[PATCH v5 00/10] arm64: Stolen time support

[PATCH v5 00/10] arm64: Stolen time support

[Steven Price]

This series add support for paravirtualized time for arm64 guests and
KVM hosts following the specification in Arm's document DEN 0057A:

https://developer.arm.com/docs/den0057/a

It implements support for stolen time, allowing the guest to
identify time when it is forcibly not executing.

Note that Live Physical Time (LPT) which was previously part of the
above specification has now been removed.

Also available as a git tree:
git://linux-arm.org/linux-sp.git stolen_time/v5

Changes from v4:
https://lore.kernel.org/kvm/20190830084255.55113-1-steven.price@arm.com/
 * Rebased to v5.4-rc1
 * Renamed KVM_ARM_VCPU_PVTIME_SET_IPA to remove _SET as it is used for
   both set/get operations
 * Added kvm/arm_hypercalls.h to header-test-$(CONFIG_ARM{,64}) as it is
   only buildable on arm/arm64
 * Documented no-steal-acc kernel parameter

Changes from v3:
https://lore.kernel.org/lkml/20190821153656.33429-1-steven.price@arm.com/
 * There's no longer a PV_TIME device, instead there are attributes on
   the VCPU. This allows the stolen time structures to be places
   arbitrarily by user space (subject to 64 byte alignment).
 * Split documentation between information on the hypercalls and the
   attributes on the VCPU
 * Fixed the type of SMCCC functions to return long not int

Changes from v2:
https://lore.kernel.org/lkml/20190819140436.12207-1-steven.price@arm.com/
 * Switched from using gfn_to_hva_cache to a new macro kvm_put_guest()
   that can provide the single-copy atomicity required (on arm64). This
   macro is added in patch 4.
 * Tidied up the locking for kvm_update_stolen_time().
   pagefault_disable() was unnecessary and the caller didn't need to
   take kvm->srcu as the function does it itself.
 * Removed struct kvm_arch_pvtime from the arm implementation, replaced
   instead with inline static functions which are empty for arm.
 * Fixed a few checkpatch --strict warnings.

Changes from v1:
https://lore.kernel.org/lkml/20190802145017.42543-1-steven.price@arm.com/
 * Host kernel no longer allocates the stolen time structure, instead it
   is allocated by user space. This means the save/restore functionality
   can be removed.
 * Refactored the code so arm has stub implementations and to avoid
   initcall
 * Rebased to pick up Documentation/{virt->virtual} change
 * Bunch of typo fixes

Christoffer Dall (1):
  KVM: arm/arm64: Factor out hypercall handling from PSCI code

Steven Price (9):
  KVM: arm64: Document PV-time interface
  KVM: arm64: Implement PV_FEATURES call
  KVM: Implement kvm_put_guest()
  KVM: arm64: Support stolen time reporting via shared structure
  KVM: Allow kvm_device_ops to be const
  KVM: arm64: Provide VCPU attributes for stolen time
  arm/arm64: Provide a wrapper for SMCCC 1.1 calls
  arm/arm64: Make use of the SMCCC 1.1 wrapper
  arm64: Retrieve stolen time as paravirtualized guest

 .../admin-guide/kernel-parameters.txt         |   6 +-
 Documentation/virt/kvm/arm/pvtime.txt         |  65 ++++++++
 Documentation/virt/kvm/devices/vcpu.txt       |  14 ++
 arch/arm/include/asm/kvm_host.h               |  26 +++
 arch/arm/kvm/Makefile                         |   2 +-
 arch/arm/kvm/handle_exit.c                    |   2 +-
 arch/arm/mm/proc-v7-bugs.c                    |  13 +-
 arch/arm64/include/asm/kvm_host.h             |  30 +++-
 arch/arm64/include/asm/paravirt.h             |   9 +-
 arch/arm64/include/asm/pvclock-abi.h          |  17 ++
 arch/arm64/include/uapi/asm/kvm.h             |   2 +
 arch/arm64/kernel/cpu_errata.c                |  80 ++++------
 arch/arm64/kernel/paravirt.c                  | 148 ++++++++++++++++++
 arch/arm64/kernel/time.c                      |   3 +
 arch/arm64/kvm/Kconfig                        |   1 +
 arch/arm64/kvm/Makefile                       |   2 +
 arch/arm64/kvm/guest.c                        |   9 ++
 arch/arm64/kvm/handle_exit.c                  |   4 +-
 include/Kbuild                                |   2 +
 include/kvm/arm_hypercalls.h                  |  43 +++++
 include/kvm/arm_psci.h                        |   2 +-
 include/linux/arm-smccc.h                     |  58 +++++++
 include/linux/cpuhotplug.h                    |   1 +
 include/linux/kvm_host.h                      |  26 ++-
 include/linux/kvm_types.h                     |   2 +
 include/uapi/linux/kvm.h                      |   2 +
 virt/kvm/arm/arm.c                            |  11 ++
 virt/kvm/arm/hypercalls.c                     |  68 ++++++++
 virt/kvm/arm/psci.c                           |  84 +---------
 virt/kvm/arm/pvtime.c                         | 124 +++++++++++++++
 virt/kvm/kvm_main.c                           |   6 +-
 31 files changed, 705 insertions(+), 157 deletions(-)
 create mode 100644 Documentation/virt/kvm/arm/pvtime.txt
 create mode 100644 arch/arm64/include/asm/pvclock-abi.h
 create mode 100644 include/kvm/arm_hypercalls.h
 create mode 100644 virt/kvm/arm/hypercalls.c
 create mode 100644 virt/kvm/arm/pvtime.c

-- 
2.20.1

[PATCH v5 01/10] KVM: arm64: Document PV-time interface

[Steven Price]

Introduce a paravirtualization interface for KVM/arm64 based on the
"Arm Paravirtualized Time for Arm-Base Systems" specification DEN 0057A.

This only adds the details about "Stolen Time" as the details of "Live
Physical Time" have not been fully agreed.

User space can specify a reserved area of memory for the guest and
inform KVM to populate the memory with information on time that the host
kernel has stolen from the guest.

A hypercall interface is provided for the guest to interrogate the
hypervisor's support for this interface and the location of the shared
memory structures.

Signed-off-by: Steven Price <steven.price@arm.com>
---
 Documentation/virt/kvm/arm/pvtime.txt   | 65 +++++++++++++++++++++++++
 Documentation/virt/kvm/devices/vcpu.txt | 14 ++++++
 2 files changed, 79 insertions(+)
 create mode 100644 Documentation/virt/kvm/arm/pvtime.txt

diff --git a/Documentation/virt/kvm/arm/pvtime.txt b/Documentation/virt/kvm/arm/pvtime.txt
new file mode 100644
index 000000000000..fa15c12eec91
--- /dev/null
+++ b/Documentation/virt/kvm/arm/pvtime.txt
@@ -0,0 +1,65 @@
+Paravirtualized time support for arm64
+======================================
+
+Arm specification DEN0057/A defined a standard for paravirtualised time
+support for AArch64 guests:
+
+https://developer.arm.com/docs/den0057/a
+
+KVM/arm64 implements the stolen time part of this specification by providing
+some hypervisor service calls to support a paravirtualized guest obtaining a
+view of the amount of time stolen from its execution.
+
+Two new SMCCC compatible hypercalls are defined:
+
+PV_FEATURES 0xC5000020
+PV_TIME_ST  0xC5000022
+
+These are only available in the SMC64/HVC64 calling convention as
+paravirtualized time is not available to 32 bit Arm guests. The existence of
+the PV_FEATURES hypercall should be probed using the SMCCC 1.1 ARCH_FEATURES
+mechanism before calling it.
+
+PV_FEATURES
+    Function ID:  (uint32)  : 0xC5000020
+    PV_func_id:   (uint32)  : The function to query for support.
+                              Currently only PV_TIME_ST is supported.
+    Return value: (int32)   : NOT_SUPPORTED (-1) or SUCCESS (0) if the relevant
+                              PV-time feature is supported by the hypervisor.
+
+PV_TIME_ST
+    Function ID:  (uint32)  : 0xC5000022
+    Return value: (int64)   : IPA of the stolen time data structure for this
+                              VCPU. On failure:
+                              NOT_SUPPORTED (-1)
+
+The IPA returned by PV_TIME_ST should be mapped by the guest as normal memory
+with inner and outer write back caching attributes, in the inner shareable
+domain. A total of 16 bytes from the IPA returned are guaranteed to be
+meaningfully filled by the hypervisor (see structure below).
+
+PV_TIME_ST returns the structure for the calling VCPU.
+
+Stolen Time
+-----------
+
+The structure pointed to by the PV_TIME_ST hypercall is as follows:
+
+  Field       | Byte Length | Byte Offset | Description
+  ----------- | ----------- | ----------- | --------------------------
+  Revision    |      4      |      0      | Must be 0 for version 0.1
+  Attributes  |      4      |      4      | Must be 0
+  Stolen time |      8      |      8      | Stolen time in unsigned
+              |             |             | nanoseconds indicating how
+              |             |             | much time this VCPU thread
+              |             |             | was involuntarily not
+              |             |             | running on a physical CPU.
+
+The structure will be updated by the hypervisor prior to scheduling a VCPU. It
+will be present within a reserved region of the normal memory given to the
+guest. The guest should not attempt to write into this memory. There is a
+structure per VCPU of the guest.
+
+For the user space interface see Documentation/virt/kvm/devices/vcpu.txt
+section "3. GROUP: KVM_ARM_VCPU_PVTIME_CTRL".
+
diff --git a/Documentation/virt/kvm/devices/vcpu.txt b/Documentation/virt/kvm/devices/vcpu.txt
index 2b5dab16c4f2..6f3bd64a05b0 100644
--- a/Documentation/virt/kvm/devices/vcpu.txt
+++ b/Documentation/virt/kvm/devices/vcpu.txt
@@ -60,3 +60,17 @@ time to use the number provided for a given timer, overwriting any previously
 configured values on other VCPUs.  Userspace should configure the interrupt
 numbers on at least one VCPU after creating all VCPUs and before running any
 VCPUs.
+
+3. GROUP: KVM_ARM_VCPU_PVTIME_CTRL
+Architectures: ARM64
+
+3.1 ATTRIBUTE: KVM_ARM_VCPU_PVTIME_IPA
+Parameters: 64-bit base address
+Returns: -ENXIO:  Stolen time not implemented
+         -EEXIST: Base address already set for this VCPU
+         -EINVAL: Base address not 64 byte aligned
+
+Specifies the base address of the stolen time structure for this VCPU. The
+base address must be 64 byte aligned and exist within a valid guest memory
+region. See Documentation/virt/kvm/arm/pvtime.txt for more information
+including the layout of the stolen time structure.
-- 
2.20.1

[PATCH v5 02/10] KVM: arm/arm64: Factor out hypercall handling from PSCI code

[Steven Price]

From: Christoffer Dall <christoffer.dall@arm.com>

We currently intertwine the KVM PSCI implementation with the general
dispatch of hypercall handling, which makes perfect sense because PSCI
is the only category of hypercalls we support.

However, as we are about to support additional hypercalls, factor out
this functionality into a separate hypercall handler file.

