Commit a102a674 authored by Sean Christopherson's avatar Sean Christopherson Committed by Paolo Bonzini
Browse files

KVM: x86/mmu: Don't drop level/direct from MMU role calculation 



Use the calculated role as-is when propagating it to kvm_mmu.mmu_role,
i.e. stop masking off meaningful fields.  The concept of masking off
fields came from kvm_mmu_pte_write(), which (correctly) ignores certain
fields when comparing kvm_mmu_page.role against kvm_mmu.mmu_role, e.g.
the current mmu's access and level have no relation to a shadow page's
access and level.

Masking off the level causes problems for 5-level paging, e.g. CR4.LA57
has its own redundant flag in the extended role, and nested EPT would
need a similar hack to support 5-level paging for L2.

Opportunistically rework the mask for kvm_mmu_pte_write() to define the
fields that should be ignored as opposed to the fields that should be
checked, i.e. make it opt-out instead of opt-in so that new fields are
automatically picked up.  While doing so, stop ignoring "direct".  The
field is effectively ignored anyways because kvm_mmu_pte_write() is only
reached with an indirect mmu and the loop only walks indirect shadow
pages, but double checking "direct" literally costs nothing.

Signed-off-by: default avatarSean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent e743664b

arch/x86/kvm/mmu/mmu.c

+18 −17
Original line number Diff line number Diff line
@@ -215,17 +215,6 @@ struct kvm_shadow_walk_iterator { 
	unsigned index;

};



static const union kvm_mmu_page_role mmu_base_role_mask = {

	.cr0_wp = 1,

	.gpte_is_8_bytes = 1,

	.nxe = 1,

	.smep_andnot_wp = 1,

	.smap_andnot_wp = 1,

	.smm = 1,

	.guest_mode = 1,

	.ad_disabled = 1,

};



#define for_each_shadow_entry_using_root(_vcpu, _root, _addr, _walker)     \

	for (shadow_walk_init_using_root(&(_walker), (_vcpu),              \

					 (_root), (_addr));                \
@@ -4930,7 +4919,6 @@ static void init_kvm_tdp_mmu(struct kvm_vcpu *vcpu) 
	union kvm_mmu_role new_role =

		kvm_calc_tdp_mmu_root_page_role(vcpu, false);



	new_role.base.word &= mmu_base_role_mask.word;

	if (new_role.as_u64 == context->mmu_role.as_u64)

		return;
@@ -5002,7 +4990,6 @@ void kvm_init_shadow_mmu(struct kvm_vcpu *vcpu) 
	union kvm_mmu_role new_role =

		kvm_calc_shadow_mmu_root_page_role(vcpu, false);



	new_role.base.word &= mmu_base_role_mask.word;

	if (new_role.as_u64 == context->mmu_role.as_u64)

		return;
@@ -5059,7 +5046,6 @@ void kvm_init_shadow_ept_mmu(struct kvm_vcpu *vcpu, bool execonly, 


	__kvm_mmu_new_cr3(vcpu, new_eptp, new_role.base, false);



	new_role.base.word &= mmu_base_role_mask.word;

	if (new_role.as_u64 == context->mmu_role.as_u64)

		return;
@@ -5100,7 +5086,6 @@ static void init_kvm_nested_mmu(struct kvm_vcpu *vcpu) 
	union kvm_mmu_role new_role = kvm_calc_mmu_role_common(vcpu, false);

	struct kvm_mmu *g_context = &vcpu->arch.nested_mmu;



	new_role.base.word &= mmu_base_role_mask.word;

	if (new_role.as_u64 == g_context->mmu_role.as_u64)

		return;
@@ -5339,6 +5324,22 @@ static u64 *get_written_sptes(struct kvm_mmu_page *sp, gpa_t gpa, int *nspte) 
	return spte;

}



/*

 * Ignore various flags when determining if a SPTE can be immediately

 * overwritten for the current MMU.

 *  - level: explicitly checked in mmu_pte_write_new_pte(), and will never

 *    match the current MMU role, as MMU's level tracks the root level.

 *  - access: updated based on the new guest PTE

 *  - quadrant: handled by get_written_sptes()

 *  - invalid: always false (loop only walks valid shadow pages)

 */

static const union kvm_mmu_page_role role_ign = {

	.level = 0xf,

	.access = 0x7,

	.quadrant = 0x3,

	.invalid = 0x1,

};



static void kvm_mmu_pte_write(struct kvm_vcpu *vcpu, gpa_t gpa,

			      const u8 *new, int bytes,

			      struct kvm_page_track_notifier_node *node)
@@ -5394,8 +5395,8 @@ static void kvm_mmu_pte_write(struct kvm_vcpu *vcpu, gpa_t gpa, 
			entry = *spte;

			mmu_page_zap_pte(vcpu->kvm, sp, spte);

			if (gentry &&

			      !((sp->role.word ^ base_role)

			      & mmu_base_role_mask.word) && rmap_can_add(vcpu))

			    !((sp->role.word ^ base_role) & ~role_ign.word) &&

			    rmap_can_add(vcpu))

				mmu_pte_write_new_pte(vcpu, sp, spte, &gentry);

			if (need_remote_flush(entry, *spte))

				remote_flush = true;

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