[PATCH 6.18.y 5/5] KVM: arm64: nv: Inject SEA if guest VNCR isn't normal memory

[Marc Zyngier <maz@kernel.org>]

From: Oliver Upton <oupton@kernel.org>

When constructing an L1 VNCR mapping, KVM unconditionally uses cacheable
memory attributes, even if the underlying PFN isn't memory. This gets
particularly hairy if the endpoint doesn't support cacheable memory
attributes, potentially throwing an SError on writeback...

While KVM does permit cacheable memory attributes on certain PFNMAP
VMAs, kvm_translate_vncr() isn't currently grabbing the VMA. So do the
simpler thing for now and just reject everything that isn't memory.

Cc: stable@vger.kernel.org
Fixes: 2a359e072596 ("KVM: arm64: nv: Handle mapping of VNCR_EL2 at EL2")
Signed-off-by: Oliver Upton <oupton@kernel.org>
Link: https://patch.msgid.link/20260618234207.1063941-5-oupton@kernel.org
Signed-off-by: Marc Zyngier <maz@kernel.org>
(cherry picked from commit 4bd7dbe0b2243e6aa735cae4d5e1ff988b30b2a6)
Signed-off-by: Marc Zyngier <maz@kernel.org>
---
 arch/arm64/kvm/nested.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/arch/arm64/kvm/nested.c b/arch/arm64/kvm/nested.c
index 0e418975649f2..10da38dff8b91 100644
--- a/arch/arm64/kvm/nested.c
+++ b/arch/arm64/kvm/nested.c
@@ -1271,6 +1271,17 @@ static int kvm_translate_vncr(struct kvm_vcpu *vcpu, bool *is_gmem)
 		writable = !(memslot->flags & KVM_MEM_READONLY);
 	}
 
+	/*
+	 * FIXME: This check is too restrictive as KVM allows cacheable memory
+	 * attributes for PFNMAP VMAs that have cacheable attributes in host
+	 * stage-1.
+	 */
+	if (!pfn_is_map_memory(pfn)) {
+		kvm_release_faultin_page(vcpu->kvm, page, true, false);
+		fail_s1_walk(&vt->wr, ESR_ELx_FSC_EXTABT, false);
+		return -EINVAL;
+	}
+
 	scoped_guard(write_lock, &vcpu->kvm->mmu_lock) {
 		if (mmu_invalidate_retry(vcpu->kvm, mmu_seq)) {
 			kvm_release_faultin_page(vcpu->kvm, page, true, false);
-- 
2.47.3