Although we've implemented PSCI 0.1, 0.2 and 1.0, we expose either 0.1
or 1.0 to a guest, defaulting to the latest version of the PSCI
implementation that is compatible with the requested version. This is
no different from doing a firmware upgrade on KVM.
But in order to give a chance to hypothetical badly implemented guests
that would have a fit by discovering something other than PSCI 0.2,
let's provide a new API that allows userspace to pick one particular
version of the API.
This is implemented as a new class of "firmware" registers, where
we expose the PSCI version. This allows the PSCI version to be
save/restored as part of a guest migration, and also set to
any supported version if the guest requires it.
Signed-off-by: Marc Zyngier <marc.zyngier@xxxxxxx>
---
This is a repost of this proposal for a firmware selection API, as
there was some discussion during the merging window. Now that the core
variant-2 stuff is merged, we can have a go at more
bikesheding. Please open fire!
Documentation/virtual/kvm/api.txt | 9 ++++-
Documentation/virtual/kvm/arm/psci.txt | 30 +++++++++++++++++
arch/arm/include/asm/kvm_host.h | 3 ++
arch/arm/include/uapi/asm/kvm.h | 6 ++++
arch/arm/kvm/guest.c | 13 ++++++++
arch/arm64/include/asm/kvm_host.h | 3 ++
arch/arm64/include/uapi/asm/kvm.h | 6 ++++
arch/arm64/kvm/guest.c | 14 +++++++-
include/kvm/arm_psci.h | 16 +++++++--
virt/kvm/arm/psci.c | 60 ++++++++++++++++++++++++++++++++++
10 files changed, 156 insertions(+), 4 deletions(-)
create mode 100644 Documentation/virtual/kvm/arm/psci.txt
diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
index 57d3ee9e4bde..d2b41e1608b4 100644
--- a/Documentation/virtual/kvm/api.txt
+++ b/Documentation/virtual/kvm/api.txt
@@ -1943,6 +1943,9 @@ ARM 32-bit VFP control registers have the following id bit patterns:
ARM 64-bit FP registers have the following id bit patterns:
0x4030 0000 0012 0 <regno:12>
+ARM firmware pseudo-registers have the following bit pattern:
+ 0x4030 0000 0014 <regno:16>
+
arm64 registers are mapped using the lower 32 bits. The upper 16 of
that is the register group type, or coprocessor number:
@@ -1959,6 +1962,9 @@ arm64 CCSIDR registers are demultiplexed by CSSELR value:
arm64 system registers have the following id bit patterns:
0x6030 0000 0013 <op0:2> <op1:3> <crn:4> <crm:4> <op2:3>
+arm64 firmware pseudo-registers have the following bit pattern:
+ 0x6030 0000 0014 <regno:16>
+
MIPS registers are mapped using the lower 32 bits. The upper 16 of that is
the register group type:
@@ -2493,7 +2499,8 @@ Possible features:
and execute guest code when KVM_RUN is called.
- KVM_ARM_VCPU_EL1_32BIT: Starts the CPU in a 32bit mode.
Depends on KVM_CAP_ARM_EL1_32BIT (arm64 only).
- - KVM_ARM_VCPU_PSCI_0_2: Emulate PSCI v0.2 for the CPU.
+ - KVM_ARM_VCPU_PSCI_0_2: Emulate PSCI v0.2 (or a future revision
+ backward compatible with v0.2) for the CPU.
Depends on KVM_CAP_ARM_PSCI_0_2.
- KVM_ARM_VCPU_PMU_V3: Emulate PMUv3 for the CPU.
Depends on KVM_CAP_ARM_PMU_V3.
diff --git a/Documentation/virtual/kvm/arm/psci.txt b/Documentation/virtual/kvm/arm/psci.txt
new file mode 100644
index 000000000000..aafdab887b04
--- /dev/null
+++ b/Documentation/virtual/kvm/arm/psci.txt
@@ -0,0 +1,30 @@
+KVM implements the PSCI (Power State Coordination Interface)
+specification in order to provide services such as CPU on/off, reset
+and power-off to the guest.
+
+The PSCI specification is regularly updated to provide new features,
+and KVM implements these updates if they make sense from a virtualization
+point of view.
+
+This means that a guest booted on two different versions of KVM can
+observe two different "firmware" revisions. This could cause issues if
+a given guest is tied to a particular PSCI revision (unlikely), or if
+a migration causes a different PSCI version to be exposed out of the
+blue to an unsuspecting guest.
