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Subject[PATCH v3 4/7] arm64/kvm: enable pointer authentication cpufeature conditionally
Date
According to userspace settings, pointer authentication cpufeature
is enabled/disabled from guests.

Signed-off-by: Amit Daniel Kachhap <amit.kachhap@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Christoffer Dall <christoffer.dall@arm.com>
Cc: Marc Zyngier <marc.zyngier@arm.com>
Cc: kvmarm@lists.cs.columbia.edu
---
arch/arm64/kvm/sys_regs.c | 33 +++++++++++++++++++++------------
1 file changed, 21 insertions(+), 12 deletions(-)

diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index 6af6c7d..ce6144a 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -1055,7 +1055,7 @@ static bool access_cntp_cval(struct kvm_vcpu *vcpu,
}

/* Read a sanitised cpufeature ID register by sys_reg_desc */
-static u64 read_id_reg(struct sys_reg_desc const *r, bool raz)
+static u64 read_id_reg(struct kvm_vcpu *vcpu, struct sys_reg_desc const *r, bool raz)
{
u32 id = sys_reg((u32)r->Op0, (u32)r->Op1,
(u32)r->CRn, (u32)r->CRm, (u32)r->Op2);
@@ -1066,6 +1066,15 @@ static u64 read_id_reg(struct sys_reg_desc const *r, bool raz)
kvm_debug("SVE unsupported for guests, suppressing\n");

val &= ~(0xfUL << ID_AA64PFR0_SVE_SHIFT);
+ } else if (id == SYS_ID_AA64ISAR1_EL1) {
+ const u64 ptrauth_mask = (0xfUL << ID_AA64ISAR1_APA_SHIFT) |
+ (0xfUL << ID_AA64ISAR1_API_SHIFT) |
+ (0xfUL << ID_AA64ISAR1_GPA_SHIFT) |
+ (0xfUL << ID_AA64ISAR1_GPI_SHIFT);
+ if (!kvm_arm_vcpu_ptrauth_allowed(vcpu)) {
+ kvm_debug("ptrauth unsupported for guests, suppressing\n");
+ val &= ~ptrauth_mask;
+ }
} else if (id == SYS_ID_AA64MMFR1_EL1) {
if (val & (0xfUL << ID_AA64MMFR1_LOR_SHIFT))
kvm_debug("LORegions unsupported for guests, suppressing\n");
@@ -1086,7 +1095,7 @@ static bool __access_id_reg(struct kvm_vcpu *vcpu,
if (p->is_write)
return write_to_read_only(vcpu, p, r);

- p->regval = read_id_reg(r, raz);
+ p->regval = read_id_reg(vcpu, r, raz);
return true;
}

@@ -1115,17 +1124,17 @@ static u64 sys_reg_to_index(const struct sys_reg_desc *reg);
* are stored, and for set_id_reg() we don't allow the effective value
* to be changed.
*/
-static int __get_id_reg(const struct sys_reg_desc *rd, void __user *uaddr,
- bool raz)
+static int __get_id_reg(struct kvm_vcpu *vcpu, const struct sys_reg_desc *rd,
+ void __user *uaddr, bool raz)
{
const u64 id = sys_reg_to_index(rd);
- const u64 val = read_id_reg(rd, raz);
+ const u64 val = read_id_reg(vcpu, rd, raz);

return reg_to_user(uaddr, &val, id);
}

-static int __set_id_reg(const struct sys_reg_desc *rd, void __user *uaddr,
- bool raz)
+static int __set_id_reg(struct kvm_vcpu *vcpu, const struct sys_reg_desc *rd,
+ void __user *uaddr, bool raz)
{
const u64 id = sys_reg_to_index(rd);
int err;
@@ -1136,7 +1145,7 @@ static int __set_id_reg(const struct sys_reg_desc *rd, void __user *uaddr,
return err;

/* This is what we mean by invariant: you can't change it. */
- if (val != read_id_reg(rd, raz))
+ if (val != read_id_reg(vcpu, rd, raz))
return -EINVAL;

return 0;
@@ -1145,25 +1154,25 @@ static int __set_id_reg(const struct sys_reg_desc *rd, void __user *uaddr,
static int get_id_reg(struct kvm_vcpu *vcpu, const struct sys_reg_desc *rd,
const struct kvm_one_reg *reg, void __user *uaddr)
{
- return __get_id_reg(rd, uaddr, false);
+ return __get_id_reg(vcpu, rd, uaddr, false);
}

static int set_id_reg(struct kvm_vcpu *vcpu, const struct sys_reg_desc *rd,
const struct kvm_one_reg *reg, void __user *uaddr)
{
- return __set_id_reg(rd, uaddr, false);
+ return __set_id_reg(vcpu, rd, uaddr, false);
}

static int get_raz_id_reg(struct kvm_vcpu *vcpu, const struct sys_reg_desc *rd,
const struct kvm_one_reg *reg, void __user *uaddr)
{
- return __get_id_reg(rd, uaddr, true);
+ return __get_id_reg(vcpu, rd, uaddr, true);
}

static int set_raz_id_reg(struct kvm_vcpu *vcpu, const struct sys_reg_desc *rd,
const struct kvm_one_reg *reg, void __user *uaddr)
{
- return __set_id_reg(rd, uaddr, true);
+ return __set_id_reg(vcpu, rd, uaddr, true);
}

/* sys_reg_desc initialiser for known cpufeature ID registers */
--
2.7.4
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