Commit 2d344105 authored by Huaitong Han's avatar Huaitong Han Committed by Paolo Bonzini
Browse files

KVM, pkeys: introduce pkru_mask to cache conditions 



PKEYS defines a new status bit in the PFEC. PFEC.PK (bit 5), if some
conditions is true, the fault is considered as a PKU violation.
pkru_mask indicates if we need to check PKRU.ADi and PKRU.WDi, and
does cache some conditions for permission_fault.

[ Huaitong: Xiao helps to modify many sections. ]

Signed-off-by: default avatarHuaitong Han <huaitong.han@intel.com>
Signed-off-by: default avatarXiao Guangrong <guangrong.xiao@linux.intel.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 1be0e61c

arch/x86/include/asm/kvm_host.h

+8 −0
Original line number Diff line number Diff line
@@ -335,6 +335,14 @@ struct kvm_mmu { 
	 */

	u8 permissions[16];



	/*

	* The pkru_mask indicates if protection key checks are needed.  It

	* consists of 16 domains indexed by page fault error code bits [4:1],

	* with PFEC.RSVD replaced by ACC_USER_MASK from the page tables.

	* Each domain has 2 bits which are ANDed with AD and WD from PKRU.

	*/

	u32 pkru_mask;



	u64 *pae_root;

	u64 *lm_root;

arch/x86/kvm/mmu.c

+80 −0
Original line number Diff line number Diff line
@@ -3923,6 +3923,81 @@ static void update_permission_bitmask(struct kvm_vcpu *vcpu, 
	}

}



/*

* PKU is an additional mechanism by which the paging controls access to

* user-mode addresses based on the value in the PKRU register.  Protection

* key violations are reported through a bit in the page fault error code.

* Unlike other bits of the error code, the PK bit is not known at the

* call site of e.g. gva_to_gpa; it must be computed directly in

* permission_fault based on two bits of PKRU, on some machine state (CR4,

* CR0, EFER, CPL), and on other bits of the error code and the page tables.

*

* In particular the following conditions come from the error code, the

* page tables and the machine state:

* - PK is always zero unless CR4.PKE=1 and EFER.LMA=1

* - PK is always zero if RSVD=1 (reserved bit set) or F=1 (instruction fetch)

* - PK is always zero if U=0 in the page tables

* - PKRU.WD is ignored if CR0.WP=0 and the access is a supervisor access.

*

* The PKRU bitmask caches the result of these four conditions.  The error

* code (minus the P bit) and the page table's U bit form an index into the

* PKRU bitmask.  Two bits of the PKRU bitmask are then extracted and ANDed

* with the two bits of the PKRU register corresponding to the protection key.

* For the first three conditions above the bits will be 00, thus masking

* away both AD and WD.  For all reads or if the last condition holds, WD

* only will be masked away.

*/

static void update_pkru_bitmask(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu,

				bool ept)

{

	unsigned bit;

	bool wp;



	if (ept) {

		mmu->pkru_mask = 0;

		return;

	}



	/* PKEY is enabled only if CR4.PKE and EFER.LMA are both set. */

	if (!kvm_read_cr4_bits(vcpu, X86_CR4_PKE) || !is_long_mode(vcpu)) {

		mmu->pkru_mask = 0;

		return;

	}



	wp = is_write_protection(vcpu);



	for (bit = 0; bit < ARRAY_SIZE(mmu->permissions); ++bit) {

		unsigned pfec, pkey_bits;

		bool check_pkey, check_write, ff, uf, wf, pte_user;



		pfec = bit << 1;

		ff = pfec & PFERR_FETCH_MASK;

		uf = pfec & PFERR_USER_MASK;

		wf = pfec & PFERR_WRITE_MASK;



		/* PFEC.RSVD is replaced by ACC_USER_MASK. */

		pte_user = pfec & PFERR_RSVD_MASK;



		/*

		 * Only need to check the access which is not an

		 * instruction fetch and is to a user page.

		 */

		check_pkey = (!ff && pte_user);

		/*

		 * write access is controlled by PKRU if it is a

		 * user access or CR0.WP = 1.

		 */

		check_write = check_pkey && wf && (uf || wp);



		/* PKRU.AD stops both read and write access. */

		pkey_bits = !!check_pkey;

		/* PKRU.WD stops write access. */

		pkey_bits |= (!!check_write) << 1;



		mmu->pkru_mask |= (pkey_bits & 3) << pfec;

	}

}



static void update_last_nonleaf_level(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu)

{

	unsigned root_level = mmu->root_level;
@@ -3941,6 +4016,7 @@ static void paging64_init_context_common(struct kvm_vcpu *vcpu, 


	reset_rsvds_bits_mask(vcpu, context);

	update_permission_bitmask(vcpu, context, false);

	update_pkru_bitmask(vcpu, context, false);

	update_last_nonleaf_level(vcpu, context);



	MMU_WARN_ON(!is_pae(vcpu));
@@ -3968,6 +4044,7 @@ static void paging32_init_context(struct kvm_vcpu *vcpu, 


	reset_rsvds_bits_mask(vcpu, context);

	update_permission_bitmask(vcpu, context, false);

	update_pkru_bitmask(vcpu, context, false);

	update_last_nonleaf_level(vcpu, context);



	context->page_fault = paging32_page_fault;
@@ -4026,6 +4103,7 @@ static void init_kvm_tdp_mmu(struct kvm_vcpu *vcpu) 
	}



	update_permission_bitmask(vcpu, context, false);

	update_pkru_bitmask(vcpu, context, false);

	update_last_nonleaf_level(vcpu, context);

	reset_tdp_shadow_zero_bits_mask(vcpu, context);

}
@@ -4078,6 +4156,7 @@ void kvm_init_shadow_ept_mmu(struct kvm_vcpu *vcpu, bool execonly) 
	context->direct_map = false;



	update_permission_bitmask(vcpu, context, true);

	update_pkru_bitmask(vcpu, context, true);

	reset_rsvds_bits_mask_ept(vcpu, context, execonly);

	reset_ept_shadow_zero_bits_mask(vcpu, context, execonly);

}
@@ -4132,6 +4211,7 @@ static void init_kvm_nested_mmu(struct kvm_vcpu *vcpu) 
	}



	update_permission_bitmask(vcpu, g_context, false);

	update_pkru_bitmask(vcpu, g_context, false);

	update_last_nonleaf_level(vcpu, g_context);

}

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