[PATCH 9/9] KVM: x86: move guest_pv_has out of user_access section

[Rishabh Bhatnagar <risbhat@amazon.com>]

From: Paolo Bonzini <pbonzini@redhat.com>

commit 3e067fd8503d6205aa0c1c8f48f6b209c592d19c upstream.

When UBSAN is enabled, the code emitted for the call to guest_pv_has
includes a call to __ubsan_handle_load_invalid_value.  objtool
complains that this call happens with UACCESS enabled; to avoid
the warning, pull the calls to user_access_begin into both arms
of the "if" statement, after the check for guest_pv_has.

Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: David Woodhouse <dwmw2@infradead.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Rishabh Bhatnagar <risbhat@amazon.com>
Tested-by: Allen Pais <apais@linux.microsoft.com>
Acked-by: Sean Christopherson <seanjc@google.com>
---
 arch/x86/kvm/x86.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 8461aa63c251..5fbae8cc0697 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3049,9 +3049,6 @@ static void record_steal_time(struct kvm_vcpu *vcpu)
 	}
 
 	st = (struct kvm_steal_time __user *)ghc->hva;
-	if (!user_access_begin(st, sizeof(*st)))
-		return;
-
 	/*
 	 * Doing a TLB flush here, on the guest's behalf, can avoid
 	 * expensive IPIs.
@@ -3060,6 +3057,9 @@ static void record_steal_time(struct kvm_vcpu *vcpu)
 		u8 st_preempted = 0;
 		int err = -EFAULT;
 
+		if (!user_access_begin(st, sizeof(*st)))
+			return;
+
 		asm volatile("1: xchgb %0, %2\n"
 			     "xor %1, %1\n"
 			     "2:\n"
@@ -3082,6 +3082,9 @@ static void record_steal_time(struct kvm_vcpu *vcpu)
 		if (!user_access_begin(st, sizeof(*st)))
 			goto dirty;
 	} else {
+		if (!user_access_begin(st, sizeof(*st)))
+			return;
+
 		unsafe_put_user(0, &st->preempted, out);
 		vcpu->arch.st.preempted = 0;
 	}
-- 
2.39.2