From: Wei Huang <whuang2@amd.com>
To: Jim Mattson <jmattson@google.com>, Oliver Upton <oupton@google.com>
Cc: kvm list <kvm@vger.kernel.org>,
Paolo Bonzini <pbonzini@redhat.com>,
Tom Lendacky <thomas.lendacky@amd.com>
Subject: Re: [PATCH v2 2/2] KVM: SVM: Enable AVIC by default
Date: Fri, 28 Feb 2020 16:47:46 -0600 [thread overview]
Message-ID: <6487d313-dedb-1210-1c7a-160db2c816ad@amd.com> (raw)
In-Reply-To: <CALMp9eRUQFDvZtGBGs6oKX=-j+Zz6SV8zTpLPukiRjmA=nO0wg@mail.gmail.com>
On 2/28/20 1:40 PM, Jim Mattson wrote:
> On Fri, Feb 28, 2020 at 12:59 AM Oliver Upton <oupton@google.com> wrote:
>>
>> Switch the default value of the 'avic' module parameter to 1.
>>
>> Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
>> Signed-off-by: Oliver Upton <oupton@google.com>
>> ---
>> arch/x86/kvm/svm.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
>> index b82a500bccb7..70d2df13eb02 100644
>> --- a/arch/x86/kvm/svm.c
>> +++ b/arch/x86/kvm/svm.c
>> @@ -358,7 +358,7 @@ static int nested = true;
>> module_param(nested, int, S_IRUGO);
>>
>> /* enable / disable AVIC */
>> -static int avic;
>> +static int avic = 1;
>> #ifdef CONFIG_X86_LOCAL_APIC
>> module_param(avic, int, S_IRUGO);
>> #endif
>> --
>> 2.25.1.481.gfbce0eb801-goog
>
> How extensively has this been tested? Why hasn't someone from AMD
> suggested this change?
I personally don't suggest enable AVIC by default. There are cases of
slow AVIC doorbell delivery, due to delivery path and contention under a
large number of guest cores.
>
next prev parent reply other threads:[~2020-02-28 22:47 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-28 8:59 [PATCH v2 1/2] KVM: SVM: Inhibit APIC virtualization for X2APIC guest Oliver Upton
2020-02-28 8:59 ` [PATCH v2 2/2] KVM: SVM: Enable AVIC by default Oliver Upton
2020-02-28 19:40 ` Jim Mattson
2020-02-28 22:47 ` Wei Huang [this message]
2020-03-02 16:19 ` Paolo Bonzini
2020-03-02 17:11 ` Wei Huang
2020-03-02 17:35 ` Paolo Bonzini
2020-03-02 17:40 ` Jim Mattson
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