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From: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> To: Wanpeng Li <kernellwp@gmail.com> Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org, "Paolo Bonzini" <pbonzini@redhat.com>, "Radim Krčmář" <rkrcmar@redhat.com>, "Tim Shearer" <tshearer@advaoptical.com>, "Liran Alon" <liran.alon@oracle.com> Subject: Re: [PATCH 3/3] KVM: VMX: Allow I/O port 0x80 bypass when userspace prefer Date: Fri, 11 May 2018 11:44:58 -0400 [thread overview] Message-ID: <20180511154458.GI27459@char.us.oracle.com> (raw) In-Reply-To: <1523943962-25415-4-git-send-email-wanpengli@tencent.com> On Mon, Apr 16, 2018 at 10:46:02PM -0700, Wanpeng Li wrote: > From: Wanpeng Li <wanpengli@tencent.com> > > Tim Shearer reported that "There is a guest which is running a packet > forwarding app based on the DPDK (dpdk.org). The packet receive routine > writes to 0xc070 using glibc's "outw_p" function which does an additional > write to I/O port 80. It does this write for every packet that's received, > causing a flood of KVM userspace context switches". He uses mpstat to > observe a CPU performing L2 packet forwarding on a pinned guest vCPU, > the guest time is 95 percent when allowing I/O port 0x80 bypass, however, > it is 65.78 percent when I/O port 0x80 bypss is disabled. > > This patch allows I/O port 0x80 bypass when userspace prefer. s/prefer/requests it/ > Perhaps: Reported-by: Tim Shearer as well? > Cc: Paolo Bonzini <pbonzini@redhat.com> > Cc: Radim Krčmář <rkrcmar@redhat.com> > Cc: Tim Shearer <tshearer@advaoptical.com> > Cc: Liran Alon <liran.alon@oracle.com> > Signed-off-by: Wanpeng Li <wanpengli@tencent.com> > --- > arch/x86/kvm/vmx.c | 7 +++++++ > 1 file changed, 7 insertions(+) > > diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c > index ebf1140..d3e5fef 100644 > --- a/arch/x86/kvm/vmx.c > +++ b/arch/x86/kvm/vmx.c > @@ -10118,6 +10118,13 @@ static int vmx_vm_init(struct kvm *kvm) > goto out; > memset(kvm_vmx->vmx_io_bitmap[i], 0xff, PAGE_SIZE); > } > + if (kvm->arch.ioport_disable_intercept) { > + /* > + * Allow direct access to the PC debug port (it is often used for I/O > + * delays, but the vmexits simply slow things down). > + */ > + clear_bit(0x80, kvm_vmx->vmx_io_bitmap[VMX_IO_BITMAP_A]); > + } > return 0; > > out: > -- > 2.7.4 >
next prev parent reply other threads:[~2018-05-11 15:45 UTC|newest] Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top 2018-04-17 5:45 [PATCH 0/3] KVM: VMX: Allow to disable ioport intercept per-VM by userspace Wanpeng Li 2018-04-17 5:46 ` [PATCH 1/3] KVM: VMX: Introduce per-VM I/O permission bitmaps Wanpeng Li 2018-05-11 15:39 ` Konrad Rzeszutek Wilk 2018-05-15 21:55 ` Jim Mattson 2018-04-17 5:46 ` [PATCH 2/3] KVM: X86: Allow userspace to disable ioport intercept Wanpeng Li 2018-05-11 15:42 ` Konrad Rzeszutek Wilk 2018-05-11 15:43 ` Konrad Rzeszutek Wilk 2018-05-15 21:56 ` Jim Mattson 2018-05-16 1:13 ` Wanpeng Li 2018-04-17 5:46 ` [PATCH 3/3] KVM: VMX: Allow I/O port 0x80 bypass when userspace prefer Wanpeng Li 2018-05-11 15:44 ` Konrad Rzeszutek Wilk [this message] 2018-05-15 21:57 ` Jim Mattson 2018-05-08 7:55 ` [PATCH 0/3] KVM: VMX: Allow to disable ioport intercept per-VM by userspace Wanpeng Li 2018-05-08 16:14 ` Paolo Bonzini 2018-05-11 15:40 ` Konrad Rzeszutek Wilk 2018-05-12 1:03 ` Wanpeng Li 2018-05-14 13:48 ` Tim Shearer
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