flush_pages >> > allocated. LAST_USER_MM_MASK has LAST_USER_MM_FLUSH_L1D bit set. >> >> You can trivially prevent this by checking l1d_flush_pages != NULL. >> > > But why would we want to flush on reinit? It is either coming back from a low > power state or initialising, is it worth adding a check for != NULL everytime > we flush to handle this case?
Fair enough. Please add a comment so the same question does not come back 3 month from now.
Thanks,
tglx
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