Patchwork [v2,3/4] uq/master: Add CPU eject handling for acpi_piix4

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Submitter Vasilis Liaskovitis
Date Jan. 24, 2012, 2:56 p.m.
Message ID <20120124145600.GA6555@dhcp-192-168-178-175.profitbricks.localdomain>
Download mbox | patch
Permalink /patch/137573/
State New
Headers show

Comments

Vasilis Liaskovitis - Jan. 24, 2012, 2:56 p.m.
On Tue, Jan 24, 2012 at 11:28:41AM +0100, Jan Kiszka wrote:
> On 2012-01-24 11:10, Vasilis Liaskovitis wrote:
> > Add stub functions for CPU eject callback. Define cpu_acpi_eject property and
> > enable eject callback only for pc-1.1 machine model.
> 
> Just to get the idea: What is the plan and advantage of introducing a
> stub first? How much more is required to have some usable feature, even
> if its just a friction of the full support?
>
There's not really an advantage to adding stubs first. The plan depends on the
lifecycle patches getting accepted in some form at some point. The code is all
out there, and some of it has been reviewed/commented on, but not accepted.

kvm needs the following patches:
https://lkml.org/lkml/2012/1/6/355 (v7, still in work)
http://patchwork.ozlabs.org/patch/127828/
This second patch introduces ioctl KVM_SETSTATE_VCPU, (qemu uses it to signal
vcpu destruction to the host) but the review mentions there should be a
simpler way. It's unclear to me whether this ioctl is desired or not.

userspace qemu/qemu-kvm need some form of these patches
http://patchwork.ozlabs.org/patch/127831/
http://patchwork.ozlabs.org/patch/127830/
http://patchwork.ozlabs.org/patch/127833/
http://patchwork.ozlabs.org/patch/127834/

Assuming that the above is further reviewed and accepted, the extra code
needed to actually make something useful in the stub functions would be something
like the following (with the above ioctl), comments welcome. This code calls
kvm function from hw/acpi_piix4.c so it's probably not well abstracted enough
for upstream.
Avi Kivity - Jan. 26, 2012, 10:46 a.m.
On 01/24/2012 04:56 PM, Vasilis Liaskovitis wrote:
> On Tue, Jan 24, 2012 at 11:28:41AM +0100, Jan Kiszka wrote:
> > On 2012-01-24 11:10, Vasilis Liaskovitis wrote:
> > > Add stub functions for CPU eject callback. Define cpu_acpi_eject property and
> > > enable eject callback only for pc-1.1 machine model.
> > 
> > Just to get the idea: What is the plan and advantage of introducing a
> > stub first? How much more is required to have some usable feature, even
> > if its just a friction of the full support?
> >
> There's not really an advantage to adding stubs first. The plan depends on the
> lifecycle patches getting accepted in some form at some point. The code is all
> out there, and some of it has been reviewed/commented on, but not accepted.
>
> kvm needs the following patches:
> https://lkml.org/lkml/2012/1/6/355 (v7, still in work)
> http://patchwork.ozlabs.org/patch/127828/
> This second patch introduces ioctl KVM_SETSTATE_VCPU, (qemu uses it to signal
> vcpu destruction to the host) but the review mentions there should be a
> simpler way. It's unclear to me whether this ioctl is desired or not.