+
+In order to remedy this situation, KVM exposes a set of "firmware
+pseudo-registers" that can be manipulated using the GET/SET_ONE_REG
+interface. These registers can be saved/restored by userspace, and set
+to a convenient value if required.
+
+The following register is defined:
+
+* KVM_REG_ARM_PSCI_VERSION:
+
+ - Only valid if the vcpu has the KVM_ARM_VCPU_PSCI_0_2 feature set
+ (and thus has already been initialized)
+ - Returns the current PSCI version on GET_ONE_REG (defaulting to the
+ highest PSCI version implemented by KVM and compatible with v0.2)
+ - Allows any PSCI version implemented by KVM and compatible with
+ v0.2 to be set with SET_ONE_REG
+ - Affects the whole VM (even if the register view is per-vcpu)
diff --git a/arch/arm/include/asm/kvm_host.h b/arch/arm/include/asm/kvm_host.h
index ef54013b5b9f..6c05e3b13081 100644
--- a/arch/arm/include/asm/kvm_host.h
+++ b/arch/arm/include/asm/kvm_host.h
@@ -75,6 +75,9 @@ struct kvm_arch {
/* Interrupt controller */
struct vgic_dist vgic;
int max_vcpus;
+
+ /* Mandated version of PSCI */
+ u32 psci_version;
};
#define KVM_NR_MEM_OBJS 40
diff --git a/arch/arm/include/uapi/asm/kvm.h b/arch/arm/include/uapi/asm/kvm.h
index 6edd177bb1c7..47dfc99f5cd0 100644
--- a/arch/arm/include/uapi/asm/kvm.h
+++ b/arch/arm/include/uapi/asm/kvm.h
@@ -186,6 +186,12 @@ struct kvm_arch_memory_slot {
#define KVM_REG_ARM_VFP_FPINST 0x1009
#define KVM_REG_ARM_VFP_FPINST2 0x100A
+/* KVM-as-firmware specific pseudo-registers */
+#define KVM_REG_ARM_FW (0x0014 << KVM_REG_ARM_COPROC_SHIFT)
+#define KVM_REG_ARM_FW_REG(r) (KVM_REG_ARM | KVM_REG_SIZE_U64 | \
+ KVM_REG_ARM_FW | ((r) & 0xffff))
+#define KVM_REG_ARM_PSCI_VERSION KVM_REG_ARM_FW_REG(0)
+
/* Device Control API: ARM VGIC */
#define KVM_DEV_ARM_VGIC_GRP_ADDR 0
#define KVM_DEV_ARM_VGIC_GRP_DIST_REGS 1
diff --git a/arch/arm/kvm/guest.c b/arch/arm/kvm/guest.c
index 1e0784ebbfd6..a18f33edc471 100644
--- a/arch/arm/kvm/guest.c
+++ b/arch/arm/kvm/guest.c
@@ -22,6 +22,7 @@
#include <linux/module.h>
#include <linux/vmalloc.h>
#include <linux/fs.h>
+#include <kvm/arm_psci.h>
#include <asm/cputype.h>
#include <linux/uaccess.h>
#include <asm/kvm.h>
@@ -176,6 +177,7 @@ static unsigned long num_core_regs(void)
unsigned long kvm_arm_num_regs(struct kvm_vcpu *vcpu)
{
return num_core_regs() + kvm_arm_num_coproc_regs(vcpu)
+ + kvm_arm_get_fw_num_regs(vcpu)
+ NUM_TIMER_REGS;
}
@@ -196,6 +198,11 @@ int kvm_arm_copy_reg_indices(struct kvm_vcpu *vcpu, u64 __user *uindices)
uindices++;
}
+ ret = kvm_arm_copy_fw_reg_indices(vcpu, uindices);
+ if (ret)
+ return ret;
+ uindices += kvm_arm_get_fw_num_regs(vcpu);
+
ret = copy_timer_indices(vcpu, uindices);
if (ret)
return ret;
@@ -214,6 +221,9 @@ int kvm_arm_get_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
if ((reg->id & KVM_REG_ARM_COPROC_MASK) == KVM_REG_ARM_CORE)
return get_core_reg(vcpu, reg);
+ if ((reg->id & KVM_REG_ARM_COPROC_MASK) == KVM_REG_ARM_FW)
+ return kvm_arm_get_fw_reg(vcpu, reg);
+
if (is_timer_reg(reg->id))
return get_timer_reg(vcpu, reg);
@@ -230,6 +240,9 @@ int kvm_arm_set_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
if ((reg->id & KVM_REG_ARM_COPROC_MASK) == KVM_REG_ARM_CORE)
return set_core_reg(vcpu, reg);
+ if ((reg->id & KVM_REG_ARM_COPROC_MASK) == KVM_REG_ARM_FW)
