Date:   Fri, 2 Sep 2022 14:38:44 +0800
From:   Yuan Yao <yuan.yao@...ux.intel.com>
To:     isaku.yamahata@...el.com
Cc:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        isaku.yamahata@...il.com, Paolo Bonzini <pbonzini@...hat.com>,
        erdemaktas@...gle.com, Sean Christopherson <seanjc@...gle.com>,
        Sagi Shahar <sagis@...gle.com>
Subject: Re: [PATCH v8 044/103] KVM: x86/tdp_mmu: Support TDX private mapping
 for TDP MMU

On Sun, Aug 07, 2022 at 03:01:29PM -0700, isaku.yamahata@...el.com wrote:
> From: Isaku Yamahata <isaku.yamahata@...el.com>
>
> Allocate protected page table for private page table, and add hooks to
> operate on protected page table.  This patch adds allocation/free of
> protected page tables and hooks.  When calling hooks to update SPTE entry,
> freeze the entry, call hooks and unfree the entry to allow concurrent
> updates on page tables.  Which is the advantage of TDP MMU.  As
> kvm_gfn_shared_mask() returns false always, those hooks aren't called yet
> with this patch.
>
> When the faulting GPA is private, the KVM fault is called private.  When
> resolving private KVM, allocate protected page table and call hooks to
> operate on protected page table. On the change of the private PTE entry,
> invoke kvm_x86_ops hook in __handle_changed_spte() to propagate the change
> to protected page table. The following depicts the relationship.
>
>   private KVM page fault   |
>       |                    |
>       V                    |
>  private GPA               |     CPU protected EPTP
>       |                    |           |
>       V                    |           V
>  private PT root           |     protected PT root
>       |                    |           |
>       V                    |           V
>    private PT --hook to propagate-->protected PT
>       |                    |           |
>       \--------------------+------\    |
>                            |      |    |
>                            |      V    V
>                            |    private guest page
>                            |
>                            |
>      non-encrypted memory  |    encrypted memory
>                            |
> PT: page table
>
> The existing KVM TDP MMU code uses atomic update of SPTE.  On populating
> the EPT entry, atomically set the entry.  However, it requires TLB
> shootdown to zap SPTE.  To address it, the entry is frozen with the special
> SPTE value that clears the present bit. After the TLB shootdown, the entry
> is set to the eventual value (unfreeze).
>
> For protected page table, hooks are called to update protected page table
> in addition to direct access to the private SPTE. For the zapping case, it
> works to freeze the SPTE. It can call hooks in addition to TLB shootdown.
> For populating the private SPTE entry, there can be a race condition
> without further protection
>
>   vcpu 1: populating 2M private SPTE
>   vcpu 2: populating 4K private SPTE
>   vcpu 2: TDX SEAMCALL to update 4K protected SPTE => error
>   vcpu 1: TDX SEAMCALL to update 2M protected SPTE
>
> To avoid the race, the frozen SPTE is utilized.  Instead of atomic update
> of the private entry, freeze the entry, call the hook that update protected
> SPTE, set the entry to the final value.
>
> Support 4K page only at this stage.  2M page support can be done in future
> patches.
>
> Add is_private member to kvm_page_fault to indicate the fault is private.
> Also is_private member to struct tdp_inter to propagate it.
>
> Co-developed-by: Kai Huang <kai.huang@...el.com>
> Signed-off-by: Kai Huang <kai.huang@...el.com>
> Signed-off-by: Isaku Yamahata <isaku.yamahata@...el.com>
> Acked-by: Isaku Yamahata <isaku.yamahata@...el.com>
> ---
>  arch/x86/include/asm/kvm-x86-ops.h |   2 +
>  arch/x86/include/asm/kvm_host.h    |  20 +++
>  arch/x86/kvm/mmu/mmu.c             |  15 +-
