Commit 18abdc34 authored by Babu Moger's avatar Babu Moger Committed by Radim Krčmář
Browse files

KVM: VMX: Remove ple_window_actual_max 



Get rid of ple_window_actual_max, because its benefits are really
minuscule and the logic is complicated.

The overflows(and underflow) are controlled in __ple_window_grow
and _ple_window_shrink respectively.

Suggested-by: default avatarRadim Krčmář <rkrcmar@redhat.com>
Signed-off-by: default avatarBabu Moger <babu.moger@amd.com>
[Fixed potential wraparound and change the max to UINT_MAX. - Radim]
Signed-off-by: default avatarRadim Krčmář <rkrcmar@redhat.com>
parent 7fbc85a5

arch/x86/kvm/vmx.c

+6 −25
Original line number Diff line number Diff line
@@ -172,8 +172,7 @@ module_param_named(preemption_timer, enable_preemption_timer, bool, S_IRUGO); 
#define KVM_VMX_DEFAULT_PLE_WINDOW        4096

#define KVM_VMX_DEFAULT_PLE_WINDOW_GROW   2

#define KVM_VMX_DEFAULT_PLE_WINDOW_SHRINK 0

#define KVM_VMX_DEFAULT_PLE_WINDOW_MAX    \

		INT_MAX / KVM_VMX_DEFAULT_PLE_WINDOW_GROW

#define KVM_VMX_DEFAULT_PLE_WINDOW_MAX    UINT_MAX



static unsigned int ple_gap = KVM_VMX_DEFAULT_PLE_GAP;

module_param(ple_gap, uint, 0444);
@@ -190,7 +189,6 @@ static unsigned int ple_window_shrink = KVM_VMX_DEFAULT_PLE_WINDOW_SHRINK; 
module_param(ple_window_shrink, uint, 0444);



/* Default is to compute the maximum so we can never overflow. */

static unsigned int ple_window_actual_max = KVM_VMX_DEFAULT_PLE_WINDOW_MAX;

static unsigned int ple_window_max        = KVM_VMX_DEFAULT_PLE_WINDOW_MAX;

module_param(ple_window_max, uint, 0444);
@@ -6986,17 +6984,17 @@ out: 


static unsigned int __grow_ple_window(unsigned int val)

{

	u64 ret = val;



	if (ple_window_grow < 1)

		return ple_window;



	val = min(val, ple_window_actual_max);



	if (ple_window_grow < ple_window)

		val *= ple_window_grow;

		ret *= ple_window_grow;

	else

		val += ple_window_grow;

		ret += ple_window_grow;



	return val;

	return min(ret, (u64)ple_window_max);

}



static unsigned int __shrink_ple_window(unsigned int val,
@@ -7040,21 +7038,6 @@ static void shrink_ple_window(struct kvm_vcpu *vcpu) 
	trace_kvm_ple_window_shrink(vcpu->vcpu_id, vmx->ple_window, old);

}



/*

 * ple_window_actual_max is computed to be one grow_ple_window() below

 * ple_window_max. (See __grow_ple_window for the reason.)

 * This prevents overflows, because ple_window_max is int.

 * ple_window_max effectively rounded down to a multiple of ple_window_grow in

 * this process.

 * ple_window_max is also prevented from setting vmx->ple_window < ple_window.

 */

static void update_ple_window_actual_max(void)

{

	ple_window_actual_max =

			__shrink_ple_window(max(ple_window_max, ple_window),

			                    ple_window_grow, INT_MIN);

}



/*

 * Handler for POSTED_INTERRUPT_WAKEUP_VECTOR.

 */
@@ -7175,8 +7158,6 @@ static __init int hardware_setup(void) 
	else

		kvm_disable_tdp();



	update_ple_window_actual_max();



	/*

	 * Only enable PML when hardware supports PML feature, and both EPT

	 * and EPT A/D bit features are enabled -- PML depends on them to work.

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