[RESEND PATCH 1/2] RISC-V: KVM: Release unused page after MMU invalidation

[Xie Bo]

If an MMU invalidation races with a G-stage fault, the fault handler skips
installing the page but leaves ret set to zero. As a result,
kvm_release_faultin_page() treats the page as used and can unnecessarily
mark it dirty.

Track the invalidation retry separately and release the page as unused,
while preserving the existing return value so that the vCPU retries the
fault.

Fixes: 2ed90cb0938a ("KVM: RISC-V: Retry fault if vma_lookup() results become invalid")
Cc: stable at vger.kernel.org
Signed-off-by: Xie Bo <xb at ultrarisc.com>
---
 arch/riscv/kvm/mmu.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/arch/riscv/kvm/mmu.c b/arch/riscv/kvm/mmu.c
index 6035b5e..d189fd5 100644
--- a/arch/riscv/kvm/mmu.c
+++ b/arch/riscv/kvm/mmu.c
@@ -627,6 +627,7 @@ int kvm_riscv_mmu_map(struct kvm_vcpu *vcpu, struct kvm_memory_slot *memslot,
 	int ret;
 	kvm_pfn_t hfn;
 	bool is_hugetlb;
+	bool unused = false;
 	bool writable;
 	unsigned int vma_pageshift;
 	gfn_t gfn = gpa >> PAGE_SHIFT;
@@ -719,8 +720,10 @@ int kvm_riscv_mmu_map(struct kvm_vcpu *vcpu, struct kvm_memory_slot *memslot,
 
 	write_lock(&kvm->mmu_lock);
 
-	if (mmu_invalidate_retry(kvm, mmu_seq))
+	if (mmu_invalidate_retry(kvm, mmu_seq)) {
+		unused = true;
 		goto out_unlock;
+	}
 
 	/*
 	 * Check if we are backed by a THP and thus use block mapping if
@@ -743,7 +746,8 @@ int kvm_riscv_mmu_map(struct kvm_vcpu *vcpu, struct kvm_memory_slot *memslot,
 		kvm_err("Failed to map in G-stage\n");
 
 out_unlock:
-	kvm_release_faultin_page(kvm, page, ret && ret != -EEXIST, writable);
+	kvm_release_faultin_page(kvm, page,
+				 unused || (ret && ret != -EEXIST), writable);
 	write_unlock(&kvm->mmu_lock);
 	return ret;
 }