[PATCH 0/3] Plumb PSCI SYSTEM_RESET2 call for guests

[PATCH 0/3] Plumb PSCI SYSTEM_RESET2 call for guests

[Will Deacon]

Hi folks,

This small series exposes the PSCI SYSTEM_RESET2 call to guests, which
allows the propagation of a "reset_type" and a "cookie" back to the VMM.
Although Linux guests only ever pass 0 for the type ("SYSTEM_WARM_RESET"),
the vendor-defined range can be used by a bootloader to provide additional
information about the reset, such as an error code.

Cheers,

Will

--->8

Will Deacon (3):
  KVM: arm64: Bump guest PSCI version to 1.1
  KVM: arm64: Expose PSCI SYSTEM_RESET2 call to the guest
  KVM: arm64: Indicate SYSTEM_RESET2 in kvm_run::system_event flags
    field

 Documentation/virt/kvm/api.rst    |  5 +++
 arch/arm64/include/uapi/asm/kvm.h |  7 ++++
 arch/arm64/kvm/psci.c             | 58 +++++++++++++++++++++++++------
 include/kvm/arm_psci.h            |  3 +-
 include/uapi/linux/psci.h         |  4 +++
 5 files changed, 66 insertions(+), 11 deletions(-)

-- 
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[PATCH 1/3] KVM: arm64: Bump guest PSCI version to 1.1

[Will Deacon]

Expose PSCI version v1.1 to the guest by default. The only difference
for now is that an updated version number is reported by PSCI_VERSION.

Cc: Marc Zyngier <maz@kernel.org>
Cc: James Morse <james.morse@arm.com>
Cc: Alexandru Elisei <alexandru.elisei@arm.com>
Cc: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: Will Deacon <will@kernel.org>
---
 arch/arm64/kvm/psci.c  | 12 +++++++++---
 include/kvm/arm_psci.h |  3 ++-
 2 files changed, 11 insertions(+), 4 deletions(-)

diff --git a/arch/arm64/kvm/psci.c b/arch/arm64/kvm/psci.c
index 3eae32876897..70d07477e712 100644
--- a/arch/arm64/kvm/psci.c
+++ b/arch/arm64/kvm/psci.c
@@ -305,16 +305,19 @@ static int kvm_psci_0_2_call(struct kvm_vcpu *vcpu)
 	return ret;
 }
 
-static int kvm_psci_1_0_call(struct kvm_vcpu *vcpu)
+static int kvm_psci_1_x_call(struct kvm_vcpu *vcpu, u32 minor)
 {
 	u32 psci_fn = smccc_get_function(vcpu);
 	u32 feature;
 	unsigned long val;
 	int ret = 1;
 
+	if (minor > 1)
+		return -EINVAL;
+
 	switch(psci_fn) {
 	case PSCI_0_2_FN_PSCI_VERSION:
-		val = KVM_ARM_PSCI_1_0;
+		val = minor == 0 ? KVM_ARM_PSCI_1_0 : KVM_ARM_PSCI_1_1;
 		break;
 	case PSCI_1_0_FN_PSCI_FEATURES:
 		feature = smccc_get_arg1(vcpu);
@@ -393,8 +396,10 @@ static int kvm_psci_0_1_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_1:
+		return kvm_psci_1_x_call(vcpu, 1);
 	case KVM_ARM_PSCI_1_0:
-		return kvm_psci_1_0_call(vcpu);
+		return kvm_psci_1_x_call(vcpu, 0);
 	case KVM_ARM_PSCI_0_2:
 		return kvm_psci_0_2_call(vcpu);
 	case KVM_ARM_PSCI_0_1:
@@ -511,6 +516,7 @@ int kvm_arm_set_fw_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
 			return 0;
 		case KVM_ARM_PSCI_0_2:
 		case KVM_ARM_PSCI_1_0:
+		case KVM_ARM_PSCI_1_1:
 			if (!wants_02)
 				return -EINVAL;
 			vcpu->kvm->arch.psci_version = val;
diff --git a/include/kvm/arm_psci.h b/include/kvm/arm_psci.h
index 5b58bd2fe088..4a1003323a0c 100644
--- a/include/kvm/arm_psci.h
+++ b/include/kvm/arm_psci.h
@@ -13,8 +13,9 @@
 #define KVM_ARM_PSCI_0_1	PSCI_VERSION(0, 1)
 #define KVM_ARM_PSCI_0_2	PSCI_VERSION(0, 2)
 #define KVM_ARM_PSCI_1_0	PSCI_VERSION(1, 0)
+#define KVM_ARM_PSCI_1_1	PSCI_VERSION(1, 1)
 
-#define KVM_ARM_PSCI_LATEST	KVM_ARM_PSCI_1_0
+#define KVM_ARM_PSCI_LATEST	KVM_ARM_PSCI_1_1
 
 /*
  * We need the KVM pointer independently from the vcpu as we can call
-- 
2.35.1.265.g69c8d7142f-goog


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[PATCH 2/3] KVM: arm64: Expose PSCI SYSTEM_RESET2 call to the guest

[Will Deacon]

PSCI v1.1 introduces the optional SYSTEM_RESET2 call, which allows the
caller to provide a vendor-specific "reset type" to request a particular
form of reset or shutdown.

