On 8/13/2020 5:09 PM, Andrew Jones wrote: > On Thu, Aug 13, 2020 at 02:05:16PM +0800, Peng Liang wrote: >> It's time to make ID registers configurable. When userspace (but not >> guest) want to set the values of ID registers, save the value in >> kvm_arch_vcpu so that guest can read the modified values. >> >> Signed-off-by: zhanghailiang <[email protected]> >> Signed-off-by: Peng Liang <[email protected]> >> --- >> arch/arm64/kvm/sys_regs.c | 23 ++++++++++++++++------- >> 1 file changed, 16 insertions(+), 7 deletions(-) >> >> diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c >> index 776c2757a01e..f98635489966 100644 >> --- a/arch/arm64/kvm/sys_regs.c >> +++ b/arch/arm64/kvm/sys_regs.c >> @@ -1111,6 +1111,14 @@ static u64 kvm_get_id_reg(struct kvm_vcpu *vcpu, u64 >> id) >> return ri->sys_val; >> } >> >> +static void kvm_set_id_reg(struct kvm_vcpu *vcpu, u64 id, u64 value) >> +{ >> + struct id_reg_info *ri = kvm_id_reg(vcpu, id); >> + >> + BUG_ON(!ri); >> + ri->sys_val = value; >> +} >> + >> /* Read a sanitised cpufeature ID register by sys_reg_desc */ >> static u64 read_id_reg(struct kvm_vcpu *vcpu, >> struct sys_reg_desc const *r, bool raz) >> @@ -1252,10 +1260,6 @@ static int set_id_aa64zfr0_el1(struct kvm_vcpu *vcpu, >> >> /* >> * cpufeature ID register user accessors >> - * >> - * For now, these registers are immutable for userspace, so no values >> - * are stored, and for set_id_reg() we don't allow the effective value >> - * to be changed. >> */ >> static int __get_id_reg(struct kvm_vcpu *vcpu, >> const struct sys_reg_desc *rd, void __user *uaddr, >> @@ -1279,9 +1283,14 @@ static int __set_id_reg(struct kvm_vcpu *vcpu, >> if (err) >> return err; >> >> - /* This is what we mean by invariant: you can't change it. */ >> - if (val != read_id_reg(vcpu, rd, raz)) >> - return -EINVAL; >> + if (raz) { >> + if (val != read_id_reg(vcpu, rd, raz)) >> + return -EINVAL; >> + } else { >> + u32 reg_id = sys_reg((u32)rd->Op0, (u32)rd->Op1, (u32)rd->CRn, >> + (u32)rd->CRm, (u32)rd->Op2); >> + kvm_set_id_reg(vcpu, reg_id, val); > > So userspace can set the ID registers to whatever they want? I think each > register should have its own sanity checks applied before accepting the > input. > > Thanks, > drew > >> + } >> >> return 0; >> } >> -- >> 2.18.4 >> > > . >
Yea, sanity checkers are necessary and I'm working on it. I think we should make sure that every ID fields should be checked to match the HW capabilities so that guest will not be confused because of a careless hypervisor. Thanks, Peng _______________________________________________ kvmarm mailing list [email protected] https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