>  arch/x86/kvm/mmu/mmu_internal.h    |  35 +++++
>  arch/x86/kvm/mmu/tdp_iter.h        |   2 +-
>  arch/x86/kvm/mmu/tdp_mmu.c         | 222 ++++++++++++++++++++++++-----
>  arch/x86/kvm/mmu/tdp_mmu.h         |   2 +-
>  virt/kvm/kvm_main.c                |   1 +
>  8 files changed, 259 insertions(+), 40 deletions(-)
>
> diff --git a/arch/x86/include/asm/kvm-x86-ops.h b/arch/x86/include/asm/kvm-x86-ops.h
> index de392bee9159..9fbef4a98fd4 100644
> --- a/arch/x86/include/asm/kvm-x86-ops.h
> +++ b/arch/x86/include/asm/kvm-x86-ops.h
> @@ -93,6 +93,8 @@ KVM_X86_OP_OPTIONAL_RET0(set_tss_addr)
>  KVM_X86_OP_OPTIONAL_RET0(set_identity_map_addr)
>  KVM_X86_OP_OPTIONAL_RET0(get_mt_mask)
>  KVM_X86_OP(load_mmu_pgd)
> +KVM_X86_OP_OPTIONAL(free_private_sp)
> +KVM_X86_OP_OPTIONAL(handle_changed_private_spte)
>  KVM_X86_OP(has_wbinvd_exit)
>  KVM_X86_OP(get_l2_tsc_offset)
>  KVM_X86_OP(get_l2_tsc_multiplier)
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index e4ecf6b8ea0b..df672d80f64e 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -466,6 +466,7 @@ struct kvm_mmu {
>  			 struct kvm_mmu_page *sp);
>  	void (*invlpg)(struct kvm_vcpu *vcpu, gva_t gva, hpa_t root_hpa);
>  	struct kvm_mmu_root_info root;
> +	hpa_t private_root_hpa;
>  	union kvm_cpu_role cpu_role;
>  	union kvm_mmu_page_role root_role;
>
> @@ -1482,6 +1483,20 @@ static inline u16 kvm_lapic_irq_dest_mode(bool dest_mode_logical)
>  	return dest_mode_logical ? APIC_DEST_LOGICAL : APIC_DEST_PHYSICAL;
>  }
>
> +struct kvm_spte {
> +	kvm_pfn_t pfn;
> +	bool is_present;
> +	bool is_last;
> +};
> +
> +struct kvm_spte_change {
> +	gfn_t gfn;
> +	enum pg_level level;
> +	struct kvm_spte old;
> +	struct kvm_spte new;
> +	void *sept_page;
> +};
> +
>  struct kvm_x86_ops {
>  	const char *name;
>
> @@ -1594,6 +1609,11 @@ struct kvm_x86_ops {
>  	void (*load_mmu_pgd)(struct kvm_vcpu *vcpu, hpa_t root_hpa,
>  			     int root_level);
>
> +	int (*free_private_sp)(struct kvm *kvm, gfn_t gfn, enum pg_level level,
> +			       void *private_sp);
> +	void (*handle_changed_private_spte)(
> +		struct kvm *kvm, const struct kvm_spte_change *change);
> +
>  	bool (*has_wbinvd_exit)(void);
>
>  	u64 (*get_l2_tsc_offset)(struct kvm_vcpu *vcpu);
> diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> index 1d8f1349e925..af5746bcf767 100644
> --- a/arch/x86/kvm/mmu/mmu.c
> +++ b/arch/x86/kvm/mmu/mmu.c
> @@ -3615,7 +3615,12 @@ static int mmu_alloc_direct_roots(struct kvm_vcpu *vcpu)
>  		goto out_unlock;
>
>  	if (is_tdp_mmu_enabled(vcpu->kvm)) {
> -		root = kvm_tdp_mmu_get_vcpu_root_hpa(vcpu);
> +		if (kvm_gfn_shared_mask(vcpu->kvm) &&
> +		    !VALID_PAGE(mmu->private_root_hpa)) {
> +			root = kvm_tdp_mmu_get_vcpu_root_hpa(vcpu, true);
> +			mmu->private_root_hpa = root;
> +		}
> +		root = kvm_tdp_mmu_get_vcpu_root_hpa(vcpu, false);
>  		mmu->root.hpa = root;
>  	} else if (shadow_root_level >= PT64_ROOT_4LEVEL) {
>  		root = mmu_alloc_root(vcpu, 0, 0, shadow_root_level);
> @@ -4284,7 +4289,7 @@ static int direct_page_fault(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault
>  	unsigned long mmu_seq;
>  	int r;
>
> -	fault->gfn = fault->addr >> PAGE_SHIFT;
> +	fault->gfn = gpa_to_gfn(fault->addr) & ~kvm_gfn_shared_mask(vcpu->kvm);
>  	fault->slot = kvm_vcpu_gfn_to_memslot(vcpu, fault->gfn);
>
>  	if (page_fault_handle_page_track(vcpu, fault))
> @@ -5830,6 +5835,7 @@ static int __kvm_mmu_create(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu)
>
>  	mmu->root.hpa = INVALID_PAGE;
>  	mmu->root.pgd = 0;
> +	mmu->private_root_hpa = INVALID_PAGE;
>  	for (i = 0; i < KVM_MMU_NUM_PREV_ROOTS; i++)
>  		mmu->prev_roots[i] = KVM_MMU_ROOT_INFO_INVALID;
>
> @@ -6064,7 +6070,7 @@ static void kvm_mmu_zap_memslot(struct kvm *kvm, struct kvm_memory_slot *slot)
>  		};
>
>  		/*
> -		 * this handles both private gfn and shared gfn.
