From: Chao Gao <chao.gao@intel.com>
To: Jason Wang <jasowang@redhat.com>
Cc: Cindy Lu <lulu@redhat.com>, Paolo Bonzini <pbonzini@redhat.com>,
"Vitaly Kuznetsov" <vkuznets@redhat.com>,
Thomas Gleixner <tglx@linutronix.de>,
"Ingo Molnar" <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
"maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)"
<x86@kernel.org>, "H. Peter Anvin" <hpa@zytor.com>,
"Peter Zijlstra (Intel)" <peterz@infradead.org>,
"Kirill A. Shutemov" <kas@kernel.org>,
"Xin Li (Intel)" <xin@zytor.com>, Rik van Riel <riel@surriel.com>,
"Ahmed S. Darwish" <darwi@linutronix.de>,
"open list:KVM PARAVIRT (KVM/paravirt)" <kvm@vger.kernel.org>,
"open list:X86 ARCHITECTURE (32-BIT AND 64-BIT)"
<linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v1] kvm: x86: implement PV send_IPI method
Date: Fri, 18 Jul 2025 19:00:44 +0800 [thread overview]
Message-ID: <aHopXN73dHW/uKaT@intel.com> (raw)
In-Reply-To: <CACGkMEv0yHC7P1CLeB8A1VumWtTF4Bw4eY2_njnPMwT75-EJkg@mail.gmail.com>
On Fri, Jul 18, 2025 at 03:52:30PM +0800, Jason Wang wrote:
>On Fri, Jul 18, 2025 at 2:25 PM Cindy Lu <lulu@redhat.com> wrote:
>>
>> From: Jason Wang <jasowang@redhat.com>
>>
>> We used to have PV version of send_IPI_mask and
>> send_IPI_mask_allbutself. This patch implements PV send_IPI method to
>> reduce the number of vmexits.
It won't reduce the number of VM-exits; in fact, it may increase them on CPUs
that support IPI virtualization.
With IPI virtualization enabled, *unicast* and physical-addressing IPIs won't
cause a VM-exit. Instead, the microcode posts interrupts directly to the target
vCPU. The PV version always causes a VM-exit.
>>
>> Signed-off-by: Jason Wang <jasowang@redhat.com>
>> Tested-by: Cindy Lu <lulu@redhat.com>
>
>I think a question here is are we able to see performance improvement
>in any kind of setup?
It may result in a negative performance impact.
>
>Thanks
>
>
next prev parent reply other threads:[~2025-07-18 11:01 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-07-18 6:24 [PATCH v1] kvm: x86: implement PV send_IPI method Cindy Lu
2025-07-18 7:52 ` Jason Wang
2025-07-18 11:00 ` Chao Gao [this message]
2025-07-18 11:15 ` Jason Wang
2025-07-18 12:19 ` Chao Gao
2025-07-18 14:01 ` Sean Christopherson
2025-07-18 15:15 ` Chao Gao
2025-07-18 15:22 ` Sean Christopherson
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