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Message-ID: <CANgfPd8mH7XpNzCbObD-XO_Pzc0TK6oNQpTw9rgSdqBV-4trFw@mail.gmail.com>
Date: Wed, 30 Sep 2020 16:15:17 -0700
From: Ben Gardon <bgardon@...gle.com>
To: Sean Christopherson <sean.j.christopherson@...el.com>
Cc: LKML <linux-kernel@...r.kernel.org>, kvm <kvm@...r.kernel.org>,
Cannon Matthews <cannonmatthews@...gle.com>,
Paolo Bonzini <pbonzini@...hat.com>,
Peter Xu <peterx@...hat.com>, Peter Shier <pshier@...gle.com>,
Peter Feiner <pfeiner@...gle.com>,
Junaid Shahid <junaids@...gle.com>,
Jim Mattson <jmattson@...gle.com>,
Yulei Zhang <yulei.kernel@...il.com>,
Wanpeng Li <kernellwp@...il.com>,
Vitaly Kuznetsov <vkuznets@...hat.com>,
Xiao Guangrong <xiaoguangrong.eric@...il.com>
Subject: Re: [PATCH 13/22] kvm: mmu: Support invalidate range MMU notifier for
TDP MMU
On Wed, Sep 30, 2020 at 10:04 AM Sean Christopherson
<sean.j.christopherson@...el.com> wrote:
>
> On Fri, Sep 25, 2020 at 02:22:53PM -0700, Ben Gardon wrote:
> > In order to interoperate correctly with the rest of KVM and other Linux
> > subsystems, the TDP MMU must correctly handle various MMU notifiers. Add
> > hooks to handle the invalidate range family of MMU notifiers.
> >
> > Tested by running kvm-unit-tests and KVM selftests on an Intel Haswell
> > machine. This series introduced no new failures.
> >
> > This series can be viewed in Gerrit at:
> > https://linux-review.googlesource.com/c/virt/kvm/kvm/+/2538
> >
> > Signed-off-by: Ben Gardon <bgardon@...gle.com>
> > ---
> > arch/x86/kvm/mmu/mmu.c | 9 ++++-
> > arch/x86/kvm/mmu/tdp_mmu.c | 80 +++++++++++++++++++++++++++++++++++---
> > arch/x86/kvm/mmu/tdp_mmu.h | 3 ++
> > 3 files changed, 86 insertions(+), 6 deletions(-)
> >
> > diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> > index 52d661a758585..0ddfdab942554 100644
> > --- a/arch/x86/kvm/mmu/mmu.c
> > +++ b/arch/x86/kvm/mmu/mmu.c
> > @@ -1884,7 +1884,14 @@ static int kvm_handle_hva(struct kvm *kvm, unsigned long hva,
> > int kvm_unmap_hva_range(struct kvm *kvm, unsigned long start, unsigned long end,
> > unsigned flags)
> > {
> > - return kvm_handle_hva_range(kvm, start, end, 0, kvm_unmap_rmapp);
> > + int r;
> > +
> > + r = kvm_handle_hva_range(kvm, start, end, 0, kvm_unmap_rmapp);
> > +
> > + if (kvm->arch.tdp_mmu_enabled)
> > + r |= kvm_tdp_mmu_zap_hva_range(kvm, start, end);
>
> Similar to an earlier question, is this intentionally additive, or can this
> instead by:
>
> if (kvm->arch.tdp_mmu_enabled)
> r = kvm_tdp_mmu_zap_hva_range(kvm, start, end);
> else
> r = kvm_handle_hva_range(kvm, start, end, 0, kvm_unmap_rmapp);
>
It is intentionally additive so the legacy/shadow MMU can handle nested.
> > +
> > + return r;
> > }
> >
> > int kvm_set_spte_hva(struct kvm *kvm, unsigned long hva, pte_t pte)
> > diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c
> > index 557e780bdf9f9..1cea58db78a13 100644
> > --- a/arch/x86/kvm/mmu/tdp_mmu.c
> > +++ b/arch/x86/kvm/mmu/tdp_mmu.c
> > @@ -60,7 +60,7 @@ bool is_tdp_mmu_root(struct kvm *kvm, hpa_t hpa)
> > }
> >
> > static bool zap_gfn_range(struct kvm *kvm, struct kvm_mmu_page *root,
> > - gfn_t start, gfn_t end);
> > + gfn_t start, gfn_t end, bool can_yield);
> >
> > static void free_tdp_mmu_root(struct kvm *kvm, struct kvm_mmu_page *root)
> > {
> > @@ -73,7 +73,7 @@ static void free_tdp_mmu_root(struct kvm *kvm, struct kvm_mmu_page *root)
> >
> > list_del(&root->link);
> >
> > - zap_gfn_range(kvm, root, 0, max_gfn);
> > + zap_gfn_range(kvm, root, 0, max_gfn, false);
> >
> > free_page((unsigned long)root->spt);
> > kmem_cache_free(mmu_page_header_cache, root);
> > @@ -361,9 +361,14 @@ static bool tdp_mmu_iter_cond_resched(struct kvm *kvm, struct tdp_iter *iter)
> > * 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.