> +		 * This handles both private gfn and shared gfn.
>  		 * All private page should be zapped on memslot deletion.
>  		 */
>  		flush = kvm_tdp_mmu_unmap_gfn_range(kvm, &range, flush, true);
> @@ -6892,6 +6898,9 @@ int kvm_mmu_vendor_module_init(void)
>  void kvm_mmu_destroy(struct kvm_vcpu *vcpu)
>  {
>  	kvm_mmu_unload(vcpu);
> +	if (is_tdp_mmu_enabled(vcpu->kvm))
> +		mmu_free_root_page(vcpu->kvm, &vcpu->arch.mmu->private_root_hpa,
> +				NULL);
>  	free_mmu_pages(&vcpu->arch.root_mmu);
>  	free_mmu_pages(&vcpu->arch.guest_mmu);
>  	mmu_free_memory_caches(vcpu);
> diff --git a/arch/x86/kvm/mmu/mmu_internal.h b/arch/x86/kvm/mmu/mmu_internal.h
> index d43c01e7e37b..4ef61220e52d 100644
> --- a/arch/x86/kvm/mmu/mmu_internal.h
> +++ b/arch/x86/kvm/mmu/mmu_internal.h
> @@ -6,6 +6,8 @@
>  #include <linux/kvm_host.h>
>  #include <asm/kvm_host.h>
>
> +#include "mmu.h"
> +
>  #undef MMU_DEBUG
>
>  #ifdef MMU_DEBUG
> @@ -200,11 +202,30 @@ static inline void kvm_mmu_alloc_private_sp(
>  	}
>  }
>
> +static inline int kvm_alloc_private_sp_for_split(
> +	struct kvm_mmu_page *sp, gfp_t gfp)
> +{
> +	gfp &= ~__GFP_ZERO;
> +	sp->private_sp = (void*)__get_free_page(gfp);
> +	if (!sp->private_sp)
> +		return -ENOMEM;
> +	return 0;
> +}
> +
>  static inline void kvm_mmu_free_private_sp(struct kvm_mmu_page *sp)
>  {
>  	if (sp->private_sp)
>  		free_page((unsigned long)sp->private_sp);
>  }
> +
> +static inline gfn_t kvm_gfn_for_root(struct kvm *kvm, struct kvm_mmu_page *root,
> +				     gfn_t gfn)
> +{
> +	if (is_private_sp(root))
> +		return kvm_gfn_private(kvm, gfn);
> +	else
> +		return kvm_gfn_shared(kvm, gfn);
> +}
>  #else
>  static inline void *kvm_mmu_private_sp(struct kvm_mmu_page *sp)
>  {
> @@ -221,9 +242,21 @@ static inline void kvm_mmu_alloc_private_sp(
>  {
>  }
>
> +static inline int kvm_alloc_private_sp_for_split(
> +	struct kvm_mmu_page *sp, gfp_t gfp)
> +{
> +	return -ENOMEM;
> +}
> +
>  static inline void kvm_mmu_free_private_sp(struct kvm_mmu_page *sp)
>  {
>  }
> +
> +static inline gfn_t kvm_gfn_for_root(struct kvm *kvm, struct kvm_mmu_page *root,
> +				     gfn_t gfn)
> +{
> +	return gfn;
> +}
>  #endif
>
>  static inline bool kvm_mmu_page_ad_need_write_protect(struct kvm_mmu_page *sp)
> @@ -273,6 +306,7 @@ struct kvm_page_fault {
>  	/* Derived from mmu and global state.  */
>  	const bool is_tdp;
>  	const bool nx_huge_page_workaround_enabled;
> +	const bool is_private;
>
>  	/*
>  	 * Whether a >4KB mapping can be created or is forbidden due to NX
> @@ -355,6 +389,7 @@ static inline int kvm_mmu_do_page_fault(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa,
>  		.is_tdp = likely(vcpu->arch.mmu->page_fault == kvm_tdp_page_fault),
>  		.nx_huge_page_workaround_enabled =
>  			is_nx_huge_page_enabled(vcpu->kvm),
> +		.is_private = kvm_is_private_gpa(vcpu->kvm, cr2_or_gpa),
>
>  		.max_level = vcpu->kvm->arch.tdp_max_page_level,
>  		.req_level = PG_LEVEL_4K,
> diff --git a/arch/x86/kvm/mmu/tdp_iter.h b/arch/x86/kvm/mmu/tdp_iter.h
> index 9e56a5b1024c..eab62baf8549 100644
> --- a/arch/x86/kvm/mmu/tdp_iter.h
> +++ b/arch/x86/kvm/mmu/tdp_iter.h
> @@ -71,7 +71,7 @@ struct tdp_iter {
>  	tdp_ptep_t pt_path[PT64_ROOT_MAX_LEVEL];
>  	/* A pointer to the current SPTE */
>  	tdp_ptep_t sptep;
> -	/* The lowest GFN mapped by the current SPTE */
