From 7edc3a68038ab151a8791ddb6217755a5e4a5809 Mon Sep 17 00:00:00 2001 From: Kai Huang Date: Thu, 28 Jul 2022 15:04:52 +1200 Subject: [PATCH] KVM, x86/mmu: Fix the comment around kvm_tdp_mmu_zap_leafs() Now kvm_tdp_mmu_zap_leafs() only zaps leaf SPTEs but not any non-root pages within that GFN range anymore, so the comment around it isn't right. Fix it by shifting the comment from tdp_mmu_zap_leafs() instead of duplicating it, as tdp_mmu_zap_leafs() is static and is only called by kvm_tdp_mmu_zap_leafs(). Opportunistically tweak the blurb about SPTEs being cleared to (a) say "zapped" instead of "cleared" because "cleared" will be wrong if/when KVM allows a non-zero value for non-present SPTE (i.e. for Intel TDX), and (b) to clarify that a flush is needed if and only if a SPTE has been zapped since MMU lock was last acquired. Fixes: f47e5bbbc92f ("KVM: x86/mmu: Zap only TDP MMU leafs in zap range and mmu_notifier unmap") Suggested-by: Sean Christopherson Reviewed-by: Sean Christopherson Signed-off-by: Kai Huang Message-Id: <20220728030452.484261-1-kai.huang@intel.com> Signed-off-by: Paolo Bonzini --- arch/x86/kvm/mmu/tdp_mmu.c | 10 +++------- 1 file changed, 3 insertions(+), 7 deletions(-) diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c index 40ccb5f..bf2ccf9 100644 --- a/arch/x86/kvm/mmu/tdp_mmu.c +++ b/arch/x86/kvm/mmu/tdp_mmu.c @@ -924,9 +924,6 @@ bool kvm_tdp_mmu_zap_sp(struct kvm *kvm, struct kvm_mmu_page *sp) } /* - * Zap leafs SPTEs for the range of gfns, [start, end). Returns true if SPTEs - * have been cleared and a TLB flush is needed before releasing the MMU lock. - * * If can_yield is true, will release the MMU lock and reschedule if the * scheduler needs the CPU or there is contention on the MMU lock. If this * function cannot yield, it will not release the MMU lock or reschedule and @@ -969,10 +966,9 @@ static bool tdp_mmu_zap_leafs(struct kvm *kvm, struct kvm_mmu_page *root, } /* - * Tears down the mappings for the range of gfns, [start, end), and frees the - * non-root pages mapping GFNs strictly within that range. Returns true if - * SPTEs have been cleared and a TLB flush is needed before releasing the - * MMU lock. + * Zap leaf SPTEs for the range of gfns, [start, end), for all roots. Returns + * true if a TLB flush is needed before releasing the MMU lock, i.e. if one or + * more SPTEs were zapped since the MMU lock was last acquired. */ bool kvm_tdp_mmu_zap_leafs(struct kvm *kvm, int as_id, gfn_t start, gfn_t end, bool can_yield, bool flush) -- 2.7.4