Thread (36 messages) 36 messages, 4 authors, 2021-08-17

Re: [PATCH v4 11/21] KVM: arm64: Allow populating software bits

From: Fuad Tabba <hidden>
Date: 2021-08-10 04:57:32
Also in: kvmarm, lkml

Hi Quentin,

On Mon, Aug 9, 2021 at 5:25 PM Quentin Perret [off-list ref] wrote:
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/ (local)

Suggested-by: Marc Zyngier <maz@kernel.org>
Signed-off-by: Quentin Perret <redacted>
---
Reviewed-by: Fuad Tabba <redacted>

Thanks,
/fuad
quoted hunk ↗ jump to hunk
 arch/arm64/include/asm/kvm_pgtable.h | 12 +++++++++++-
 arch/arm64/kvm/hyp/pgtable.c         |  5 +++++
 2 files changed, 16 insertions(+), 1 deletion(-)
diff --git a/arch/arm64/include/asm/kvm_pgtable.h b/arch/arm64/include/asm/kvm_pgtable.h
index 2c090b0eee77..ff9d52f8073a 100644
--- 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 e25d829587b9..cff744136044 100644
--- 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;

--
2.32.0.605.g8dce9f2422-goog
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