Those patches are not strictly needed.  On a kernel that doesn't have
them, you can simply park the vcpu thread in userspace until it is
re-added.  I suggest writing the qemu patches without the assumption
that you're running on a 3.4+ kernel.
Vasilis Liaskovitis - Jan. 30, 2012, 10:14 a.m.
On Thu, Jan 26, 2012 at 12:46:18PM +0200, Avi Kivity wrote:
> On 01/24/2012 04:56 PM, Vasilis Liaskovitis wrote:
> > On Tue, Jan 24, 2012 at 11:28:41AM +0100, Jan Kiszka wrote:
> > > On 2012-01-24 11:10, Vasilis Liaskovitis wrote:
> > > > Add stub functions for CPU eject callback. Define cpu_acpi_eject property and
> > > > enable eject callback only for pc-1.1 machine model.
> > > 
> > > Just to get the idea: What is the plan and advantage of introducing a
> > > stub first? How much more is required to have some usable feature, even
> > > if its just a friction of the full support?
> > >
> > There's not really an advantage to adding stubs first. The plan depends on the
> > lifecycle patches getting accepted in some form at some point. The code is all
> > out there, and some of it has been reviewed/commented on, but not accepted.
> >
> > kvm needs the following patches:
> > https://lkml.org/lkml/2012/1/6/355 (v7, still in work)
> > http://patchwork.ozlabs.org/patch/127828/
> > This second patch introduces ioctl KVM_SETSTATE_VCPU, (qemu uses it to signal
> > vcpu destruction to the host) but the review mentions there should be a
> > simpler way. It's unclear to me whether this ioctl is desired or not.
> 
> Those patches are not strictly needed.  On a kernel that doesn't have
> them, you can simply park the vcpu thread in userspace until it is
> re-added.  I suggest writing the qemu patches without the assumption
> that you're running on a 3.4+ kernel.

ok, I will try to handle CPU ejection without relying on the lifecycle
patches.

thanks,

- Vasilis

Patch

diff --git a/hw/acpi_piix4.c b/hw/acpi_piix4.c
index 8475aa6..b5fcb4a 100644
--- a/hw/acpi_piix4.c
+++ b/hw/acpi_piix4.c
@@ -509,6 +509,20 @@  static uint32_t cpuej_read(void *opaque, uint32_t addr)
 
 static void cpuej_write(void *opaque, uint32_t addr, uint32_t val)
 {
+    PIIX4PMState *s = opaque;
+    CPUState *env;
+    int cpu;
+    int ret;
+
+    cpu = ffs(val);
+    /* zero means no bit was set, i.e. no CPU ejection happened */
+    if (!cpu)
+       return;
+    cpu--;
+    env = cpu_phyid_to_cpu((uint64_t)cpu);
+    if (s->kvm_enabled && env != NULL) {
+        kvm_eject_vcpu(env);
+    }
     PIIX4_DPRINTF("cpuej write %x <== %d\n", addr, val);
 }
 
diff --git a/kvm-all.c b/kvm-all.c
index 88f1156..d3e53f5 100644
--- a/kvm-all.c
+++ b/kvm-all.c
@@ -193,6 +193,13 @@  static void kvm_reset_vcpu(void *opaque)
     kvm_arch_reset_vcpu(env);
 }
 
+static void kvm_eject_vcpu(void *opaque)
+{
+    CPUState *env = opaque;
+
+    kvm_arch_eject_vcpu(env);
+}
+
 int kvm_irqchip_in_kernel(void)
 {
     return kvm_state->irqchip_in_kernel;
diff --git a/kvm.h b/kvm.h
index 40b5ffc..ace28a8 100644
--- a/kvm.h
+++ b/kvm.h
@@ -125,6 +125,8 @@  int kvm_arch_init_vcpu(CPUState *env);
 
 void kvm_arch_reset_vcpu(CPUState *env);
 
+void kvm_arch_eject_vcpu(CPUState *env);
+
 int kvm_arch_on_sigbus_vcpu(CPUState *env, int code, void *addr);
 int kvm_arch_on_sigbus(int code, void *addr);
 
diff --git a/target-i386/kvm.c b/target-i386/kvm.c
index e41de39..f8239c0 100644
--- a/target-i386/kvm.c
+++ b/target-i386/kvm.c
@@ -589,6 +589,21 @@  void kvm_arch_reset_vcpu(CPUState *env)
     }
 }
 
+void kvm_arch_eject_vcpu(CPUState *env)
+{
+    struct kvm_vcpu_state state;
+    int ret = 0;
+
+    if (env->state == CPU_STATE_ZAPREQ) {
+        state.vcpu_id = env->cpu_index;
+        state.state = 1;
+        ret = kvm_vm_ioctl(env->kvm_state, KVM_SETSTATE_VCPU, &state);
+        if (ret)
+            fprintf(stderr, "KVM_SETSTATE_VCPU failed: %s\n",
+                    strerror(ret));
+    }
+}
+
 static int kvm_get_supported_msrs(KVMState *s)
 {
     static int kvm_supported_msrs;