KVM: x86: introduce do_shl32_div32
This is similar to the existing div_frac function, but it returns the
remainder too. Unlike div_frac, it can be used to implement long
division, e.g. (a << 64) / b for 32-bit a and b.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h
index f2afa5f..34f4164 100644
--- a/arch/x86/kvm/x86.h
+++ b/arch/x86/kvm/x86.h
@@ -192,4 +192,19 @@
extern unsigned int lapic_timer_advance_ns;
extern struct static_key kvm_no_apic_vcpu;
+
+/* Same "calling convention" as do_div:
+ * - divide (n << 32) by base
+ * - put result in n
+ * - return remainder
+ */
+#define do_shl32_div32(n, base) \
+ ({ \
+ u32 __quot, __rem; \
+ asm("divl %2" : "=a" (__quot), "=d" (__rem) \
+ : "rm" (base), "0" (0), "1" ((u32) n)); \
+ n = __quot; \
+ __rem; \
+ })
+
#endif