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Date: Mon, 28 Mar 2022 20:21:35 +0000
From: David Matlack <dmatlack@...gle.com>
To: Ben Gardon <bgardon@...gle.com>
Cc: linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
Paolo Bonzini <pbonzini@...hat.com>,
Peter Xu <peterx@...hat.com>,
Sean Christopherson <seanjc@...gle.com>,
Jim Mattson <jmattson@...gle.com>,
David Dunn <daviddunn@...gle.com>,
Jing Zhang <jingzhangos@...gle.com>,
Junaid Shahid <junaids@...gle.com>
Subject: Re: [PATCH v2 08/11] KVM: x86/MMU: Track NX hugepages on a per-VM
basis
On Mon, Mar 21, 2022 at 04:48:41PM -0700, Ben Gardon wrote:
> Track whether NX hugepages are enabled on a per-VM basis instead of as a
> host-wide setting. With this commit, the per-VM state will always be the
> same as the host-wide setting, but in future commits, it will be allowed
> to differ.
>
> No functional change intended.
>
> Signed-off-by: Ben Gardon <bgardon@...gle.com>
Reviewed-by: David Matlack <dmatlack@...gle.com>
> ---
> arch/x86/include/asm/kvm_host.h | 2 ++
> arch/x86/kvm/mmu.h | 8 ++++----
> arch/x86/kvm/mmu/mmu.c | 7 +++++--
> arch/x86/kvm/mmu/spte.c | 7 ++++---
> arch/x86/kvm/mmu/spte.h | 3 ++-
> arch/x86/kvm/mmu/tdp_mmu.c | 3 ++-
> 6 files changed, 19 insertions(+), 11 deletions(-)
>
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index f72e80178ffc..0a0c54639dd8 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -1240,6 +1240,8 @@ struct kvm_arch {
> hpa_t hv_root_tdp;
> spinlock_t hv_root_tdp_lock;
> #endif
> +
> + bool nx_huge_pages;
> };
>
> struct kvm_vm_stat {
> diff --git a/arch/x86/kvm/mmu.h b/arch/x86/kvm/mmu.h
> index bf8dbc4bb12a..dd28fe8d13ae 100644
> --- a/arch/x86/kvm/mmu.h
> +++ b/arch/x86/kvm/mmu.h
> @@ -173,9 +173,9 @@ struct kvm_page_fault {
> int kvm_tdp_page_fault(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault);
>
> extern int nx_huge_pages;
> -static inline bool is_nx_huge_page_enabled(void)
> +static inline bool is_nx_huge_page_enabled(struct kvm *kvm)
> {
> - return READ_ONCE(nx_huge_pages);
> + return READ_ONCE(kvm->arch.nx_huge_pages);
> }
>
> static inline int kvm_mmu_do_page_fault(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa,
> @@ -191,8 +191,8 @@ static inline int kvm_mmu_do_page_fault(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa,
> .user = err & PFERR_USER_MASK,
> .prefetch = prefetch,
> .is_tdp = likely(vcpu->arch.mmu->page_fault == kvm_tdp_page_fault),
> - .nx_huge_page_workaround_enabled = is_nx_huge_page_enabled(),
> -
> + .nx_huge_page_workaround_enabled =
> + is_nx_huge_page_enabled(vcpu->kvm),
> .max_level = KVM_MAX_HUGEPAGE_LEVEL,
> .req_level = PG_LEVEL_4K,
> .goal_level = PG_LEVEL_4K,
> diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> index 1b59b56642f1..dc9672f70468 100644
> --- a/arch/x86/kvm/mmu/mmu.c
> +++ b/arch/x86/kvm/mmu/mmu.c
> @@ -6195,8 +6195,10 @@ static void __set_nx_huge_pages(bool val)
> nx_huge_pages = itlb_multihit_kvm_mitigation = val;
> }
>
> -static int kvm_update_nx_huge_pages(struct kvm *kvm)
> +static void kvm_update_nx_huge_pages(struct kvm *kvm)
> {
> + kvm->arch.nx_huge_pages = nx_huge_pages;
> +
> mutex_lock(&kvm->slots_lock);
> kvm_mmu_zap_all_fast(kvm);
> mutex_unlock(&kvm->slots_lock);