Signed-off-by: Christoffer Dall <christoffer.dall@arm.com>
[steven.price@arm.com: rebased]
Signed-off-by: Steven Price <steven.price@arm.com>
---
 arch/arm/kvm/Makefile        |  2 +-
 arch/arm/kvm/handle_exit.c   |  2 +-
 arch/arm64/kvm/Makefile      |  1 +
 arch/arm64/kvm/handle_exit.c |  4 +-
 include/Kbuild               |  2 +
 include/kvm/arm_hypercalls.h | 43 ++++++++++++++++++
 include/kvm/arm_psci.h       |  2 +-
 virt/kvm/arm/hypercalls.c    | 59 +++++++++++++++++++++++++
 virt/kvm/arm/psci.c          | 84 +-----------------------------------
 9 files changed, 112 insertions(+), 87 deletions(-)
 create mode 100644 include/kvm/arm_hypercalls.h
 create mode 100644 virt/kvm/arm/hypercalls.c

diff --git a/arch/arm/kvm/Makefile b/arch/arm/kvm/Makefile
index b76b75bd9e00..e442d82821df 100644
--- a/arch/arm/kvm/Makefile
+++ b/arch/arm/kvm/Makefile
@@ -24,7 +24,7 @@ obj-y += kvm-arm.o init.o interrupts.o
 obj-y += handle_exit.o guest.o emulate.o reset.o
 obj-y += coproc.o coproc_a15.o coproc_a7.o   vgic-v3-coproc.o
 obj-y += $(KVM)/arm/arm.o $(KVM)/arm/mmu.o $(KVM)/arm/mmio.o
-obj-y += $(KVM)/arm/psci.o $(KVM)/arm/perf.o
+obj-y += $(KVM)/arm/psci.o $(KVM)/arm/perf.o $(KVM)/arm/hypercalls.o
 obj-y += $(KVM)/arm/aarch32.o
 
 obj-y += $(KVM)/arm/vgic/vgic.o
diff --git a/arch/arm/kvm/handle_exit.c b/arch/arm/kvm/handle_exit.c
index 2a6a1394d26e..e58a89d2f13f 100644
--- a/arch/arm/kvm/handle_exit.c
+++ b/arch/arm/kvm/handle_exit.c
@@ -9,7 +9,7 @@
 #include <asm/kvm_emulate.h>
 #include <asm/kvm_coproc.h>
 #include <asm/kvm_mmu.h>
-#include <kvm/arm_psci.h>
+#include <kvm/arm_hypercalls.h>
 #include <trace/events/kvm.h>
 
 #include "trace.h"
diff --git a/arch/arm64/kvm/Makefile b/arch/arm64/kvm/Makefile
index 3ac1a64d2fb9..73dce4d47d47 100644
--- a/arch/arm64/kvm/Makefile
+++ b/arch/arm64/kvm/Makefile
@@ -13,6 +13,7 @@ obj-$(CONFIG_KVM_ARM_HOST) += hyp/
 kvm-$(CONFIG_KVM_ARM_HOST) += $(KVM)/kvm_main.o $(KVM)/coalesced_mmio.o $(KVM)/eventfd.o $(KVM)/vfio.o
 kvm-$(CONFIG_KVM_ARM_HOST) += $(KVM)/arm/arm.o $(KVM)/arm/mmu.o $(KVM)/arm/mmio.o
 kvm-$(CONFIG_KVM_ARM_HOST) += $(KVM)/arm/psci.o $(KVM)/arm/perf.o
+kvm-$(CONFIG_KVM_ARM_HOST) += $(KVM)/arm/hypercalls.o
 
 kvm-$(CONFIG_KVM_ARM_HOST) += inject_fault.o regmap.o va_layout.o
 kvm-$(CONFIG_KVM_ARM_HOST) += hyp.o hyp-init.o handle_exit.o
diff --git a/arch/arm64/kvm/handle_exit.c b/arch/arm64/kvm/handle_exit.c
index 706cca23f0d2..aacfc55de44c 100644
--- a/arch/arm64/kvm/handle_exit.c
+++ b/arch/arm64/kvm/handle_exit.c
@@ -11,8 +11,6 @@
 #include <linux/kvm.h>
 #include <linux/kvm_host.h>
 
-#include <kvm/arm_psci.h>
-
 #include <asm/esr.h>
 #include <asm/exception.h>
 #include <asm/kvm_asm.h>
@@ -22,6 +20,8 @@
 #include <asm/debug-monitors.h>
 #include <asm/traps.h>
 
+#include <kvm/arm_hypercalls.h>
+
 #define CREATE_TRACE_POINTS
 #include "trace.h"
 
diff --git a/include/Kbuild b/include/Kbuild
index ffba79483cc5..e8154f8bcac5 100644
--- a/include/Kbuild
+++ b/include/Kbuild
@@ -67,6 +67,8 @@ header-test-			+= keys/big_key-type.h
 header-test-			+= keys/request_key_auth-type.h
 header-test-			+= keys/trusted.h
 header-test-			+= kvm/arm_arch_timer.h
+header-test-$(CONFIG_ARM)	+= kvm/arm_hypercalls.h
+header-test-$(CONFIG_ARM64)	+= kvm/arm_hypercalls.h
 header-test-			+= kvm/arm_pmu.h
 header-test-$(CONFIG_ARM)	+= kvm/arm_psci.h
 header-test-$(CONFIG_ARM64)	+= kvm/arm_psci.h
diff --git a/include/kvm/arm_hypercalls.h b/include/kvm/arm_hypercalls.h
new file mode 100644
index 000000000000..0e2509d27910
--- /dev/null
+++ b/include/kvm/arm_hypercalls.h
@@ -0,0 +1,43 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/* Copyright (C) 2019 Arm Ltd. */
+
+#ifndef __KVM_ARM_HYPERCALLS_H
+#define __KVM_ARM_HYPERCALLS_H
+
+#include <asm/kvm_emulate.h>
+
+int kvm_hvc_call_handler(struct kvm_vcpu *vcpu);
+
+static inline u32 smccc_get_function(struct kvm_vcpu *vcpu)
+{
+	return vcpu_get_reg(vcpu, 0);
+}
+
+static inline unsigned long smccc_get_arg1(struct kvm_vcpu *vcpu)
+{
+	return vcpu_get_reg(vcpu, 1);
+}
+
+static inline unsigned long smccc_get_arg2(struct kvm_vcpu *vcpu)
+{
+	return vcpu_get_reg(vcpu, 2);
+}
+
+static inline unsigned long smccc_get_arg3(struct kvm_vcpu *vcpu)
+{
+	return vcpu_get_reg(vcpu, 3);
+}
+
+static inline void smccc_set_retval(struct kvm_vcpu *vcpu,
+				    unsigned long a0,
+				    unsigned long a1,
+				    unsigned long a2,
+				    unsigned long a3)
+{
+	vcpu_set_reg(vcpu, 0, a0);
+	vcpu_set_reg(vcpu, 1, a1);
+	vcpu_set_reg(vcpu, 2, a2);
+	vcpu_set_reg(vcpu, 3, a3);
+}
+
+#endif
diff --git a/include/kvm/arm_psci.h b/include/kvm/arm_psci.h
index 632e78bdef4d..5b58bd2fe088 100644
--- a/include/kvm/arm_psci.h
+++ b/include/kvm/arm_psci.h
@@ -40,7 +40,7 @@ static inline int kvm_psci_version(struct kvm_vcpu *vcpu, struct kvm *kvm)
 }
 
 
-int kvm_hvc_call_handler(struct kvm_vcpu *vcpu);
+int kvm_psci_call(struct kvm_vcpu *vcpu);
 
 struct kvm_one_reg;
 
diff --git a/virt/kvm/arm/hypercalls.c b/virt/kvm/arm/hypercalls.c
new file mode 100644
index 000000000000..f875241bd030
--- /dev/null
+++ b/virt/kvm/arm/hypercalls.c
@@ -0,0 +1,59 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (C) 2019 Arm Ltd.
+
+#include <linux/arm-smccc.h>
+#include <linux/kvm_host.h>
+
+#include <asm/kvm_emulate.h>
+
+#include <kvm/arm_hypercalls.h>
+#include <kvm/arm_psci.h>
+
+int kvm_hvc_call_handler(struct kvm_vcpu *vcpu)
+{
+	u32 func_id = smccc_get_function(vcpu);
+	u32 val = SMCCC_RET_NOT_SUPPORTED;
+	u32 feature;
+
+	switch (func_id) {
+	case ARM_SMCCC_VERSION_FUNC_ID:
+		val = ARM_SMCCC_VERSION_1_1;
+		break;
+	case ARM_SMCCC_ARCH_FEATURES_FUNC_ID:
+		feature = smccc_get_arg1(vcpu);
+		switch (feature) {
+		case ARM_SMCCC_ARCH_WORKAROUND_1:
+			switch (kvm_arm_harden_branch_predictor()) {
+			case KVM_BP_HARDEN_UNKNOWN:
+				break;
+			case KVM_BP_HARDEN_WA_NEEDED:
+				val = SMCCC_RET_SUCCESS;
+				break;
+			case KVM_BP_HARDEN_NOT_REQUIRED:
+				val = SMCCC_RET_NOT_REQUIRED;
+				break;
+			}
+			break;
+		case ARM_SMCCC_ARCH_WORKAROUND_2:
+			switch (kvm_arm_have_ssbd()) {
+			case KVM_SSBD_FORCE_DISABLE:
+			case KVM_SSBD_UNKNOWN:
+				break;
+			case KVM_SSBD_KERNEL:
+				val = SMCCC_RET_SUCCESS;
+				break;
+			case KVM_SSBD_FORCE_ENABLE:
+			case KVM_SSBD_MITIGATED:
+				val = SMCCC_RET_NOT_REQUIRED;
+				break;
+			}
+			break;
+		}
+		break;
+	default:
+		return kvm_psci_call(vcpu);
+	}
+
+	smccc_set_retval(vcpu, val, 0, 0, 0);
+	return 1;
+}
diff --git a/virt/kvm/arm/psci.c b/virt/kvm/arm/psci.c
index 87927f7e1ee7..17e2bdd4b76f 100644
--- a/virt/kvm/arm/psci.c
+++ b/virt/kvm/arm/psci.c
@@ -15,6 +15,7 @@
 #include <asm/kvm_host.h>
 
 #include <kvm/arm_psci.h>
+#include <kvm/arm_hypercalls.h>
 
 /*
  * This is an implementation of the Power State Coordination Interface
@@ -23,38 +24,6 @@
 
 #define AFFINITY_MASK(level)	~((0x1UL << ((level) * MPIDR_LEVEL_BITS)) - 1)
 
-static u32 smccc_get_function(struct kvm_vcpu *vcpu)
-{
-	return vcpu_get_reg(vcpu, 0);
-}
-
-static unsigned long smccc_get_arg1(struct kvm_vcpu *vcpu)
-{
-	return vcpu_get_reg(vcpu, 1);
-}
-
-static unsigned long smccc_get_arg2(struct kvm_vcpu *vcpu)
-{
-	return vcpu_get_reg(vcpu, 2);
-}
-
-static unsigned long smccc_get_arg3(struct kvm_vcpu *vcpu)
-{
-	return vcpu_get_reg(vcpu, 3);
-}
-
-static void smccc_set_retval(struct kvm_vcpu *vcpu,
-			     unsigned long a0,
-			     unsigned long a1,
-			     unsigned long a2,
-			     unsigned long a3)
-{
-	vcpu_set_reg(vcpu, 0, a0);
-	vcpu_set_reg(vcpu, 1, a1);
-	vcpu_set_reg(vcpu, 2, a2);
-	vcpu_set_reg(vcpu, 3, a3);
-}
-
 static unsigned long psci_affinity_mask(unsigned long affinity_level)
 {
 	if (affinity_level <= 3)
@@ -373,7 +342,7 @@ static int kvm_psci_0_1_call(struct kvm_vcpu *vcpu)
  * Errors:
  * -EINVAL: Unrecognized PSCI function
  */
-static int kvm_psci_call(struct kvm_vcpu *vcpu)
+int kvm_psci_call(struct kvm_vcpu *vcpu)
 {
 	switch (kvm_psci_version(vcpu, vcpu->kvm)) {
 	case KVM_ARM_PSCI_1_0:
@@ -387,55 +356,6 @@ static int kvm_psci_call(struct kvm_vcpu *vcpu)
 	};
 }
 
-int kvm_hvc_call_handler(struct kvm_vcpu *vcpu)
-{
-	u32 func_id = smccc_get_function(vcpu);
-	u32 val = SMCCC_RET_NOT_SUPPORTED;
-	u32 feature;
-
-	switch (func_id) {
-	case ARM_SMCCC_VERSION_FUNC_ID:
-		val = ARM_SMCCC_VERSION_1_1;
-		break;
-	case ARM_SMCCC_ARCH_FEATURES_FUNC_ID:
-		feature = smccc_get_arg1(vcpu);
-		switch(feature) {
-		case ARM_SMCCC_ARCH_WORKAROUND_1:
-			switch (kvm_arm_harden_branch_predictor()) {
-			case KVM_BP_HARDEN_UNKNOWN:
-				break;
-			case KVM_BP_HARDEN_WA_NEEDED:
-				val = SMCCC_RET_SUCCESS;
-				break;
-			case KVM_BP_HARDEN_NOT_REQUIRED:
-				val = SMCCC_RET_NOT_REQUIRED;
-				break;
-			}
-			break;
-		case ARM_SMCCC_ARCH_WORKAROUND_2:
-			switch (kvm_arm_have_ssbd()) {
-			case KVM_SSBD_FORCE_DISABLE:
-			case KVM_SSBD_UNKNOWN:
-				break;
-			case KVM_SSBD_KERNEL:
-				val = SMCCC_RET_SUCCESS;
-				break;
-			case KVM_SSBD_FORCE_ENABLE:
-			case KVM_SSBD_MITIGATED:
-				val = SMCCC_RET_NOT_REQUIRED;
-				break;
-			}
-			break;
-		}
-		break;
-	default:
-		return kvm_psci_call(vcpu);
-	}
-
-	smccc_set_retval(vcpu, val, 0, 0, 0);
-	return 1;
-}
-
 int kvm_arm_get_fw_num_regs(struct kvm_vcpu *vcpu)
 {
 	return 3;		/* PSCI version and two workaround registers */
-- 
2.20.1

[PATCH v5 03/10] KVM: arm64: Implement PV_FEATURES call

[Steven Price]

This provides a mechanism for querying which paravirtualized features
are available in this hypervisor.