> +	/* The lowest GFN (shared bits included) mapped by the current SPTE */
>  	gfn_t gfn;
>  	/* The level of the root page given to the iterator */
>  	int root_level;
> diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c
> index 6a680e0a9260..59fe111e742a 100644
> --- a/arch/x86/kvm/mmu/tdp_mmu.c
> +++ b/arch/x86/kvm/mmu/tdp_mmu.c
> @@ -285,6 +285,11 @@ static struct kvm_mmu_page *tdp_mmu_alloc_sp(struct kvm_vcpu *vcpu,
>  	sp->spt = kvm_mmu_memory_cache_alloc(&vcpu->arch.mmu_shadow_page_cache);
>  	sp->role = role;
>
> +	if (kvm_mmu_page_role_is_private(role))
> +		kvm_mmu_alloc_private_sp(vcpu, NULL, sp);
> +	else
> +		kvm_mmu_init_private_sp(sp, NULL);
> +
>  	return sp;
>  }
>
> @@ -301,12 +306,12 @@ static void tdp_mmu_init_sp(struct kvm_mmu_page *sp, tdp_ptep_t sptep,
>  	sp->gfn = gfn;
>  	sp->ptep = sptep;
>  	sp->tdp_mmu_page = true;
> -	kvm_mmu_init_private_sp(sp, NULL);
>
>  	trace_kvm_mmu_get_page(sp, true);
>  }
>
> -hpa_t kvm_tdp_mmu_get_vcpu_root_hpa(struct kvm_vcpu *vcpu)
> +static struct kvm_mmu_page *kvm_tdp_mmu_get_vcpu_root(struct kvm_vcpu *vcpu,
> +						      bool private)
>  {
>  	union kvm_mmu_page_role role = vcpu->arch.mmu->root_role;
>  	struct kvm *kvm = vcpu->kvm;
> @@ -318,6 +323,8 @@ hpa_t kvm_tdp_mmu_get_vcpu_root_hpa(struct kvm_vcpu *vcpu)
>  	 * Check for an existing root before allocating a new one.  Note, the
>  	 * role check prevents consuming an invalid root.
>  	 */
> +	if (private)
> +		kvm_mmu_page_role_set_private(&role);
>  	for_each_tdp_mmu_root(kvm, root, kvm_mmu_role_as_id(role)) {
>  		if (root->role.word == role.word &&
>  		    kvm_tdp_mmu_get_root(root))
> @@ -334,12 +341,17 @@ hpa_t kvm_tdp_mmu_get_vcpu_root_hpa(struct kvm_vcpu *vcpu)
>  	spin_unlock(&kvm->arch.tdp_mmu_pages_lock);
>
>  out:
> -	return __pa(root->spt);
> +	return root;
> +}
> +
> +hpa_t kvm_tdp_mmu_get_vcpu_root_hpa(struct kvm_vcpu *vcpu, bool private)
> +{
> +	return __pa(kvm_tdp_mmu_get_vcpu_root(vcpu, private)->spt);
>  }
>
>  static void handle_changed_spte(struct kvm *kvm, int as_id, gfn_t gfn,
> -				u64 old_spte, u64 new_spte, int level,
> -				bool shared);
> +				u64 old_spte, u64 new_spte,
> +				union kvm_mmu_page_role role, bool shared);
>
>  static void handle_changed_spte_acc_track(u64 old_spte, u64 new_spte, int level)
>  {
> @@ -365,6 +377,8 @@ static void handle_changed_spte_dirty_log(struct kvm *kvm, int as_id, gfn_t gfn,
>
>  	if ((!is_writable_pte(old_spte) || pfn_changed) &&
>  	    is_writable_pte(new_spte)) {
> +		/* For memory slot operations, use GFN without aliasing */
> +		gfn = gfn & ~kvm_gfn_shared_mask(kvm);
>  		slot = __gfn_to_memslot(__kvm_memslots(kvm, as_id), gfn);
>  		mark_page_dirty_in_slot(kvm, slot, gfn);
>  	}
> @@ -489,7 +503,18 @@ static void handle_removed_pt(struct kvm *kvm, tdp_ptep_t pt, bool shared)
>  							  REMOVED_SPTE, level);
>  		}
>  		handle_changed_spte(kvm, kvm_mmu_page_as_id(sp), gfn,
> -				    old_spte, REMOVED_SPTE, level, shared);
> +				    old_spte, REMOVED_SPTE, sp->role, shared);
> +	}
> +
> +	if (is_private_sp(sp) && WARN_ON(static_call(kvm_x86_free_private_sp)(
> +						   kvm, sp->gfn, sp->role.level,
> +						   kvm_mmu_private_sp(sp)))) {
> +		/*
> +		 * Failed to unlink Secure EPT page and there is nothing to do
> +		 * further.  Intentionally leak the page to prevent the kernel
> +		 * from accessing the encrypted page.
