[PATCH v7 17/27] KVM: arm64: Reject ioctl access to FPSIMD V-regs on SVE vcpus

Dave Martin
2019-03-29T13:31:54Z

In order to avoid the pointless complexity of maintaining two ioctl
register access views of the same data, this patch blocks ioctl
access to the FPSIMD V-registers on vcpus that support SVE.

This will make it more straightforward to add SVE register access
support.

Since SVE is an opt-in feature for userspace, this will not affect
existing users.

Signed-off-by: Dave Martin <Dave.Martin@arm.com>
Reviewed-by: Julien Thierry <julien.thierry@arm.com>
Tested-by: zhang.lei <zhang.lei@jp.fujitsu.com>

---

Changes since v5:

* Refactored to cope with the removal of core_reg_size_from_offset()
(which was added by another series which will now be handled
independently).

This leaves some duplication in that we still filter the V-regs out
in two places, but this no worse than other existing code in guest.c.
I plan to tidy this up independently later on.
---
arch/arm64/kvm/guest.c | 48 ++++++++++++++++++++++++++++++++++++------------
1 file changed, 36 insertions(+), 12 deletions(-)

diff --git a/arch/arm64/kvm/guest.c b/arch/arm64/kvm/guest.c
index a391a61..756d0d6 100644
--- a/arch/arm64/kvm/guest.c
+++ b/arch/arm64/kvm/guest.c
@@ -54,12 +54,19 @@ int kvm_arch_vcpu_setup(struct kvm_vcpu *vcpu)
return 0;
}

+static bool core_reg_offset_is_vreg(u64 off)
+{
+ return off >= KVM_REG_ARM_CORE_REG(fp_regs.vregs) &&
+ off < KVM_REG_ARM_CORE_REG(fp_regs.fpsr);
+}
+
static u64 core_reg_offset_from_id(u64 id)
{
return id & ~(KVM_REG_ARCH_MASK | KVM_REG_SIZE_MASK | KVM_REG_ARM_CORE);
}

-static int validate_core_offset(const struct kvm_one_reg *reg)
+static int validate_core_offset(const struct kvm_vcpu *vcpu,
+ const struct kvm_one_reg *reg)
{
u64 off = core_reg_offset_from_id(reg->id);
int size;
@@ -91,11 +98,19 @@ static int validate_core_offset(const struct kvm_one_reg *reg)
return -EINVAL;
}

- if (KVM_REG_SIZE(reg->id) == size &&
- IS_ALIGNED(off, size / sizeof(__u32)))
- return 0;
+ if (KVM_REG_SIZE(reg->id) != size ||
+ !IS_ALIGNED(off, size / sizeof(__u32)))
+ return -EINVAL;

- return -EINVAL;
+ /*
+ * The KVM_REG_ARM64_SVE regs must be used instead of
+ * KVM_REG_ARM_CORE for accessing the FPSIMD V-registers on
+ * SVE-enabled vcpus:
+ */
+ if (vcpu_has_sve(vcpu) && core_reg_offset_is_vreg(off))
+ return -EINVAL;
+
+ return 0;
}

static int get_core_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
@@ -117,7 +132,7 @@ static int get_core_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
(off + (KVM_REG_SIZE(reg->id) / sizeof(__u32))) >= nr_regs)
return -ENOENT;

- if (validate_core_offset(reg))
+ if (validate_core_offset(vcpu, reg))
return -EINVAL;

if (copy_to_user(uaddr, ((u32 *)regs) + off, KVM_REG_SIZE(reg->id)))
@@ -142,7 +157,7 @@ static int set_core_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
(off + (KVM_REG_SIZE(reg->id) / sizeof(__u32))) >= nr_regs)
return -ENOENT;

- if (validate_core_offset(reg))
+ if (validate_core_offset(vcpu, reg))
return -EINVAL;

if (KVM_REG_SIZE(reg->id) > sizeof(tmp))
@@ -195,13 +210,22 @@ int kvm_arch_vcpu_ioctl_set_regs(struct kvm_vcpu *vcpu, struct kvm_regs *regs)
return -EINVAL;
}

-static int kvm_arm_copy_core_reg_indices(u64 __user *uindices)
+static int copy_core_reg_indices(const struct kvm_vcpu *vcpu,
+ u64 __user *uindices)
{
unsigned int i;
int n = 0;
const u64 core_reg = KVM_REG_ARM64 | KVM_REG_SIZE_U64 | KVM_REG_ARM_CORE;

for (i = 0; i < sizeof(struct kvm_regs) / sizeof(__u32); i++) {
+ /*
+ * The KVM_REG_ARM64_SVE regs must be used instead of
+ * KVM_REG_ARM_CORE for accessing the FPSIMD V-registers on
+ * SVE-enabled vcpus:
+ */
+ if (vcpu_has_sve(vcpu) && core_reg_offset_is_vreg(i))
+ continue;
+
if (uindices) {
if (put_user(core_reg | i, uindices))
return -EFAULT;
@@ -214,9 +238,9 @@ static int kvm_arm_copy_core_reg_indices(u64 __user *uindices)
return n;
}

-static unsigned long num_core_regs(void)
+static unsigned long num_core_regs(const struct kvm_vcpu *vcpu)
{
- return kvm_arm_copy_core_reg_indices(NULL);
+ return copy_core_reg_indices(vcpu, NULL);
}

/**
@@ -281,7 +305,7 @@ unsigned long kvm_arm_num_regs(struct kvm_vcpu *vcpu)
{
unsigned long res = 0;

- res += num_core_regs();
+ res += num_core_regs(vcpu);
res += kvm_arm_num_sys_reg_descs(vcpu);
res += kvm_arm_get_fw_num_regs(vcpu);
res += NUM_TIMER_REGS;
@@ -298,7 +322,7 @@ int kvm_arm_copy_reg_indices(struct kvm_vcpu *vcpu, u64 __user *uindices)
{
int ret;

- ret = kvm_arm_copy_core_reg_indices(uindices);
+ ret = copy_core_reg_indices(vcpu, uindices);
if (ret)
return ret;
uindices += ret;
--
2.1.4