Also add the header file which defines the ABI for the paravirtualized
clock features we're about to add.

Signed-off-by: Steven Price <steven.price@arm.com>
---
 arch/arm/include/asm/kvm_host.h      |  6 ++++++
 arch/arm64/include/asm/kvm_host.h    |  2 ++
 arch/arm64/include/asm/pvclock-abi.h | 17 +++++++++++++++++
 arch/arm64/kvm/Makefile              |  1 +
 include/linux/arm-smccc.h            | 14 ++++++++++++++
 virt/kvm/arm/hypercalls.c            |  8 +++++++-
 virt/kvm/arm/pvtime.c                | 21 +++++++++++++++++++++
 7 files changed, 68 insertions(+), 1 deletion(-)
 create mode 100644 arch/arm64/include/asm/pvclock-abi.h
 create mode 100644 virt/kvm/arm/pvtime.c

diff --git a/arch/arm/include/asm/kvm_host.h b/arch/arm/include/asm/kvm_host.h
index 8a37c8e89777..5a0c3569ebde 100644
--- a/arch/arm/include/asm/kvm_host.h
+++ b/arch/arm/include/asm/kvm_host.h
@@ -7,6 +7,7 @@
 #ifndef __ARM_KVM_HOST_H__
 #define __ARM_KVM_HOST_H__
 
+#include <linux/arm-smccc.h>
 #include <linux/errno.h>
 #include <linux/types.h>
 #include <linux/kvm_types.h>
@@ -323,6 +324,11 @@ static inline int kvm_arch_vm_ioctl_check_extension(struct kvm *kvm, long ext)
 int kvm_perf_init(void);
 int kvm_perf_teardown(void);
 
+static inline long kvm_hypercall_pv_features(struct kvm_vcpu *vcpu)
+{
+	return SMCCC_RET_NOT_SUPPORTED;
+}
+
 void kvm_mmu_wp_memory_region(struct kvm *kvm, int slot);
 
 struct kvm_vcpu *kvm_mpidr_to_vcpu(struct kvm *kvm, unsigned long mpidr);
diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index f656169db8c3..93b46d9526d0 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -478,6 +478,8 @@ void handle_exit_early(struct kvm_vcpu *vcpu, struct kvm_run *run,
 int kvm_perf_init(void);
 int kvm_perf_teardown(void);
 
+long kvm_hypercall_pv_features(struct kvm_vcpu *vcpu);
+
 void kvm_set_sei_esr(struct kvm_vcpu *vcpu, u64 syndrome);
 
 struct kvm_vcpu *kvm_mpidr_to_vcpu(struct kvm *kvm, unsigned long mpidr);
diff --git a/arch/arm64/include/asm/pvclock-abi.h b/arch/arm64/include/asm/pvclock-abi.h
new file mode 100644
index 000000000000..c4f1c0a0789c
--- /dev/null
+++ b/arch/arm64/include/asm/pvclock-abi.h
@@ -0,0 +1,17 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/* Copyright (C) 2019 Arm Ltd. */
+
+#ifndef __ASM_PVCLOCK_ABI_H
+#define __ASM_PVCLOCK_ABI_H
+
+/* The below structure is defined in ARM DEN0057A */
+
+struct pvclock_vcpu_stolen_time {
+	__le32 revision;
+	__le32 attributes;
+	__le64 stolen_time;
+	/* Structure must be 64 byte aligned, pad to that size */
+	u8 padding[48];
+} __packed;
+
+#endif
diff --git a/arch/arm64/kvm/Makefile b/arch/arm64/kvm/Makefile
index 73dce4d47d47..5ffbdc39e780 100644
--- a/arch/arm64/kvm/Makefile
+++ b/arch/arm64/kvm/Makefile
@@ -14,6 +14,7 @@ kvm-$(CONFIG_KVM_ARM_HOST) += $(KVM)/kvm_main.o $(KVM)/coalesced_mmio.o $(KVM)/e
 kvm-$(CONFIG_KVM_ARM_HOST) += $(KVM)/arm/arm.o $(KVM)/arm/mmu.o $(KVM)/arm/mmio.o
 kvm-$(CONFIG_KVM_ARM_HOST) += $(KVM)/arm/psci.o $(KVM)/arm/perf.o
 kvm-$(CONFIG_KVM_ARM_HOST) += $(KVM)/arm/hypercalls.o
+kvm-$(CONFIG_KVM_ARM_HOST) += $(KVM)/arm/pvtime.o
 
 kvm-$(CONFIG_KVM_ARM_HOST) += inject_fault.o regmap.o va_layout.o
 kvm-$(CONFIG_KVM_ARM_HOST) += hyp.o hyp-init.o handle_exit.o
diff --git a/include/linux/arm-smccc.h b/include/linux/arm-smccc.h
index 080012a6f025..e7f129f26ebd 100644
--- a/include/linux/arm-smccc.h
+++ b/include/linux/arm-smccc.h
@@ -45,6 +45,7 @@
 #define ARM_SMCCC_OWNER_SIP		2
 #define ARM_SMCCC_OWNER_OEM		3
 #define ARM_SMCCC_OWNER_STANDARD	4
+#define ARM_SMCCC_OWNER_STANDARD_HYP	5
 #define ARM_SMCCC_OWNER_TRUSTED_APP	48
 #define ARM_SMCCC_OWNER_TRUSTED_APP_END	49
 #define ARM_SMCCC_OWNER_TRUSTED_OS	50
@@ -302,5 +303,18 @@ asmlinkage void __arm_smccc_hvc(unsigned long a0, unsigned long a1,
 #define SMCCC_RET_NOT_SUPPORTED			-1
 #define SMCCC_RET_NOT_REQUIRED			-2
 
+/* Paravirtualised time calls (defined by ARM DEN0057A) */
+#define ARM_SMCCC_HV_PV_FEATURES				\
+	ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL,			\
+			   ARM_SMCCC_SMC_64,			\
+			   ARM_SMCCC_OWNER_STANDARD_HYP,	\
+			   0x20)
+
+#define ARM_SMCCC_HV_PV_TIME_ST					\
+	ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL,			\
+			   ARM_SMCCC_SMC_64,			\
+			   ARM_SMCCC_OWNER_STANDARD_HYP,	\
+			   0x22)
+
 #endif /*__ASSEMBLY__*/
 #endif /*__LINUX_ARM_SMCCC_H*/
diff --git a/virt/kvm/arm/hypercalls.c b/virt/kvm/arm/hypercalls.c
index f875241bd030..e2521e0d3978 100644
--- a/virt/kvm/arm/hypercalls.c
+++ b/virt/kvm/arm/hypercalls.c
@@ -12,7 +12,7 @@
 int kvm_hvc_call_handler(struct kvm_vcpu *vcpu)
 {
 	u32 func_id = smccc_get_function(vcpu);
-	u32 val = SMCCC_RET_NOT_SUPPORTED;
+	long val = SMCCC_RET_NOT_SUPPORTED;
 	u32 feature;
 
 	switch (func_id) {
@@ -48,8 +48,14 @@ int kvm_hvc_call_handler(struct kvm_vcpu *vcpu)
 				break;
 			}
 			break;
+		case ARM_SMCCC_HV_PV_FEATURES:
+			val = SMCCC_RET_SUCCESS;
+			break;
 		}
 		break;
+	case ARM_SMCCC_HV_PV_FEATURES:
+		val = kvm_hypercall_pv_features(vcpu);
+		break;
 	default:
 		return kvm_psci_call(vcpu);
 	}
diff --git a/virt/kvm/arm/pvtime.c b/virt/kvm/arm/pvtime.c
new file mode 100644
index 000000000000..7887a61651c6
--- /dev/null
+++ b/virt/kvm/arm/pvtime.c
@@ -0,0 +1,21 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (C) 2019 Arm Ltd.
+
+#include <linux/arm-smccc.h>
+
+#include <kvm/arm_hypercalls.h>
+
+long kvm_hypercall_pv_features(struct kvm_vcpu *vcpu)
+{
+	u32 feature = smccc_get_arg1(vcpu);
+	long val = SMCCC_RET_NOT_SUPPORTED;
+
+	switch (feature) {
+	case ARM_SMCCC_HV_PV_FEATURES:
+		val = SMCCC_RET_SUCCESS;
+		break;
+	}
+
+	return val;
+}
+
-- 
2.20.1

[PATCH v5 04/10] KVM: Implement kvm_put_guest()

[Steven Price]

kvm_put_guest() is analogous to put_user() - it writes a single value to
the guest physical address. The implementation is built upon put_user()
and so it has the same single copy atomic properties.

Signed-off-by: Steven Price <steven.price@arm.com>
---
 include/linux/kvm_host.h | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index fcb46b3374c6..bf0ae1825b9c 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -746,6 +746,28 @@ int kvm_write_guest_offset_cached(struct kvm *kvm, struct gfn_to_hva_cache *ghc,
 				  unsigned long len);
 int kvm_gfn_to_hva_cache_init(struct kvm *kvm, struct gfn_to_hva_cache *ghc,
 			      gpa_t gpa, unsigned long len);
+
+#define __kvm_put_guest(kvm, gfn, offset, value, type)			\
+({									\
+	unsigned long __addr = gfn_to_hva(kvm, gfn);			\
+	type __user *__uaddr = (type __user *)(__addr + offset);	\
+	int __ret = -EFAULT;						\
+									\
+	if (!kvm_is_error_hva(__addr))					\
+		__ret = put_user(value, __uaddr);			\
+	if (!__ret)							\
+		mark_page_dirty(kvm, gfn);				\
+	__ret;								\
+})
+
+#define kvm_put_guest(kvm, gpa, value, type)				\
+({									\
+	gpa_t __gpa = gpa;						\
+	struct kvm *__kvm = kvm;					\
+	__kvm_put_guest(__kvm, __gpa >> PAGE_SHIFT,			\
+			offset_in_page(__gpa), (value), type);		\
+})
+
 int kvm_clear_guest_page(struct kvm *kvm, gfn_t gfn, int offset, int len);
 int kvm_clear_guest(struct kvm *kvm, gpa_t gpa, unsigned long len);
 struct kvm_memory_slot *gfn_to_memslot(struct kvm *kvm, gfn_t gfn);
-- 
2.20.1

[PATCH v5 05/10] KVM: arm64: Support stolen time reporting via shared structure

[Steven Price]

Implement the service call for configuring a shared structure between a
VCPU and the hypervisor in which the hypervisor can write the time
stolen from the VCPU's execution time by other tasks on the host.

User space allocates memory which is placed at an IPA also chosen by user
space. The hypervisor then updates the shared structure using
kvm_put_guest() to ensure single copy atomicity of the 64-bit value
reporting the stolen time in nanoseconds.

Whenever stolen time is enabled by the guest, the stolen time counter is
reset.

The stolen time itself is retrieved from the sched_info structure
maintained by the Linux scheduler code. We enable SCHEDSTATS when
selecting KVM Kconfig to ensure this value is meaningful.

