[PATCH v4 08/14] KVM: arm64: Propagate EHWPOISON in kvm_s2_fault_pin_pfn()

["Lorenzo Stoakes (ARM)" <ljs@kernel.org>]

Currently kvm_s2_fault_pin_pfn() handles a poisoned page directly by
sending a SIGBUS signal itself.

This is an odd place to do it, the caller should decide what to do with
errors, so move the handling to the sole caller, user_mem_abort().

This lays the foundation for stage 2 pre-faulting which, arising from a
synthetic fault, should not send a signal.

In order to do so, check to see if user_mem_abort()'s caller has set result
- i.e. whether it wants to be informed about the outcome of the fault
handling.

If it does, then it is implied that it should handle the -EHWPOISON error
itself. This is the case for pre-faulting.

Otherwise this is real hardware, so send the signal.

No functional change intended.

Reviewed-by: Oliver Upton <oupton@kernel.org>
Reviewed-by: Fuad Tabba <fuad.tabba@linux.dev>
Signed-off-by: Lorenzo Stoakes (ARM) <ljs@kernel.org>
---
 arch/arm64/kvm/mmu.c | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
index cd4bc1d1bcdb..476a98cbe05d 100644
--- a/arch/arm64/kvm/mmu.c
+++ b/arch/arm64/kvm/mmu.c
@@ -2018,10 +2018,8 @@ static int kvm_s2_fault_pin_pfn(const struct kvm_s2_fault_desc *s2fd,
 				      kvm_s2_fault_is_write(s2fd) ? FOLL_WRITE : 0,
 				      &s2vi->map_writable, &s2vi->page);
 	if (unlikely(is_error_noslot_pfn(s2vi->pfn))) {
-		if (s2vi->pfn == KVM_PFN_ERR_HWPOISON) {
-			kvm_send_hwpoison_signal(s2fd->hva, __ffs(s2vi->vma_pagesize));
-			return 0;
-		}
+		if (s2vi->pfn == KVM_PFN_ERR_HWPOISON)
+			return -EHWPOISON;
 		return -EFAULT;
 	}
 
@@ -2263,6 +2261,13 @@ static int user_mem_abort(const struct kvm_s2_fault_desc *s2fd,
 	 * get block mapping for device MMIO region.
 	 */
 	ret = kvm_s2_fault_pin_pfn(s2fd, &s2vi);
+	if (ret == -EHWPOISON) {
+		/* If result is specified, let the caller handle this. */
+		if (result)
+			return -EHWPOISON;
+		kvm_send_hwpoison_signal(s2fd->hva, __ffs(s2vi.vma_pagesize));
+		return 0;
+	}
 	if (ret != 1)
 		return ret;
 

-- 
2.55.0