Re: [PATCHv3 RFC 0/2] kvm: direct msix injection

["Michael S. Tsirkin" <mst@redhat.com>]

On Mon, Jul 02, 2012 at 11:08:20AM -0600, Alex Williamson wrote:
> On Mon, 2012-06-25 at 11:32 +0200, Jan Kiszka wrote:
> > On 2012-06-11 13:19, Michael S. Tsirkin wrote:
> > > We can deliver certain interrupts, notably MSIX,
> > > from atomic context.
> > > Here's an untested patch to do this (compiled only).
> > > 
> > > Changes from v2:
> > > Don't inject broadcast interrupts directly
> > > Changes from v1:
> > > Tried to address comments from v1, except unifying
> > > with kvm_set_irq: passing flags to it looks too ugly.
> > > Added a comment.
> > > 
> > > Jan, you said you can test this?
> > > 
> > > 
> > > Michael S. Tsirkin (2):
> > >   kvm: implement kvm_set_msi_inatomic
> > >   kvm: deliver msix interrupts from irq handler
> > > 
> > >  include/linux/kvm_host.h |  3 ++
> > >  virt/kvm/assigned-dev.c  | 31 ++++++++++++++++++--
> > >  virt/kvm/irq_comm.c      | 75 ++++++++++++++++++++++++++++++++++++++++++++----
> > >  3 files changed, 102 insertions(+), 7 deletions(-)
> > > 
> > 
> > Finally-tested-by: Jan Kiszka <jan.kiszka@siemens.com>
> 
> Michael, we need either this or the simple oneshot patch to get device
> assignment working again for 3.5.  Are you planning to push this for
> 3.5?  Thanks,
> 
> Alex
> 

Avi wants this reworked using an injection cache. I agree with Jan
though: oneshot looks too ugly. Just so you can make progress, can't we
add a stub handler returning IRQ_WAKE_THREAD unconditionally for now?
I.e. like the below (warning: completely untested).

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

--

diff --git a/virt/kvm/assigned-dev.c b/virt/kvm/assigned-dev.c
index b1e091a..18cc36e 100644
--- a/virt/kvm/assigned-dev.c
+++ b/virt/kvm/assigned-dev.c
@@ -334,6 +334,11 @@ static int assigned_device_enable_host_intx(struct kvm *kvm,
 }
 
 #ifdef __KVM_HAVE_MSI
+static irqreturn_t kvm_assigned_dev_msi(int irq, void *dev_id)
+{
+       return IRQ_WAKE_THREAD;
+}
+
 static int assigned_device_enable_host_msi(struct kvm *kvm,
 					   struct kvm_assigned_dev_kernel *dev)
 {
@@ -346,7 +351,7 @@ static int assigned_device_enable_host_msi(struct kvm *kvm,
 	}
 
 	dev->host_irq = dev->dev->irq;
-	if (request_threaded_irq(dev->host_irq, NULL,
+	if (request_threaded_irq(dev->host_irq, kvm_assigned_dev_msi,
 				 kvm_assigned_dev_thread_msi, 0,
 				 dev->irq_name, dev)) {
 		pci_disable_msi(dev->dev);
@@ -358,6 +363,11 @@ static int assigned_device_enable_host_msi(struct kvm *kvm,
 #endif
 
 #ifdef __KVM_HAVE_MSIX
+static irqreturn_t kvm_assigned_dev_msix(int irq, void *dev_id)
+{
+       return IRQ_WAKE_THREAD;
+}
+
 static int assigned_device_enable_host_msix(struct kvm *kvm,
 					    struct kvm_assigned_dev_kernel *dev)
 {
@@ -374,7 +384,8 @@ static int assigned_device_enable_host_msix(struct kvm *kvm,
 
 	for (i = 0; i < dev->entries_nr; i++) {
 		r = request_threaded_irq(dev->host_msix_entries[i].vector,
-					 NULL, kvm_assigned_dev_thread_msix,
+					 kvm_assigned_dev_msix,
+					 kvm_assigned_dev_thread_msix,
 					 0, dev->irq_name, dev);
 		if (r)
 			goto err;
-- 
MST