Hi,

On 03/07/15 10:05, Andre Przywara wrote:

Hi Pavel,

On 02/07/15 08:26, Pavel Fedin wrote:

quoted

 Hello!

quoted

-----Original Message-----
From: kvm-owner at vger.kernel.org [mailto:kvm-owner at vger.kernel.org] On Behalf Of Eric Auger
Sent: Monday, June 29, 2015 6:37 PM
To: eric.auger at st.com; eric.auger at linaro.org; linux-arm-kernel at lists.infradead.org;
marc.zyngier at arm.com; christoffer.dall at linaro.org; andre.przywara at arm.com;
kvmarm at lists.cs.columbia.edu; kvm at vger.kernel.org
Cc: linux-kernel at vger.kernel.org; patches at linaro.org; p.fedin at samsung.com; pbonzini at redhat.com
Subject: [PATCH 1/7] KVM: api: add kvm_irq_routing_extended_msi

On ARM, the MSI msg (address and data) comes along with
out-of-band device ID information. The device ID encodes the device
that composes the MSI msg. Let's create a new routing entry type,
dubbed KVM_IRQ_ROUTING_EXTENDED_MSI and use the __u32 pad space
to convey the device ID.

Signed-off-by: Eric Auger <redacted>

---

RFC -> PATCH
- remove kvm_irq_routing_extended_msi and use union instead
---
 Documentation/virtual/kvm/api.txt | 9 ++++++++-
 include/uapi/linux/kvm.h          | 6 +++++-
 2 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
index d20fd94..6426ae9 100644
--- a/Documentation/virtual/kvm/api.txt
+++ b/Documentation/virtual/kvm/api.txt

@@ -1414,7 +1414,10 @@ struct kvm_irq_routing_entry {
 	__u32 gsi;
 	__u32 type;
 	__u32 flags;
-	__u32 pad;
+	union {
+		__u32 pad;
+		__u32 devid;
+	};
 	union {
 		struct kvm_irq_routing_irqchip irqchip;
 		struct kvm_irq_routing_msi msi;

 devid is actually a part of MSI bunch. Shouldn't it be a part of struct kvm_irq_routing_msi then?
It also has reserved pad.

quoted

@@ -1427,6 +1430,10 @@ struct kvm_irq_routing_entry {
 #define KVM_IRQ_ROUTING_IRQCHIP 1
 #define KVM_IRQ_ROUTING_MSI 2
 #define KVM_IRQ_ROUTING_S390_ADAPTER 3
+#define KVM_IRQ_ROUTING_EXTENDED_MSI 4
+
+In case of KVM_IRQ_ROUTING_EXTENDED_MSI routing type, devid is used to convey
+the device ID.

 No flags are specified so far, the corresponding field must be set to zero.

What if we use KVM_MSI_VALID_DEVID flag instead of new KVM_IRQ_ROUTING_EXTENDED_MSI definition? I
believe this would make an API more consistent and introduce less new definitions.

I like this approach, but it runs into problems:
As you read above the current documentation says that the flags field
must be zero and the current KVM_SET_GSI_ROUTING handler bails out if it
isn't. So userland would need to know whether it's safe to set that
field. Introducing a new KVM_CAP_... value seems overkill if we could
just have a new routing entry type. So we could still reuse the existing
struct kvm_irq_routing_msi (and extend that with the devid field), but
we would have to add a new routing type number.

Maybe we could collapse this into the existing MSI type + flag when
handing it further down the kernel?

FWIW, I gave this a try, this doesn't look to bad. I carried the new
type down till virt/kvm/arm/vgic.c:kvm_set_routing_entry(), where the
EXTENDED type got turned back into the normal MSI type while setting the
flag in the internal struct kvm_kernel_irq_routing_entry. This keeps the
new type only to the userland facing side, with the kernel code staying
mostly the same.
Together with a new KVM_CAP_MSIS_REQUIRE_DEVID capability I can now
drive both GICv2M and ITS emulation from the same userland base in a
sane manner.
If someone wants to have a look now, tell me, otherwise I will wait for
Eric's upcoming code drop and comment on that then.

Cheers,
Andre.

Cheers,
Andre.

quoted

quoted

diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index 2a23705..8484681 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h

@@ -841,12 +841,16 @@ struct kvm_irq_routing_s390_adapter {
 #define KVM_IRQ_ROUTING_IRQCHIP 1
 #define KVM_IRQ_ROUTING_MSI 2
 #define KVM_IRQ_ROUTING_S390_ADAPTER 3
+#define KVM_IRQ_ROUTING_EXTENDED_MSI 4

 struct kvm_irq_routing_entry {
 	__u32 gsi;
 	__u32 type;
 	__u32 flags;
-	__u32 pad;
+	union {
+		__u32 pad;
+		__u32 devid;
+	};
 	union {
 		struct kvm_irq_routing_irqchip irqchip;
 		struct kvm_irq_routing_msi msi;
--

1.9.1

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Kind regards,
Pavel Fedin
Expert Engineer
Samsung Electronics Research center Russia