[PATCH 09/14] KVM: PPC: Add generic single register ioctls

Alexander Graf
2011-10-31T07:53:11Z

Right now we transfer a static struct every time we want to get or set
registers. Unfortunately, over time we realize that there are more of
these than we thought of before and the extensibility and flexibility of
transferring a full struct every time is limited.

So this is a new approach to the problem. With these new ioctls, we can
get and set a single register that is identified by an ID. This allows for
very precise and limited transmittal of data. When we later realize that
it's a better idea to shove over multiple registers at once, we can reuse
most of the infrastructure and simply implement a GET_MANY_REGS / SET_MANY_REGS
interface.

The only downpoint I see to this one is that it needs to pad to 1024 bits
(hardware is already on 512 bit registers, so I wanted to leave some room)
which is slightly too much for transmitting only 64 bits. But if that's all
the tradeoff we have to do for getting an extensible interface, I'd say go
for it nevertheless.

Signed-off-by: Alexander Graf <agraf@suse.de>
---
Documentation/virtual/kvm/api.txt | 47 ++++++++++++++++++++++++++++++++++
arch/powerpc/kvm/powerpc.c | 51 +++++++++++++++++++++++++++++++++++++
include/linux/kvm.h | 32 +++++++++++++++++++++++
3 files changed, 130 insertions(+), 0 deletions(-)

diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
index ab1136f..a23fe62 100644
--- a/Documentation/virtual/kvm/api.txt
+++ b/Documentation/virtual/kvm/api.txt
@@ -1482,6 +1482,53 @@ is supported; 2 if the processor requires all virtual machines to have
an RMA, or 1 if the processor can use an RMA but doesn't require it,
because it supports the Virtual RMA (VRMA) facility.

+4.64 KVM_SET_ONE_REG
+
+Capability: KVM_CAP_ONE_REG
+Architectures: all
+Type: vcpu ioctl
+Parameters: struct kvm_one_reg (in)
+Returns: 0 on success, negative value on failure
+
+struct kvm_one_reg {
+ __u64 id;
+ union {
+ __u8 reg8;
+ __u16 reg16;
+ __u32 reg32;
+ __u64 reg64;
+ __u8 reg128[16];
+ __u8 reg256[32];
+ __u8 reg512[64];
+ __u8 reg1024[128];
+ } u;
+};
+
+Using this ioctl, a single vcpu register can be set to a specific value
+defined by user space with the passed in struct kvm_one_reg. There can
+be architecture agnostic and architecture specific registers. Each have
+their own range of operation and their own constants and width. To keep
+track of the implemented registers, find a list below:
+
+ Arch | Register | Width (bits)
+ | |
+
+4.65 KVM_GET_ONE_REG
+
+Capability: KVM_CAP_ONE_REG
+Architectures: all
+Type: vcpu ioctl
+Parameters: struct kvm_one_reg (in and out)
+Returns: 0 on success, negative value on failure
+
+This ioctl allows to receive the value of a single register implemented
+in a vcpu. The register to read is indicated by the "id" field of the
+kvm_one_reg struct passed in. On success, the register value can be found
+in the respective width field of the struct after this call.
+
+The list of registers accessible using this interface is identical to the
+list in 4.64.
+
5. The kvm_run structure

Application code obtains a pointer to the kvm_run structure by
diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
index e75c5ac..39cdb3f 100644
--- a/arch/powerpc/kvm/powerpc.c
+++ b/arch/powerpc/kvm/powerpc.c
@@ -214,6 +214,7 @@ int kvm_dev_ioctl_check_extension(long ext)
case KVM_CAP_PPC_UNSET_IRQ:
case KVM_CAP_PPC_IRQ_LEVEL:
case KVM_CAP_ENABLE_CAP:
+ case KVM_CAP_ONE_REG:
r = 1;
break;
#ifndef CONFIG_KVM_BOOK3S_64_HV
@@ -627,6 +628,32 @@ static int kvm_vcpu_ioctl_enable_cap(struct kvm_vcpu *vcpu,
return r;
}

