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: Marc Zyngier <maz@kernel.org>
Tested-by: Marc Zyngier <maz@kernel.org>
Link: https://msgid.link/20251124190158.177318-3-oupton@kernel.org
Signed-off-by: Oliver Upton <oupton@kernel.org>

diff --git a/arch/arm64/include/asm/kvm_pgtable.h b/arch/arm64/include/asm/kvm_pgtable.h
index 2888b5d037573621c4e126a42f5f21ff9e30b9bd..c72149a607d678a21a3f3892f1965d6136e8314a 100644 (file)
--- a/arch/arm64/include/asm/kvm_pgtable.h
+++ b/arch/arm64/include/asm/kvm_pgtable.h
@@ -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),

diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c
index c351b4abd5dbfbcbe738ba0f9efc41a1c99ecc05..e1d75f965027a9018ed7235c38f791ef7a33e7d0 100644 (file)
--- a/arch/arm64/kvm/hyp/pgtable.c
+++ b/arch/arm64/kvm/hyp/pgtable.c
@@ -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)