linux-kernel - [PATCH v1] kvm: x86: implement PV send

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Message-ID: <20250718062429.238723-1-lulu@redhat.com>
Date: Fri, 18 Jul 2025 14:24:00 +0800
From: Cindy Lu <lulu@...hat.com>
To: Paolo Bonzini <pbonzini@...hat.com>,
	Vitaly Kuznetsov <vkuznets@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	x86@...nel.org (maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)),
	"H. Peter Anvin" <hpa@...or.com>,
	"Peter Zijlstra (Intel)" <peterz@...radead.org>,
	"Kirill A. Shutemov" <kas@...nel.org>,
	"Xin Li (Intel)" <xin@...or.com>,
	Rik van Riel <riel@...riel.com>,
	Jason Wang <jasowang@...hat.com>,
	"Ahmed S. Darwish" <darwi@...utronix.de>,
	kvm@...r.kernel.org (open list:KVM PARAVIRT (KVM/paravirt)),
	linux-kernel@...r.kernel.org (open list:X86 ARCHITECTURE (32-BIT AND 64-BIT)),
	lulu@...hat.com
Subject: [PATCH v1] kvm: x86: implement PV send_IPI method

From: Jason Wang <jasowang@...hat.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.

Signed-off-by: Jason Wang <jasowang@...hat.com>
Tested-by: Cindy Lu <lulu@...hat.com>
---
 arch/x86/kernel/kvm.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
index 921c1c783bc1..b920cfd10441 100644
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -557,6 +557,11 @@ static void __send_ipi_mask(const struct cpumask *mask, int vector)
 	local_irq_restore(flags);
 }
 
+static void kvm_send_ipi(int cpu, int vector)
+{
+	__send_ipi_mask(cpumask_of(cpu), vector);
+}
+
 static void kvm_send_ipi_mask(const struct cpumask *mask, int vector)
 {
 	__send_ipi_mask(mask, vector);
@@ -628,6 +633,7 @@ late_initcall(setup_efi_kvm_sev_migration);
  */
 static __init void kvm_setup_pv_ipi(void)
 {
+	apic_update_callback(send_IPI, kvm_send_ipi);
 	apic_update_callback(send_IPI_mask, kvm_send_ipi_mask);
 	apic_update_callback(send_IPI_mask_allbutself, kvm_send_ipi_mask_allbutself);
 	pr_info("setup PV IPIs\n");
-- 
2.45.0