linux-kernel - Re: [PATCH 1/3] KVM: selftests: riscv: Set PTE A and D bits in VS-stage page table

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Date:   Tue, 5 Apr 2022 12:48:03 +0530
From:   Anup Patel <anup@...infault.org>
To:     Anup Patel <apatel@...tanamicro.com>
Cc:     Paolo Bonzini <pbonzini@...hat.com>,
        Atish Patra <atishp@...shpatra.org>,
        Palmer Dabbelt <palmer@...belt.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Alistair Francis <Alistair.Francis@....com>,
        KVM General <kvm@...r.kernel.org>,
        "open list:KERNEL VIRTUAL MACHINE FOR RISC-V (KVM/riscv)" 
        <kvm-riscv@...ts.infradead.org>,
        linux-riscv <linux-riscv@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org List" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/3] KVM: selftests: riscv: Set PTE A and D bits in
 VS-stage page table

On Tue, Mar 29, 2022 at 12:59 PM Anup Patel <apatel@...tanamicro.com> wrote:
>
> Supporting hardware updates of PTE A and D bits is optional for any
> RISC-V implementation so current software strategy is to always set
> these bits in both G-stage (hypervisor) and VS-stage (guest kernel).
>
> If PTE A and D bits are not set by software (hypervisor or guest)
> then RISC-V implementations not supporting hardware updates of these
> bits will cause traps even for perfectly valid PTEs.
>
> Based on above explanation, the VS-stage page table created by various
> KVM selftest applications is not correct because PTE A and D bits are
> not set. This patch fixes VS-stage page table programming of PTE A and
> D bits for KVM selftests.
>
> Fixes: 3e06cdf10520 ("KVM: selftests: Add initial support for RISC-V
> 64-bit")
> Signed-off-by: Anup Patel <apatel@...tanamicro.com>

I have queued this patch for RC fixes.

Thanks,
Anup

> ---
>  tools/testing/selftests/kvm/include/riscv/processor.h | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/tools/testing/selftests/kvm/include/riscv/processor.h b/tools/testing/selftests/kvm/include/riscv/processor.h
> index dc284c6bdbc3..eca5c622efd2 100644
> --- a/tools/testing/selftests/kvm/include/riscv/processor.h
> +++ b/tools/testing/selftests/kvm/include/riscv/processor.h
> @@ -101,7 +101,9 @@ static inline void set_reg(struct kvm_vm *vm, uint32_t vcpuid, uint64_t id,
>  #define PGTBL_PTE_WRITE_SHIFT                  2
>  #define PGTBL_PTE_READ_MASK                    0x0000000000000002ULL
>  #define PGTBL_PTE_READ_SHIFT                   1
> -#define PGTBL_PTE_PERM_MASK                    (PGTBL_PTE_EXECUTE_MASK | \
> +#define PGTBL_PTE_PERM_MASK                    (PGTBL_PTE_ACCESSED_MASK | \
> +                                                PGTBL_PTE_DIRTY_MASK | \
> +                                                PGTBL_PTE_EXECUTE_MASK | \
>                                                  PGTBL_PTE_WRITE_MASK | \
>                                                  PGTBL_PTE_READ_MASK)
>  #define PGTBL_PTE_VALID_MASK                   0x0000000000000001ULL
> --
> 2.25.1
>