From: Paolo Bonzini <pbonzini@redhat.com>
To: linux-kernel@vger.kernel.org, kvm@vger.kernel.org
Cc: bsd@redhat.com, rkrcmar@redhat.com
Subject: [RFC PATCH 2/2] KVM: x86: use __kvm_guest_exit
Date: Thu, 16 Jun 2016 10:21:37 +0200 [thread overview]
Message-ID: <1466065297-4644-3-git-send-email-pbonzini@redhat.com> (raw)
In-Reply-To: <1466065297-4644-1-git-send-email-pbonzini@redhat.com>
This gains ~20 clock cycles per vmexit. On Intel there is no need
anymore to enable the interrupts in vmx_handle_external_intr, since we
are using the "acknowledge interrupt on exit" feature. AMD needs to do
that temporarily, and must be careful to avoid the interrupt shadow.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
arch/x86/kvm/svm.c | 6 ++++++
arch/x86/kvm/vmx.c | 4 +---
arch/x86/kvm/x86.c | 11 ++---------
3 files changed, 9 insertions(+), 12 deletions(-)
diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 5ff292778110..5bfdbbf1ce79 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -4935,6 +4935,12 @@ out:
static void svm_handle_external_intr(struct kvm_vcpu *vcpu)
{
local_irq_enable();
+ /*
+ * We must execute an instruction with interrupts enabled, so
+ * the "cli" doesn't fall right on the interrupt shadow.
+ */
+ asm("nop");
+ local_irq_disable();
}
static void svm_sched_in(struct kvm_vcpu *vcpu, int cpu)
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 4e9657730bf6..a46bce9e3683 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -8544,7 +8544,6 @@ static void vmx_handle_external_intr(struct kvm_vcpu *vcpu)
"push %[sp]\n\t"
#endif
"pushf\n\t"
- "orl $0x200, (%%" _ASM_SP ")\n\t"
__ASM_SIZE(push) " $%c[cs]\n\t"
"call *%[entry]\n\t"
:
@@ -8557,8 +8556,7 @@ static void vmx_handle_external_intr(struct kvm_vcpu *vcpu)
[ss]"i"(__KERNEL_DS),
[cs]"i"(__KERNEL_CS)
);
- } else
- local_irq_enable();
+ }
}
static bool vmx_has_high_real_mode_segbase(void)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 7e3041ef050f..cc741b68139c 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -6706,21 +6706,13 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
kvm_put_guest_xcr0(vcpu);
- /* Interrupt is enabled by handle_external_intr() */
kvm_x86_ops->handle_external_intr(vcpu);
++vcpu->stat.exits;
- /*
- * We must have an instruction between local_irq_enable() and
- * kvm_guest_exit(), so the timer interrupt isn't delayed by
- * the interrupt shadow. The stat.exits increment will do nicely.
- * But we need to prevent reordering, hence this barrier():
- */
- barrier();
-
- kvm_guest_exit();
+ __kvm_guest_exit();
+ local_irq_enable();
preempt_enable();
vcpu->srcu_idx = srcu_read_lock(&vcpu->kvm->srcu);
--
1.8.3.1
next prev parent reply other threads:[~2016-06-16 8:21 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-06-16 8:21 [RFC PATCH 0/2] KVM: x86: guest exit microoptimization Paolo Bonzini
2016-06-16 8:21 ` [RFC PATCH 1/2] KVM: x86: always use "acknowledge interrupt on exit" Paolo Bonzini
2016-06-16 21:53 ` Bandan Das
2016-06-16 8:21 ` Paolo Bonzini [this message]
2016-06-16 16:43 ` [RFC PATCH 2/2] KVM: x86: use __kvm_guest_exit David Matlack
2016-06-16 16:47 ` Paolo Bonzini
2016-06-16 17:03 ` David Matlack
2016-06-16 17:21 ` Paolo Bonzini
2016-06-16 22:01 ` Bandan Das
2016-06-17 5:20 ` Paolo Bonzini
2016-07-01 16:45 ` [RFC PATCH 0/2] KVM: x86: guest exit microoptimization Paolo Bonzini
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=1466065297-4644-3-git-send-email-pbonzini@redhat.com \
--to=pbonzini@redhat.com \
--cc=bsd@redhat.com \
--cc=kvm@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=rkrcmar@redhat.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).