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Commit b51012de authored by Paolo Bonzini's avatar Paolo Bonzini
Browse files

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: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 765bdb40

arch/x86/kvm/x86.c

+2 −8
Original line number Diff line number Diff line
@@ -1196,14 +1196,8 @@ static void kvm_write_wall_clock(struct kvm *kvm, gpa_t wall_clock) 


static uint32_t div_frac(uint32_t dividend, uint32_t divisor)

{

	uint32_t quotient, remainder;



	/* Don't try to replace with do_div(), this one calculates

	 * "(dividend << 32) / divisor" */

	__asm__ ( "divl %4"

		  : "=a" (quotient), "=d" (remainder)

		  : "0" (0), "1" (dividend), "r" (divisor) );

	return quotient;

	do_shl32_div32(dividend, divisor);

	return dividend;

}



static void kvm_get_time_scale(uint32_t scaled_khz, uint32_t base_khz,

arch/x86/kvm/x86.h

+15 −0
Original line number Diff line number Diff line
@@ -192,4 +192,19 @@ extern unsigned int min_timer_period_us; 
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