> +		 */
> +		kvm_mmu_init_private_sp(sp, NULL);
>  	}
>
>  	call_rcu(&sp->rcu_head, tdp_mmu_free_sp_rcu_callback);
> @@ -502,7 +527,7 @@ static void handle_removed_pt(struct kvm *kvm, tdp_ptep_t pt, bool shared)
>   * @gfn: the base GFN that was mapped by the SPTE
>   * @old_spte: The value of the SPTE before the change
>   * @new_spte: The value of the SPTE after the change
> - * @level: the level of the PT the SPTE is part of in the paging structure
> + * @role: the role of the PT the SPTE is part of in the paging structure
>   * @shared: This operation may not be running under the exclusive use of
>   *	    the MMU lock and the operation must synchronize with other
>   *	    threads that might be modifying SPTEs.
> @@ -511,14 +536,34 @@ static void handle_removed_pt(struct kvm *kvm, tdp_ptep_t pt, bool shared)
>   * This function must be called for all TDP SPTE modifications.
>   */
>  static void __handle_changed_spte(struct kvm *kvm, int as_id, gfn_t gfn,
> -				  u64 old_spte, u64 new_spte, int level,
> -				  bool shared)
> +				  u64 old_spte, u64 new_spte,
> +				  union kvm_mmu_page_role role, bool shared)
>  {
> +	bool is_private = kvm_mmu_page_role_is_private(role);
> +	int level = role.level;
>  	bool was_present = is_shadow_present_pte(old_spte);
>  	bool is_present = is_shadow_present_pte(new_spte);
> -	bool was_leaf = was_present && is_last_spte(old_spte, level);
> -	bool is_leaf = is_present && is_last_spte(new_spte, level);
> -	bool pfn_changed = spte_to_pfn(old_spte) != spte_to_pfn(new_spte);
> +	bool was_last = is_last_spte(old_spte, level);
> +	bool is_last = is_last_spte(new_spte, level);
> +	bool was_leaf = was_present && was_last;
> +	bool is_leaf = is_present && is_last;
> +	kvm_pfn_t old_pfn = spte_to_pfn(old_spte);
> +	kvm_pfn_t new_pfn = spte_to_pfn(new_spte);
> +	bool pfn_changed = old_pfn != new_pfn;
> +	struct kvm_spte_change change = {
> +		.gfn = gfn,
> +		.level = level,
> +		.old = {
> +			.pfn = old_pfn,
> +			.is_present = was_present,
> +			.is_last = was_last,
> +		},
> +		.new = {
> +			.pfn = new_pfn,
> +			.is_present = is_present,
> +			.is_last = is_last,
> +		},
> +	};
>
>  	WARN_ON(level > PT64_ROOT_MAX_LEVEL);
>  	WARN_ON(level < PG_LEVEL_4K);
> @@ -585,7 +630,7 @@ static void __handle_changed_spte(struct kvm *kvm, int as_id, gfn_t gfn,
>
>  	if (was_leaf && is_dirty_spte(old_spte) &&
>  	    (!is_present || !is_dirty_spte(new_spte) || pfn_changed))
> -		kvm_set_pfn_dirty(spte_to_pfn(old_spte));
> +		kvm_set_pfn_dirty(old_pfn);
>
>  	/*
>  	 * Recursively handle child PTs if the change removed a subtree from
> @@ -594,19 +639,48 @@ static void __handle_changed_spte(struct kvm *kvm, int as_id, gfn_t gfn,
>  	 * pages are kernel allocations and should never be migrated.
>  	 */
>  	if (was_present && !was_leaf &&
> -	    (is_leaf || !is_present || WARN_ON_ONCE(pfn_changed)))
> +	    (is_leaf || !is_present || WARN_ON_ONCE(pfn_changed))) {
> +		WARN_ON(is_private !=
> +			is_private_sptep(spte_to_child_pt(old_spte, level)));
>  		handle_removed_pt(kvm, spte_to_child_pt(old_spte, level), shared);
> +	}
> +
> +	/*
> +	 * Special handling for the private mapping.  We are either
> +	 * setting up new mapping at middle level page table, or leaf,
> +	 * or tearing down existing mapping.