Signed-off-by: Steven Price <steven.price@arm.com>
---
 arch/arm/include/asm/kvm_host.h   | 20 +++++++++++
 arch/arm64/include/asm/kvm_host.h | 21 +++++++++++-
 arch/arm64/kvm/Kconfig            |  1 +
 include/linux/kvm_types.h         |  2 ++
 virt/kvm/arm/arm.c                | 11 ++++++
 virt/kvm/arm/hypercalls.c         |  3 ++
 virt/kvm/arm/pvtime.c             | 56 +++++++++++++++++++++++++++++++
 7 files changed, 113 insertions(+), 1 deletion(-)

diff --git a/arch/arm/include/asm/kvm_host.h b/arch/arm/include/asm/kvm_host.h
index 5a0c3569ebde..5c401482d62d 100644
--- a/arch/arm/include/asm/kvm_host.h
+++ b/arch/arm/include/asm/kvm_host.h
@@ -39,6 +39,7 @@
 	KVM_ARCH_REQ_FLAGS(0, KVM_REQUEST_WAIT | KVM_REQUEST_NO_WAKEUP)
 #define KVM_REQ_IRQ_PENDING	KVM_ARCH_REQ(1)
 #define KVM_REQ_VCPU_RESET	KVM_ARCH_REQ(2)
+#define KVM_REQ_RECORD_STEAL	KVM_ARCH_REQ(3)
 
 DECLARE_STATIC_KEY_FALSE(userspace_irqchip_in_use);
 
@@ -329,6 +330,25 @@ static inline long kvm_hypercall_pv_features(struct kvm_vcpu *vcpu)
 	return SMCCC_RET_NOT_SUPPORTED;
 }
 
+static inline long kvm_hypercall_stolen_time(struct kvm_vcpu *vcpu)
+{
+	return SMCCC_RET_NOT_SUPPORTED;
+}
+
+static inline int kvm_update_stolen_time(struct kvm_vcpu *vcpu, bool init)
+{
+	return -ENOTSUPP;
+}
+
+static inline void kvm_arm_pvtime_vcpu_init(struct kvm_vcpu_arch *vcpu_arch)
+{
+}
+
+static inline bool kvm_arm_is_pvtime_enabled(struct kvm_vcpu_arch *vcpu_arch)
+{
+	return false;
+}
+
 void kvm_mmu_wp_memory_region(struct kvm *kvm, int slot);
 
 struct kvm_vcpu *kvm_mpidr_to_vcpu(struct kvm *kvm, unsigned long mpidr);
diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 93b46d9526d0..1697e63f6dd8 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -44,6 +44,7 @@
 	KVM_ARCH_REQ_FLAGS(0, KVM_REQUEST_WAIT | KVM_REQUEST_NO_WAKEUP)
 #define KVM_REQ_IRQ_PENDING	KVM_ARCH_REQ(1)
 #define KVM_REQ_VCPU_RESET	KVM_ARCH_REQ(2)
+#define KVM_REQ_RECORD_STEAL	KVM_ARCH_REQ(3)
 
 DECLARE_STATIC_KEY_FALSE(userspace_irqchip_in_use);
 
@@ -338,8 +339,14 @@ struct kvm_vcpu_arch {
 	/* True when deferrable sysregs are loaded on the physical CPU,
 	 * see kvm_vcpu_load_sysregs and kvm_vcpu_put_sysregs. */
 	bool sysregs_loaded_on_cpu;
-};
 
+	/* Guest PV state */
+	struct {
+		u64 steal;
+		u64 last_steal;
+		gpa_t base;
+	} steal;
+};
 /* Pointer to the vcpu's SVE FFR for sve_{save,load}_state() */
 #define vcpu_sve_pffr(vcpu) ((void *)((char *)((vcpu)->arch.sve_state) + \
 				      sve_ffr_offset((vcpu)->arch.sve_max_vl)))
@@ -479,6 +486,18 @@ int kvm_perf_init(void);
 int kvm_perf_teardown(void);
 
 long kvm_hypercall_pv_features(struct kvm_vcpu *vcpu);
+long kvm_hypercall_stolen_time(struct kvm_vcpu *vcpu);
+int kvm_update_stolen_time(struct kvm_vcpu *vcpu, bool init);
+
+static inline void kvm_arm_pvtime_vcpu_init(struct kvm_vcpu_arch *vcpu_arch)
+{
+	vcpu_arch->steal.base = GPA_INVALID;
+}
+
+static inline bool kvm_arm_is_pvtime_enabled(struct kvm_vcpu_arch *vcpu_arch)
+{
+	return (vcpu_arch->steal.base != GPA_INVALID);
+}
 
 void kvm_set_sei_esr(struct kvm_vcpu *vcpu, u64 syndrome);
 
diff --git a/arch/arm64/kvm/Kconfig b/arch/arm64/kvm/Kconfig
index a67121d419a2..d8b88e40d223 100644
--- a/arch/arm64/kvm/Kconfig
+++ b/arch/arm64/kvm/Kconfig
@@ -39,6 +39,7 @@ config KVM
 	select IRQ_BYPASS_MANAGER
 	select HAVE_KVM_IRQ_BYPASS
 	select HAVE_KVM_VCPU_RUN_PID_CHANGE
+	select SCHEDSTATS
 	---help---
 	  Support hosting virtualized guest machines.
 	  We don't support KVM with 16K page tables yet, due to the multiple
diff --git a/include/linux/kvm_types.h b/include/linux/kvm_types.h
index bde5374ae021..1c88e69db3d9 100644
--- a/include/linux/kvm_types.h
+++ b/include/linux/kvm_types.h
@@ -35,6 +35,8 @@ typedef unsigned long  gva_t;
 typedef u64            gpa_t;
 typedef u64            gfn_t;
 
+#define GPA_INVALID	(~(gpa_t)0)
+
 typedef unsigned long  hva_t;
 typedef u64            hpa_t;
 typedef u64            hfn_t;
diff --git a/virt/kvm/arm/arm.c b/virt/kvm/arm/arm.c
index 86c6aa1cb58e..5d3059aeadb1 100644
--- a/virt/kvm/arm/arm.c
+++ b/virt/kvm/arm/arm.c
@@ -40,6 +40,10 @@
 #include <asm/kvm_coproc.h>
 #include <asm/sections.h>
 
+#include <kvm/arm_hypercalls.h>
+#include <kvm/arm_pmu.h>
+#include <kvm/arm_psci.h>
+
 #ifdef REQUIRES_VIRT
 __asm__(".arch_extension	virt");
 #endif
@@ -351,6 +355,8 @@ int kvm_arch_vcpu_init(struct kvm_vcpu *vcpu)
 
 	kvm_arm_reset_debug_ptr(vcpu);
 
+	kvm_arm_pvtime_vcpu_init(&vcpu->arch);
+
 	return kvm_vgic_vcpu_init(vcpu);
 }
 
@@ -380,6 +386,8 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
 	kvm_vcpu_load_sysregs(vcpu);
 	kvm_arch_vcpu_load_fp(vcpu);
 	kvm_vcpu_pmu_restore_guest(vcpu);
+	if (kvm_arm_is_pvtime_enabled(&vcpu->arch))
+		kvm_make_request(KVM_REQ_RECORD_STEAL, vcpu);
 
 	if (single_task_running())
 		vcpu_clear_wfe_traps(vcpu);
@@ -645,6 +653,9 @@ static void check_vcpu_requests(struct kvm_vcpu *vcpu)
 		 * that a VCPU sees new virtual interrupts.
 		 */
 		kvm_check_request(KVM_REQ_IRQ_PENDING, vcpu);
+
+		if (kvm_check_request(KVM_REQ_RECORD_STEAL, vcpu))
+			kvm_update_stolen_time(vcpu, false);
 	}
 }
 
diff --git a/virt/kvm/arm/hypercalls.c b/virt/kvm/arm/hypercalls.c
index e2521e0d3978..3091a5d2e842 100644
--- a/virt/kvm/arm/hypercalls.c
+++ b/virt/kvm/arm/hypercalls.c
@@ -56,6 +56,9 @@ int kvm_hvc_call_handler(struct kvm_vcpu *vcpu)
 	case ARM_SMCCC_HV_PV_FEATURES:
 		val = kvm_hypercall_pv_features(vcpu);
 		break;
+	case ARM_SMCCC_HV_PV_TIME_ST:
+		val = kvm_hypercall_stolen_time(vcpu);
+		break;
 	default:
 		return kvm_psci_call(vcpu);
 	}
diff --git a/virt/kvm/arm/pvtime.c b/virt/kvm/arm/pvtime.c
index 7887a61651c6..d9d0dbc6994b 100644
--- a/virt/kvm/arm/pvtime.c
+++ b/virt/kvm/arm/pvtime.c
@@ -3,8 +3,45 @@
 
 #include <linux/arm-smccc.h>
 
+#include <asm/pvclock-abi.h>
+
 #include <kvm/arm_hypercalls.h>
 
+int kvm_update_stolen_time(struct kvm_vcpu *vcpu, bool init)
+{
+	struct kvm *kvm = vcpu->kvm;
+	u64 steal;
+	u64 steal_le;
+	u64 offset;
+	int idx;
+	u64 base = vcpu->arch.steal.base;
+
+	if (base == GPA_INVALID)
+		return -ENOTSUPP;
+
+	/* Let's do the local bookkeeping */
+	steal = vcpu->arch.steal.steal;
+	steal += current->sched_info.run_delay - vcpu->arch.steal.last_steal;
+	vcpu->arch.steal.last_steal = current->sched_info.run_delay;
+	vcpu->arch.steal.steal = steal;
+
+	steal_le = cpu_to_le64(steal);
+	idx = srcu_read_lock(&kvm->srcu);
+	if (init) {
+		struct pvclock_vcpu_stolen_time init_values = {
+			.revision = 0,
+			.attributes = 0
+		};
+		kvm_write_guest(kvm, base, &init_values,
+				sizeof(init_values));
+	}
+	offset = offsetof(struct pvclock_vcpu_stolen_time, stolen_time);
+	kvm_put_guest(kvm, base + offset, steal_le, u64);
+	srcu_read_unlock(&kvm->srcu, idx);
+
+	return 0;
+}
+
 long kvm_hypercall_pv_features(struct kvm_vcpu *vcpu)
 {
 	u32 feature = smccc_get_arg1(vcpu);
@@ -12,6 +49,7 @@ long kvm_hypercall_pv_features(struct kvm_vcpu *vcpu)
 
 	switch (feature) {
 	case ARM_SMCCC_HV_PV_FEATURES:
+	case ARM_SMCCC_HV_PV_TIME_ST:
 		val = SMCCC_RET_SUCCESS;
 		break;
 	}
@@ -19,3 +57,21 @@ long kvm_hypercall_pv_features(struct kvm_vcpu *vcpu)
 	return val;
 }
 
+long kvm_hypercall_stolen_time(struct kvm_vcpu *vcpu)
+{
+	int err;
+
+	/*
+	 * Start counting stolen time from the time the guest requests
+	 * the feature enabled.
+	 */
+	vcpu->arch.steal.steal = 0;
+	vcpu->arch.steal.last_steal = current->sched_info.run_delay;
+
+	err = kvm_update_stolen_time(vcpu, true);
+
+	if (err)
+		return SMCCC_RET_NOT_SUPPORTED;
+
+	return vcpu->arch.steal.base;
+}
-- 
2.20.1

[PATCH v5 06/10] KVM: Allow kvm_device_ops to be const

[Steven Price]

Currently a kvm_device_ops structure cannot be const without triggering
compiler warnings. However the structure doesn't need to be written to
and, by marking it const, it can be read-only in memory. Add some more
const keywords to allow this.

Signed-off-by: Steven Price <steven.price@arm.com>
---
 include/linux/kvm_host.h | 4 ++--
 virt/kvm/kvm_main.c      | 6 +++---
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index bf0ae1825b9c..4e65f7566913 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -1260,7 +1260,7 @@ extern unsigned int halt_poll_ns_grow_start;
 extern unsigned int halt_poll_ns_shrink;
 
 struct kvm_device {
-	struct kvm_device_ops *ops;
+	const struct kvm_device_ops *ops;
 	struct kvm *kvm;
 	void *private;
 	struct list_head vm_node;
@@ -1313,7 +1313,7 @@ struct kvm_device_ops {
 void kvm_device_get(struct kvm_device *dev);
 void kvm_device_put(struct kvm_device *dev);
 struct kvm_device *kvm_device_from_filp(struct file *filp);
-int kvm_register_device_ops(struct kvm_device_ops *ops, u32 type);
+int kvm_register_device_ops(const struct kvm_device_ops *ops, u32 type);
 void kvm_unregister_device_ops(u32 type);
 
 extern struct kvm_device_ops kvm_mpic_ops;
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index e6de3159e682..e9bb79a1022b 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -3045,14 +3045,14 @@ struct kvm_device *kvm_device_from_filp(struct file *filp)
 	return filp->private_data;
 }
 
-static struct kvm_device_ops *kvm_device_ops_table[KVM_DEV_TYPE_MAX] = {
+static const struct kvm_device_ops *kvm_device_ops_table[KVM_DEV_TYPE_MAX] = {
 #ifdef CONFIG_KVM_MPIC
 	[KVM_DEV_TYPE_FSL_MPIC_20]	= &kvm_mpic_ops,
 	[KVM_DEV_TYPE_FSL_MPIC_42]	= &kvm_mpic_ops,
 #endif
 };
 
-int kvm_register_device_ops(struct kvm_device_ops *ops, u32 type)
+int kvm_register_device_ops(const struct kvm_device_ops *ops, u32 type)
 {
 	if (type >= ARRAY_SIZE(kvm_device_ops_table))
 		return -ENOSPC;
@@ -3073,7 +3073,7 @@ void kvm_unregister_device_ops(u32 type)
 static int kvm_ioctl_create_device(struct kvm *kvm,
 				   struct kvm_create_device *cd)
 {
-	struct kvm_device_ops *ops = NULL;
+	const struct kvm_device_ops *ops = NULL;
 	struct kvm_device *dev;
 	bool test = cd->flags & KVM_CREATE_DEVICE_TEST;
 	int type;
-- 
2.20.1

[PATCH v5 07/10] KVM: arm64: Provide VCPU attributes for stolen time

[Steven Price]

Allow user space to inform the KVM host where in the physical memory
map the paravirtualized time structures should be located.

