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From: Sasha Levin <sashal@kernel.org>
To: linux-kernel@vger.kernel.org, stable@vger.kernel.org
Cc: Sergey Senozhatsky <senozhatsky@chromium.org>,
	Paolo Bonzini <pbonzini@redhat.com>,
	Sasha Levin <sashal@kernel.org>,
	kvm@vger.kernel.org
Subject: [PATCH MANUALSEL 5.14 3/9] KVM: do not shrink halt_poll_ns below grow_start
Date: Wed,  6 Oct 2021 09:30:15 -0400	[thread overview]
Message-ID: <20211006133021.271905-3-sashal@kernel.org> (raw)
In-Reply-To: <20211006133021.271905-1-sashal@kernel.org>

From: Sergey Senozhatsky <senozhatsky@chromium.org>

[ Upstream commit ae232ea460888dc5a8b37e840c553b02521fbf18 ]

grow_halt_poll_ns() ignores values between 0 and
halt_poll_ns_grow_start (10000 by default). However,
when we shrink halt_poll_ns we may fall way below
halt_poll_ns_grow_start and endup with halt_poll_ns
values that don't make a lot of sense: like 1 or 9,
or 19.

VCPU1 trace (halt_poll_ns_shrink equals 2):

VCPU1 grow 10000
VCPU1 shrink 5000
VCPU1 shrink 2500
VCPU1 shrink 1250
VCPU1 shrink 625
VCPU1 shrink 312
VCPU1 shrink 156
VCPU1 shrink 78
VCPU1 shrink 39
VCPU1 shrink 19
VCPU1 shrink 9
VCPU1 shrink 4

Mirror what grow_halt_poll_ns() does and set halt_poll_ns
to 0 as soon as new shrink-ed halt_poll_ns value falls
below halt_poll_ns_grow_start.

Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <20210902031100.252080-1-senozhatsky@chromium.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 virt/kvm/kvm_main.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index b50dbe269f4b..1a11dcb670a3 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -3053,15 +3053,19 @@ static void grow_halt_poll_ns(struct kvm_vcpu *vcpu)
 
 static void shrink_halt_poll_ns(struct kvm_vcpu *vcpu)
 {
-	unsigned int old, val, shrink;
+	unsigned int old, val, shrink, grow_start;
 
 	old = val = vcpu->halt_poll_ns;
 	shrink = READ_ONCE(halt_poll_ns_shrink);
+	grow_start = READ_ONCE(halt_poll_ns_grow_start);
 	if (shrink == 0)
 		val = 0;
 	else
 		val /= shrink;
 
+	if (val < grow_start)
+		val = 0;
+
 	vcpu->halt_poll_ns = val;
 	trace_kvm_halt_poll_ns_shrink(vcpu->vcpu_id, val, old);
 }
-- 
2.33.0


  parent reply	other threads:[~2021-10-06 13:30 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-10-06 13:30 [PATCH MANUALSEL 5.14 1/9] selftests: KVM: Align SMCCC call with the spec in steal_time Sasha Levin
2021-10-06 13:30 ` [PATCH MANUALSEL 5.14 2/9] KVM: x86: Handle SRCU initialization failure during page track init Sasha Levin
2021-10-06 13:36   ` Paolo Bonzini
2021-10-06 13:30 ` Sasha Levin [this message]
2021-10-06 13:36   ` [PATCH MANUALSEL 5.14 3/9] KVM: do not shrink halt_poll_ns below grow_start Paolo Bonzini
2021-10-06 13:30 ` [PATCH MANUALSEL 5.14 4/9] KVM: x86: reset pdptrs_from_userspace when exiting smm Sasha Levin
2021-10-06 13:36   ` Paolo Bonzini
2021-10-07 15:23     ` Naresh Kamboju
2021-10-07 17:47       ` Paolo Bonzini
2021-10-06 13:30 ` [PATCH MANUALSEL 5.14 5/9] KVM: x86: VMX: synthesize invalid VM exit when emulating invalid guest state Sasha Levin
2021-10-06 13:35   ` Paolo Bonzini
2021-10-06 13:30 ` [PATCH MANUALSEL 5.14 6/9] KVM: x86: nVMX: don't fail nested VM entry on invalid guest state if !from_vmentry Sasha Levin
2021-10-06 13:36   ` Paolo Bonzini
2021-10-06 13:30 ` [PATCH MANUALSEL 5.14 7/9] kvm: x86: Add AMD PMU MSRs to msrs_to_save_all[] Sasha Levin
2021-10-06 13:36   ` Paolo Bonzini
2021-10-06 13:30 ` [PATCH MANUALSEL 5.14 8/9] KVM: x86: nSVM: restore int_vector in svm_clear_vintr Sasha Levin
2021-10-06 13:36   ` Paolo Bonzini
2021-10-06 13:30 ` [PATCH MANUALSEL 5.14 9/9] ALSA: pcsp: Make hrtimer forwarding more robust Sasha Levin
2021-10-06 13:36 ` [PATCH MANUALSEL 5.14 1/9] selftests: KVM: Align SMCCC call with the spec in steal_time Paolo Bonzini

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