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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: Radim Krčmář <rkrcmar@redhat.com>
Signed-off-by: Babu Moger <babu.moger@amd.com>
[Fixed potential wraparound and change the max to UINT_MAX. - Radim]
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
This commit is contained in:
Babu Moger 2018-03-16 16:37:23 -04:00 committed by Radim Krčmář
parent 7fbc85a5fb
commit 18abdc3425
1 changed files with 6 additions and 25 deletions
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31
arch/x86/kvm/vmx.c
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@ -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 4096
#define KVM_VMX_DEFAULT_PLE_WINDOW_GROW 2 #define KVM_VMX_DEFAULT_PLE_WINDOW_GROW 2
#define KVM_VMX_DEFAULT_PLE_WINDOW_SHRINK 0 #define KVM_VMX_DEFAULT_PLE_WINDOW_SHRINK 0
#define KVM_VMX_DEFAULT_PLE_WINDOW_MAX \ #define KVM_VMX_DEFAULT_PLE_WINDOW_MAX UINT_MAX
INT_MAX / KVM_VMX_DEFAULT_PLE_WINDOW_GROW
static unsigned int ple_gap = KVM_VMX_DEFAULT_PLE_GAP; static unsigned int ple_gap = KVM_VMX_DEFAULT_PLE_GAP;
module_param(ple_gap, uint, 0444); 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); module_param(ple_window_shrink, uint, 0444);
/* Default is to compute the maximum so we can never overflow. */ /* 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; static unsigned int ple_window_max = KVM_VMX_DEFAULT_PLE_WINDOW_MAX;
module_param(ple_window_max, uint, 0444); module_param(ple_window_max, uint, 0444);
@ -6986,17 +6984,17 @@ static int handle_invalid_guest_state(struct kvm_vcpu *vcpu)
static unsigned int __grow_ple_window(unsigned int val) static unsigned int __grow_ple_window(unsigned int val)
{ {
u64 ret = val;
if (ple_window_grow < 1) if (ple_window_grow < 1)
return ple_window; return ple_window;
val = min(val, ple_window_actual_max);
if (ple_window_grow < ple_window) if (ple_window_grow < ple_window)
val *= ple_window_grow; ret *= ple_window_grow;
else 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, 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); 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. * Handler for POSTED_INTERRUPT_WAKEUP_VECTOR.
*/ */
@ -7175,8 +7158,6 @@ static __init int hardware_setup(void)
else else
kvm_disable_tdp(); kvm_disable_tdp();
update_ple_window_actual_max();
/* /*
* Only enable PML when hardware supports PML feature, and both EPT * 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. * and EPT A/D bit features are enabled -- PML depends on them to work.