Expose this call to the guest and handle it in the same way as PSCI
SYSTEM_RESET, along with some basic range checking on the argument.

Cc: Marc Zyngier <maz@kernel.org>
Cc: James Morse <james.morse@arm.com>
Cc: Alexandru Elisei <alexandru.elisei@arm.com>
Cc: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: Will Deacon <will@kernel.org>
---
 arch/arm64/kvm/psci.c     | 33 +++++++++++++++++++++++++++++----
 include/uapi/linux/psci.h |  4 ++++
 2 files changed, 33 insertions(+), 4 deletions(-)

diff --git a/arch/arm64/kvm/psci.c b/arch/arm64/kvm/psci.c
index 70d07477e712..30fcc5a99483 100644
--- a/arch/arm64/kvm/psci.c
+++ b/arch/arm64/kvm/psci.c
@@ -308,7 +308,7 @@ static int kvm_psci_0_2_call(struct kvm_vcpu *vcpu)
 static int kvm_psci_1_x_call(struct kvm_vcpu *vcpu, u32 minor)
 {
 	u32 psci_fn = smccc_get_function(vcpu);
-	u32 feature;
+	u32 arg;
 	unsigned long val;
 	int ret = 1;
 
@@ -320,12 +320,12 @@ static int kvm_psci_1_x_call(struct kvm_vcpu *vcpu, u32 minor)
 		val = minor == 0 ? KVM_ARM_PSCI_1_0 : KVM_ARM_PSCI_1_1;
 		break;
 	case PSCI_1_0_FN_PSCI_FEATURES:
-		feature = smccc_get_arg1(vcpu);
-		val = kvm_psci_check_allowed_function(vcpu, feature);
+		arg = smccc_get_arg1(vcpu);
+		val = kvm_psci_check_allowed_function(vcpu, arg);
 		if (val)
 			break;
 
-		switch(feature) {
+		switch(arg) {
 		case PSCI_0_2_FN_PSCI_VERSION:
 		case PSCI_0_2_FN_CPU_SUSPEND:
 		case PSCI_0_2_FN64_CPU_SUSPEND:
@@ -341,11 +341,36 @@ static int kvm_psci_1_x_call(struct kvm_vcpu *vcpu, u32 minor)
 		case ARM_SMCCC_VERSION_FUNC_ID:
 			val = 0;
 			break;
+		case PSCI_1_1_FN_SYSTEM_RESET2:
+		case PSCI_1_1_FN64_SYSTEM_RESET2:
+			if (minor >= 1) {
+				val = 0;
+				break;
+			}
+			fallthrough;
 		default:
 			val = PSCI_RET_NOT_SUPPORTED;
 			break;
 		}
 		break;
+	case PSCI_1_1_FN_SYSTEM_RESET2:
+		kvm_psci_narrow_to_32bit(vcpu);
+		fallthrough;
+	case PSCI_1_1_FN64_SYSTEM_RESET2:
+		if (minor >= 1) {
+			arg = smccc_get_arg1(vcpu);
+
+			if (arg > PSCI_1_1_RESET_TYPE_SYSTEM_WARM_RESET &&
+			    arg < PSCI_1_1_RESET_TYPE_VENDOR_START) {
+				val = PSCI_RET_INVALID_PARAMS;
+			} else {
+				kvm_psci_system_reset(vcpu);
+				val = PSCI_RET_INTERNAL_FAILURE;
+				ret = 0;
+			}
+			break;
+		};
+		fallthrough;
 	default:
 		return kvm_psci_0_2_call(vcpu);
 	}
diff --git a/include/uapi/linux/psci.h b/include/uapi/linux/psci.h
index 2fcad1dd0b0e..2bf93c0d6354 100644
--- a/include/uapi/linux/psci.h
+++ b/include/uapi/linux/psci.h
@@ -82,6 +82,10 @@
 #define PSCI_0_2_TOS_UP_NO_MIGRATE		1
 #define PSCI_0_2_TOS_MP				2
 
+/* PSCI v1.1 reset type encoding for SYSTEM_RESET2 */
+#define PSCI_1_1_RESET_TYPE_SYSTEM_WARM_RESET	0
+#define PSCI_1_1_RESET_TYPE_VENDOR_START	0x80000000U
+
 /* PSCI version decoding (independent of PSCI version) */
 #define PSCI_VERSION_MAJOR_SHIFT		16
 #define PSCI_VERSION_MINOR_MASK			\
-- 
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[PATCH 3/3] KVM: arm64: Indicate SYSTEM_RESET2 in kvm_run::system_event flags field

[Will Deacon]

When handling reset and power-off PSCI calls from the guest, we
initialise X0 to PSCI_RET_INTERNAL_FAILURE in case the VMM tries to
re-run the vCPU after issuing the call.

Unfortunately, this also means that the VMM cannot see which PSCI call
was issued and therefore cannot distinguish between PSCI SYSTEM_RESET
and SYSTEM_RESET2 calls, which is necessary in order to determine the
validity of the "reset_type" in X1.

