KVM: PPC: Book3S: Controls for in-kernel sPAPR hypercall handling

This provides a way for userspace controls which sPAPR hcalls get
handled in the kernel.  Each hcall can be individually enabled or
disabled for in-kernel handling, except for H_RTAS.  The exception
for H_RTAS is because userspace can already control whether
individual RTAS functions are handled in-kernel or not via the
KVM_PPC_RTAS_DEFINE_TOKEN ioctl, and because the numeric value for
H_RTAS is out of the normal sequence of hcall numbers.

Hcalls are enabled or disabled using the KVM_ENABLE_CAP ioctl for the
KVM_CAP_PPC_ENABLE_HCALL capability on the file descriptor for the VM.
The args field of the struct kvm_enable_cap specifies the hcall number
in args[0] and the enable/disable flag in args[1]; 0 means disable
in-kernel handling (so that the hcall will always cause an exit to
userspace) and 1 means enable.  Enabling or disabling in-kernel
handling of an hcall is effective across the whole VM.

The ability for KVM_ENABLE_CAP to be used on a VM file descriptor
on PowerPC is new, added by this commit.  The KVM_CAP_ENABLE_CAP_VM
capability advertises that this ability exists.

When a VM is created, an initial set of hcalls are enabled for
in-kernel handling.  The set that is enabled is the set that have
an in-kernel implementation at this point.  Any new hcall
implementations from this point onwards should not be added to the
default set without a good reason.

No distinction is made between real-mode and virtual-mode hcall
implementations; the one setting controls them both.

Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Alexander Graf <agraf@suse.de>

1 files changed, 37 insertions, 0 deletions

diff --git a/arch/powerpc/kvm/book3s_pr_papr.c b/arch/powerpc/kvm/book3s_pr_papr.c
index f7c25c625a5b..eacaa6e4876e 100644
--- a/arch/powerpc/kvm/book3s_pr_papr.c
+++ b/arch/powerpc/kvm/book3s_pr_papr.c
@@ -267,6 +267,10 @@ static int kvmppc_h_pr_xics_hcall(struct kvm_vcpu *vcpu, u32 cmd)
 
 int kvmppc_h_pr(struct kvm_vcpu *vcpu, unsigned long cmd)
 {
+	if (cmd <= MAX_HCALL_OPCODE &&
+	    !test_bit(cmd/4, vcpu->kvm->arch.enabled_hcalls))
+		return EMULATE_FAIL;
+
 	switch (cmd) {
 	case H_ENTER:
 		return kvmppc_h_pr_enter(vcpu);
@@ -304,3 +308,36 @@ int kvmppc_h_pr(struct kvm_vcpu *vcpu, unsigned long cmd)
 
 	return EMULATE_FAIL;
 }
+
+
+/*
+ * List of hcall numbers to enable by default.
+ * For compatibility with old userspace, we enable by default
+ * all hcalls that were implemented before the hcall-enabling
+ * facility was added.  Note this list should not include H_RTAS.
+ */
+static unsigned int default_hcall_list[] = {
+	H_ENTER,
+	H_REMOVE,
+	H_PROTECT,
+	H_BULK_REMOVE,
+	H_PUT_TCE,
+	H_CEDE,
+#ifdef CONFIG_KVM_XICS
+	H_XIRR,
+	H_CPPR,
+	H_EOI,
+	H_IPI,
+	H_IPOLL,
+	H_XIRR_X,
+#endif
+	0
+};
+
+void kvmppc_pr_init_default_hcalls(struct kvm *kvm)
+{
+	int i;
+
+	for (i = 0; default_hcall_list[i]; ++i)
+		__set_bit(default_hcall_list[i] / 4, kvm->arch.enabled_hcalls);
+}