Re: [PATCH] KVM: RISC-V: reset smstateen CSRs

On Tue, Mar 25, 2025 at 12:01 AM Radim Krčmář rkrcmar@ventanamicro.com wrote:

Hi, I'm sending this early to ventana-sw as we hit the issue in today's slack discussion. I only compile-tested it so far and it will take me a while to trigger a bug and verify the solution.

---8<-- The smstateen CSRs control which stateful features are enabled in VU-mode. SU-mode must properly context switch the state of all enabled features.

Reset the smstateen CSRs, because SU-mode might not know that it must context switch the state. Reset unconditionally as it is shorter and safer, and not that much slower.

Fixes: 81f0f314fec9 ("RISCV: KVM: Add sstateen0 context save/restore") Cc: stable@vger.kernel.org Signed-off-by: Radim Krčmář rkrcmar@ventanamicro.com

How about moving "struct kvm_vcpu_smstateen_csr smstateen" from "struct kvm_vcpu_arch" to "struct kvm_vcpu_csr". This way we will not need an extra "struct kvm_vcpu_smstateen_csr reset_smstateen_csr" in "struct kvm_vcpu_csr".

Regards, Anup

---

arch/riscv/include/asm/kvm_host.h | 3 +++ arch/riscv/kvm/vcpu.c | 4 ++++ 2 files changed, 7 insertions(+)

diff --git a/arch/riscv/include/asm/kvm_host.h b/arch/riscv/include/asm/kvm_host.h index cc33e35cd628..1e9fe3cbecd3 100644 --- a/arch/riscv/include/asm/kvm_host.h +++ b/arch/riscv/include/asm/kvm_host.h @@ -234,6 +234,9 @@ struct kvm_vcpu_arch { /* CPU CSR context upon Guest VCPU reset */ struct kvm_vcpu_csr guest_reset_csr;

•   /* CPU smstateen CSR context upon Guest VCPU reset */
  

•   struct kvm_vcpu_smstateen_csr reset_smstateen_csr;
  

•   /*
     * VCPU interrupts
     *
  

diff --git a/arch/riscv/kvm/vcpu.c b/arch/riscv/kvm/vcpu.c index 60d684c76c58..b11b4027a859 100644 --- a/arch/riscv/kvm/vcpu.c +++ b/arch/riscv/kvm/vcpu.c @@ -57,6 +57,8 @@ static void kvm_riscv_reset_vcpu(struct kvm_vcpu *vcpu) struct kvm_vcpu_csr *reset_csr = &vcpu->arch.guest_reset_csr; struct kvm_cpu_context *cntx = &vcpu->arch.guest_context; struct kvm_cpu_context *reset_cntx = &vcpu->arch.guest_reset_context;

•   struct kvm_vcpu_smstateen_csr *smstateen_csr = &vcpu->arch.smstateen_csr;
  

•   struct kvm_vcpu_smstateen_csr *reset_smstateen_csr = &vcpu->arch.reset_smstateen_csr;
    bool loaded;
  
    /**
  

@@ -73,6 +75,8 @@ static void kvm_riscv_reset_vcpu(struct kvm_vcpu *vcpu)

    memcpy(csr, reset_csr, sizeof(*csr));

•   memcpy(smstateen_csr, reset_smstateen_csr, sizeof(*smstateen_csr));
  

•   spin_lock(&vcpu->arch.reset_cntx_lock);
    memcpy(cntx, reset_cntx, sizeof(*cntx));
    spin_unlock(&vcpu->arch.reset_cntx_lock);
  

-- 2.48.1