Re: [PATCH 04/13] RISC-V: KVM: Break down the __kvm_riscv_switch_to() into macros

Atish Patra
2024-10-16T21:37:58Z

On Fri, Jul 19, 2024 at 9:09 AM Anup Patel <apatel@ventanamicro.com> wrote:
>
> Break down the __kvm_riscv_switch_to() function into macros so that
> these macros can be later re-used by SBI NACL extension based low-level
> switch function.
>
> Signed-off-by: Anup Patel <apatel@ventanamicro.com>
> ---
> arch/riscv/kvm/vcpu_switch.S | 52 +++++++++++++++++++++++++++---------
> 1 file changed, 40 insertions(+), 12 deletions(-)
>
> diff --git a/arch/riscv/kvm/vcpu_switch.S b/arch/riscv/kvm/vcpu_switch.S
> index 3f8cbc21a644..9f13e5ce6a18 100644
> --- a/arch/riscv/kvm/vcpu_switch.S
> +++ b/arch/riscv/kvm/vcpu_switch.S
> @@ -11,11 +11,7 @@
> #include <asm/asm-offsets.h>
> #include <asm/csr.h>
>
> - .text
> - .altmacro
> - .option norelax
> -
> -SYM_FUNC_START(__kvm_riscv_switch_to)
> +.macro SAVE_HOST_GPRS
> /* Save Host GPRs (except A0 and T0-T6) */
> REG_S ra, (KVM_ARCH_HOST_RA)(a0)
> REG_S sp, (KVM_ARCH_HOST_SP)(a0)
> @@ -40,10 +36,12 @@ SYM_FUNC_START(__kvm_riscv_switch_to)
> REG_S s9, (KVM_ARCH_HOST_S9)(a0)
> REG_S s10, (KVM_ARCH_HOST_S10)(a0)
> REG_S s11, (KVM_ARCH_HOST_S11)(a0)
> +.endm
>
> +.macro SAVE_HOST_AND_RESTORE_GUEST_CSRS __resume_addr
> /* Load Guest CSR values */
> REG_L t0, (KVM_ARCH_GUEST_SSTATUS)(a0)
> - la t1, .Lkvm_switch_return
> + la t1, \__resume_addr
> REG_L t2, (KVM_ARCH_GUEST_SEPC)(a0)
>
> /* Save Host and Restore Guest SSTATUS */
> @@ -62,7 +60,9 @@ SYM_FUNC_START(__kvm_riscv_switch_to)
> REG_S t0, (KVM_ARCH_HOST_SSTATUS)(a0)
> REG_S t1, (KVM_ARCH_HOST_STVEC)(a0)
> REG_S t3, (KVM_ARCH_HOST_SSCRATCH)(a0)
> +.endm
>
> +.macro RESTORE_GUEST_GPRS
> /* Restore Guest GPRs (except A0) */
> REG_L ra, (KVM_ARCH_GUEST_RA)(a0)
> REG_L sp, (KVM_ARCH_GUEST_SP)(a0)
> @@ -97,13 +97,9 @@ SYM_FUNC_START(__kvm_riscv_switch_to)
>
> /* Restore Guest A0 */
> REG_L a0, (KVM_ARCH_GUEST_A0)(a0)
> +.endm
>
> - /* Resume Guest */
> - sret
> -
> - /* Back to Host */
> - .align 2
> -.Lkvm_switch_return:
> +.macro SAVE_GUEST_GPRS
> /* Swap Guest A0 with SSCRATCH */
> csrrw a0, CSR_SSCRATCH, a0
>
> @@ -138,7 +134,9 @@ SYM_FUNC_START(__kvm_riscv_switch_to)
> REG_S t4, (KVM_ARCH_GUEST_T4)(a0)
> REG_S t5, (KVM_ARCH_GUEST_T5)(a0)
> REG_S t6, (KVM_ARCH_GUEST_T6)(a0)
> +.endm
>
> +.macro SAVE_GUEST_AND_RESTORE_HOST_CSRS
> /* Load Host CSR values */
> REG_L t0, (KVM_ARCH_HOST_STVEC)(a0)
> REG_L t1, (KVM_ARCH_HOST_SSCRATCH)(a0)
> @@ -160,7 +158,9 @@ SYM_FUNC_START(__kvm_riscv_switch_to)
> REG_S t1, (KVM_ARCH_GUEST_A0)(a0)
> REG_S t2, (KVM_ARCH_GUEST_SSTATUS)(a0)
> REG_S t3, (KVM_ARCH_GUEST_SEPC)(a0)
> +.endm
>
> +.macro RESTORE_HOST_GPRS
> /* Restore Host GPRs (except A0 and T0-T6) */
> REG_L ra, (KVM_ARCH_HOST_RA)(a0)
> REG_L sp, (KVM_ARCH_HOST_SP)(a0)
> @@ -185,6 +185,34 @@ SYM_FUNC_START(__kvm_riscv_switch_to)
> REG_L s9, (KVM_ARCH_HOST_S9)(a0)
> REG_L s10, (KVM_ARCH_HOST_S10)(a0)
> REG_L s11, (KVM_ARCH_HOST_S11)(a0)
> +.endm
> +
> + .text
> + .altmacro
> + .option norelax
> +
> + /*
> + * Parameters:
> + * A0 <= Pointer to struct kvm_vcpu_arch
> + */
> +SYM_FUNC_START(__kvm_riscv_switch_to)
> + SAVE_HOST_GPRS
> +
> + SAVE_HOST_AND_RESTORE_GUEST_CSRS .Lkvm_switch_return
> +
> + RESTORE_GUEST_GPRS
> +
> + /* Resume Guest using SRET */
> + sret
> +
> + /* Back to Host */
> + .align 2
> +.Lkvm_switch_return:
> + SAVE_GUEST_GPRS
> +
> + SAVE_GUEST_AND_RESTORE_HOST_CSRS
> +
> + RESTORE_HOST_GPRS
>
> /* Return to C code */
> ret
> --
> 2.34.1
>

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

--
Regards,
Atish