User space can set an attribute on the VCPU providing the IPA base
address of the stolen time structure for that VCPU. This must be
repeated for every VCPU in the VM.

The address is given in terms of the physical address visible to
the guest and must be 64 byte aligned. The guest will discover the
address via a hypercall.

Signed-off-by: Steven Price <steven.price@arm.com>
---
 arch/arm64/include/asm/kvm_host.h |  7 +++++
 arch/arm64/include/uapi/asm/kvm.h |  2 ++
 arch/arm64/kvm/guest.c            |  9 ++++++
 include/uapi/linux/kvm.h          |  2 ++
 virt/kvm/arm/pvtime.c             | 47 +++++++++++++++++++++++++++++++
 5 files changed, 67 insertions(+)

diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 1697e63f6dd8..6af16b29a41f 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -489,6 +489,13 @@ long kvm_hypercall_pv_features(struct kvm_vcpu *vcpu);
 long kvm_hypercall_stolen_time(struct kvm_vcpu *vcpu);
 int kvm_update_stolen_time(struct kvm_vcpu *vcpu, bool init);
 
+int kvm_arm_pvtime_set_attr(struct kvm_vcpu *vcpu,
+			    struct kvm_device_attr *attr);
+int kvm_arm_pvtime_get_attr(struct kvm_vcpu *vcpu,
+			    struct kvm_device_attr *attr);
+int kvm_arm_pvtime_has_attr(struct kvm_vcpu *vcpu,
+			    struct kvm_device_attr *attr);
+
 static inline void kvm_arm_pvtime_vcpu_init(struct kvm_vcpu_arch *vcpu_arch)
 {
 	vcpu_arch->steal.base = GPA_INVALID;
diff --git a/arch/arm64/include/uapi/asm/kvm.h b/arch/arm64/include/uapi/asm/kvm.h
index 67c21f9bdbad..cff1ba12c768 100644
--- a/arch/arm64/include/uapi/asm/kvm.h
+++ b/arch/arm64/include/uapi/asm/kvm.h
@@ -323,6 +323,8 @@ struct kvm_vcpu_events {
 #define KVM_ARM_VCPU_TIMER_CTRL		1
 #define   KVM_ARM_VCPU_TIMER_IRQ_VTIMER		0
 #define   KVM_ARM_VCPU_TIMER_IRQ_PTIMER		1
+#define KVM_ARM_VCPU_PVTIME_CTRL	2
+#define   KVM_ARM_VCPU_PVTIME_IPA	0
 
 /* KVM_IRQ_LINE irq field index values */
 #define KVM_ARM_IRQ_VCPU2_SHIFT		28
diff --git a/arch/arm64/kvm/guest.c b/arch/arm64/kvm/guest.c
index dfd626447482..d3ac9d2fd405 100644
--- a/arch/arm64/kvm/guest.c
+++ b/arch/arm64/kvm/guest.c
@@ -858,6 +858,9 @@ int kvm_arm_vcpu_arch_set_attr(struct kvm_vcpu *vcpu,
 	case KVM_ARM_VCPU_TIMER_CTRL:
 		ret = kvm_arm_timer_set_attr(vcpu, attr);
 		break;
+	case KVM_ARM_VCPU_PVTIME_CTRL:
+		ret = kvm_arm_pvtime_set_attr(vcpu, attr);
+		break;
 	default:
 		ret = -ENXIO;
 		break;
@@ -878,6 +881,9 @@ int kvm_arm_vcpu_arch_get_attr(struct kvm_vcpu *vcpu,
 	case KVM_ARM_VCPU_TIMER_CTRL:
 		ret = kvm_arm_timer_get_attr(vcpu, attr);
 		break;
+	case KVM_ARM_VCPU_PVTIME_CTRL:
+		ret = kvm_arm_pvtime_get_attr(vcpu, attr);
+		break;
 	default:
 		ret = -ENXIO;
 		break;
@@ -898,6 +904,9 @@ int kvm_arm_vcpu_arch_has_attr(struct kvm_vcpu *vcpu,
 	case KVM_ARM_VCPU_TIMER_CTRL:
 		ret = kvm_arm_timer_has_attr(vcpu, attr);
 		break;
+	case KVM_ARM_VCPU_PVTIME_CTRL:
+		ret = kvm_arm_pvtime_has_attr(vcpu, attr);
+		break;
 	default:
 		ret = -ENXIO;
 		break;
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index 52641d8ca9e8..a540c8357049 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -1227,6 +1227,8 @@ enum kvm_device_type {
 #define KVM_DEV_TYPE_ARM_VGIC_ITS	KVM_DEV_TYPE_ARM_VGIC_ITS
 	KVM_DEV_TYPE_XIVE,
 #define KVM_DEV_TYPE_XIVE		KVM_DEV_TYPE_XIVE
+	KVM_DEV_TYPE_ARM_PV_TIME,
+#define KVM_DEV_TYPE_ARM_PV_TIME	KVM_DEV_TYPE_ARM_PV_TIME
 	KVM_DEV_TYPE_MAX,
 };
 
diff --git a/virt/kvm/arm/pvtime.c b/virt/kvm/arm/pvtime.c
index d9d0dbc6994b..e8eba3e89197 100644
--- a/virt/kvm/arm/pvtime.c
+++ b/virt/kvm/arm/pvtime.c
@@ -2,7 +2,9 @@
 // Copyright (C) 2019 Arm Ltd.
 
 #include <linux/arm-smccc.h>
+#include <linux/kvm_host.h>
 
+#include <asm/kvm_mmu.h>
 #include <asm/pvclock-abi.h>
 
 #include <kvm/arm_hypercalls.h>
@@ -75,3 +77,48 @@ long kvm_hypercall_stolen_time(struct kvm_vcpu *vcpu)
 
 	return vcpu->arch.steal.base;
 }
+
+int kvm_arm_pvtime_set_attr(struct kvm_vcpu *vcpu,
+			    struct kvm_device_attr *attr)
+{
+	u64 __user *user = (u64 __user *)attr->addr;
+	u64 ipa;
+
+	if (attr->attr != KVM_ARM_VCPU_PVTIME_IPA)
+		return -ENXIO;
+
+	if (get_user(ipa, user))
+		return -EFAULT;
+	if (!IS_ALIGNED(ipa, 64))
+		return -EINVAL;
+	if (vcpu->arch.steal.base != GPA_INVALID)
+		return -EEXIST;
+	vcpu->arch.steal.base = ipa;
+	return 0;
+}
+
+int kvm_arm_pvtime_get_attr(struct kvm_vcpu *vcpu,
+			    struct kvm_device_attr *attr)
+{
+	u64 __user *user = (u64 __user *)attr->addr;
+	u64 ipa;
+
+	if (attr->attr != KVM_ARM_VCPU_PVTIME_IPA)
+		return -ENXIO;
+
+	ipa = vcpu->arch.steal.base;
+
+	if (put_user(ipa, user))
+		return -EFAULT;
+	return 0;
+}
+
+int kvm_arm_pvtime_has_attr(struct kvm_vcpu *vcpu,
+			    struct kvm_device_attr *attr)
+{
+	switch (attr->attr) {
+	case KVM_ARM_VCPU_PVTIME_IPA:
+		return 0;
+	}
+	return -ENXIO;
+}
-- 
2.20.1

[PATCH v5 08/10] arm/arm64: Provide a wrapper for SMCCC 1.1 calls

[Steven Price]

SMCCC 1.1 calls may use either HVC or SMC depending on the PSCI
conduit. Rather than coding this in every call site provide a macro
which uses the correct instruction. The macro also handles the case
where no PSCI conduit is configured returning a not supported error
in res, along with returning the conduit used for the call.

This allow us to remove some duplicated code and will be useful later
when adding paravirtualized time hypervisor calls.

Signed-off-by: Steven Price <steven.price@arm.com>
Acked-by: Will Deacon <will@kernel.org>
---
 include/linux/arm-smccc.h | 44 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 44 insertions(+)

diff --git a/include/linux/arm-smccc.h b/include/linux/arm-smccc.h
index e7f129f26ebd..eee1e832221d 100644
--- a/include/linux/arm-smccc.h
+++ b/include/linux/arm-smccc.h
@@ -303,6 +303,50 @@ asmlinkage void __arm_smccc_hvc(unsigned long a0, unsigned long a1,
 #define SMCCC_RET_NOT_SUPPORTED			-1
 #define SMCCC_RET_NOT_REQUIRED			-2
 
+/* Like arm_smccc_1_1* but always returns SMCCC_RET_NOT_SUPPORTED.
+ * Used when the PSCI conduit is not defined. The empty asm statement
+ * avoids compiler warnings about unused variables.
+ */
+#define __fail_smccc_1_1(...)						\
+	do {								\
+		__declare_args(__count_args(__VA_ARGS__), __VA_ARGS__);	\
+		asm ("" __constraints(__count_args(__VA_ARGS__)));	\
+		if (___res)						\
+			___res->a0 = SMCCC_RET_NOT_SUPPORTED;		\
+	} while (0)
+
+/*
+ * arm_smccc_1_1_invoke() - make an SMCCC v1.1 compliant call
+ *
+ * This is a variadic macro taking one to eight source arguments, and
+ * an optional return structure.
+ *
+ * @a0-a7: arguments passed in registers 0 to 7
+ * @res: result values from registers 0 to 3
+ *
+ * This macro will make either an HVC call or an SMC call depending on the
+ * current PSCI conduit. If no valid conduit is available then -1
+ * (SMCCC_RET_NOT_SUPPORTED) is returned in @res.a0 (if supplied).
+ *
+ * The return value also provides the conduit that was used.
+ */
+#define arm_smccc_1_1_invoke(...) ({					\
+		int method = psci_ops.conduit;				\
+		switch (method) {					\
+		case PSCI_CONDUIT_HVC:					\
+			arm_smccc_1_1_hvc(__VA_ARGS__);			\
+			break;						\
+		case PSCI_CONDUIT_SMC:					\
+			arm_smccc_1_1_smc(__VA_ARGS__);			\
+			break;						\
+		default:						\
+			__fail_smccc_1_1(__VA_ARGS__);			\
+			method = PSCI_CONDUIT_NONE;			\
+			break;						\
+		}							\
+		method;							\
+	})
+
 /* Paravirtualised time calls (defined by ARM DEN0057A) */
 #define ARM_SMCCC_HV_PV_FEATURES				\
 	ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL,			\
-- 
2.20.1

[PATCH v5 09/10] arm/arm64: Make use of the SMCCC 1.1 wrapper

[Steven Price]

Rather than directly choosing which function to use based on
psci_ops.conduit, use the new arm_smccc_1_1 wrapper instead.

In some cases we still need to do some operations based on the
conduit, but the code duplication is removed.

No functional change.

