This is a note to let you know that I've just added the patch titled
x86/kvm: Don't use pv tlb/ipi/sched_yield if on 1 vCPU
to the 5.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
x86-kvm-don-t-use-pv-tlb-ipi-sched_yield-if-on-1-vcp.patch
and it can be found in the queue-5.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit e53db0c238e3bbc69959db57d7b3d7d63d54563d
Author: Wanpeng Li <wanpengli@xxxxxxxxxxx>
Date: Fri Feb 18 00:10:38 2022 -0800
x86/kvm: Don't use pv tlb/ipi/sched_yield if on 1 vCPU
[ Upstream commit ec756e40e271866f951d77c5e923d8deb6002b15 ]
Inspired by commit 3553ae5690a (x86/kvm: Don't use pvqspinlock code if
only 1 vCPU), on a VM with only 1 vCPU, there is no need to enable
pv tlb/ipi/sched_yield and we can save the memory for __pv_cpu_mask.
Signed-off-by: Wanpeng Li <wanpengli@xxxxxxxxxxx>
Message-Id: <1645171838-2855-1-git-send-email-wanpengli@xxxxxxxxxxx>
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
index b656456c3a94..811c7aaf23aa 100644
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -457,19 +457,22 @@ static bool pv_tlb_flush_supported(void)
{
return (kvm_para_has_feature(KVM_FEATURE_PV_TLB_FLUSH) &&
!kvm_para_has_hint(KVM_HINTS_REALTIME) &&
- kvm_para_has_feature(KVM_FEATURE_STEAL_TIME));
+ kvm_para_has_feature(KVM_FEATURE_STEAL_TIME) &&
+ (num_possible_cpus() != 1));
}
static bool pv_ipi_supported(void)
{
- return kvm_para_has_feature(KVM_FEATURE_PV_SEND_IPI);
+ return (kvm_para_has_feature(KVM_FEATURE_PV_SEND_IPI) &&
+ (num_possible_cpus() != 1));
}
static bool pv_sched_yield_supported(void)
{
return (kvm_para_has_feature(KVM_FEATURE_PV_SCHED_YIELD) &&
!kvm_para_has_hint(KVM_HINTS_REALTIME) &&
- kvm_para_has_feature(KVM_FEATURE_STEAL_TIME));
+ kvm_para_has_feature(KVM_FEATURE_STEAL_TIME) &&
+ (num_possible_cpus() != 1));
}
#define KVM_IPI_CLUSTER_SIZE (2 * BITS_PER_LONG)
