[PATCH 03/13] RISC-V: KVM: Save/restore SCOUNTEREN in C source

Anup Patel
2024-07-19T16:09:36Z

The SCOUNTEREN CSR need not be saved/restored in the low-level
__kvm_riscv_switch_to() function hence move the SCOUNTEREN CSR
save/restore to the kvm_riscv_vcpu_swap_in_guest_state() and
kvm_riscv_vcpu_swap_in_host_state() functions in C sources.

Also, re-arrange the CSR save/restore and related GPR usage in
the low-level __kvm_riscv_switch_to() low-level function.

Signed-off-by: Anup Patel <apatel@ventanamicro.com>
---
arch/riscv/kvm/vcpu.c | 2 ++
arch/riscv/kvm/vcpu_switch.S | 52 +++++++++++++++---------------------
2 files changed, 23 insertions(+), 31 deletions(-)

diff --git a/arch/riscv/kvm/vcpu.c b/arch/riscv/kvm/vcpu.c
index 93b1ce043482..957e1a5e081b 100644
--- a/arch/riscv/kvm/vcpu.c
+++ b/arch/riscv/kvm/vcpu.c
@@ -691,6 +691,7 @@ static __always_inline void kvm_riscv_vcpu_swap_in_guest_state(struct kvm_vcpu *
struct kvm_vcpu_csr *csr = &vcpu->arch.guest_csr;
struct kvm_vcpu_config *cfg = &vcpu->arch.cfg;

+ vcpu->arch.host_scounteren = csr_swap(CSR_SCOUNTEREN, csr->scounteren);
vcpu->arch.host_senvcfg = csr_swap(CSR_SENVCFG, csr->senvcfg);
if (riscv_has_extension_unlikely(RISCV_ISA_EXT_SMSTATEEN) &&
(cfg->hstateen0 & SMSTATEEN0_SSTATEEN0))
@@ -704,6 +705,7 @@ static __always_inline void kvm_riscv_vcpu_swap_in_host_state(struct kvm_vcpu *v
struct kvm_vcpu_csr *csr = &vcpu->arch.guest_csr;
struct kvm_vcpu_config *cfg = &vcpu->arch.cfg;

+ csr->scounteren = csr_swap(CSR_SCOUNTEREN, vcpu->arch.host_scounteren);
csr->senvcfg = csr_swap(CSR_SENVCFG, vcpu->arch.host_senvcfg);
if (riscv_has_extension_unlikely(RISCV_ISA_EXT_SMSTATEEN) &&
(cfg->hstateen0 & SMSTATEEN0_SSTATEEN0))
diff --git a/arch/riscv/kvm/vcpu_switch.S b/arch/riscv/kvm/vcpu_switch.S
index f83643c4fdb9..3f8cbc21a644 100644
--- a/arch/riscv/kvm/vcpu_switch.S
+++ b/arch/riscv/kvm/vcpu_switch.S
@@ -43,30 +43,25 @@ SYM_FUNC_START(__kvm_riscv_switch_to)

/* Load Guest CSR values */
REG_L t0, (KVM_ARCH_GUEST_SSTATUS)(a0)
- REG_L t1, (KVM_ARCH_GUEST_SCOUNTEREN)(a0)
- la t3, .Lkvm_switch_return
- REG_L t4, (KVM_ARCH_GUEST_SEPC)(a0)
+ la t1, .Lkvm_switch_return
+ REG_L t2, (KVM_ARCH_GUEST_SEPC)(a0)

/* Save Host and Restore Guest SSTATUS */
csrrw t0, CSR_SSTATUS, t0

- /* Save Host and Restore Guest SCOUNTEREN */
- csrrw t1, CSR_SCOUNTEREN, t1
-
/* Save Host STVEC and change it to return path */
- csrrw t3, CSR_STVEC, t3
-
- /* Save Host SSCRATCH and change it to struct kvm_vcpu_arch pointer */
- csrrw t2, CSR_SSCRATCH, a0
+ csrrw t1, CSR_STVEC, t1

/* Restore Guest SEPC */
- csrw CSR_SEPC, t4
+ csrw CSR_SEPC, t2
+
+ /* Save Host SSCRATCH and change it to struct kvm_vcpu_arch pointer */
+ csrrw t3, CSR_SSCRATCH, a0

/* Store Host CSR values */
REG_S t0, (KVM_ARCH_HOST_SSTATUS)(a0)
- REG_S t1, (KVM_ARCH_HOST_SCOUNTEREN)(a0)
- REG_S t2, (KVM_ARCH_HOST_SSCRATCH)(a0)
- REG_S t3, (KVM_ARCH_HOST_STVEC)(a0)
+ REG_S t1, (KVM_ARCH_HOST_STVEC)(a0)
+ REG_S t3, (KVM_ARCH_HOST_SSCRATCH)(a0)

/* Restore Guest GPRs (except A0) */
REG_L ra, (KVM_ARCH_GUEST_RA)(a0)
@@ -145,31 +140,26 @@ SYM_FUNC_START(__kvm_riscv_switch_to)
REG_S t6, (KVM_ARCH_GUEST_T6)(a0)

/* Load Host CSR values */
- REG_L t1, (KVM_ARCH_HOST_STVEC)(a0)
- REG_L t2, (KVM_ARCH_HOST_SSCRATCH)(a0)
- REG_L t3, (KVM_ARCH_HOST_SCOUNTEREN)(a0)
- REG_L t4, (KVM_ARCH_HOST_SSTATUS)(a0)
-
- /* Save Guest SEPC */
- csrr t0, CSR_SEPC
+ REG_L t0, (KVM_ARCH_HOST_STVEC)(a0)
+ REG_L t1, (KVM_ARCH_HOST_SSCRATCH)(a0)
+ REG_L t2, (KVM_ARCH_HOST_SSTATUS)(a0)

/* Save Guest A0 and Restore Host SSCRATCH */
- csrrw t2, CSR_SSCRATCH, t2
+ csrrw t1, CSR_SSCRATCH, t1

- /* Restore Host STVEC */
- csrw CSR_STVEC, t1
+ /* Save Guest SEPC */
+ csrr t3, CSR_SEPC

- /* Save Guest and Restore Host SCOUNTEREN */
- csrrw t3, CSR_SCOUNTEREN, t3
+ /* Restore Host STVEC */
+ csrw CSR_STVEC, t0

/* Save Guest and Restore Host SSTATUS */
- csrrw t4, CSR_SSTATUS, t4
+ csrrw t2, CSR_SSTATUS, t2

/* Store Guest CSR values */
- REG_S t0, (KVM_ARCH_GUEST_SEPC)(a0)
- REG_S t2, (KVM_ARCH_GUEST_A0)(a0)
- REG_S t3, (KVM_ARCH_GUEST_SCOUNTEREN)(a0)
- REG_S t4, (KVM_ARCH_GUEST_SSTATUS)(a0)
+ REG_S t1, (KVM_ARCH_GUEST_A0)(a0)
+ REG_S t2, (KVM_ARCH_GUEST_SSTATUS)(a0)
+ REG_S t3, (KVM_ARCH_GUEST_SEPC)(a0)

/* Restore Host GPRs (except A0 and T0-T6) */
REG_L ra, (KVM_ARCH_HOST_RA)(a0)
--
2.34.1