+ return kvm_arm_set_fw_reg(vcpu, reg);
+
if (is_timer_reg(reg->id))
return set_timer_reg(vcpu, reg);
diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index a73f63aca68e..448d3b9a58cb 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -73,6 +73,9 @@ struct kvm_arch {
/* Interrupt controller */
struct vgic_dist vgic;
+
+ /* Mandated version of PSCI */
+ u32 psci_version;
};
#define KVM_NR_MEM_OBJS 40
diff --git a/arch/arm64/include/uapi/asm/kvm.h b/arch/arm64/include/uapi/asm/kvm.h
index 9abbf3044654..04b3256f8e6d 100644
--- a/arch/arm64/include/uapi/asm/kvm.h
+++ b/arch/arm64/include/uapi/asm/kvm.h
@@ -206,6 +206,12 @@ struct kvm_arch_memory_slot {
#define KVM_REG_ARM_TIMER_CNT ARM64_SYS_REG(3, 3, 14, 3, 2)
#define KVM_REG_ARM_TIMER_CVAL ARM64_SYS_REG(3, 3, 14, 0, 2)
+/* KVM-as-firmware specific pseudo-registers */
+#define KVM_REG_ARM_FW (0x0014 << KVM_REG_ARM_COPROC_SHIFT)
+#define KVM_REG_ARM_FW_REG(r) (KVM_REG_ARM64 | KVM_REG_SIZE_U64 | \
+ KVM_REG_ARM_FW | ((r) & 0xffff))
+#define KVM_REG_ARM_PSCI_VERSION KVM_REG_ARM_FW_REG(0)
+
/* Device Control API: ARM VGIC */
#define KVM_DEV_ARM_VGIC_GRP_ADDR 0
#define KVM_DEV_ARM_VGIC_GRP_DIST_REGS 1
diff --git a/arch/arm64/kvm/guest.c b/arch/arm64/kvm/guest.c
index 5c7f657dd207..811f04c5760e 100644
--- a/arch/arm64/kvm/guest.c
+++ b/arch/arm64/kvm/guest.c
@@ -25,6 +25,7 @@
#include <linux/module.h>
#include <linux/vmalloc.h>
#include <linux/fs.h>
+#include <kvm/arm_psci.h>
#include <asm/cputype.h>
#include <linux/uaccess.h>
#include <asm/kvm.h>
@@ -205,7 +206,7 @@ static int get_timer_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
unsigned long kvm_arm_num_regs(struct kvm_vcpu *vcpu)
{
return num_core_regs() + kvm_arm_num_sys_reg_descs(vcpu)
- + NUM_TIMER_REGS;
+ + kvm_arm_get_fw_num_regs(vcpu) + NUM_TIMER_REGS;
}
/**
@@ -225,6 +226,11 @@ int kvm_arm_copy_reg_indices(struct kvm_vcpu *vcpu, u64 __user *uindices)
uindices++;
}
+ ret = kvm_arm_copy_fw_reg_indices(vcpu, uindices);
+ if (ret)
+ return ret;
+ uindices += kvm_arm_get_fw_num_regs(vcpu);
+
ret = copy_timer_indices(vcpu, uindices);
if (ret)
return ret;
@@ -243,6 +249,9 @@ int kvm_arm_get_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
if ((reg->id & KVM_REG_ARM_COPROC_MASK) == KVM_REG_ARM_CORE)
return get_core_reg(vcpu, reg);
+ if ((reg->id & KVM_REG_ARM_COPROC_MASK) == KVM_REG_ARM_FW)
+ return kvm_arm_get_fw_reg(vcpu, reg);
+
if (is_timer_reg(reg->id))
return get_timer_reg(vcpu, reg);
@@ -259,6 +268,9 @@ int kvm_arm_set_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
if ((reg->id & KVM_REG_ARM_COPROC_MASK) == KVM_REG_ARM_CORE)
return set_core_reg(vcpu, reg);
+ if ((reg->id & KVM_REG_ARM_COPROC_MASK) == KVM_REG_ARM_FW)
+ return kvm_arm_set_fw_reg(vcpu, reg);
+
if (is_timer_reg(reg->id))
return set_timer_reg(vcpu, reg);
diff --git a/include/kvm/arm_psci.h b/include/kvm/arm_psci.h
index e518e4e3dfb5..4b1548129fa2 100644
--- a/include/kvm/arm_psci.h
+++ b/include/kvm/arm_psci.h
@@ -37,10 +37,15 @@ static inline int kvm_psci_version(struct kvm_vcpu *vcpu, struct kvm *kvm)
* Our PSCI implementation stays the same across versions from
* v0.2 onward, only adding the few mandatory functions (such
* as FEATURES with 1.0) that are required by newer
- * revisions. It is thus safe to return the latest.
