Re: [PATCH 7/9] RISC-V: KVM: Save mvendorid, marchid, and mimpid when creating VCPU

Atish Patra
2022-11-28T21:09:16Z

On Mon, Nov 28, 2022 at 8:15 AM Anup Patel <apatel@ventanamicro.com> wrote:
>
> We should save VCPU mvendorid, marchid, and mimpid at the time
> of creating VCPU so that we don't have to do host SBI call every
> time Guest/VM ask for these details.
>
> Signed-off-by: Anup Patel <apatel@ventanamicro.com>
> ---
> arch/riscv/include/asm/kvm_host.h | 5 +++++
> arch/riscv/kvm/vcpu.c | 6 ++++++
> arch/riscv/kvm/vcpu_sbi_base.c | 11 +++++------
> 3 files changed, 16 insertions(+), 6 deletions(-)
>
> diff --git a/arch/riscv/include/asm/kvm_host.h b/arch/riscv/include/asm/kvm_host.h
> index 91c74b09a970..93f43a3e7886 100644
> --- a/arch/riscv/include/asm/kvm_host.h
> +++ b/arch/riscv/include/asm/kvm_host.h
> @@ -165,6 +165,11 @@ struct kvm_vcpu_arch {
> /* ISA feature bits (similar to MISA) */
> DECLARE_BITMAP(isa, RISCV_ISA_EXT_MAX);
>
> + /* Vendor, Arch, and Implementation details */
> + unsigned long mvendorid;
> + unsigned long marchid;
> + unsigned long mimpid;
> +
> /* SSCRATCH, STVEC, and SCOUNTEREN of Host */
> unsigned long host_sscratch;
> unsigned long host_stvec;
> diff --git a/arch/riscv/kvm/vcpu.c b/arch/riscv/kvm/vcpu.c
> index 68c86f632d37..312a8a926867 100644
> --- a/arch/riscv/kvm/vcpu.c
> +++ b/arch/riscv/kvm/vcpu.c
> @@ -21,6 +21,7 @@
> #include <asm/csr.h>
> #include <asm/cacheflush.h>
> #include <asm/hwcap.h>
> +#include <asm/sbi.h>
>
> const struct _kvm_stats_desc kvm_vcpu_stats_desc[] = {
> KVM_GENERIC_VCPU_STATS(),
> @@ -171,6 +172,11 @@ int kvm_arch_vcpu_create(struct kvm_vcpu *vcpu)
> set_bit(host_isa, vcpu->arch.isa);
> }
>
> + /* Setup vendor, arch, and implementation details */
> + vcpu->arch.mvendorid = sbi_get_mvendorid();
> + vcpu->arch.marchid = sbi_get_marchid();
> + vcpu->arch.mimpid = sbi_get_mimpid();
> +
> /* Setup VCPU hfence queue */
> spin_lock_init(&vcpu->arch.hfence_lock);
>
> diff --git a/arch/riscv/kvm/vcpu_sbi_base.c b/arch/riscv/kvm/vcpu_sbi_base.c
> index 0c806f61c629..5d65c634d301 100644
> --- a/arch/riscv/kvm/vcpu_sbi_base.c
> +++ b/arch/riscv/kvm/vcpu_sbi_base.c
> @@ -19,7 +19,6 @@ static int kvm_sbi_ext_base_handler(struct kvm_vcpu *vcpu, struct kvm_run *run,
> {
> int ret = 0;
> struct kvm_cpu_context *cp = &vcpu->arch.guest_context;
> - struct sbiret ecall_ret;
>
> switch (cp->a6) {
> case SBI_EXT_BASE_GET_SPEC_VERSION:
> @@ -48,13 +47,13 @@ static int kvm_sbi_ext_base_handler(struct kvm_vcpu *vcpu, struct kvm_run *run,
> *out_val = kvm_vcpu_sbi_find_ext(cp->a0) ? 1 : 0;
> break;
> case SBI_EXT_BASE_GET_MVENDORID:
> + *out_val = vcpu->arch.mvendorid;
> + break;
> case SBI_EXT_BASE_GET_MARCHID:
> + *out_val = vcpu->arch.marchid;
> + break;
> case SBI_EXT_BASE_GET_MIMPID:
> - ecall_ret = sbi_ecall(SBI_EXT_BASE, cp->a6, 0, 0, 0, 0, 0, 0);
> - if (!ecall_ret.error)
> - *out_val = ecall_ret.value;
> - /*TODO: We are unnecessarily converting the error twice */
> - ret = sbi_err_map_linux_errno(ecall_ret.error);
> + *out_val = vcpu->arch.mimpid;
> break;
> default:
> ret = -EOPNOTSUPP;
> --
> 2.34.1
>

Reviewed-by: Atish Patra <atishp@rivosinc.com>

--
Regards,
Atish