> +	 *
> +	 * This is after handling lower page table by above
> +	 * handle_remove_tdp_mmu_page().  S-EPT requires to remove S-EPT tables

s/handle_remove_tdp_mmu_page/handle_removed_pt

> +	 * after removing childrens.
> +	 */
> +	if (is_private &&
> +	    /* Ignore change of software only bits. e.g. host_writable */
> +	    (was_leaf != is_leaf || was_present != is_present || pfn_changed)) {
> +		void *sept_page = NULL;
> +
> +		if (is_present && !is_leaf) {
> +			struct kvm_mmu_page *sp = to_shadow_page(pfn_to_hpa(new_pfn));
> +
> +			sept_page = kvm_mmu_private_sp(sp);
> +			WARN_ON(!sept_page);
> +			WARN_ON(sp->role.level + 1 != level);
> +			WARN_ON(sp->gfn != gfn);
> +		}
> +		change.sept_page = sept_page;
> +
> +		static_call(kvm_x86_handle_changed_private_spte)(kvm, &change);
> +	}
>  }
>
>  static void handle_changed_spte(struct kvm *kvm, int as_id, gfn_t gfn,
> -				u64 old_spte, u64 new_spte, int level,
> -				bool shared)
> +				u64 old_spte, u64 new_spte,
> +				union kvm_mmu_page_role role, bool shared)
>  {
> -	__handle_changed_spte(kvm, as_id, gfn, old_spte, new_spte, level,
> -			      shared);
> -	handle_changed_spte_acc_track(old_spte, new_spte, level);
> +	__handle_changed_spte(kvm, as_id, gfn, old_spte, new_spte, role, shared);
> +	handle_changed_spte_acc_track(old_spte, new_spte, role.level);
>  	handle_changed_spte_dirty_log(kvm, as_id, gfn, old_spte,
> -				      new_spte, level);
> +				      new_spte, role.level);
>  }
>
>  /*
> @@ -630,6 +704,24 @@ static inline int tdp_mmu_set_spte_atomic(struct kvm *kvm,
>  					  struct tdp_iter *iter,
>  					  u64 new_spte)
>  {
> +	/*
> +	 * For conventional page table, the update flow is
> +	 * - update STPE with atomic operation
> +	 * - hanlde changed SPTE. __handle_changed_spte()
> +	 * NOTE: __handle_changed_spte() (and functions) must be safe against
> +	 * concurrent update.  It is an exception to zap SPTE.  See
> +	 * tdp_mmu_zap_spte_atomic().
> +	 *
> +	 * For private page table, callbacks are needed to propagate SPTE
> +	 * change into the protected page table.  In order to atomically update
> +	 * both the SPTE and the protected page tables with callbacks, utilize
> +	 * freezing SPTE.
> +	 * - Freeze the SPTE. Set entry to REMOVED_SPTE.
> +	 * - Trigger callbacks for protected page tables. __handle_changed_spte()
> +	 * - Unfreeze the SPTE.  Set the entry to new_spte.
> +	 */
> +	bool freeze_spte = is_private_sptep(iter->sptep) && !is_removed_spte(new_spte);
> +	u64 tmp_spte = freeze_spte ? REMOVED_SPTE : new_spte;
>  	u64 *sptep = rcu_dereference(iter->sptep);
>
>  	/*
> @@ -646,13 +738,17 @@ static inline int tdp_mmu_set_spte_atomic(struct kvm *kvm,
>  	 * Note, fast_pf_fix_direct_spte() can also modify TDP MMU SPTEs and
>  	 * does not hold the mmu_lock.
>  	 */
> -	if (!try_cmpxchg64(sptep, &iter->old_spte, new_spte))
> +	if (!try_cmpxchg64(sptep, &iter->old_spte, tmp_spte))
>  		return -EBUSY;
>
> -	__handle_changed_spte(kvm, iter->as_id, iter->gfn, iter->old_spte,
> -			      new_spte, iter->level, true);
> +	__handle_changed_spte(
> +		kvm, iter->as_id, iter->gfn,
> +		iter->old_spte, new_spte, sptep_to_sp(sptep)->role, true);
>  	handle_changed_spte_acc_track(iter->old_spte, new_spte, iter->level);
>
> +	if (freeze_spte)
> +		__kvm_tdp_mmu_write_spte(sptep, new_spte);
> +
>  	return 0;
>  }
>
> @@ -719,9 +815,11 @@ static inline int tdp_mmu_zap_spte_atomic(struct kvm *kvm,
>   * SPTE had voldatile bits.