Signed-off-by: Steven Price <steven.price@arm.com>
---
 arch/arm/mm/proc-v7-bugs.c     | 13 +++---
 arch/arm64/kernel/cpu_errata.c | 80 ++++++++++++----------------------
 2 files changed, 33 insertions(+), 60 deletions(-)

diff --git a/arch/arm/mm/proc-v7-bugs.c b/arch/arm/mm/proc-v7-bugs.c
index 9a07916af8dd..8eb52f3385e7 100644
--- a/arch/arm/mm/proc-v7-bugs.c
+++ b/arch/arm/mm/proc-v7-bugs.c
@@ -78,12 +78,13 @@ static void cpu_v7_spectre_init(void)
 		if (psci_ops.smccc_version == SMCCC_VERSION_1_0)
 			break;
 
+		arm_smccc_1_1_invoke(ARM_SMCCC_ARCH_FEATURES_FUNC_ID,
+				     ARM_SMCCC_ARCH_WORKAROUND_1, &res);
+		if ((int)res.a0 != 0)
+			return;
+
 		switch (psci_ops.conduit) {
 		case PSCI_CONDUIT_HVC:
-			arm_smccc_1_1_hvc(ARM_SMCCC_ARCH_FEATURES_FUNC_ID,
-					  ARM_SMCCC_ARCH_WORKAROUND_1, &res);
-			if ((int)res.a0 != 0)
-				break;
 			per_cpu(harden_branch_predictor_fn, cpu) =
 				call_hvc_arch_workaround_1;
 			cpu_do_switch_mm = cpu_v7_hvc_switch_mm;
@@ -91,10 +92,6 @@ static void cpu_v7_spectre_init(void)
 			break;
 
 		case PSCI_CONDUIT_SMC:
-			arm_smccc_1_1_smc(ARM_SMCCC_ARCH_FEATURES_FUNC_ID,
-					  ARM_SMCCC_ARCH_WORKAROUND_1, &res);
-			if ((int)res.a0 != 0)
-				break;
 			per_cpu(harden_branch_predictor_fn, cpu) =
 				call_smc_arch_workaround_1;
 			cpu_do_switch_mm = cpu_v7_smc_switch_mm;
diff --git a/arch/arm64/kernel/cpu_errata.c b/arch/arm64/kernel/cpu_errata.c
index 1e43ba5c79b7..400a49aaae85 100644
--- a/arch/arm64/kernel/cpu_errata.c
+++ b/arch/arm64/kernel/cpu_errata.c
@@ -215,40 +215,31 @@ static int detect_harden_bp_fw(void)
 	if (psci_ops.smccc_version == SMCCC_VERSION_1_0)
 		return -1;
 
+	arm_smccc_1_1_invoke(ARM_SMCCC_ARCH_FEATURES_FUNC_ID,
+			     ARM_SMCCC_ARCH_WORKAROUND_1, &res);
+
+	switch ((int)res.a0) {
+	case 1:
+		/* Firmware says we're just fine */
+		return 0;
+	case 0:
+		break;
+	default:
+		return -1;
+	}
+
 	switch (psci_ops.conduit) {
 	case PSCI_CONDUIT_HVC:
-		arm_smccc_1_1_hvc(ARM_SMCCC_ARCH_FEATURES_FUNC_ID,
-				  ARM_SMCCC_ARCH_WORKAROUND_1, &res);
-		switch ((int)res.a0) {
-		case 1:
-			/* Firmware says we're just fine */
-			return 0;
-		case 0:
-			cb = call_hvc_arch_workaround_1;
-			/* This is a guest, no need to patch KVM vectors */
-			smccc_start = NULL;
-			smccc_end = NULL;
-			break;
-		default:
-			return -1;
-		}
+		cb = call_hvc_arch_workaround_1;
+		/* This is a guest, no need to patch KVM vectors */
+		smccc_start = NULL;
+		smccc_end = NULL;
 		break;
 
 	case PSCI_CONDUIT_SMC:
-		arm_smccc_1_1_smc(ARM_SMCCC_ARCH_FEATURES_FUNC_ID,
-				  ARM_SMCCC_ARCH_WORKAROUND_1, &res);
-		switch ((int)res.a0) {
-		case 1:
-			/* Firmware says we're just fine */
-			return 0;
-		case 0:
-			cb = call_smc_arch_workaround_1;
-			smccc_start = __smccc_workaround_1_smc_start;
-			smccc_end = __smccc_workaround_1_smc_end;
-			break;
-		default:
-			return -1;
-		}
+		cb = call_smc_arch_workaround_1;
+		smccc_start = __smccc_workaround_1_smc_start;
+		smccc_end = __smccc_workaround_1_smc_end;
 		break;
 
 	default:
@@ -338,6 +329,7 @@ void __init arm64_enable_wa2_handling(struct alt_instr *alt,
 
 void arm64_set_ssbd_mitigation(bool state)
 {
+	int conduit;
 	if (!IS_ENABLED(CONFIG_ARM64_SSBD)) {
 		pr_info_once("SSBD disabled by kernel configuration\n");
 		return;
@@ -351,19 +343,10 @@ void arm64_set_ssbd_mitigation(bool state)
 		return;
 	}
 
-	switch (psci_ops.conduit) {
-	case PSCI_CONDUIT_HVC:
-		arm_smccc_1_1_hvc(ARM_SMCCC_ARCH_WORKAROUND_2, state, NULL);
-		break;
+	conduit = arm_smccc_1_1_invoke(ARM_SMCCC_ARCH_WORKAROUND_2, state,
+				       NULL);
 
-	case PSCI_CONDUIT_SMC:
-		arm_smccc_1_1_smc(ARM_SMCCC_ARCH_WORKAROUND_2, state, NULL);
-		break;
-
-	default:
-		WARN_ON_ONCE(1);
-		break;
-	}
+	WARN_ON_ONCE(conduit == PSCI_CONDUIT_NONE);
 }
 
 static bool has_ssbd_mitigation(const struct arm64_cpu_capabilities *entry,
@@ -373,6 +356,7 @@ static bool has_ssbd_mitigation(const struct arm64_cpu_capabilities *entry,
 	bool required = true;
 	s32 val;
 	bool this_cpu_safe = false;
+	int conduit;
 
 	WARN_ON(scope != SCOPE_LOCAL_CPU || preemptible());
 
@@ -397,18 +381,10 @@ static bool has_ssbd_mitigation(const struct arm64_cpu_capabilities *entry,
 		return false;
 	}
 
-	switch (psci_ops.conduit) {
-	case PSCI_CONDUIT_HVC:
-		arm_smccc_1_1_hvc(ARM_SMCCC_ARCH_FEATURES_FUNC_ID,
-				  ARM_SMCCC_ARCH_WORKAROUND_2, &res);
-		break;
-
-	case PSCI_CONDUIT_SMC:
-		arm_smccc_1_1_smc(ARM_SMCCC_ARCH_FEATURES_FUNC_ID,
-				  ARM_SMCCC_ARCH_WORKAROUND_2, &res);
-		break;
+	conduit = arm_smccc_1_1_invoke(ARM_SMCCC_ARCH_FEATURES_FUNC_ID,
+				       ARM_SMCCC_ARCH_WORKAROUND_2, &res);
 
-	default:
+	if (conduit == PSCI_CONDUIT_NONE) {
 		ssbd_state = ARM64_SSBD_UNKNOWN;
 		if (!this_cpu_safe)
 			__ssb_safe = false;
-- 
2.20.1

[PATCH v5 10/10] arm64: Retrieve stolen time as paravirtualized guest

[Steven Price]

Enable paravirtualization features when running under a hypervisor
supporting the PV_TIME_ST hypercall.

For each (v)CPU, we ask the hypervisor for the location of a shared
page which the hypervisor will use to report stolen time to us. We set
pv_time_ops to the stolen time function which simply reads the stolen
value from the shared page for a VCPU. We guarantee single-copy
atomicity using READ_ONCE which means we can also read the stolen
time for another VCPU than the currently running one while it is
potentially being updated by the hypervisor.

Signed-off-by: Steven Price <steven.price@arm.com>
---
 .../admin-guide/kernel-parameters.txt         |   6 +-
 arch/arm64/include/asm/paravirt.h             |   9 +-
 arch/arm64/kernel/paravirt.c                  | 148 ++++++++++++++++++
 arch/arm64/kernel/time.c                      |   3 +
 include/linux/cpuhotplug.h                    |   1 +
 5 files changed, 163 insertions(+), 4 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index c7ac2f3ac99f..346b1c7a4afb 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -3083,9 +3083,9 @@
 			[X86,PV_OPS] Disable paravirtualized VMware scheduler
 			clock and use the default one.
 
-	no-steal-acc	[X86,KVM] Disable paravirtualized steal time accounting.
-			steal time is computed, but won't influence scheduler
-			behaviour
+	no-steal-acc	[X86,KVM,ARM64] Disable paravirtualized steal time
+			accounting. steal time is computed, but won't
+			influence scheduler behaviour
 
 	nolapic		[X86-32,APIC] Do not enable or use the local APIC.
 
diff --git a/arch/arm64/include/asm/paravirt.h b/arch/arm64/include/asm/paravirt.h
index 799d9dd6f7cc..125c26c42902 100644
--- a/arch/arm64/include/asm/paravirt.h
+++ b/arch/arm64/include/asm/paravirt.h
@@ -21,6 +21,13 @@ static inline u64 paravirt_steal_clock(int cpu)
 {
 	return pv_ops.time.steal_clock(cpu);
 }
-#endif
+
+int __init kvm_guest_init(void);
+
+#else
+
+#define kvm_guest_init()
+
+#endif // CONFIG_PARAVIRT
 
 #endif
diff --git a/arch/arm64/kernel/paravirt.c b/arch/arm64/kernel/paravirt.c
index 4cfed91fe256..5bf3be7ccf7e 100644
--- a/arch/arm64/kernel/paravirt.c
+++ b/arch/arm64/kernel/paravirt.c
@@ -6,13 +6,161 @@
  * Author: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
  */
 
+#define pr_fmt(fmt) "kvmarm-pv: " fmt
+
+#include <linux/arm-smccc.h>
+#include <linux/cpuhotplug.h>
 #include <linux/export.h>
+#include <linux/io.h>
 #include <linux/jump_label.h>
+#include <linux/printk.h>
+#include <linux/psci.h>
+#include <linux/reboot.h>
+#include <linux/slab.h>
 #include <linux/types.h>
+
 #include <asm/paravirt.h>
+#include <asm/pvclock-abi.h>
+#include <asm/smp_plat.h>
 
 struct static_key paravirt_steal_enabled;
 struct static_key paravirt_steal_rq_enabled;
 
 struct paravirt_patch_template pv_ops;
 EXPORT_SYMBOL_GPL(pv_ops);
+
+struct kvmarm_stolen_time_region {
+	struct pvclock_vcpu_stolen_time *kaddr;
+};
+
+static DEFINE_PER_CPU(struct kvmarm_stolen_time_region, stolen_time_region);
+
+static bool steal_acc = true;
+static int __init parse_no_stealacc(char *arg)
+{
+	steal_acc = false;
+	return 0;
+}
+
+early_param("no-steal-acc", parse_no_stealacc);
+
+/* return stolen time in ns by asking the hypervisor */
+static u64 kvm_steal_clock(int cpu)
+{
+	struct kvmarm_stolen_time_region *reg;
+
+	reg = per_cpu_ptr(&stolen_time_region, cpu);
+	if (!reg->kaddr) {
+		pr_warn_once("stolen time enabled but not configured for cpu %d\n",
+			     cpu);
+		return 0;
+	}
+
+	return le64_to_cpu(READ_ONCE(reg->kaddr->stolen_time));
+}
+
+static int disable_stolen_time_current_cpu(void)
+{
+	struct kvmarm_stolen_time_region *reg;
+
+	reg = this_cpu_ptr(&stolen_time_region);
+	if (!reg->kaddr)
+		return 0;
+
+	memunmap(reg->kaddr);
+	memset(reg, 0, sizeof(*reg));
+
+	return 0;
+}
+
+static int stolen_time_dying_cpu(unsigned int cpu)
+{
+	return disable_stolen_time_current_cpu();
+}
+
+static int init_stolen_time_cpu(unsigned int cpu)
+{
+	struct kvmarm_stolen_time_region *reg;
+	struct arm_smccc_res res;
+
+	reg = this_cpu_ptr(&stolen_time_region);
+
+	arm_smccc_1_1_invoke(ARM_SMCCC_HV_PV_TIME_ST, &res);
+
+	if ((long)res.a0 < 0)
+		return -EINVAL;
+
+	reg->kaddr = memremap(res.a0,
+			      sizeof(struct pvclock_vcpu_stolen_time),
+			      MEMREMAP_WB);
+
+	if (!reg->kaddr) {
+		pr_warn("Failed to map stolen time data structure\n");
+		return -ENOMEM;
+	}
+
+	if (le32_to_cpu(reg->kaddr->revision) != 0 ||
+	    le32_to_cpu(reg->kaddr->attributes) != 0) {
+		pr_warn("Unexpected revision or attributes in stolen time data\n");
+		return -ENXIO;
+	}
+
+	return 0;
+}
+
+static int kvm_arm_init_stolen_time(void)
+{
+	int ret;
+
+	ret = cpuhp_setup_state(CPUHP_AP_ARM_KVMPV_STARTING,
+				"hypervisor/kvmarm/pv:starting",
+				init_stolen_time_cpu, stolen_time_dying_cpu);
+	if (ret < 0)
+		return ret;
+	return 0;
+}
+
+static bool has_kvm_steal_clock(void)
+{
+	struct arm_smccc_res res;
+
+	/* To detect the presence of PV time support we require SMCCC 1.1+ */
+	if (psci_ops.smccc_version < SMCCC_VERSION_1_1)
+		return false;
+
+	arm_smccc_1_1_invoke(ARM_SMCCC_ARCH_FEATURES_FUNC_ID,
+			     ARM_SMCCC_HV_PV_FEATURES, &res);
+
+	if (res.a0 != SMCCC_RET_SUCCESS)
+		return false;
+
+	arm_smccc_1_1_invoke(ARM_SMCCC_HV_PV_FEATURES,
+			     ARM_SMCCC_HV_PV_TIME_ST, &res);
+
+	if (res.a0 != SMCCC_RET_SUCCESS)
+		return false;
+
+	return true;
+}
+
+int __init kvm_guest_init(void)
+{
+	int ret;
+
+	if (!has_kvm_steal_clock())
+		return 0;
+
+	ret = kvm_arm_init_stolen_time();
+	if (ret)
+		return ret;
+
+	pv_ops.time.steal_clock = kvm_steal_clock;
+
+	static_key_slow_inc(&paravirt_steal_enabled);
+	if (steal_acc)
+		static_key_slow_inc(&paravirt_steal_rq_enabled);
+
+	pr_info("using stolen time PV\n");
+
+	return 0;
+}
diff --git a/arch/arm64/kernel/time.c b/arch/arm64/kernel/time.c
index 0b2946414dc9..a52aea14c6ec 100644
--- a/arch/arm64/kernel/time.c
+++ b/arch/arm64/kernel/time.c
@@ -30,6 +30,7 @@
 
