RISC-V: KVM: Save/restore HSTATUS in C source

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>
Reviewed-by: Atish Patra <atishp@rivosinc.com>
Link: https://lore.kernel.org/r/20241020194734.58686-3-apatel@ventanamicro.com
Signed-off-by: Anup Patel <anup@brainfault.org>

diff --git a/arch/riscv/kvm/vcpu.c b/arch/riscv/kvm/vcpu.c
index e8ffb34568988665aaf2e2fc3c546c5654e5a2f4..c9933ea170f40f369a57c13b8cd38bcf80f88a51 100644 (file)
--- a/arch/riscv/kvm/vcpu.c
+++ b/arch/riscv/kvm/vcpu.c
@@ -727,9 +727,18 @@ 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 0c26189aa01cf5b0ca5c6ef6ddbaa70153f3132c..f83643c4fdb9031f10ef18bd11f17f2a80887a4c 100644 (file)
--- 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)