> > + * 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 zap_gfn_range(struct kvm *kvm, struct kvm_mmu_page *root,
> > - gfn_t start, gfn_t end)
> > + gfn_t start, gfn_t end, bool can_yield)
> > {
> > struct tdp_iter iter;
> > bool flush_needed = false;
> > @@ -387,7 +392,10 @@ static bool zap_gfn_range(struct kvm *kvm, struct kvm_mmu_page *root,
> > handle_changed_spte(kvm, as_id, iter.gfn, iter.old_spte, 0,
> > iter.level);
> >
> > - flush_needed = !tdp_mmu_iter_cond_resched(kvm, &iter);
> > + if (can_yield)
> > + flush_needed = !tdp_mmu_iter_cond_resched(kvm, &iter);
>
> flush_needed = !can_yield || !tdp_mmu_iter_cond_resched(kvm, &iter);
>
> > + else
> > + flush_needed = true;
> > }
> > return flush_needed;
> > }
> > @@ -410,7 +418,7 @@ bool kvm_tdp_mmu_zap_gfn_range(struct kvm *kvm, gfn_t start, gfn_t end)
> > */
> > get_tdp_mmu_root(kvm, root);
> >
> > - flush = zap_gfn_range(kvm, root, start, end) || flush;
> > + flush = zap_gfn_range(kvm, root, start, end, true) || flush;
> >
> > put_tdp_mmu_root(kvm, root);
> > }
> > @@ -551,3 +559,65 @@ int kvm_tdp_mmu_page_fault(struct kvm_vcpu *vcpu, int write, int map_writable,
> >
> > return ret;
> > }
> > +
> > +static int kvm_tdp_mmu_handle_hva_range(struct kvm *kvm, unsigned long start,
> > + unsigned long end, unsigned long data,
> > + int (*handler)(struct kvm *kvm, struct kvm_memory_slot *slot,
> > + struct kvm_mmu_page *root, gfn_t start,
> > + gfn_t end, unsigned long data))
> > +{
> > + struct kvm_memslots *slots;
> > + struct kvm_memory_slot *memslot;
> > + struct kvm_mmu_page *root;
> > + int ret = 0;
> > + int as_id;
> > +
> > + for_each_tdp_mmu_root(kvm, root) {
> > + /*
> > + * Take a reference on the root so that it cannot be freed if
> > + * this thread releases the MMU lock and yields in this loop.
> > + */
> > + get_tdp_mmu_root(kvm, root);
> > +
> > + as_id = kvm_mmu_page_as_id(root);
> > + slots = __kvm_memslots(kvm, as_id);
> > + kvm_for_each_memslot(memslot, slots) {
> > + unsigned long hva_start, hva_end;
> > + gfn_t gfn_start, gfn_end;
> > +
> > + hva_start = max(start, memslot->userspace_addr);
> > + hva_end = min(end, memslot->userspace_addr +
> > + (memslot->npages << PAGE_SHIFT));
> > + if (hva_start >= hva_end)
> > + continue;
> > + /*
> > + * {gfn(page) | page intersects with [hva_start, hva_end)} =
> > + * {gfn_start, gfn_start+1, ..., gfn_end-1}.
> > + */
> > + gfn_start = hva_to_gfn_memslot(hva_start, memslot);
> > + gfn_end = hva_to_gfn_memslot(hva_end + PAGE_SIZE - 1, memslot);
> > +
> > + ret |= handler(kvm, memslot, root, gfn_start,
> > + gfn_end, data);
>
> Eh, I'd say let this one poke out, the above hva_to_gfn_memslot() already
> overruns 80 chars. IMO it's more readable without the wraps.
Will do.
>
> > + }
> > +
> > + put_tdp_mmu_root(kvm, root);
> > + }
> > +
> > + return ret;
> > +}
> > +
> > +static int zap_gfn_range_hva_wrapper(struct kvm *kvm,
> > + struct kvm_memory_slot *slot,
> > + struct kvm_mmu_page *root, gfn_t start,
> > + gfn_t end, unsigned long unused)
> > +{
> > + return zap_gfn_range(kvm, root, start, end, false);
> > +}
> > +
> > +int kvm_tdp_mmu_zap_hva_range(struct kvm *kvm, unsigned long start,
> > + unsigned long end)
> > +{
> > + return kvm_tdp_mmu_handle_hva_range(kvm, start, end, 0,
> > + zap_gfn_range_hva_wrapper);
> > +}
> > diff --git a/arch/x86/kvm/mmu/tdp_mmu.h b/arch/x86/kvm/mmu/tdp_mmu.h
> > index abf23dc0ab7ad..ce804a97bfa1d 100644
> > --- a/arch/x86/kvm/mmu/tdp_mmu.h
> > +++ b/arch/x86/kvm/mmu/tdp_mmu.h
> > @@ -18,4 +18,7 @@ void kvm_tdp_mmu_zap_all(struct kvm *kvm);
> > int kvm_tdp_mmu_page_fault(struct kvm_vcpu *vcpu, int write, int map_writable,
> > int level, gpa_t gpa, kvm_pfn_t pfn, bool prefault,
> > bool lpage_disallowed);
> > +
> > +int kvm_tdp_mmu_zap_hva_range(struct kvm *kvm, unsigned long start,
> > + unsigned long end);
> > #endif /* __KVM_X86_MMU_TDP_MMU_H */
> > --
> > 2.28.0.709.gb0816b6eb0-goog
> >
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