 #include <asm/thread_info.h>
 #include <asm/stacktrace.h>
+#include <asm/paravirt.h>
 
 unsigned long profile_pc(struct pt_regs *regs)
 {
@@ -65,4 +66,6 @@ void __init time_init(void)
 
 	/* Calibrate the delay loop directly */
 	lpj_fine = arch_timer_rate / HZ;
+
+	kvm_guest_init();
 }
diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h
index 068793a619ca..89d75edb5750 100644
--- a/include/linux/cpuhotplug.h
+++ b/include/linux/cpuhotplug.h
@@ -136,6 +136,7 @@ enum cpuhp_state {
 	/* Must be the last timer callback */
 	CPUHP_AP_DUMMY_TIMER_STARTING,
 	CPUHP_AP_ARM_XEN_STARTING,
+	CPUHP_AP_ARM_KVMPV_STARTING,
 	CPUHP_AP_ARM_CORESIGHT_STARTING,
 	CPUHP_AP_ARM64_ISNDEP_STARTING,
 	CPUHP_AP_SMPCFD_DYING,
-- 
2.20.1

Re: [PATCH v5 01/10] KVM: arm64: Document PV-time interface

[Andrew Jones]

On Wed, Oct 02, 2019 at 03:50:28PM +0100, Steven Price wrote:
> Introduce a paravirtualization interface for KVM/arm64 based on the
> "Arm Paravirtualized Time for Arm-Base Systems" specification DEN 0057A.
> 
> This only adds the details about "Stolen Time" as the details of "Live
> Physical Time" have not been fully agreed.
> 
> User space can specify a reserved area of memory for the guest and
> inform KVM to populate the memory with information on time that the host
> kernel has stolen from the guest.
> 
> A hypercall interface is provided for the guest to interrogate the
> hypervisor's support for this interface and the location of the shared
> memory structures.
> 
> Signed-off-by: Steven Price <steven.price@arm.com>
> ---
>  Documentation/virt/kvm/arm/pvtime.txt   | 65 +++++++++++++++++++++++++
>  Documentation/virt/kvm/devices/vcpu.txt | 14 ++++++
>  2 files changed, 79 insertions(+)
>  create mode 100644 Documentation/virt/kvm/arm/pvtime.txt
> 
> diff --git a/Documentation/virt/kvm/arm/pvtime.txt b/Documentation/virt/kvm/arm/pvtime.txt
> new file mode 100644
> index 000000000000..fa15c12eec91
> --- /dev/null
> +++ b/Documentation/virt/kvm/arm/pvtime.txt

Maybe use .rst instead of .txt?

> @@ -0,0 +1,65 @@
> +Paravirtualized time support for arm64
> +======================================
> +
> +Arm specification DEN0057/A defined a standard for paravirtualised time

s/defined/defines/ ?

> +support for AArch64 guests:
> +
> +https://developer.arm.com/docs/den0057/a
> +
> +KVM/arm64 implements the stolen time part of this specification by providing
> +some hypervisor service calls to support a paravirtualized guest obtaining a
> +view of the amount of time stolen from its execution.
> +
> +Two new SMCCC compatible hypercalls are defined:
> +
> +PV_FEATURES 0xC5000020

The spec calls this PV_TIME_FEATURES.

> +PV_TIME_ST  0xC5000022

This is 0xC5000021 in the spec.

> +
> +These are only available in the SMC64/HVC64 calling convention as
> +paravirtualized time is not available to 32 bit Arm guests. The existence of
> +the PV_FEATURES hypercall should be probed using the SMCCC 1.1 ARCH_FEATURES
> +mechanism before calling it.
> +
> +PV_FEATURES
> +    Function ID:  (uint32)  : 0xC5000020
> +    PV_func_id:   (uint32)  : The function to query for support.
> +                              Currently only PV_TIME_ST is supported.

The spec calls this PV_call_id, but maybe PV_func_id would have been better.

> +    Return value: (int32)   : NOT_SUPPORTED (-1) or SUCCESS (0) if the relevant
> +                              PV-time feature is supported by the hypervisor.

This is an int64 in the spec.

> +
> +PV_TIME_ST
> +    Function ID:  (uint32)  : 0xC5000022
> +    Return value: (int64)   : IPA of the stolen time data structure for this
> +                              VCPU. On failure:
> +                              NOT_SUPPORTED (-1)
> +
> +The IPA returned by PV_TIME_ST should be mapped by the guest as normal memory
> +with inner and outer write back caching attributes, in the inner shareable
> +domain. A total of 16 bytes from the IPA returned are guaranteed to be
> +meaningfully filled by the hypervisor (see structure below).
> +
> +PV_TIME_ST returns the structure for the calling VCPU.
> +
> +Stolen Time
> +-----------
> +
> +The structure pointed to by the PV_TIME_ST hypercall is as follows:
> +
> +  Field       | Byte Length | Byte Offset | Description
> +  ----------- | ----------- | ----------- | --------------------------
> +  Revision    |      4      |      0      | Must be 0 for version 0.1

The spec version is 1.0 and Table 1 says "For implementations compliant
with this revision of the specification...". So I think this description
should be "Must be 0 for version 1.0".

> +  Attributes  |      4      |      4      | Must be 0
> +  Stolen time |      8      |      8      | Stolen time in unsigned
> +              |             |             | nanoseconds indicating how
> +              |             |             | much time this VCPU thread
> +              |             |             | was involuntarily not
> +              |             |             | running on a physical CPU.
> +
> +The structure will be updated by the hypervisor prior to scheduling a VCPU. It
> +will be present within a reserved region of the normal memory given to the
> +guest. The guest should not attempt to write into this memory. There is a
> +structure per VCPU of the guest.
> +
> +For the user space interface see Documentation/virt/kvm/devices/vcpu.txt
> +section "3. GROUP: KVM_ARM_VCPU_PVTIME_CTRL".
> +
> diff --git a/Documentation/virt/kvm/devices/vcpu.txt b/Documentation/virt/kvm/devices/vcpu.txt
> index 2b5dab16c4f2..6f3bd64a05b0 100644
> --- a/Documentation/virt/kvm/devices/vcpu.txt
> +++ b/Documentation/virt/kvm/devices/vcpu.txt
> @@ -60,3 +60,17 @@ time to use the number provided for a given timer, overwriting any previously
>  configured values on other VCPUs.  Userspace should configure the interrupt
>  numbers on at least one VCPU after creating all VCPUs and before running any
>  VCPUs.
> +
> +3. GROUP: KVM_ARM_VCPU_PVTIME_CTRL
> +Architectures: ARM64
> +
> +3.1 ATTRIBUTE: KVM_ARM_VCPU_PVTIME_IPA
> +Parameters: 64-bit base address
> +Returns: -ENXIO:  Stolen time not implemented
> +         -EEXIST: Base address already set for this VCPU
> +         -EINVAL: Base address not 64 byte aligned
> +
> +Specifies the base address of the stolen time structure for this VCPU. The
> +base address must be 64 byte aligned and exist within a valid guest memory
> +region. See Documentation/virt/kvm/arm/pvtime.txt for more information
> +including the layout of the stolen time structure.
> -- 
> 2.20.1
>

Thanks,
drew 

Re: [PATCH v5 02/10] KVM: arm/arm64: Factor out hypercall handling from PSCI code

[Andrew Jones]

On Wed, Oct 02, 2019 at 03:50:29PM +0100, Steven Price wrote:
> From: Christoffer Dall <christoffer.dall@arm.com>
> 
> We currently intertwine the KVM PSCI implementation with the general
> dispatch of hypercall handling, which makes perfect sense because PSCI
> is the only category of hypercalls we support.
> 
> However, as we are about to support additional hypercalls, factor out
> this functionality into a separate hypercall handler file.
> 
> Signed-off-by: Christoffer Dall <christoffer.dall@arm.com>
> [steven.price@arm.com: rebased]
> Signed-off-by: Steven Price <steven.price@arm.com>
> ---
>  arch/arm/kvm/Makefile        |  2 +-
>  arch/arm/kvm/handle_exit.c   |  2 +-
>  arch/arm64/kvm/Makefile      |  1 +
>  arch/arm64/kvm/handle_exit.c |  4 +-
>  include/Kbuild               |  2 +
>  include/kvm/arm_hypercalls.h | 43 ++++++++++++++++++
>  include/kvm/arm_psci.h       |  2 +-
>  virt/kvm/arm/hypercalls.c    | 59 +++++++++++++++++++++++++
>  virt/kvm/arm/psci.c          | 84 +-----------------------------------
>  9 files changed, 112 insertions(+), 87 deletions(-)
>  create mode 100644 include/kvm/arm_hypercalls.h
>  create mode 100644 virt/kvm/arm/hypercalls.c
>

Reviewed-by: Andrew Jones <drjones@redhat.com>

Re: [PATCH v5 05/10] KVM: arm64: Support stolen time reporting via shared structure

[Andrew Jones]

On Wed, Oct 02, 2019 at 03:50:32PM +0100, Steven Price wrote:
> +int kvm_update_stolen_time(struct kvm_vcpu *vcpu, bool init)
> +{
> +	struct kvm *kvm = vcpu->kvm;
> +	u64 steal;
> +	u64 steal_le;
> +	u64 offset;
> +	int idx;
> +	u64 base = vcpu->arch.steal.base;
> +
> +	if (base == GPA_INVALID)
> +		return -ENOTSUPP;
> +
> +	/* Let's do the local bookkeeping */
> +	steal = vcpu->arch.steal.steal;
> +	steal += current->sched_info.run_delay - vcpu->arch.steal.last_steal;
> +	vcpu->arch.steal.last_steal = current->sched_info.run_delay;
> +	vcpu->arch.steal.steal = steal;
> +
> +	steal_le = cpu_to_le64(steal);

Agreeing on a byte order for this interface makes sense, but I don't see
it documented anywhere. Is this an SMCCC thing? Because I skimmed some
of those specs and other users too but didn't see anything obvious. Anyway
even if everybody but me knows that all data returned from SMCCC calls
should be LE, it might be nice to document that in the pvtime doc.

