KVM: arm64: Allow populating software bits

Introduce infrastructure allowing to manipulate software bits in stage-1
and stage-2 page-tables using additional entries in the kvm_pgtable_prot
enum.

This is heavily inspired by Marc's implementation of a similar feature
in the NV patch series, but adapted to allow stage-1 changes as well:

  https://lore.kernel.org/kvmarm/20210510165920.1913477-56-maz@kernel.org/

Suggested-by: Marc Zyngier <maz@kernel.org>
Signed-off-by: Quentin Perret <qperret@google.com>
Reviewed-by: Fuad Tabba <tabba@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20210809152448.1810400-12-qperret@google.com

diff --git a/arch/arm64/include/asm/kvm_pgtable.h b/arch/arm64/include/asm/kvm_pgtable.h
index ca0c039547b53f765db13a923b98ecab24aab8f8..bfea573703d7f8b34bd8a6db99d7d53d5015d954 100644 (file)
--- a/arch/arm64/include/asm/kvm_pgtable.h
+++ b/arch/arm64/include/asm/kvm_pgtable.h
@@ -121,6 +121,10 @@ enum kvm_pgtable_stage2_flags {
  * @KVM_PGTABLE_PROT_W:                Write permission.
  * @KVM_PGTABLE_PROT_R:                Read permission.
  * @KVM_PGTABLE_PROT_DEVICE:   Device attributes.
+ * @KVM_PGTABLE_PROT_SW0:      Software bit 0.
+ * @KVM_PGTABLE_PROT_SW1:      Software bit 1.
+ * @KVM_PGTABLE_PROT_SW2:      Software bit 2.
+ * @KVM_PGTABLE_PROT_SW3:      Software bit 3.
  */
 enum kvm_pgtable_prot {
        KVM_PGTABLE_PROT_X                      = BIT(0),
@@ -128,6 +132,11 @@ enum kvm_pgtable_prot {
        KVM_PGTABLE_PROT_R                      = BIT(2),
 
        KVM_PGTABLE_PROT_DEVICE                 = BIT(3),
+
+       KVM_PGTABLE_PROT_SW0                    = BIT(55),
+       KVM_PGTABLE_PROT_SW1                    = BIT(56),
+       KVM_PGTABLE_PROT_SW2                    = BIT(57),
+       KVM_PGTABLE_PROT_SW3                    = BIT(58),
 };
 
 #define KVM_PGTABLE_PROT_RW    (KVM_PGTABLE_PROT_R | KVM_PGTABLE_PROT_W)
@@ -420,7 +429,8 @@ kvm_pte_t kvm_pgtable_stage2_mkold(struct kvm_pgtable *pgt, u64 addr);
  * If there is a valid, leaf page-table entry used to translate @addr, then
  * relax the permissions in that entry according to the read, write and
  * execute permissions specified by @prot. No permissions are removed, and
- * TLB invalidation is performed after updating the entry.
+ * TLB invalidation is performed after updating the entry. Software bits cannot
+ * be set or cleared using kvm_pgtable_stage2_relax_perms().
  *
  * Return: 0 on success, negative error code on failure.
  */

diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c
index e25d829587b909859c893d4af8db5ecbd07a29c4..cff7441360448f025ac6dfe04534a6086d994aa4 100644 (file)
--- a/arch/arm64/kvm/hyp/pgtable.c
+++ b/arch/arm64/kvm/hyp/pgtable.c
@@ -357,6 +357,7 @@ static int hyp_set_prot_attr(enum kvm_pgtable_prot prot, kvm_pte_t *ptep)
        attr |= FIELD_PREP(KVM_PTE_LEAF_ATTR_LO_S1_AP, ap);
        attr |= FIELD_PREP(KVM_PTE_LEAF_ATTR_LO_S1_SH, sh);
        attr |= KVM_PTE_LEAF_ATTR_LO_S1_AF;
+       attr |= prot & KVM_PTE_LEAF_ATTR_HI_SW;
        *ptep = attr;
 
        return 0;
@@ -558,6 +559,7 @@ static int stage2_set_prot_attr(struct kvm_pgtable *pgt, enum kvm_pgtable_prot p
 
        attr |= FIELD_PREP(KVM_PTE_LEAF_ATTR_LO_S2_SH, sh);
        attr |= KVM_PTE_LEAF_ATTR_LO_S2_AF;
+       attr |= prot & KVM_PTE_LEAF_ATTR_HI_SW;
        *ptep = attr;
 
        return 0;
@@ -1025,6 +1027,9 @@ int kvm_pgtable_stage2_relax_perms(struct kvm_pgtable *pgt, u64 addr,
        u32 level;
        kvm_pte_t set = 0, clr = 0;
 
+       if (prot & KVM_PTE_LEAF_ATTR_HI_SW)
+               return -EINVAL;
+
        if (prot & KVM_PGTABLE_PROT_R)
                set |= KVM_PTE_LEAF_ATTR_LO_S2_S2AP_R;