Re: [PATCH v2 08/18] KVM: x86/mmu: do not pass vcpu to root freeing functions

Maxim Levitsky
2022-02-23T15:17:19Z

On Thu, 2022-02-17 at 16:03 -0500, Paolo Bonzini wrote:
> These functions only operate on a given MMU, of which there are two in a vCPU.
> They also need a struct kvm in order to lock the mmu_lock, but they do not
> needed anything else in the struct kvm_vcpu. So, pass the vcpu->kvm directly
> to them.
>
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> ---
> arch/x86/include/asm/kvm_host.h | 4 ++--
> arch/x86/kvm/mmu/mmu.c | 21 +++++++++++----------
> arch/x86/kvm/vmx/nested.c | 8 ++++----
> arch/x86/kvm/x86.c | 4 ++--
> 4 files changed, 19 insertions(+), 18 deletions(-)
>
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index 6442facfd5c0..79f37ccc8726 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -1780,9 +1780,9 @@ void kvm_inject_nmi(struct kvm_vcpu *vcpu);
> void kvm_update_dr7(struct kvm_vcpu *vcpu);
>
> int kvm_mmu_unprotect_page(struct kvm *kvm, gfn_t gfn);
> -void kvm_mmu_free_roots(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu,
> +void kvm_mmu_free_roots(struct kvm *kvm, struct kvm_mmu *mmu,
> ulong roots_to_free);
> -void kvm_mmu_free_guest_mode_roots(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu);
> +void kvm_mmu_free_guest_mode_roots(struct kvm *kvm, struct kvm_mmu *mmu);
> gpa_t kvm_mmu_gva_to_gpa_read(struct kvm_vcpu *vcpu, gva_t gva,
> struct x86_exception *exception);
> gpa_t kvm_mmu_gva_to_gpa_fetch(struct kvm_vcpu *vcpu, gva_t gva,
> diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> index e1578f71feae..0f2de811e871 100644
> --- a/arch/x86/kvm/mmu/mmu.c
> +++ b/arch/x86/kvm/mmu/mmu.c
> @@ -3234,10 +3234,9 @@ static void mmu_free_root_page(struct kvm *kvm, hpa_t *root_hpa,
> }
>
> /* roots_to_free must be some combination of the KVM_MMU_ROOT_* flags */
> -void kvm_mmu_free_roots(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu,
> +void kvm_mmu_free_roots(struct kvm *kvm, struct kvm_mmu *mmu,
> ulong roots_to_free)
> {
> - struct kvm *kvm = vcpu->kvm;
> int i;
> LIST_HEAD(invalid_list);
> bool free_active_root;
> @@ -3287,7 +3286,7 @@ void kvm_mmu_free_roots(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu,
> }
> EXPORT_SYMBOL_GPL(kvm_mmu_free_roots);
>
> -void kvm_mmu_free_guest_mode_roots(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu)
> +void kvm_mmu_free_guest_mode_roots(struct kvm *kvm, struct kvm_mmu *mmu)
> {
> unsigned long roots_to_free = 0;
> hpa_t root_hpa;
> @@ -3309,7 +3308,7 @@ void kvm_mmu_free_guest_mode_roots(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu)
> roots_to_free |= KVM_MMU_ROOT_PREVIOUS(i);
> }
>
> - kvm_mmu_free_roots(vcpu, mmu, roots_to_free);
> + kvm_mmu_free_roots(kvm, mmu, roots_to_free);
> }
> EXPORT_SYMBOL_GPL(kvm_mmu_free_guest_mode_roots);
>
> @@ -3710,7 +3709,7 @@ void kvm_mmu_sync_prev_roots(struct kvm_vcpu *vcpu)
> roots_to_free |= KVM_MMU_ROOT_PREVIOUS(i);
>
> /* sync prev_roots by simply freeing them */
> - kvm_mmu_free_roots(vcpu, vcpu->arch.mmu, roots_to_free);
> + kvm_mmu_free_roots(vcpu->kvm, vcpu->arch.mmu, roots_to_free);
> }
>
> static gpa_t nonpaging_gva_to_gpa(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu,
> @@ -4159,8 +4158,10 @@ static bool fast_pgd_switch(struct kvm_vcpu *vcpu, gpa_t new_pgd,
> static void __kvm_mmu_new_pgd(struct kvm_vcpu *vcpu, gpa_t new_pgd,
> union kvm_mmu_page_role new_role)
> {
> + struct kvm_mmu *mmu = vcpu->arch.mmu;
> +
> if (!fast_pgd_switch(vcpu, new_pgd, new_role)) {
> - kvm_mmu_free_roots(vcpu, vcpu->arch.mmu, KVM_MMU_ROOT_CURRENT);
