Re: [PATCH 1/3] KVM: PPC: Book3S: Controls for in-kernel PAPR hypercall handling

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On 26.05.14 14:17, Paul Mackerras wrote:
This provides a way for userspace controls which PAPR 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.  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, even though the KVM_ENABLE_CAP ioctl is
applied to a vcpu.

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.

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

Signed-off-by: Paul Mackerras <paulus@xxxxxxxxx>
---
  Documentation/virtual/kvm/api.txt       | 17 +++++++++++
  arch/powerpc/include/asm/kvm_book3s.h   |  1 +
  arch/powerpc/include/asm/kvm_host.h     |  2 ++
  arch/powerpc/kernel/asm-offsets.c       |  1 +
  arch/powerpc/kvm/book3s_hv.c            | 51 +++++++++++++++++++++++++++++++++
  arch/powerpc/kvm/book3s_hv_rmhandlers.S | 11 +++++++
  arch/powerpc/kvm/book3s_pr.c            |  5 ++++
  arch/powerpc/kvm/book3s_pr_papr.c       | 37 ++++++++++++++++++++++++
  arch/powerpc/kvm/powerpc.c              | 19 ++++++++++++
  include/uapi/linux/kvm.h                |  1 +
  10 files changed, 145 insertions(+)

diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
index 6b0225d..dfd6e0c 100644
--- a/Documentation/virtual/kvm/api.txt
+++ b/Documentation/virtual/kvm/api.txt
@@ -2983,3 +2983,20 @@ Parameters: args[0] is the XICS device fd
              args[1] is the XICS CPU number (server ID) for this vcpu
This capability connects the vcpu to an in-kernel XICS device.
+
+6.8 KVM_CAP_PPC_ENABLE_HCALL
+
+Architectures: ppc
+Parameters: args[0] is the PAPR hcall number
+	    args[1] is 0 to disable, 1 to enable in-kernel handling
+
+This capability controls whether individual PAPR hypercalls (hcalls)
+get handled by the kernel or not.  Enabling or disabling in-kernel
+handling of an hcall is effective across the VM.  On creation, an

Hrm. Could we move the CAP to vm level then?