>   */
>  static u64 __tdp_mmu_set_spte(struct kvm *kvm, int as_id, tdp_ptep_t sptep,
> -			      u64 old_spte, u64 new_spte, gfn_t gfn, int level,
> -			      bool record_acc_track, bool record_dirty_log)
> +			       u64 old_spte, u64 new_spte, gfn_t gfn, int level,
> +			       bool record_acc_track, bool record_dirty_log)
>  {
> +	union kvm_mmu_page_role role;
> +
>  	lockdep_assert_held_write(&kvm->mmu_lock);
>
>  	/*
> @@ -735,7 +833,9 @@ static u64 __tdp_mmu_set_spte(struct kvm *kvm, int as_id, tdp_ptep_t sptep,
>
>  	old_spte = kvm_tdp_mmu_write_spte(sptep, old_spte, new_spte, level);
>
> -	__handle_changed_spte(kvm, as_id, gfn, old_spte, new_spte, level, false);
> +	role = sptep_to_sp(sptep)->role;
> +	role.level = level;
> +	__handle_changed_spte(kvm, as_id, gfn, old_spte, new_spte, role, false);
>
>  	if (record_acc_track)
>  		handle_changed_spte_acc_track(old_spte, new_spte, level);
> @@ -787,8 +887,11 @@ static inline void tdp_mmu_set_spte_no_dirty_log(struct kvm *kvm,
>  			continue;					\
>  		else
>
> -#define tdp_mmu_for_each_pte(_iter, _mmu, _start, _end)		\
> -	for_each_tdp_pte(_iter, to_shadow_page(_mmu->root.hpa), _start, _end)
> +#define tdp_mmu_for_each_pte(_iter, _mmu, _private, _start, _end)	\
> +	for_each_tdp_pte(_iter,						\
> +		 to_shadow_page((_private) ? _mmu->private_root_hpa :	\
> +				_mmu->root.hpa),			\
> +		_start, _end)
>
>  /*
>   * Yield if the MMU lock is contended or this thread needs to return control
> @@ -951,6 +1054,14 @@ static bool tdp_mmu_zap_leafs(struct kvm *kvm, struct kvm_mmu_page *root,
>  	if (!zap_private && is_private_sp(root))
>  		return false;
>
> +	/*
> +	 * start and end doesn't have GFN shared bit.  This function zaps
> +	 * a region including alias.  Adjust shared bit of [start, end) if the
> +	 * root is shared.
> +	 */
> +	start = kvm_gfn_for_root(kvm, root, start);
> +	end = kvm_gfn_for_root(kvm, root, end);
> +
>  	rcu_read_lock();
>
>  	for_each_tdp_pte_min_level(iter, root, PG_LEVEL_4K, start, end) {
> @@ -1079,10 +1190,19 @@ static int tdp_mmu_map_handle_target_level(struct kvm_vcpu *vcpu,
>  	WARN_ON(sp->role.level != fault->goal_level);
>  	if (unlikely(!fault->slot))
>  		new_spte = make_mmio_spte(vcpu, iter->gfn, ACC_ALL);
> -	else
> -		wrprot = make_spte(vcpu, sp, fault->slot, ACC_ALL, iter->gfn,
> -					 fault->pfn, iter->old_spte, fault->prefetch, true,
> -					 fault->map_writable, &new_spte);
> +	else {
> +		unsigned long pte_access = ACC_ALL;
> +		gfn_t gfn_unalias = iter->gfn & ~kvm_gfn_shared_mask(vcpu->kvm);
> +
> +		/* TDX shared GPAs are no executable, enforce this for the SDV. */
> +		if (kvm_gfn_shared_mask(vcpu->kvm) && !fault->is_private)
> +			pte_access &= ~ACC_EXEC_MASK;
> +
> +		wrprot = make_spte(vcpu, sp, fault->slot, pte_access,
> +				   gfn_unalias, fault->pfn, iter->old_spte,
> +				   fault->prefetch, true, fault->map_writable,
> +				   &new_spte);
> +	}
>
>  	if (new_spte == iter->old_spte)
>  		ret = RET_PF_SPURIOUS;
> @@ -1181,6 +1301,8 @@ 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;
> +	gfn_t raw_gfn;
> +	bool is_private = fault->is_private;
>  	int ret;
>
>  	kvm_mmu_hugepage_adjust(vcpu, fault);
> @@ -1189,7 +1311,17 @@ int kvm_tdp_mmu_map(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault)
>
>  	rcu_read_lock();
>
> -	tdp_mmu_for_each_pte(iter, mmu, fault->gfn, fault->gfn + 1) {
> +	raw_gfn = gpa_to_gfn(fault->addr);
> +
> +	if (is_error_noslot_pfn(fault->pfn) ||
> +	    !kvm_pfn_to_refcounted_page(fault->pfn)) {
> +		if (is_private) {
> +			rcu_read_unlock();
> +			return -EFAULT;
> +		}
> +	}
> +
> +	tdp_mmu_for_each_pte(iter, mmu, is_private, raw_gfn, raw_gfn + 1) {
>  		if (fault->nx_huge_page_workaround_enabled)
>  			disallowed_hugepage_adjust(fault, iter.old_spte, iter.level);
>
> @@ -1205,6 +1337,12 @@ int kvm_tdp_mmu_map(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault)
>  		    is_large_pte(iter.old_spte)) {
>  			if (tdp_mmu_zap_spte_atomic(vcpu->kvm, &iter))
>  				break;
> +			/*
> +			 * TODO: large page support.
