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 | Sat, 18 Apr 2020 11:59:48 +0200 |
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"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.
Thanks,
tglx
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