+initial set of hcalls are enabled for in-kernel handling, which
+consists of those hcalls for which in-kernel handlers were implemented
+before this capability was implemented.  If disabled, the kernel will
+not to attempt to handle the hcall, but will always exit to userspace
+to handle it.  Note that it may not make sense to enable some and
+disable others of a group of related hcalls, but KVM will not prevent
+userspace from doing that.
diff --git a/arch/powerpc/include/asm/kvm_book3s.h b/arch/powerpc/include/asm/kvm_book3s.h
index f52f656..772044b 100644
--- a/arch/powerpc/include/asm/kvm_book3s.h
+++ b/arch/powerpc/include/asm/kvm_book3s.h
@@ -189,6 +189,7 @@ extern void kvmppc_hv_entry_trampoline(void);
  extern u32 kvmppc_alignment_dsisr(struct kvm_vcpu *vcpu, unsigned int inst);
  extern ulong kvmppc_alignment_dar(struct kvm_vcpu *vcpu, unsigned int inst);
  extern int kvmppc_h_pr(struct kvm_vcpu *vcpu, unsigned long cmd);
+extern void kvmppc_pr_init_default_hcalls(struct kvm *kvm);
  extern void kvmppc_copy_to_svcpu(struct kvmppc_book3s_shadow_vcpu *svcpu,
  				 struct kvm_vcpu *vcpu);
  extern void kvmppc_copy_from_svcpu(struct kvm_vcpu *vcpu,
diff --git a/arch/powerpc/include/asm/kvm_host.h b/arch/powerpc/include/asm/kvm_host.h
index bb66d8b..2889587 100644
--- a/arch/powerpc/include/asm/kvm_host.h
+++ b/arch/powerpc/include/asm/kvm_host.h
@@ -34,6 +34,7 @@
  #include <asm/processor.h>
  #include <asm/page.h>
  #include <asm/cacheflush.h>
+#include <asm/hvcall.h>
#define KVM_MAX_VCPUS NR_CPUS
  #define KVM_MAX_VCORES		NR_CPUS
@@ -263,6 +264,7 @@ struct kvm_arch {
  #ifdef CONFIG_PPC_BOOK3S_64
  	struct list_head spapr_tce_tables;
  	struct list_head rtas_tokens;
+	DECLARE_BITMAP(enabled_hcalls, MAX_HCALL_OPCODE/4 + 1);
  #endif
  #ifdef CONFIG_KVM_MPIC
  	struct openpic *mpic;
diff --git a/arch/powerpc/kernel/asm-offsets.c b/arch/powerpc/kernel/asm-offsets.c
index 93e1465..c427b51 100644
--- a/arch/powerpc/kernel/asm-offsets.c
+++ b/arch/powerpc/kernel/asm-offsets.c
@@ -492,6 +492,7 @@ int main(void)
  	DEFINE(KVM_HOST_SDR1, offsetof(struct kvm, arch.host_sdr1));
  	DEFINE(KVM_TLBIE_LOCK, offsetof(struct kvm, arch.tlbie_lock));
  	DEFINE(KVM_NEED_FLUSH, offsetof(struct kvm, arch.need_tlb_flush.bits));
+	DEFINE(KVM_ENABLED_HCALLS, offsetof(struct kvm, arch.enabled_hcalls));
  	DEFINE(KVM_LPCR, offsetof(struct kvm, arch.lpcr));
  	DEFINE(KVM_RMOR, offsetof(struct kvm, arch.rmor));
  	DEFINE(KVM_VRMA_SLB_V, offsetof(struct kvm, arch.vrma_slb_v));
diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
index aba05bb..84e695d 100644
--- a/arch/powerpc/kvm/book3s_hv.c
+++ b/arch/powerpc/kvm/book3s_hv.c
@@ -67,6 +67,8 @@
  /* Used as a "null" value for timebase values */
  #define TB_NIL	(~(u64)0)
+static DECLARE_BITMAP(default_enabled_hcalls, MAX_HCALL_OPCODE/4 + 1);
+
  static void kvmppc_end_cede(struct kvm_vcpu *vcpu);
  static int kvmppc_hv_setup_htab_rma(struct kvm_vcpu *vcpu);
@@ -562,6 +564,10 @@ int kvmppc_pseries_do_hcall(struct kvm_vcpu *vcpu)
  	struct kvm_vcpu *tvcpu;
  	int idx, rc;
+ if (req <= MAX_HCALL_OPCODE &&
+	    !test_bit(req/4, vcpu->kvm->arch.enabled_hcalls))
+		return RESUME_HOST;
+
  	switch (req) {
  	case H_ENTER:
  		idx = srcu_read_lock(&vcpu->kvm->srcu);
@@ -2275,6 +2281,10 @@ static int kvmppc_core_init_vm_hv(struct kvm *kvm)
  	 */
  	cpumask_setall(&kvm->arch.need_tlb_flush);
+ /* Start out with the default set of hcalls enabled */
+	memcpy(kvm->arch.enabled_hcalls, default_enabled_hcalls,
+	       sizeof(kvm->arch.enabled_hcalls));
+
  	kvm->arch.rma = NULL;
kvm->arch.host_sdr1 = mfspr(SPRN_SDR1);
@@ -2413,6 +2423,45 @@ static long kvm_arch_vm_ioctl_hv(struct file *filp,
  	return r;
  }
+/*
+ * 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_REMOVE,
+	H_ENTER,
+	H_READ,
+	H_PROTECT,
+	H_BULK_REMOVE,
+	H_GET_TCE,
+	H_PUT_TCE,
+	H_SET_DABR,
+	H_SET_XDABR,
+	H_CEDE,
+	H_PROD,
+	H_CONFER,
+	H_REGISTER_VPA,
+#ifdef CONFIG_KVM_XICS
+	H_EOI,
+	H_CPPR,
+	H_IPI,
+	H_IPOLL,
+	H_XIRR,
+	H_XIRR_X,
+#endif
+	0
+};
+
+static void init_default_hcalls(void)
+{
+	int i;
+
+	for (i = 0; default_hcall_list[i]; ++i)

BUG_ON(default_hcall_list[i] > MAX_HCALL_OPCODE);


