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KVM: x86/mmu: Consolidate logic to atomically install a new TDP MMU page table

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Consolidate the logic to atomically replace an SPTE with an SPTE that
points to a new page table into a single helper function. This will be
used in a follow-up commit to split huge pages, which involves replacing
each huge page SPTE with an SPTE that points to a page table.

Opportunistically drop the call to trace_kvm_mmu_get_page() in
kvm_tdp_mmu_map() since it is redundant with the identical tracepoint in
tdp_mmu_alloc_sp().

No functional change intended.

Reviewed-by: Peter Xu <peterx@redhat.com>
Signed-off-by: David Matlack <dmatlack@google.com>
Message-Id: <20220119230739.2234394-8-dmatlack@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
David Matlack 2022-01-19 23:07:28 +00:00 committed by Paolo Bonzini
parent 0f53dfa34e
commit 7b7e1ab6fd
1 changed files with 36 additions and 32 deletions
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68
arch/x86/kvm/mmu/tdp_mmu.c
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@ -268,24 +268,6 @@ static void handle_changed_spte_dirty_log(struct kvm *kvm, int as_id, gfn_t gfn,
}
}
/**
* tdp_mmu_link_sp() - Add a new shadow page to the list of used pages
*
* @kvm: kvm instance
* @sp: the new page
* @account_nx: This page replaces a NX large page and should be marked for
* eventual reclaim.
*/
static void tdp_mmu_link_sp(struct kvm *kvm, struct kvm_mmu_page *sp,
bool account_nx)
{
spin_lock(&kvm->arch.tdp_mmu_pages_lock);
list_add(&sp->link, &kvm->arch.tdp_mmu_pages);
if (account_nx)
account_huge_nx_page(kvm, sp);
spin_unlock(&kvm->arch.tdp_mmu_pages_lock);
}
/**
* tdp_mmu_unlink_sp() - Remove a shadow page from the list of used pages
*
@ -979,6 +961,38 @@ static int tdp_mmu_map_handle_target_level(struct kvm_vcpu *vcpu,
return ret;
}
/*
* tdp_mmu_link_sp_atomic - Atomically replace the given spte with an spte
* pointing to the provided page table.
*
* @kvm: kvm instance
* @iter: a tdp_iter instance currently on the SPTE that should be set
* @sp: The new TDP page table to install.
* @account_nx: True if this page table is being installed to split a
* non-executable huge page.
*
* Returns: 0 if the new page table was installed. Non-0 if the page table
* could not be installed (e.g. the atomic compare-exchange failed).
*/
static int tdp_mmu_link_sp_atomic(struct kvm *kvm, struct tdp_iter *iter,
struct kvm_mmu_page *sp, bool account_nx)
{
u64 spte = make_nonleaf_spte(sp->spt, !shadow_accessed_mask);
int ret;
ret = tdp_mmu_set_spte_atomic(kvm, iter, spte);
if (ret)
return ret;
spin_lock(&kvm->arch.tdp_mmu_pages_lock);
list_add(&sp->link, &kvm->arch.tdp_mmu_pages);
if (account_nx)
account_huge_nx_page(kvm, sp);
spin_unlock(&kvm->arch.tdp_mmu_pages_lock);
return 0;
}
/*
* Handle a TDP page fault (NPT/EPT violation/misconfiguration) by installing
* page tables and SPTEs to translate the faulting guest physical address.
@ -988,8 +1002,6 @@ int kvm_tdp_mmu_map(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault)
struct kvm_mmu *mmu = vcpu->arch.mmu;
struct tdp_iter iter;
struct kvm_mmu_page *sp;
u64 *child_pt;
u64 new_spte;
int ret;
kvm_mmu_hugepage_adjust(vcpu, fault);
@ -1024,6 +1036,9 @@ int kvm_tdp_mmu_map(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault)
}
if (!is_shadow_present_pte(iter.old_spte)) {
bool account_nx = fault->huge_page_disallowed &&
fault->req_level >= iter.level;
/*
* If SPTE has been frozen by another thread, just
* give up and retry, avoiding unnecessary page table
@ -1033,18 +1048,7 @@ int kvm_tdp_mmu_map(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault)
break;
sp = tdp_mmu_alloc_sp(vcpu, iter.gfn, iter.level - 1);
child_pt = sp->spt;
new_spte = make_nonleaf_spte(child_pt,
!shadow_accessed_mask);
if (!tdp_mmu_set_spte_atomic(vcpu->kvm, &iter, new_spte)) {
tdp_mmu_link_sp(vcpu->kvm, sp,
fault->huge_page_disallowed &&
fault->req_level >= iter.level);
trace_kvm_mmu_get_page(sp, true);
} else {
if (tdp_mmu_link_sp_atomic(vcpu->kvm, &iter, sp, account_nx)) {
tdp_mmu_free_sp(sp);
break;
}