At the moment, we're killing the i-cache each time we map a page
in stage-2, as we have no idea if this page is used as a data or
code page.
In order to preserve the cache a bit more, mark all pages with the
XN flag. If we get an exec permission fault, invalidate the i-cache
and clear the XN bit.
We end up getting more faults, but we preserve the i-cache.
Signed-off-by: Marc Zyngier <marc.zyngier@xxxxxxx>
---
arch/arm/include/asm/kvm_mmu.h | 5 +++++
arch/arm/include/asm/pgtable.h | 2 +-
arch/arm/kvm/mmu.c | 7 +++++--
3 files changed, 11 insertions(+), 3 deletions(-)
diff --git a/arch/arm/include/asm/kvm_mmu.h b/arch/arm/include/asm/kvm_mmu.h
index 257e2bc..dbfeea1 100644
--- a/arch/arm/include/asm/kvm_mmu.h
+++ b/arch/arm/include/asm/kvm_mmu.h
@@ -95,6 +95,11 @@ static inline void kvm_set_s2pte_writable(pte_t *pte)
pte_val(*pte) |= L_PTE_S2_RDWR;
}
+static inline void kvm_set_s2pte_exec(pte_t *pte)
+{
+ pte_val(*pte) &= ~L_PTE_XN;
+}
+
struct kvm;
static inline void coherent_icache_guest_page(struct kvm *kvm, gfn_t gfn)
diff --git a/arch/arm/include/asm/pgtable.h b/arch/arm/include/asm/pgtable.h
index f30ac3b..0bb73cc 100644
--- a/arch/arm/include/asm/pgtable.h
+++ b/arch/arm/include/asm/pgtable.h
@@ -87,7 +87,7 @@ extern pgprot_t pgprot_s2_device;
#define PAGE_KERNEL_EXEC pgprot_kernel
#define PAGE_HYP _MOD_PROT(pgprot_kernel, L_PTE_HYP)
#define PAGE_HYP_DEVICE _MOD_PROT(pgprot_hyp_device, L_PTE_HYP)
-#define PAGE_S2 _MOD_PROT(pgprot_s2, L_PTE_S2_RDONLY)
+#define PAGE_S2 _MOD_PROT(pgprot_s2, L_PTE_S2_RDONLY | L_PTE_XN)
#define PAGE_S2_DEVICE _MOD_PROT(pgprot_s2_device, L_PTE_USER | L_PTE_S2_RDONLY)
#define __PAGE_NONE __pgprot(_L_PTE_DEFAULT | L_PTE_RDONLY | L_PTE_XN | L_PTE_NONE)
diff --git a/arch/arm/kvm/mmu.c b/arch/arm/kvm/mmu.c
index 58a45d1..d727a4f 100644
--- a/arch/arm/kvm/mmu.c
+++ b/arch/arm/kvm/mmu.c
@@ -543,8 +543,6 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
if (is_error_pfn(pfn))
return -EFAULT;
- coherent_icache_guest_page(vcpu->kvm, gfn);
-
spin_lock(&vcpu->kvm->mmu_lock);
if (mmu_notifier_retry(vcpu->kvm, mmu_seq))
goto out_unlock;
@@ -560,6 +558,11 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
kvm_set_pfn_dirty(pfn);
}
+ if (fault_type == KVM_EXEC_FAULT) {
+ kvm_set_s2pte_exec(&new_pte);
+ coherent_icache_guest_page(vcpu->kvm, gfn);
+ }
+
stage2_set_pte_at(vcpu->kvm, fault_ipa, ptep, new_pte);
out_unlock:
--
1.8.1.2
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