Alex

+		__set_bit(default_hcall_list[i] / 4, default_enabled_hcalls);
+}
+
  static struct kvmppc_ops kvm_ops_hv = {
  	.get_sregs = kvm_arch_vcpu_ioctl_get_sregs_hv,
  	.set_sregs = kvm_arch_vcpu_ioctl_set_sregs_hv,
@@ -2460,6 +2509,8 @@ static int kvmppc_book3s_init_hv(void)
  	kvm_ops_hv.owner = THIS_MODULE;
  	kvmppc_hv_ops = &kvm_ops_hv;
+ init_default_hcalls();
+
  	r = kvmppc_mmu_hv_init();
  	return r;
  }
diff --git a/arch/powerpc/kvm/book3s_hv_rmhandlers.S b/arch/powerpc/kvm/book3s_hv_rmhandlers.S
index 220aefb..c26b0e2 100644
--- a/arch/powerpc/kvm/book3s_hv_rmhandlers.S
+++ b/arch/powerpc/kvm/book3s_hv_rmhandlers.S
@@ -1795,6 +1795,17 @@ hcall_try_real_mode:
  	clrrdi	r3,r3,2
  	cmpldi	r3,hcall_real_table_end - hcall_real_table
  	bge	guest_exit_cont
+	/* See if this hcall is enabled for in-kernel handling */
+	ld	r4, VCPU_KVM(r9)
+	srdi	r0, r3, 8	/* r0 = (r3 / 4) >> 6 */
+	sldi	r0, r0, 3	/* index into kvm->arch.enabled_hcalls[] */
+	add	r4, r4, r0
+	ld	r0, KVM_ENABLED_HCALLS(r4)
+	rlwinm	r4, r3, 32-2, 0x3f	/* r4 = (r3 / 4) & 0x3f */
+	srd	r0, r0, r4
+	andi.	r0, r0, 1
+	beq	guest_exit_cont
+	/* Get pointer to handler, if any, and call it */
  	LOAD_REG_ADDR(r4, hcall_real_table)
  	lwax	r3,r3,r4
  	cmpwi	r3,0
diff --git a/arch/powerpc/kvm/book3s_pr.c b/arch/powerpc/kvm/book3s_pr.c
index 23367a7..59dc94e 100644
--- a/arch/powerpc/kvm/book3s_pr.c
+++ b/arch/powerpc/kvm/book3s_pr.c
@@ -1568,6 +1568,11 @@ static int kvmppc_core_init_vm_pr(struct kvm *kvm)
  {
  	mutex_init(&kvm->arch.hpt_mutex);
+#ifdef CONFIG_PPC_BOOK3S_64
+	/* Start out with the default set of hcalls enabled */
+	kvmppc_pr_init_default_hcalls(kvm);
+#endif
+
  	if (firmware_has_feature(FW_FEATURE_SET_MODE)) {
  		spin_lock(&kvm_global_user_count_lock);
  		if (++kvm_global_user_count == 1)
diff --git a/arch/powerpc/kvm/book3s_pr_papr.c b/arch/powerpc/kvm/book3s_pr_papr.c
index 52a63bf..c5afde2 100644
--- a/arch/powerpc/kvm/book3s_pr_papr.c
+++ b/arch/powerpc/kvm/book3s_pr_papr.c
@@ -266,6 +266,10 @@ 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);
@@ -303,3 +307,36 @@ 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);
+}
diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
index 154f352..5690c74 100644
--- a/arch/powerpc/kvm/powerpc.c
+++ b/arch/powerpc/kvm/powerpc.c
@@ -416,6 +416,7 @@ int kvm_dev_ioctl_check_extension(long ext)
  	case KVM_CAP_SPAPR_TCE:
  	case KVM_CAP_PPC_ALLOC_HTAB:
  	case KVM_CAP_PPC_RTAS:
+	case KVM_CAP_PPC_ENABLE_HCALL:
  #ifdef CONFIG_KVM_XICS
  	case KVM_CAP_IRQ_XICS:
  #endif
@@ -964,6 +965,24 @@ static int kvm_vcpu_ioctl_enable_cap(struct kvm_vcpu *vcpu,
  		break;
  	}
  #endif /* CONFIG_KVM_XICS */
+#ifdef CONFIG_KVM_BOOK3S_64_HANDLER
+	case KVM_CAP_PPC_ENABLE_HCALL: {
+		unsigned long hcall = cap->args[0];
+
+		r = -EINVAL;
+		if (!vcpu->arch.papr_enabled)
+			break;
+		if (hcall > MAX_HCALL_OPCODE || (hcall & 3) ||
+		    cap->args[1] > 1)
+			break;
+		if (cap->args[1])
+			set_bit(hcall / 4, vcpu->kvm->arch.enabled_hcalls);
+		else
+			clear_bit(hcall / 4, vcpu->kvm->arch.enabled_hcalls);
+		r = 0;
+		break;
+	}
+#endif
  	default:
  		r = -EINVAL;
  		break;
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index 836e15b..79e4532 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -746,6 +746,7 @@ struct kvm_ppc_smmu_info {
  #define KVM_CAP_S390_IRQCHIP 99
  #define KVM_CAP_IOEVENTFD_NO_LENGTH 100
  #define KVM_CAP_VM_ATTRIBUTES 101
+#define KVM_CAP_PPC_ENABLE_HCALL 102
#ifdef KVM_CAP_IRQ_ROUTING

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