+ * revisions. It is thus safe to return the latest, unless
+ * userspace has instructed us otherwise.
*/
- if (test_bit(KVM_ARM_VCPU_PSCI_0_2, vcpu->arch.features))
+ if (test_bit(KVM_ARM_VCPU_PSCI_0_2, vcpu->arch.features)) {
+ if (vcpu->kvm->arch.psci_version)
+ return vcpu->kvm->arch.psci_version;
+
return KVM_ARM_PSCI_LATEST;
+ }
return KVM_ARM_PSCI_0_1;
}
@@ -48,4 +53,11 @@ static inline int kvm_psci_version(struct kvm_vcpu *vcpu, struct kvm *kvm)
int kvm_hvc_call_handler(struct kvm_vcpu *vcpu);
+struct kvm_one_reg;
+
+int kvm_arm_get_fw_num_regs(struct kvm_vcpu *vcpu);
+int kvm_arm_copy_fw_reg_indices(struct kvm_vcpu *vcpu, u64 __user *uindices);
+int kvm_arm_get_fw_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg);
+int kvm_arm_set_fw_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg);
+
#endif /* __KVM_ARM_PSCI_H__ */
diff --git a/virt/kvm/arm/psci.c b/virt/kvm/arm/psci.c
index 6919352cbf15..c4762bef13c6 100644
--- a/virt/kvm/arm/psci.c
+++ b/virt/kvm/arm/psci.c
@@ -18,6 +18,7 @@
#include <linux/arm-smccc.h>
#include <linux/preempt.h>
#include <linux/kvm_host.h>
+#include <linux/uaccess.h>
#include <linux/wait.h>
#include <asm/cputype.h>
@@ -427,3 +428,62 @@ int kvm_hvc_call_handler(struct kvm_vcpu *vcpu)
smccc_set_retval(vcpu, val, 0, 0, 0);
return 1;
}
+
+int kvm_arm_get_fw_num_regs(struct kvm_vcpu *vcpu)
+{
+ return 1; /* PSCI version */
+}
+
+int kvm_arm_copy_fw_reg_indices(struct kvm_vcpu *vcpu, u64 __user *uindices)
+{
+ if (put_user(KVM_REG_ARM_PSCI_VERSION, uindices))
+ return -EFAULT;
+
+ return 0;
+}
+
+int kvm_arm_get_fw_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
+{
+ if (reg->id == KVM_REG_ARM_PSCI_VERSION) {
+ void __user *uaddr = (void __user *)(long)reg->addr;
+ u64 val;
+
+ val = kvm_psci_version(vcpu, vcpu->kvm);
+ if (copy_to_user(uaddr, &val, KVM_REG_SIZE(reg->id)))
+ return -EFAULT;
+
+ return 0;
+ }
+
+ return -EINVAL;
+}
+
+int kvm_arm_set_fw_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
+{
+ if (reg->id == KVM_REG_ARM_PSCI_VERSION) {
+ void __user *uaddr = (void __user *)(long)reg->addr;
+ bool wants_02;
+ u64 val;
+
+ if (copy_from_user(&val, uaddr, KVM_REG_SIZE(reg->id)))
+ return -EFAULT;
+
+ wants_02 = test_bit(KVM_ARM_VCPU_PSCI_0_2, vcpu->arch.features);
+
+ switch (val) {
+ case KVM_ARM_PSCI_0_1:
+ if (wants_02)
+ return -EINVAL;
+ vcpu->kvm->arch.psci_version = val;
+ return 0;
+ case KVM_ARM_PSCI_0_2:
+ case KVM_ARM_PSCI_1_0:
+ if (!wants_02)
+ return -EINVAL;
+ vcpu->kvm->arch.psci_version = val;
+ return 0;
+ }
+ }
+
+ return -EINVAL;
+}
--
2.14.2
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