linux-kernel - [PATCH v2] KVM: guest-memfd: fix unused-function warning

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Date:   Fri,  8 Dec 2023 13:49:08 -0500
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc:     Arnd Bergmann <arnd@...db.de>,
        Sean Christopherson <seanjc@...gle.com>
Subject: [PATCH v2] KVM: guest-memfd: fix unused-function warning

With migration disabled, one function becomes unused:

virt/kvm/guest_memfd.c:262:12: error: 'kvm_gmem_migrate_folio' defined but not used [-Werror=unused-function]
  262 | static int kvm_gmem_migrate_folio(struct address_space *mapping,
      |            ^~~~~~~~~~~~~~~~~~~~~~

Remove the #ifdef around the reference so that fallback_migrate_folio()
is never used.  The gmem implementation of the hook is trivial; since
the gmem mapping is unmovable, the pages should not be migrated anyway.

Fixes: a7800aa80ea4 ("KVM: Add KVM_CREATE_GUEST_MEMFD ioctl() for guest-specific backing memory")
Reported-by: Arnd Bergmann <arnd@...db.de>
Suggested-by: Sean Christopherson <seanjc@...gle.com>
Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
---
 virt/kvm/guest_memfd.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c
index b99272396119..c2e2371720a9 100644
--- a/virt/kvm/guest_memfd.c
+++ b/virt/kvm/guest_memfd.c
@@ -300,9 +300,7 @@ static int kvm_gmem_error_page(struct address_space *mapping, struct page *page)
 
 static const struct address_space_operations kvm_gmem_aops = {
 	.dirty_folio = noop_dirty_folio,
-#ifdef CONFIG_MIGRATION
 	.migrate_folio	= kvm_gmem_migrate_folio,
-#endif
 	.error_remove_page = kvm_gmem_error_page,
 };
 
-- 
2.39.1