+static int kvm_vcpu_ioctl_get_one_reg(struct kvm_vcpu *vcpu,
+ struct kvm_one_reg *reg)
+{
+ int r = -EINVAL;
+
+ switch (reg->id) {
+ default:
+ break;
+ }
+
+ return r;
+}
+
+static int kvm_vcpu_ioctl_set_one_reg(struct kvm_vcpu *vcpu,
+ struct kvm_one_reg *reg)
+{
+ int r = -EINVAL;
+
+ switch (reg->id) {
+ default:
+ break;
+ }
+
+ return r;
+}
+
int kvm_arch_vcpu_ioctl_get_mpstate(struct kvm_vcpu *vcpu,
struct kvm_mp_state *mp_state)
{
@@ -666,6 +693,30 @@ long kvm_arch_vcpu_ioctl(struct file *filp,
break;
}

+ case KVM_GET_ONE_REG:
+ {
+ struct kvm_one_reg reg;
+ r = -EFAULT;
+ if (copy_from_user(&reg, argp, sizeof(reg)))
+ goto out;
+ r = kvm_vcpu_ioctl_get_one_reg(vcpu, &reg);
+ if (copy_to_user(argp, &reg, sizeof(reg))) {
+ r = -EFAULT;
+ goto out;
+ }
+ break;
+ }
+
+ case KVM_SET_ONE_REG:
+ {
+ struct kvm_one_reg reg;
+ r = -EFAULT;
+ if (copy_from_user(&reg, argp, sizeof(reg)))
+ goto out;
+ r = kvm_vcpu_ioctl_set_one_reg(vcpu, &reg);
+ break;
+ }
+
#ifdef CONFIG_KVM_E500
case KVM_DIRTY_TLB: {
struct kvm_dirty_tlb dirty;
diff --git a/include/linux/kvm.h b/include/linux/kvm.h
index a6b1295..e652a7b 100644
--- a/include/linux/kvm.h
+++ b/include/linux/kvm.h
@@ -557,6 +557,7 @@ struct kvm_ppc_pvinfo {
#define KVM_CAP_MAX_VCPUS 66 /* returns max vcpus per vm */
#define KVM_CAP_PPC_PAPR 68
#define KVM_CAP_SW_TLB 69
+#define KVM_CAP_ONE_REG 70
#define KVM_CAP_S390_GMAP 71

#ifdef KVM_CAP_IRQ_ROUTING
@@ -652,6 +653,34 @@ struct kvm_dirty_tlb {
__u32 num_dirty;
};

+/* Available with KVM_CAP_ONE_REG */
+
+#define KVM_ONE_REG_GENERIC 0x0000000000000000ULL
+
+/*
+ * Architecture specific registers are to be defined in arch headers and
+ * ORed with the arch identifier.
+ */
+#define KVM_ONE_REG_PPC 0x1000000000000000ULL
+#define KVM_ONE_REG_X86 0x2000000000000000ULL
+#define KVM_ONE_REG_IA64 0x3000000000000000ULL
+#define KVM_ONE_REG_ARM 0x4000000000000000ULL
+#define KVM_ONE_REG_S390 0x5000000000000000ULL
+
+struct kvm_one_reg {
+ __u64 id;
+ union {
+ __u8 reg8;
+ __u16 reg16;
+ __u32 reg32;
+ __u64 reg64;
+ __u8 reg128[16];
+ __u8 reg256[32];
+ __u8 reg512[64];
+ __u8 reg1024[128];
+ } u;
+};
+
/*
* ioctls for VM fds
*/
@@ -780,6 +809,9 @@ struct kvm_dirty_tlb {
#define KVM_ALLOCATE_RMA _IOR(KVMIO, 0xa9, struct kvm_allocate_rma)
/* Available with KVM_CAP_SW_TLB */
#define KVM_DIRTY_TLB _IOW(KVMIO, 0xaa, struct kvm_dirty_tlb)
+/* Available with KVM_CAP_ONE_REG */
+#define KVM_GET_ONE_REG _IOWR(KVMIO, 0xab, struct kvm_one_reg)
+#define KVM_SET_ONE_REG _IOW(KVMIO, 0xac, struct kvm_one_reg)

#define KVM_DEV_ASSIGN_ENABLE_IOMMU (1 << 0)

--
1.6.0.2