linux-kernel - Re: [PATCH 4/4] KVM: riscv: selftests: Selectively filter-out AIA registers

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Message-ID: <20230920-d9e483ee61b25b834af160bb@orel>
Date:   Wed, 20 Sep 2023 07:26:13 +0200
From:   Andrew Jones <ajones@...tanamicro.com>
To:     Atish Patra <atishp@...shpatra.org>
Cc:     Anup Patel <apatel@...tanamicro.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Shuah Khan <shuah@...nel.org>,
        Palmer Dabbelt <palmer@...belt.com>,
        Paul Walmsley <paul.walmsley@...ive.com>, kvm@...r.kernel.org,
        kvm-riscv@...ts.infradead.org, linux-riscv@...ts.infradead.org,
        linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org
Subject: Re: [PATCH 4/4] KVM: riscv: selftests: Selectively filter-out AIA
 registers

On Wed, Sep 20, 2023 at 06:48:11AM +0200, Andrew Jones wrote:
> On Tue, Sep 19, 2023 at 01:12:47PM -0700, Atish Patra wrote:
> > On Mon, Sep 18, 2023 at 11:07 AM Anup Patel <apatel@...tanamicro.com> 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@...tanamicro.com>
> > > ---
> > >  .../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;
> > 
> > Ahh I guess. you do need the switch case for AIA CSRs but for ISA
> > extensions can be avoided as it is contiguous.
> 
> I guess we could so something like
> 
> case KVM_REG_RISCV_ISA_EXT ... KVM_REG_RISCV_ISA_EXT | KVM_RISCV_ISA_EXT_MAX:
> 
> for the ISA extensions.
>

On second thought, I think I like them each listed explicitly. When we add
a new extension it will show up in the new register list, which will not
only remind us that it needs to be filtered, but also that we should
probably also create a specific config for it.

Thanks,
drew