On Wed, Sep 20, 2023 at 07:24:16AM +0200, Andrew Jones wrote:
> On Mon, Sep 18, 2023 at 11:36:46PM +0530, Anup Patel wrote:
> > Currently the AIA ONE_REG registers are reported by get-reg-list
> > as new registers for various vcpu_reg_list configs whenever Ssaia
> > is available on the host because Ssaia extension can only be
> > disabled by Smstateen extension which is not always available.
> >
> > To tackle this, we should filter-out AIA ONE_REG registers only
> > when Ssaia can't be disabled for a VCPU.
> >
> > Fixes: 477069398ed6 ("KVM: riscv: selftests: Add get-reg-list test")
> > Signed-off-by: Anup Patel <apatel@xxxxxxxxxxxxxxxx>
> > ---
> > .../selftests/kvm/riscv/get-reg-list.c | 23 +++++++++++++++++--
> > 1 file changed, 21 insertions(+), 2 deletions(-)
> >
> > diff --git a/tools/testing/selftests/kvm/riscv/get-reg-list.c b/tools/testing/selftests/kvm/riscv/get-reg-list.c
> > index 76c0ad11e423..85907c86b835 100644
> > --- a/tools/testing/selftests/kvm/riscv/get-reg-list.c
> > +++ b/tools/testing/selftests/kvm/riscv/get-reg-list.c
> > @@ -12,6 +12,8 @@
> >
> > #define REG_MASK (KVM_REG_ARCH_MASK | KVM_REG_SIZE_MASK)
> >
> > +static bool isa_ext_cant_disable[KVM_RISCV_ISA_EXT_MAX];
> > +
> > bool filter_reg(__u64 reg)
> > {
> > switch (reg & ~REG_MASK) {
> > @@ -48,6 +50,15 @@ bool filter_reg(__u64 reg)
> > case KVM_REG_RISCV_ISA_EXT | KVM_RISCV_ISA_EXT_ZIFENCEI:
> > case KVM_REG_RISCV_ISA_EXT | KVM_RISCV_ISA_EXT_ZIHPM:
> > return true;
> > + /* AIA registers are always available when Ssaia can't be disabled */
> > + case KVM_REG_RISCV_CSR | KVM_REG_RISCV_CSR_AIA | KVM_REG_RISCV_CSR_AIA_REG(siselect):
> > + case KVM_REG_RISCV_CSR | KVM_REG_RISCV_CSR_AIA | KVM_REG_RISCV_CSR_AIA_REG(iprio1):
> > + case KVM_REG_RISCV_CSR | KVM_REG_RISCV_CSR_AIA | KVM_REG_RISCV_CSR_AIA_REG(iprio2):
> > + case KVM_REG_RISCV_CSR | KVM_REG_RISCV_CSR_AIA | KVM_REG_RISCV_CSR_AIA_REG(sieh):
> > + case KVM_REG_RISCV_CSR | KVM_REG_RISCV_CSR_AIA | KVM_REG_RISCV_CSR_AIA_REG(siph):
> > + case KVM_REG_RISCV_CSR | KVM_REG_RISCV_CSR_AIA | KVM_REG_RISCV_CSR_AIA_REG(iprio1h):
> > + case KVM_REG_RISCV_CSR | KVM_REG_RISCV_CSR_AIA | KVM_REG_RISCV_CSR_AIA_REG(iprio2h):
> > + return isa_ext_cant_disable[KVM_RISCV_ISA_EXT_SSAIA] ? true : false;
>
> No need for the '? true : false'
>
> > default:
> > break;
> > }
> > @@ -71,14 +82,22 @@ static inline bool vcpu_has_ext(struct kvm_vcpu *vcpu, int ext)
> >
> > void finalize_vcpu(struct kvm_vcpu *vcpu, struct vcpu_reg_list *c)
> > {
> > + int rc;
> > struct vcpu_reg_sublist *s;
> > + unsigned long isa_ext_state[KVM_RISCV_ISA_EXT_MAX] = { 0 };
>
> nit: I think we prefer reverse xmas tree in kselftests, but whatever.
>
> > +
> > + for (int i = 0; i < KVM_RISCV_ISA_EXT_MAX; i++)
> > + __vcpu_get_reg(vcpu, RISCV_ISA_EXT_REG(i), &isa_ext_state[i]);
> >
> > /*
> > * Disable all extensions which were enabled by default
> > * if they were available in the risc-v host.
> > */
> > - for (int i = 0; i < KVM_RISCV_ISA_EXT_MAX; i++)
> > - __vcpu_set_reg(vcpu, RISCV_ISA_EXT_REG(i), 0);
> > + for (int i = 0; i < KVM_RISCV_ISA_EXT_MAX; i++) {
> > + rc = __vcpu_set_reg(vcpu, RISCV_ISA_EXT_REG(i), 0);
> > + if (rc && isa_ext_state[i])
>
> How helpful is it to check that isa_ext_state[i] isn't zero? The value of
> the register could be zero, right? Shouldn't we instead capture the return
> values from __vcpu_get_reg and if the return value is zero for a get,
> but nonzero for a set, then we know we have it, but can't disable it.
Eh, never mind. After sending this, I felt like there was something fishy
about my interpretation of how this works, so I took a second look. The
patch is correct as is, since we're checking for when the ISA extension
is present, but we can't disable it (just like it says it's doing :-) I
was thinking too much about AIA registers and not ISA extension registers.
>
> > + isa_ext_cant_disable[i] = true;
> > + }
> >
> > for_each_sublist(c, s) {
> > if (!s->feature)
> > --
> > 2.34.1
> >
>
Reviewed-by: Andrew Jones <ajones@xxxxxxxxxxxxxxxx>
Thanks,
drew