Allocate bit 0 of the previously unused 'flags' field of the
system_event structure so that we can indicate the PSCI call used to
initiate the reset.

Cc: Marc Zyngier <maz@kernel.org>
Cc: James Morse <james.morse@arm.com>
Cc: Alexandru Elisei <alexandru.elisei@arm.com>
Cc: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: Will Deacon <will@kernel.org>
---
 Documentation/virt/kvm/api.rst    |  5 +++++
 arch/arm64/include/uapi/asm/kvm.h |  7 +++++++
 arch/arm64/kvm/psci.c             | 15 +++++++++++----
 3 files changed, 23 insertions(+), 4 deletions(-)

diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
index a4267104db50..7339e57a226a 100644
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst
@@ -5939,6 +5939,11 @@ Valid values for 'type' are:
    to ignore the request, or to gather VM memory core dump and/or
    reset/shutdown of the VM.
 
+Valid flags are:
+
+ - KVM_SYSTEM_EVENT_RESET_FLAG_PSCI_RESET2 (arm64 only) -- the guest issued
+   a PSCI SYSTEM_RESET2 call with a "reset type" passed in register X1.
+
 ::
 
 		/* KVM_EXIT_IOAPIC_EOI */
diff --git a/arch/arm64/include/uapi/asm/kvm.h b/arch/arm64/include/uapi/asm/kvm.h
index b3edde68bc3e..c2356203d67d 100644
--- a/arch/arm64/include/uapi/asm/kvm.h
+++ b/arch/arm64/include/uapi/asm/kvm.h
@@ -413,6 +413,13 @@ struct kvm_arm_copy_mte_tags {
 #define KVM_PSCI_RET_INVAL		PSCI_RET_INVALID_PARAMS
 #define KVM_PSCI_RET_DENIED		PSCI_RET_DENIED
 
+/* arm64-specific kvm_run::system_event flags */
+/*
+ * Reset caused by a PSCI SYSTEM_RESET2 call with a "reset_type" in x1.
+ * Valid only when the system event has a type of KVM_SYSTEM_EVENT_RESET.
+ */
+#define KVM_SYSTEM_EVENT_RESET_FLAG_PSCI_RESET2	(1ULL << 0)
+
 #endif
 
 #endif /* __ARM_KVM_H__ */
diff --git a/arch/arm64/kvm/psci.c b/arch/arm64/kvm/psci.c
index 30fcc5a99483..ecb4b74cb12a 100644
--- a/arch/arm64/kvm/psci.c
+++ b/arch/arm64/kvm/psci.c
@@ -162,7 +162,7 @@ static unsigned long kvm_psci_vcpu_affinity_info(struct kvm_vcpu *vcpu)
 	return PSCI_0_2_AFFINITY_LEVEL_OFF;
 }
 
-static void kvm_prepare_system_event(struct kvm_vcpu *vcpu, u32 type)
+static void kvm_prepare_system_event(struct kvm_vcpu *vcpu, u32 type, u64 flags)
 {
 	unsigned long i;
 	struct kvm_vcpu *tmp;
@@ -182,17 +182,24 @@ static void kvm_prepare_system_event(struct kvm_vcpu *vcpu, u32 type)
 
 	memset(&vcpu->run->system_event, 0, sizeof(vcpu->run->system_event));
 	vcpu->run->system_event.type = type;
+	vcpu->run->system_event.flags = flags;
 	vcpu->run->exit_reason = KVM_EXIT_SYSTEM_EVENT;
 }
 
 static void kvm_psci_system_off(struct kvm_vcpu *vcpu)
 {
-	kvm_prepare_system_event(vcpu, KVM_SYSTEM_EVENT_SHUTDOWN);
+	kvm_prepare_system_event(vcpu, KVM_SYSTEM_EVENT_SHUTDOWN, 0);
 }
 
 static void kvm_psci_system_reset(struct kvm_vcpu *vcpu)
 {
-	kvm_prepare_system_event(vcpu, KVM_SYSTEM_EVENT_RESET);
+	kvm_prepare_system_event(vcpu, KVM_SYSTEM_EVENT_RESET, 0);
+}
+
+static void kvm_psci_system_reset2(struct kvm_vcpu *vcpu)
+{
+	kvm_prepare_system_event(vcpu, KVM_SYSTEM_EVENT_RESET,
+				 KVM_SYSTEM_EVENT_RESET_FLAG_PSCI_RESET2);
 }
 
 static void kvm_psci_narrow_to_32bit(struct kvm_vcpu *vcpu)
@@ -364,7 +371,7 @@ static int kvm_psci_1_x_call(struct kvm_vcpu *vcpu, u32 minor)
 			    arg < PSCI_1_1_RESET_TYPE_VENDOR_START) {
 				val = PSCI_RET_INVALID_PARAMS;
 			} else {
-				kvm_psci_system_reset(vcpu);
+				kvm_psci_system_reset2(vcpu);
 				val = PSCI_RET_INTERNAL_FAILURE;
 				ret = 0;
 			}
-- 
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