> @@ -6227,7 +6229,7 @@ static int set_nx_huge_pages(const char *val, const struct kernel_param *kp)
> mutex_lock(&kvm_lock);
>
> list_for_each_entry(kvm, &vm_list, vm_list)
> - kvm_set_nx_huge_pages(kvm);
> + kvm_update_nx_huge_pages(kvm);
> mutex_unlock(&kvm_lock);
> }
>
> @@ -6448,6 +6450,7 @@ int kvm_mmu_post_init_vm(struct kvm *kvm)
> {
> int err;
>
> + kvm->arch.nx_huge_pages = READ_ONCE(nx_huge_pages);
> err = kvm_vm_create_worker_thread(kvm, kvm_nx_lpage_recovery_worker, 0,
> "kvm-nx-lpage-recovery",
> &kvm->arch.nx_lpage_recovery_thread);
> diff --git a/arch/x86/kvm/mmu/spte.c b/arch/x86/kvm/mmu/spte.c
> index 4739b53c9734..877ad30bc7ad 100644
> --- a/arch/x86/kvm/mmu/spte.c
> +++ b/arch/x86/kvm/mmu/spte.c
> @@ -116,7 +116,7 @@ bool make_spte(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp,
> spte |= spte_shadow_accessed_mask(spte);
>
> if (level > PG_LEVEL_4K && (pte_access & ACC_EXEC_MASK) &&
> - is_nx_huge_page_enabled()) {
> + is_nx_huge_page_enabled(vcpu->kvm)) {
> pte_access &= ~ACC_EXEC_MASK;
> }
>
> @@ -215,7 +215,8 @@ static u64 make_spte_executable(u64 spte)
> * This is used during huge page splitting to build the SPTEs that make up the
> * new page table.
> */
> -u64 make_huge_page_split_spte(u64 huge_spte, int huge_level, int index)
> +u64 make_huge_page_split_spte(struct kvm *kvm, u64 huge_spte, int huge_level,
> + int index)
> {
> u64 child_spte;
> int child_level;
> @@ -243,7 +244,7 @@ u64 make_huge_page_split_spte(u64 huge_spte, int huge_level, int index)
> * When splitting to a 4K page, mark the page executable as the
> * NX hugepage mitigation no longer applies.
> */
> - if (is_nx_huge_page_enabled())
> + if (is_nx_huge_page_enabled(kvm))
> child_spte = make_spte_executable(child_spte);
> }
>
> diff --git a/arch/x86/kvm/mmu/spte.h b/arch/x86/kvm/mmu/spte.h
> index 73f12615416f..e4142caff4b1 100644
> --- a/arch/x86/kvm/mmu/spte.h
> +++ b/arch/x86/kvm/mmu/spte.h
> @@ -415,7 +415,8 @@ bool make_spte(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp,
> unsigned int pte_access, gfn_t gfn, kvm_pfn_t pfn,
> u64 old_spte, bool prefetch, bool can_unsync,
> bool host_writable, u64 *new_spte);
> -u64 make_huge_page_split_spte(u64 huge_spte, int huge_level, int index);
> +u64 make_huge_page_split_spte(struct kvm *kvm, u64 huge_spte, int huge_level,
> + int index);
> u64 make_nonleaf_spte(u64 *child_pt, bool ad_disabled);
> u64 make_mmio_spte(struct kvm_vcpu *vcpu, u64 gfn, unsigned int access);
> u64 mark_spte_for_access_track(u64 spte);
> diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c
> index af60922906ef..98a45a87f0b2 100644
> --- a/arch/x86/kvm/mmu/tdp_mmu.c
> +++ b/arch/x86/kvm/mmu/tdp_mmu.c
> @@ -1466,7 +1466,8 @@ static int tdp_mmu_split_huge_page(struct kvm *kvm, struct tdp_iter *iter,
> * not been linked in yet and thus is not reachable from any other CPU.
> */
> for (i = 0; i < PT64_ENT_PER_PAGE; i++)
> - sp->spt[i] = make_huge_page_split_spte(huge_spte, level, i);
> + sp->spt[i] = make_huge_page_split_spte(kvm, huge_spte,
> + level, i);
>
> /*
> * Replace the huge spte with a pointer to the populated lower level
> --
> 2.35.1.894.gb6a874cedc-goog
>
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