Thanks,
drew

Re: [PATCH v5 06/10] KVM: Allow kvm_device_ops to be const

[Andrew Jones]

On Wed, Oct 02, 2019 at 03:50:33PM +0100, Steven Price wrote:
> Currently a kvm_device_ops structure cannot be const without triggering
> compiler warnings. However the structure doesn't need to be written to
> and, by marking it const, it can be read-only in memory. Add some more
> const keywords to allow this.
> 
> Signed-off-by: Steven Price <steven.price@arm.com>
> ---
>  include/linux/kvm_host.h | 4 ++--
>  virt/kvm/kvm_main.c      | 6 +++---
>  2 files changed, 5 insertions(+), 5 deletions(-)
>

Reviewed-by: Andrew Jones <drjones@redhat.com>

Re: [PATCH v5 05/10] KVM: arm64: Support stolen time reporting via shared structure

[Andrew Jones]

On Thu, Oct 03, 2019 at 03:22:35PM +0200, Andrew Jones wrote:
> On Wed, Oct 02, 2019 at 03:50:32PM +0100, Steven Price wrote:
> > +int kvm_update_stolen_time(struct kvm_vcpu *vcpu, bool init)
> > +{
> > +	struct kvm *kvm = vcpu->kvm;
> > +	u64 steal;
> > +	u64 steal_le;
> > +	u64 offset;
> > +	int idx;
> > +	u64 base = vcpu->arch.steal.base;
> > +
> > +	if (base == GPA_INVALID)
> > +		return -ENOTSUPP;
> > +
> > +	/* Let's do the local bookkeeping */
> > +	steal = vcpu->arch.steal.steal;
> > +	steal += current->sched_info.run_delay - vcpu->arch.steal.last_steal;
> > +	vcpu->arch.steal.last_steal = current->sched_info.run_delay;
> > +	vcpu->arch.steal.steal = steal;
> > +
> > +	steal_le = cpu_to_le64(steal);
> 
> Agreeing on a byte order for this interface makes sense, but I don't see
> it documented anywhere. Is this an SMCCC thing? Because I skimmed some
> of those specs and other users too but didn't see anything obvious. Anyway
> even if everybody but me knows that all data returned from SMCCC calls
> should be LE, it might be nice to document that in the pvtime doc.
>

I have another [potentially dumb] SMCCC byte order question. If we need
to worry about using LE for the members of this structure, then why don't
we need to worry about the actual return values of the SMCCC calls? Like
the IPA of the structure?

Thanks,
drew

Re: [PATCH v5 01/10] KVM: arm64: Document PV-time interface

[Steven Price]

On 03/10/2019 13:19, Andrew Jones wrote:
> On Wed, Oct 02, 2019 at 03:50:28PM +0100, Steven Price wrote:
>> Introduce a paravirtualization interface for KVM/arm64 based on the
>> "Arm Paravirtualized Time for Arm-Base Systems" specification DEN 0057A.
>>
>> This only adds the details about "Stolen Time" as the details of "Live
>> Physical Time" have not been fully agreed.
>>
>> User space can specify a reserved area of memory for the guest and
>> inform KVM to populate the memory with information on time that the host
>> kernel has stolen from the guest.
>>
>> A hypercall interface is provided for the guest to interrogate the
>> hypervisor's support for this interface and the location of the shared
>> memory structures.
>>
>> Signed-off-by: Steven Price <steven.price@arm.com>
>> ---
>>  Documentation/virt/kvm/arm/pvtime.txt   | 65 +++++++++++++++++++++++++
>>  Documentation/virt/kvm/devices/vcpu.txt | 14 ++++++
>>  2 files changed, 79 insertions(+)
>>  create mode 100644 Documentation/virt/kvm/arm/pvtime.txt
>>
>> diff --git a/Documentation/virt/kvm/arm/pvtime.txt b/Documentation/virt/kvm/arm/pvtime.txt
>> new file mode 100644
>> index 000000000000..fa15c12eec91
>> --- /dev/null
>> +++ b/Documentation/virt/kvm/arm/pvtime.txt
> 
> Maybe use .rst instead of .txt?

Fair point - I guess .rst is the way of the future!

>> @@ -0,0 +1,65 @@
>> +Paravirtualized time support for arm64
>> +======================================
>> +
>> +Arm specification DEN0057/A defined a standard for paravirtualised time
> 
> s/defined/defines/ ?
> 
>> +support for AArch64 guests:
>> +
>> +https://developer.arm.com/docs/den0057/a
>> +
>> +KVM/arm64 implements the stolen time part of this specification by providing
>> +some hypervisor service calls to support a paravirtualized guest obtaining a
>> +view of the amount of time stolen from its execution.
>> +
>> +Two new SMCCC compatible hypercalls are defined:
>> +
>> +PV_FEATURES 0xC5000020
> 
> The spec calls this PV_TIME_FEATURES.
> 
>> +PV_TIME_ST  0xC5000022
> 
> This is 0xC5000021 in the spec.

This is somewhat embarrassing. Apparently when I was reviewing the new
specification I didn't notice these (subtle) changes. Thanks for
pointing it out to me! I'll update the code to match.

>> +
>> +These are only available in the SMC64/HVC64 calling convention as
>> +paravirtualized time is not available to 32 bit Arm guests. The existence of
>> +the PV_FEATURES hypercall should be probed using the SMCCC 1.1 ARCH_FEATURES
>> +mechanism before calling it.
>> +
>> +PV_FEATURES
>> +    Function ID:  (uint32)  : 0xC5000020
>> +    PV_func_id:   (uint32)  : The function to query for support.
>> +                              Currently only PV_TIME_ST is supported.
> 
> The spec calls this PV_call_id, but maybe PV_func_id would have been better.

I guess they are generally called "hypercalls" not "hyperfunctions" - so
I'll match the spec here.

>> +    Return value: (int32)   : NOT_SUPPORTED (-1) or SUCCESS (0) if the relevant
>> +                              PV-time feature is supported by the hypervisor.
> 
> This is an int64 in the spec.

True - although the values easily fit in int32 too! But I'll update to
be consistent with the spec.

>> +
>> +PV_TIME_ST
>> +    Function ID:  (uint32)  : 0xC5000022
>> +    Return value: (int64)   : IPA of the stolen time data structure for this
>> +                              VCPU. On failure:
>> +                              NOT_SUPPORTED (-1)
>> +
>> +The IPA returned by PV_TIME_ST should be mapped by the guest as normal memory
>> +with inner and outer write back caching attributes, in the inner shareable
>> +domain. A total of 16 bytes from the IPA returned are guaranteed to be
>> +meaningfully filled by the hypervisor (see structure below).
>> +
>> +PV_TIME_ST returns the structure for the calling VCPU.
>> +
>> +Stolen Time
>> +-----------
>> +
>> +The structure pointed to by the PV_TIME_ST hypercall is as follows:
>> +
>> +  Field       | Byte Length | Byte Offset | Description
>> +  ----------- | ----------- | ----------- | --------------------------
>> +  Revision    |      4      |      0      | Must be 0 for version 0.1
> 
> The spec version is 1.0 and Table 1 says "For implementations compliant
> with this revision of the specification...". So I think this description
> should be "Must be 0 for version 1.0".

Will update.

Thanks,

Steve

>> +  Attributes  |      4      |      4      | Must be 0
>> +  Stolen time |      8      |      8      | Stolen time in unsigned
>> +              |             |             | nanoseconds indicating how
>> +              |             |             | much time this VCPU thread
>> +              |             |             | was involuntarily not
>> +              |             |             | running on a physical CPU.
>> +
>> +The structure will be updated by the hypervisor prior to scheduling a VCPU. It
>> +will be present within a reserved region of the normal memory given to the
>> +guest. The guest should not attempt to write into this memory. There is a
>> +structure per VCPU of the guest.
>> +
>> +For the user space interface see Documentation/virt/kvm/devices/vcpu.txt
>> +section "3. GROUP: KVM_ARM_VCPU_PVTIME_CTRL".
>> +
>> diff --git a/Documentation/virt/kvm/devices/vcpu.txt b/Documentation/virt/kvm/devices/vcpu.txt
>> index 2b5dab16c4f2..6f3bd64a05b0 100644
>> --- a/Documentation/virt/kvm/devices/vcpu.txt
>> +++ b/Documentation/virt/kvm/devices/vcpu.txt
>> @@ -60,3 +60,17 @@ time to use the number provided for a given timer, overwriting any previously
>>  configured values on other VCPUs.  Userspace should configure the interrupt
>>  numbers on at least one VCPU after creating all VCPUs and before running any
>>  VCPUs.
>> +
>> +3. GROUP: KVM_ARM_VCPU_PVTIME_CTRL
>> +Architectures: ARM64
>> +
>> +3.1 ATTRIBUTE: KVM_ARM_VCPU_PVTIME_IPA
>> +Parameters: 64-bit base address
>> +Returns: -ENXIO:  Stolen time not implemented
>> +         -EEXIST: Base address already set for this VCPU
>> +         -EINVAL: Base address not 64 byte aligned
>> +
>> +Specifies the base address of the stolen time structure for this VCPU. The
>> +base address must be 64 byte aligned and exist within a valid guest memory
>> +region. See Documentation/virt/kvm/arm/pvtime.txt for more information
>> +including the layout of the stolen time structure.
>> -- 
>> 2.20.1
>>
> 
> Thanks,
> drew 
> 

Re: [PATCH v5 05/10] KVM: arm64: Support stolen time reporting via shared structure

[Steven Price]

On 04/10/2019 08:03, Andrew Jones wrote:
> On Thu, Oct 03, 2019 at 03:22:35PM +0200, Andrew Jones wrote:
>> On Wed, Oct 02, 2019 at 03:50:32PM +0100, Steven Price wrote:
>>> +int kvm_update_stolen_time(struct kvm_vcpu *vcpu, bool init)
>>> +{
>>> +	struct kvm *kvm = vcpu->kvm;
>>> +	u64 steal;
>>> +	u64 steal_le;
>>> +	u64 offset;
>>> +	int idx;
>>> +	u64 base = vcpu->arch.steal.base;
>>> +
>>> +	if (base == GPA_INVALID)
>>> +		return -ENOTSUPP;
>>> +
>>> +	/* Let's do the local bookkeeping */
>>> +	steal = vcpu->arch.steal.steal;
>>> +	steal += current->sched_info.run_delay - vcpu->arch.steal.last_steal;
>>> +	vcpu->arch.steal.last_steal = current->sched_info.run_delay;
>>> +	vcpu->arch.steal.steal = steal;
>>> +
>>> +	steal_le = cpu_to_le64(steal);
>>
>> Agreeing on a byte order for this interface makes sense, but I don't see
>> it documented anywhere. Is this an SMCCC thing? Because I skimmed some
>> of those specs and other users too but didn't see anything obvious. Anyway
>> even if everybody but me knows that all data returned from SMCCC calls
>> should be LE, it might be nice to document that in the pvtime doc.

A very good point - I'll document this in the Linux document and feed
that back for DEN0057A.

> 
> I have another [potentially dumb] SMCCC byte order question. If we need
> to worry about using LE for the members of this structure, then why don't
> we need to worry about the actual return values of the SMCCC calls? Like
> the IPA of the structure?

The SMCCC calls pass values in registers. It's only when reading/writing
these values from/to memory that the endianness actually has any meaning.

Steve

Re: [PATCH v5 05/10] KVM: arm64: Support stolen time reporting via shared structure

[Andrew Jones]

On Fri, Oct 04, 2019 at 10:13:40AM +0100, Steven Price wrote:
> On 04/10/2019 08:03, Andrew Jones wrote:
> > On Thu, Oct 03, 2019 at 03:22:35PM +0200, Andrew Jones wrote:
> >> On Wed, Oct 02, 2019 at 03:50:32PM +0100, Steven Price wrote:
> >>> +int kvm_update_stolen_time(struct kvm_vcpu *vcpu, bool init)
> >>> +{
> >>> +	struct kvm *kvm = vcpu->kvm;
> >>> +	u64 steal;
> >>> +	u64 steal_le;
> >>> +	u64 offset;
> >>> +	int idx;
> >>> +	u64 base = vcpu->arch.steal.base;
> >>> +
> >>> +	if (base == GPA_INVALID)
> >>> +		return -ENOTSUPP;
> >>> +
> >>> +	/* Let's do the local bookkeeping */
> >>> +	steal = vcpu->arch.steal.steal;
> >>> +	steal += current->sched_info.run_delay - vcpu->arch.steal.last_steal;
> >>> +	vcpu->arch.steal.last_steal = current->sched_info.run_delay;
> >>> +	vcpu->arch.steal.steal = steal;
> >>> +
> >>> +	steal_le = cpu_to_le64(steal);
> >>
> >> Agreeing on a byte order for this interface makes sense, but I don't see
> >> it documented anywhere. Is this an SMCCC thing? Because I skimmed some
> >> of those specs and other users too but didn't see anything obvious. Anyway
> >> even if everybody but me knows that all data returned from SMCCC calls
> >> should be LE, it might be nice to document that in the pvtime doc.
> 
> A very good point - I'll document this in the Linux document and feed
> that back for DEN0057A.
> 
> > 
> > I have another [potentially dumb] SMCCC byte order question. If we need
> > to worry about using LE for the members of this structure, then why don't
> > we need to worry about the actual return values of the SMCCC calls? Like
> > the IPA of the structure?
> 
> The SMCCC calls pass values in registers. It's only when reading/writing
> these values from/to memory that the endianness actually has any meaning.
>

Ah yes, of course.

Thanks,
drew