[PATCH v2 09/13] RISC-V: KVM: Implement SBI STA extension

[Anup Patel]

On Thu, Dec 14, 2023 at 3:46 PM Andrew Jones <ajones at ventanamicro.com> wrote:
>
> Add a select SCHED_INFO to the KVM config in order to get run_delay
> info. Then implement SBI STA's set-steal-time-shmem function and
> kvm_riscv_vcpu_record_steal_time() to provide the steal-time info
> to guests.
>
> Signed-off-by: Andrew Jones <ajones at ventanamicro.com>

LGTM.

Reviewed-by: Anup Patel <anup at brainfault.org>

Regards,
Anup

> ---
>  arch/riscv/kvm/Kconfig        |  1 +
>  arch/riscv/kvm/vcpu_sbi_sta.c | 96 ++++++++++++++++++++++++++++++++++-
>  2 files changed, 95 insertions(+), 2 deletions(-)
>
> diff --git a/arch/riscv/kvm/Kconfig b/arch/riscv/kvm/Kconfig
> index dfc237d7875b..148e52b516cf 100644
> --- a/arch/riscv/kvm/Kconfig
> +++ b/arch/riscv/kvm/Kconfig
> @@ -32,6 +32,7 @@ config KVM
>         select KVM_XFER_TO_GUEST_WORK
>         select MMU_NOTIFIER
>         select PREEMPT_NOTIFIERS
> +       select SCHED_INFO
>         help
>           Support hosting virtualized guest machines.
>
> diff --git a/arch/riscv/kvm/vcpu_sbi_sta.c b/arch/riscv/kvm/vcpu_sbi_sta.c
> index 073bc47013b7..8b8dbee5500a 100644
> --- a/arch/riscv/kvm/vcpu_sbi_sta.c
> +++ b/arch/riscv/kvm/vcpu_sbi_sta.c
> @@ -6,21 +6,113 @@
>  #include <linux/kconfig.h>
>  #include <linux/kernel.h>
>  #include <linux/kvm_host.h>
> +#include <linux/mm.h>
> +#include <linux/sizes.h>
>
> +#include <asm/bug.h>
> +#include <asm/current.h>
>  #include <asm/kvm_vcpu_sbi.h>
> +#include <asm/page.h>
>  #include <asm/sbi.h>
> +#include <asm/uaccess.h>
>
>  void kvm_riscv_vcpu_record_steal_time(struct kvm_vcpu *vcpu)
>  {
>         gpa_t shmem = vcpu->arch.sta.shmem;
> +       u64 last_steal = vcpu->arch.sta.last_steal;
> +       u32 *sequence_ptr, sequence;
> +       u64 *steal_ptr, steal;
> +       unsigned long hva;
> +       gfn_t gfn;
>
>         if (shmem == INVALID_GPA)
>                 return;
> +
> +       /*
> +        * shmem is 64-byte aligned (see the enforcement in
> +        * kvm_sbi_sta_steal_time_set_shmem()) and the size of sbi_sta_struct
> +        * is 64 bytes, so we know all its offsets are in the same page.
> +        */
> +       gfn = shmem >> PAGE_SHIFT;
> +       hva = kvm_vcpu_gfn_to_hva(vcpu, gfn);
> +
> +       if (WARN_ON(kvm_is_error_hva(hva))) {
> +               vcpu->arch.sta.shmem = INVALID_GPA;
> +               return;
> +       }
> +
> +       sequence_ptr = (u32 *)(hva + offset_in_page(shmem) +
> +                              offsetof(struct sbi_sta_struct, sequence));
> +       steal_ptr = (u64 *)(hva + offset_in_page(shmem) +
> +                           offsetof(struct sbi_sta_struct, steal));
> +
> +       if (WARN_ON(get_user(sequence, sequence_ptr)))
> +               return;
> +
> +       sequence = le32_to_cpu(sequence);
> +       sequence += 1;
> +
> +       if (WARN_ON(put_user(cpu_to_le32(sequence), sequence_ptr)))
> +               return;
> +
> +       if (!WARN_ON(get_user(steal, steal_ptr))) {
> +               steal = le64_to_cpu(steal);
> +               vcpu->arch.sta.last_steal = READ_ONCE(current->sched_info.run_delay);
> +               steal += vcpu->arch.sta.last_steal - last_steal;
> +               WARN_ON(put_user(cpu_to_le64(steal), steal_ptr));
> +       }
> +
> +       sequence += 1;
> +       WARN_ON(put_user(cpu_to_le32(sequence), sequence_ptr));
> +
> +       kvm_vcpu_mark_page_dirty(vcpu, gfn);
>  }
>
>  static int kvm_sbi_sta_steal_time_set_shmem(struct kvm_vcpu *vcpu)
>  {
> -       return SBI_ERR_FAILURE;
> +       struct kvm_cpu_context *cp = &vcpu->arch.guest_context;
> +       unsigned long shmem_phys_lo = cp->a0;
> +       unsigned long shmem_phys_hi = cp->a1;
> +       u32 flags = cp->a2;
> +       struct sbi_sta_struct zero_sta = {0};
> +       unsigned long hva;
> +       bool writable;
> +       gpa_t shmem;
> +       int ret;
> +
> +       if (flags != 0)
> +               return SBI_ERR_INVALID_PARAM;
> +
> +       if (shmem_phys_lo == SBI_STA_SHMEM_DISABLE &&
> +           shmem_phys_hi == SBI_STA_SHMEM_DISABLE) {
> +               vcpu->arch.sta.shmem = INVALID_GPA;
> +               return 0;
> +       }
> +
> +       if (shmem_phys_lo & (SZ_64 - 1))
> +               return SBI_ERR_INVALID_PARAM;
> +
> +       shmem = shmem_phys_lo;
> +
> +       if (shmem_phys_hi != 0) {
> +               if (IS_ENABLED(CONFIG_32BIT))
> +                       shmem |= ((gpa_t)shmem_phys_hi << 32);
> +               else
> +                       return SBI_ERR_INVALID_ADDRESS;
> +       }
> +
> +       hva = kvm_vcpu_gfn_to_hva_prot(vcpu, shmem >> PAGE_SHIFT, &writable);
> +       if (kvm_is_error_hva(hva) || !writable)
> +               return SBI_ERR_INVALID_ADDRESS;
> +
> +       ret = kvm_vcpu_write_guest(vcpu, shmem, &zero_sta, sizeof(zero_sta));
> +       if (ret)
> +               return SBI_ERR_FAILURE;
> +
> +       vcpu->arch.sta.shmem = shmem;
> +       vcpu->arch.sta.last_steal = current->sched_info.run_delay;
> +
> +       return 0;
>  }
>
>  static int kvm_sbi_ext_sta_handler(struct kvm_vcpu *vcpu, struct kvm_run *run,
> @@ -46,7 +138,7 @@ static int kvm_sbi_ext_sta_handler(struct kvm_vcpu *vcpu, struct kvm_run *run,
>
>  static unsigned long kvm_sbi_ext_sta_probe(struct kvm_vcpu *vcpu)
>  {
> -       return 0;
> +       return !!sched_info_on();
>  }
>
>  const struct kvm_vcpu_sbi_extension vcpu_sbi_ext_sta = {
> --
> 2.43.0
>