Commit 2608563b authored by Oliver Upton's avatar Oliver Upton
Browse files

KVM: arm64: Add support for FEAT_XNX stage-2 permissions 



FEAT_XNX adds support for encoding separate execute permissions for EL0
and EL1 at stage-2. Add support for this to the page table library,
hiding the unintuitive encoding scheme behind generic pX and uX
permission flags.

Reviewed-by: default avatarMarc Zyngier <maz@kernel.org>
Tested-by: default avatarMarc Zyngier <maz@kernel.org>
Link: https://msgid.link/20251124190158.177318-3-oupton@kernel.org


Signed-off-by: default avatarOliver Upton <oupton@kernel.org>
parent dc311243

arch/arm64/include/asm/kvm_pgtable.h

+10 −7
Original line number Diff line number Diff line
@@ -89,7 +89,7 @@ typedef u64 kvm_pte_t; 


#define KVM_PTE_LEAF_ATTR_HI_S1_XN	BIT(54)



#define KVM_PTE_LEAF_ATTR_HI_S2_XN	BIT(54)

#define KVM_PTE_LEAF_ATTR_HI_S2_XN	GENMASK(54, 53)



#define KVM_PTE_LEAF_ATTR_HI_S1_GP	BIT(50)
@@ -251,12 +251,15 @@ enum kvm_pgtable_stage2_flags { 
 * @KVM_PGTABLE_PROT_SW3:	Software bit 3.

 */

enum kvm_pgtable_prot {

	KVM_PGTABLE_PROT_X			= BIT(0),

	KVM_PGTABLE_PROT_W			= BIT(1),

	KVM_PGTABLE_PROT_R			= BIT(2),



	KVM_PGTABLE_PROT_DEVICE			= BIT(3),

	KVM_PGTABLE_PROT_NORMAL_NC		= BIT(4),

	KVM_PGTABLE_PROT_PX			= BIT(0),

	KVM_PGTABLE_PROT_UX			= BIT(1),

	KVM_PGTABLE_PROT_X			= KVM_PGTABLE_PROT_PX	|

						  KVM_PGTABLE_PROT_UX,

	KVM_PGTABLE_PROT_W			= BIT(2),

	KVM_PGTABLE_PROT_R			= BIT(3),



	KVM_PGTABLE_PROT_DEVICE			= BIT(4),

	KVM_PGTABLE_PROT_NORMAL_NC		= BIT(5),



	KVM_PGTABLE_PROT_SW0			= BIT(55),

	KVM_PGTABLE_PROT_SW1			= BIT(56),

arch/arm64/kvm/hyp/pgtable.c

+50 −8
Original line number Diff line number Diff line
@@ -661,11 +661,37 @@ void kvm_tlb_flush_vmid_range(struct kvm_s2_mmu *mmu, 


#define KVM_S2_MEMATTR(pgt, attr) PAGE_S2_MEMATTR(attr, stage2_has_fwb(pgt))



static int stage2_set_xn_attr(enum kvm_pgtable_prot prot, kvm_pte_t *attr)

{

	bool px, ux;

	u8 xn;



	px = prot & KVM_PGTABLE_PROT_PX;

	ux = prot & KVM_PGTABLE_PROT_UX;



	if (!cpus_have_final_cap(ARM64_HAS_XNX) && px != ux)

		return -EINVAL;



	if (px && ux)

		xn = 0b00;

	else if (!px && ux)

		xn = 0b01;

	else if (!px && !ux)

		xn = 0b10;

	else

		xn = 0b11;



	*attr &= ~KVM_PTE_LEAF_ATTR_HI_S2_XN;

	*attr |= FIELD_PREP(KVM_PTE_LEAF_ATTR_HI_S2_XN, xn);

	return 0;

}



static int stage2_set_prot_attr(struct kvm_pgtable *pgt, enum kvm_pgtable_prot prot,

				kvm_pte_t *ptep)

{

	kvm_pte_t attr;

	u32 sh = KVM_PTE_LEAF_ATTR_LO_S2_SH_IS;

	int r;



	switch (prot & (KVM_PGTABLE_PROT_DEVICE |

			KVM_PGTABLE_PROT_NORMAL_NC)) {
@@ -685,8 +711,9 @@ static int stage2_set_prot_attr(struct kvm_pgtable *pgt, enum kvm_pgtable_prot p 
		attr = KVM_S2_MEMATTR(pgt, NORMAL);

	}



	if (!(prot & KVM_PGTABLE_PROT_X))

		attr |= KVM_PTE_LEAF_ATTR_HI_S2_XN;

	r = stage2_set_xn_attr(prot, &attr);

	if (r)

		return r;



	if (prot & KVM_PGTABLE_PROT_R)

		attr |= KVM_PTE_LEAF_ATTR_LO_S2_S2AP_R;
@@ -715,8 +742,19 @@ enum kvm_pgtable_prot kvm_pgtable_stage2_pte_prot(kvm_pte_t pte) 
		prot |= KVM_PGTABLE_PROT_R;

	if (pte & KVM_PTE_LEAF_ATTR_LO_S2_S2AP_W)

		prot |= KVM_PGTABLE_PROT_W;

	if (!(pte & KVM_PTE_LEAF_ATTR_HI_S2_XN))

		prot |= KVM_PGTABLE_PROT_X;



	switch (FIELD_GET(KVM_PTE_LEAF_ATTR_HI_S2_XN, pte)) {

	case 0b00:

		prot |= KVM_PGTABLE_PROT_PX | KVM_PGTABLE_PROT_UX;

		break;

	case 0b01:

		prot |= KVM_PGTABLE_PROT_UX;

		break;

	case 0b11:

		prot |= KVM_PGTABLE_PROT_PX;

		break;

	default:

	}



	return prot;

}
@@ -1290,9 +1328,9 @@ bool kvm_pgtable_stage2_test_clear_young(struct kvm_pgtable *pgt, u64 addr, 
int kvm_pgtable_stage2_relax_perms(struct kvm_pgtable *pgt, u64 addr,

				   enum kvm_pgtable_prot prot, enum kvm_pgtable_walk_flags flags)

{

	int ret;

	kvm_pte_t xn = 0, set = 0, clr = 0;

	s8 level;

	kvm_pte_t set = 0, clr = 0;

	int ret;



	if (prot & KVM_PTE_LEAF_ATTR_HI_SW)

		return -EINVAL;
@@ -1303,8 +1341,12 @@ int kvm_pgtable_stage2_relax_perms(struct kvm_pgtable *pgt, u64 addr, 
	if (prot & KVM_PGTABLE_PROT_W)

		set |= KVM_PTE_LEAF_ATTR_LO_S2_S2AP_W;



	if (prot & KVM_PGTABLE_PROT_X)

		clr |= KVM_PTE_LEAF_ATTR_HI_S2_XN;

	ret = stage2_set_xn_attr(prot, &xn);

	if (ret)

		return ret;



	set |= xn & KVM_PTE_LEAF_ATTR_HI_S2_XN;

	clr |= ~xn & KVM_PTE_LEAF_ATTR_HI_S2_XN;



	ret = stage2_update_leaf_attrs(pgt, addr, 1, set, clr, NULL, &level, flags);

	if (!ret || ret == -EAGAIN)