forked from Minki/linux
KVM: MMU: flush tlb if the spte can be locklessly modified
Relax the tlb flush condition since we will write-protect the spte out of mmu lock. Note lockless write-protection only marks the writable spte to readonly and the spte can be writable only if both SPTE_HOST_WRITEABLE and SPTE_MMU_WRITEABLE are set (that are tested by spte_is_locklessly_modifiable) This patch is used to avoid this kind of race: VCPU 0 VCPU 1 lockless wirte protection: set spte.w = 0 lock mmu-lock write protection the spte to sync shadow page, see spte.w = 0, then without flush tlb unlock mmu-lock !!! At this point, the shadow page can still be writable due to the corrupt tlb entry Flush all TLB Reviewed-by: Marcelo Tosatti <mtosatti@redhat.com> Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
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@ -595,7 +595,8 @@ static bool mmu_spte_update(u64 *sptep, u64 new_spte)
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* we always atomicly update it, see the comments in
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* spte_has_volatile_bits().
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*/
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if (is_writable_pte(old_spte) && !is_writable_pte(new_spte))
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if (spte_is_locklessly_modifiable(old_spte) &&
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!is_writable_pte(new_spte))
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ret = true;
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if (!shadow_accessed_mask)
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