[PATCH 02/13] RISC-V: KVM: Save/restore HSTATUS in C source

Anup Patel
2024-07-19T16:09:32Z

We will be optimizing HSTATUS CSR access via shared memory setup
using the SBI nested acceleration extension. To facilitate this,
we first move HSTATUS save/restore in kvm_riscv_vcpu_enter_exit().

Signed-off-by: Anup Patel <apatel@ventanamicro.com>
---
arch/riscv/kvm/vcpu.c | 9 +++++++++
arch/riscv/kvm/vcpu_switch.S | 36 +++++++++++++-----------------------
2 files changed, 22 insertions(+), 23 deletions(-)

diff --git a/arch/riscv/kvm/vcpu.c b/arch/riscv/kvm/vcpu.c
index 449e5bb948c2..93b1ce043482 100644
--- a/arch/riscv/kvm/vcpu.c
+++ b/arch/riscv/kvm/vcpu.c
@@ -720,9 +720,18 @@ static __always_inline void kvm_riscv_vcpu_swap_in_host_state(struct kvm_vcpu *v
*/
static void noinstr kvm_riscv_vcpu_enter_exit(struct kvm_vcpu *vcpu)
{
+ struct kvm_cpu_context *gcntx = &vcpu->arch.guest_context;
+ struct kvm_cpu_context *hcntx = &vcpu->arch.host_context;
+
kvm_riscv_vcpu_swap_in_guest_state(vcpu);
guest_state_enter_irqoff();
+
+ hcntx->hstatus = csr_swap(CSR_HSTATUS, gcntx->hstatus);
+
__kvm_riscv_switch_to(&vcpu->arch);
+
+ gcntx->hstatus = csr_swap(CSR_HSTATUS, hcntx->hstatus);
+
vcpu->arch.last_exit_cpu = vcpu->cpu;
guest_state_exit_irqoff();
kvm_riscv_vcpu_swap_in_host_state(vcpu);
diff --git a/arch/riscv/kvm/vcpu_switch.S b/arch/riscv/kvm/vcpu_switch.S
index 0c26189aa01c..f83643c4fdb9 100644
--- a/arch/riscv/kvm/vcpu_switch.S
+++ b/arch/riscv/kvm/vcpu_switch.S
@@ -43,35 +43,30 @@ 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_HSTATUS)(a0)
- REG_L t2, (KVM_ARCH_GUEST_SCOUNTEREN)(a0)
- la t4, .Lkvm_switch_return
- REG_L t5, (KVM_ARCH_GUEST_SEPC)(a0)
+ REG_L t1, (KVM_ARCH_GUEST_SCOUNTEREN)(a0)
+ la t3, .Lkvm_switch_return
+ REG_L t4, (KVM_ARCH_GUEST_SEPC)(a0)

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

- /* Save Host and Restore Guest HSTATUS */
- csrrw t1, CSR_HSTATUS, t1
-
/* Save Host and Restore Guest SCOUNTEREN */
- csrrw t2, CSR_SCOUNTEREN, t2
+ csrrw t1, CSR_SCOUNTEREN, t1

/* Save Host STVEC and change it to return path */
- csrrw t4, CSR_STVEC, t4
+ csrrw t3, CSR_STVEC, t3

/* Save Host SSCRATCH and change it to struct kvm_vcpu_arch pointer */
- csrrw t3, CSR_SSCRATCH, a0
+ csrrw t2, CSR_SSCRATCH, a0

/* Restore Guest SEPC */
- csrw CSR_SEPC, t5
+ csrw CSR_SEPC, t4

/* Store Host CSR values */
REG_S t0, (KVM_ARCH_HOST_SSTATUS)(a0)
- REG_S t1, (KVM_ARCH_HOST_HSTATUS)(a0)
- REG_S t2, (KVM_ARCH_HOST_SCOUNTEREN)(a0)
- REG_S t3, (KVM_ARCH_HOST_SSCRATCH)(a0)
- REG_S t4, (KVM_ARCH_HOST_STVEC)(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)

/* Restore Guest GPRs (except A0) */
REG_L ra, (KVM_ARCH_GUEST_RA)(a0)
@@ -153,8 +148,7 @@ SYM_FUNC_START(__kvm_riscv_switch_to)
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_HSTATUS)(a0)
- REG_L t5, (KVM_ARCH_HOST_SSTATUS)(a0)
+ REG_L t4, (KVM_ARCH_HOST_SSTATUS)(a0)

/* Save Guest SEPC */
csrr t0, CSR_SEPC
@@ -168,18 +162,14 @@ SYM_FUNC_START(__kvm_riscv_switch_to)
/* Save Guest and Restore Host SCOUNTEREN */
csrrw t3, CSR_SCOUNTEREN, t3

- /* Save Guest and Restore Host HSTATUS */
- csrrw t4, CSR_HSTATUS, t4
-
/* Save Guest and Restore Host SSTATUS */
- csrrw t5, CSR_SSTATUS, t5
+ csrrw t4, CSR_SSTATUS, t4

/* 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_HSTATUS)(a0)
- REG_S t5, (KVM_ARCH_GUEST_SSTATUS)(a0)
+ REG_S t4, (KVM_ARCH_GUEST_SSTATUS)(a0)

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