@@ -42,6 +42,7 @@
*/
static int set_id_reg(struct kvm_vcpu *vcpu, const struct sys_reg_desc *rd, u64 val);
+static u64 kvm_arm_update_id_reg(const struct kvm_vcpu *vcpu, u32 id, u64 val);
static u64 kvm_arm_read_id_reg(const struct kvm_vcpu *vcpu, u32 encoding);
static u64 sys_reg_to_index(const struct sys_reg_desc *reg);
@@ -1241,6 +1242,7 @@ static int arm64_check_features(struct kvm_vcpu *vcpu,
/* For hidden and unallocated idregs without reset, only val = 0 is allowed. */
if (rd->reset) {
limit = rd->reset(vcpu, rd);
+ limit = kvm_arm_update_id_reg(vcpu, id, limit);
ftr_reg = get_arm64_ftr_reg(id);
if (!ftr_reg)
return -EINVAL;
@@ -1347,10 +1349,8 @@ static u64 general_read_kvm_sanitised_reg(struct kvm_vcpu *vcpu, const struct sy
return read_sanitised_ftr_reg(reg_to_encoding(rd));
}
-static u64 kvm_arm_read_id_reg(const struct kvm_vcpu *vcpu, u32 encoding)
+static u64 kvm_arm_update_id_reg(const struct kvm_vcpu *vcpu, u32 encoding, u64 val)
{
- u64 val = IDREG(vcpu->kvm, encoding);
-
switch (encoding) {
case SYS_ID_AA64PFR0_EL1:
if (!vcpu_has_sve(vcpu))
@@ -1402,6 +1402,13 @@ static u64 kvm_arm_read_id_reg(const struct kvm_vcpu *vcpu, u32 encoding)
return val;
}
+static u64 kvm_arm_read_id_reg(const struct kvm_vcpu *vcpu, u32 encoding)
+{
+ u64 val = IDREG(vcpu->kvm, encoding);
+
+ return kvm_arm_update_id_reg(vcpu, encoding, val);
+}
+
/* Read a sanitised cpufeature ID register by sys_reg_desc */
static u64 read_id_reg(const struct kvm_vcpu *vcpu, struct sys_reg_desc const *r)
{
There are multiple features the availability of which is enabled/disabled and tracked on a per vcpu level in vcpu->arch.flagset e.g. sve, ptrauth, and pmu. While the vm wide value of the id regs which represent the availability of these features is stored in the id_regs kvm struct their value needs to be manipulated on a per vcpu basis. This is done at read time in kvm_arm_read_id_reg(). The value of these per vcpu flags needs to be factored in when calculating the id_reg limit value in check_features() as otherwise we can run into the following scenario. [ running on cpu which supports sve ] 1. AA64PFR0.SVE set in id_reg by kvm_arm_init_id_regs() (cpu supports it and so is set in value returned from read_sanitised_ftr_reg()) 2. vcpus created without sve feature enabled 3. vmm reads AA64PFR0 and attempts to write the same value back (writing the same value back is allowed) 4. write fails in check_features() as limit has AA64PFR0.SVE set however it is not set in the value being written and although a lower value is allowed for this feature it is not in the mask of bits which can be modified and so much match exactly. Thus add a step in check_features() to update the limit returned from id_reg->reset() with the per vcpu features which may have been enabled/disabled at vcpu creation time after the id_regs were initialised. Split this update into a new function named kvm_arm_update_id_reg() so it can be called from check_features() as well as kvm_arm_read_id_reg() to dedup code. Signed-off-by: Suraj Jitindar Singh <surajjs@amazon.com> --- arch/arm64/kvm/sys_regs.c | 13 ++++++++++--- 1 file changed, 10 insertions(+), 3 deletions(-)