> +			 * Doesn't support large page for TDX now
> +			 */
> +			WARN_ON(is_private_sptep(iter.sptep));
> +
>
>  			/*
>  			 * The iter must explicitly re-read the spte here
> @@ -1448,6 +1586,12 @@ static struct kvm_mmu_page *__tdp_mmu_alloc_sp_for_split(
>
>  	sp->role = role;
>  	sp->spt = (void *)__get_free_page(gfp);
> +	if (kvm_mmu_page_role_is_private(role)) {
> +		if (kvm_alloc_private_sp_for_split(sp, gfp)) {
> +			free_page((unsigned long)sp->spt);
> +			sp->spt = NULL;
> +		}
> +	}
>  	if (!sp->spt) {
>  		kmem_cache_free(mmu_page_header_cache, sp);
>  		return NULL;
> @@ -1463,6 +1607,11 @@ static struct kvm_mmu_page *tdp_mmu_alloc_sp_for_split(struct kvm *kvm,
>  	union kvm_mmu_page_role role = tdp_iter_child_role(iter);
>  	struct kvm_mmu_page *sp;
>
> +	WARN_ON(kvm_mmu_page_role_is_private(role) !=
> +		is_private_sptep(iter->sptep));
> +	/* TODO: Large page isn't supported for private SPTE yet. */
> +	WARN_ON(kvm_mmu_page_role_is_private(role));
> +
>  	/*
>  	 * Since we are allocating while under the MMU lock we have to be
>  	 * careful about GFP flags. Use GFP_NOWAIT to avoid blocking on direct
> @@ -1897,7 +2046,7 @@ int kvm_tdp_mmu_get_walk(struct kvm_vcpu *vcpu, u64 addr, u64 *sptes,
>  	if (WARN_ON(kvm_gfn_shared_mask(vcpu->kvm)))
>  		return leaf;
>
> -	tdp_mmu_for_each_pte(iter, mmu, gfn, gfn + 1) {
> +	tdp_mmu_for_each_pte(iter, mmu, false, gfn, gfn + 1) {
>  		leaf = iter.level;
>  		sptes[leaf] = iter.old_spte;
>  	}
> @@ -1924,7 +2073,10 @@ u64 *kvm_tdp_mmu_fast_pf_get_last_sptep(struct kvm_vcpu *vcpu, u64 addr,
>  	gfn_t gfn = addr >> PAGE_SHIFT;
>  	tdp_ptep_t sptep = NULL;
>
> -	tdp_mmu_for_each_pte(iter, mmu, gfn, gfn + 1) {
> +	/* fast page fault for private GPA isn't supported. */
> +	WARN_ON_ONCE(kvm_is_private_gpa(vcpu->kvm, addr));
> +
> +	tdp_mmu_for_each_pte(iter, mmu, false, gfn, gfn + 1) {
>  		*spte = iter.old_spte;
>  		sptep = iter.sptep;
>  	}
> diff --git a/arch/x86/kvm/mmu/tdp_mmu.h b/arch/x86/kvm/mmu/tdp_mmu.h
> index c98c7df449a8..695175c921a5 100644
> --- a/arch/x86/kvm/mmu/tdp_mmu.h
> +++ b/arch/x86/kvm/mmu/tdp_mmu.h
> @@ -5,7 +5,7 @@
>
>  #include <linux/kvm_host.h>
>
> -hpa_t kvm_tdp_mmu_get_vcpu_root_hpa(struct kvm_vcpu *vcpu);
> +hpa_t kvm_tdp_mmu_get_vcpu_root_hpa(struct kvm_vcpu *vcpu, bool private);
>
>  __must_check static inline bool kvm_tdp_mmu_get_root(struct kvm_mmu_page *root)
>  {
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index 8a36844b423c..c44e5d7d418f 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -213,6 +213,7 @@ struct page *kvm_pfn_to_refcounted_page(kvm_pfn_t pfn)
>
>  	return NULL;
>  }
> +EXPORT_SYMBOL_GPL(kvm_pfn_to_refcounted_page);
>
>  /*
>   * Switches to specified vcpu, until a matching vcpu_put()
> --
> 2.25.1
>

Powered by blists - more mailing lists