On Tue, 2022-07-12 at 17:47 +0000, Sean Christopherson wrote:
> On Tue, Jul 12, 2022, Kai Huang wrote:
> > Now kvm_tdp_mmu_zap_leafs() only zaps leaf SPTEs but not any non-root
> > pages within that GFN range anymore, so the comment isn't right.
> >
> > Fixes: f47e5bbbc92f ("KVM: x86/mmu: Zap only TDP MMU leafs in zap range and mmu_notifier unmap")
> > Signed-off-by: Kai Huang <kai.huang@xxxxxxxxx>
> > ---
> > arch/x86/kvm/mmu/tdp_mmu.c | 7 +++----
> > 1 file changed, 3 insertions(+), 4 deletions(-)
> >
> > diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c
> > index f3a430d64975..7692e6273462 100644
> > --- a/arch/x86/kvm/mmu/tdp_mmu.c
> > +++ b/arch/x86/kvm/mmu/tdp_mmu.c
> > @@ -969,10 +969,9 @@ 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 leafs SPTEs for the range of gfns, [start, end) for all roots. Returns
> > + * true if SPTEs have been cleared and a TLB flush is needed before releasing
> > + * the MMU lock.
>
> What about shifting the comment from tdp_mmu_zap_leafs() instead of duplicating it?
> tdp_mmu_zap_leafs() is static and kvm_tdp_mmu_zap_leafs() is the sole caller. And
> opportunistically tweak the blurb about SPTEs being cleared to (a) say "zapped"
> instead of "cleared" because "cleared" will be wrong if/when KVM sets SUPPRESS_VE,
> and (b) to clarify that a flush is needed if and only if a SPTE has been zapped
> since MMU lock was last acquired.
>
> E.g.
>
> /*
> * 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
> * the caller must ensure it does not supply too large a GFN range, or the
> * operation can cause a soft lockup.
> */
> static bool tdp_mmu_zap_leafs(struct kvm *kvm, struct kvm_mmu_page *root,
> gfn_t start, gfn_t end, bool can_yield, bool flush)
>
> /*
> * Zap leafs 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)
Yes looks better. Will send out a new patch soon. Thanks.
--
Thanks,
-Kai