> + kvm_mmu_free_roots(vcpu->kvm, mmu, KVM_MMU_ROOT_CURRENT);
> return;
> }
>
> @@ -5083,10 +5084,10 @@ int kvm_mmu_load(struct kvm_vcpu *vcpu)
> return r;
> }
>
> -static void __kvm_mmu_unload(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu)
> +static void __kvm_mmu_unload(struct kvm *kvm, struct kvm_mmu *mmu)
> {
> int i;
> - kvm_mmu_free_roots(vcpu, mmu, KVM_MMU_ROOTS_ALL);
> + kvm_mmu_free_roots(kvm, mmu, KVM_MMU_ROOTS_ALL);
> WARN_ON(VALID_PAGE(mmu->root.hpa));
> if (mmu->pae_root) {
> for (i = 0; i < 4; ++i)
> @@ -5096,8 +5097,8 @@ static void __kvm_mmu_unload(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu)
>
> void kvm_mmu_unload(struct kvm_vcpu *vcpu)
> {
> - __kvm_mmu_unload(vcpu, &vcpu->arch.root_mmu);
> - __kvm_mmu_unload(vcpu, &vcpu->arch.guest_mmu);
> + __kvm_mmu_unload(vcpu->kvm, &vcpu->arch.root_mmu);
> + __kvm_mmu_unload(vcpu->kvm, &vcpu->arch.guest_mmu);
> }
>
> static bool need_remote_flush(u64 old, u64 new)
> diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
> index 29289ecca223..b7bc634d35e2 100644
> --- a/arch/x86/kvm/vmx/nested.c
> +++ b/arch/x86/kvm/vmx/nested.c
> @@ -321,7 +321,7 @@ static void free_nested(struct kvm_vcpu *vcpu)
> kvm_vcpu_unmap(vcpu, &vmx->nested.pi_desc_map, true);
> vmx->nested.pi_desc = NULL;
>
> - kvm_mmu_free_roots(vcpu, &vcpu->arch.guest_mmu, KVM_MMU_ROOTS_ALL);
> + kvm_mmu_free_roots(vcpu->kvm, &vcpu->arch.guest_mmu, KVM_MMU_ROOTS_ALL);
>
> nested_release_evmcs(vcpu);
>
> @@ -5007,7 +5007,7 @@ static inline void nested_release_vmcs12(struct kvm_vcpu *vcpu)
> vmx->nested.current_vmptr >> PAGE_SHIFT,
> vmx->nested.cached_vmcs12, 0, VMCS12_SIZE);
>
> - kvm_mmu_free_roots(vcpu, &vcpu->arch.guest_mmu, KVM_MMU_ROOTS_ALL);
> + kvm_mmu_free_roots(vcpu->kvm, &vcpu->arch.guest_mmu, KVM_MMU_ROOTS_ALL);
>
> vmx->nested.current_vmptr = INVALID_GPA;
> }
> @@ -5486,7 +5486,7 @@ static int handle_invept(struct kvm_vcpu *vcpu)
> }
>
> if (roots_to_free)
> - kvm_mmu_free_roots(vcpu, mmu, roots_to_free);
> + kvm_mmu_free_roots(vcpu->kvm, mmu, roots_to_free);
>
> return nested_vmx_succeed(vcpu);
> }
> @@ -5575,7 +5575,7 @@ static int handle_invvpid(struct kvm_vcpu *vcpu)
> * TODO: sync only the affected SPTEs for INVDIVIDUAL_ADDR.
> */
> if (!enable_ept)
> - kvm_mmu_free_guest_mode_roots(vcpu, &vcpu->arch.root_mmu);
> + kvm_mmu_free_guest_mode_roots(vcpu->kvm, &vcpu->arch.root_mmu);
>
> return nested_vmx_succeed(vcpu);
> }
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index c0d7256e3a78..6aefd7ac7039 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -855,7 +855,7 @@ int load_pdptrs(struct kvm_vcpu *vcpu, unsigned long cr3)
> * Shadow page roots need to be reconstructed instead.
> */
> if (!tdp_enabled && memcmp(mmu->pdptrs, pdpte, sizeof(mmu->pdptrs)))
> - kvm_mmu_free_roots(vcpu, mmu, KVM_MMU_ROOT_CURRENT);
> + kvm_mmu_free_roots(vcpu->kvm, mmu, KVM_MMU_ROOT_CURRENT);
>
> memcpy(mmu->pdptrs, pdpte, sizeof(mmu->pdptrs));
> kvm_register_mark_dirty(vcpu, VCPU_EXREG_PDPTR);
> @@ -1156,7 +1156,7 @@ static void kvm_invalidate_pcid(struct kvm_vcpu *vcpu, unsigned long pcid)
> if (kvm_get_pcid(vcpu, mmu->prev_roots[i].pgd) == pcid)
> roots_to_free |= KVM_MMU_ROOT_PREVIOUS(i);
>
> - kvm_mmu_free_roots(vcpu, mmu, roots_to_free);
> + kvm_mmu_free_roots(vcpu->kvm, mmu, roots_to_free);
> }
>
> int kvm_set_cr3(struct kvm_vcpu *vcpu, unsigned long cr3)

IMHO anything that is related to guest memory should work on
VM level (that is struct kvm).

It is just ironically sad that writing to a guest page requires
these days a vCPU due to dirty ring tracking.

Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>

Best regards,
Maxim Levitsky