From f9ad50eedd179051153ce09345cecab222b482d6 Mon Sep 17 00:00:00 2001 From: Fangyu Yu Date: Wed, 20 Aug 2025 20:59:51 +0800 Subject: [PATCH 1/2] RISC-V: KVM: Write hgatp register with valid mode bits According to the RISC-V Privileged Architecture Spec, when MODE=Bare is selected,software must write zero to the remaining fields of hgatp. We have detected the valid mode supported by the HW before, So using a valid mode to detect how many vmid bits are supported. Fixes: fd7bb4a251df ("RISC-V: KVM: Implement VMID allocator") Reviewed-by: Nutty Liu Reviewed-by: Troy Mitchell Reviewed-by: Guo Ren Signed-off-by: Fangyu Yu Signed-off-by: Linux RISC-V bot --- arch/riscv/kvm/vmid.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/arch/riscv/kvm/vmid.c b/arch/riscv/kvm/vmid.c index 3b426c800480c8..5f33625f407065 100644 --- a/arch/riscv/kvm/vmid.c +++ b/arch/riscv/kvm/vmid.c @@ -14,6 +14,7 @@ #include #include #include +#include #include #include @@ -28,7 +29,7 @@ void __init kvm_riscv_gstage_vmid_detect(void) /* Figure-out number of VMID bits in HW */ old = csr_read(CSR_HGATP); - csr_write(CSR_HGATP, old | HGATP_VMID); + csr_write(CSR_HGATP, (kvm_riscv_gstage_mode << HGATP_MODE_SHIFT) | HGATP_VMID); vmid_bits = csr_read(CSR_HGATP); vmid_bits = (vmid_bits & HGATP_VMID) >> HGATP_VMID_SHIFT; vmid_bits = fls_long(vmid_bits); From eda996cd006e007675ededed5e645741b79d81d4 Mon Sep 17 00:00:00 2001 From: "Guo Ren (Alibaba DAMO Academy)" Date: Wed, 20 Aug 2025 20:59:52 +0800 Subject: [PATCH 2/2] RISC-V KVM: Remove unnecessary HGATP csr_read The HGATP has been set to zero in gstage_mode_detect(), so there is no need to save the old context. Unify the code convention with gstage_mode_detect(). Signed-off-by: Guo Ren (Alibaba DAMO Academy) Signed-off-by: Fangyu Yu Signed-off-by: Linux RISC-V bot --- arch/riscv/kvm/vmid.c | 5 +---- 1 file changed, 1 insertion(+), 4 deletions(-) diff --git a/arch/riscv/kvm/vmid.c b/arch/riscv/kvm/vmid.c index 5f33625f407065..abb1c2bf254234 100644 --- a/arch/riscv/kvm/vmid.c +++ b/arch/riscv/kvm/vmid.c @@ -25,15 +25,12 @@ static DEFINE_SPINLOCK(vmid_lock); void __init kvm_riscv_gstage_vmid_detect(void) { - unsigned long old; - /* Figure-out number of VMID bits in HW */ - old = csr_read(CSR_HGATP); csr_write(CSR_HGATP, (kvm_riscv_gstage_mode << HGATP_MODE_SHIFT) | HGATP_VMID); vmid_bits = csr_read(CSR_HGATP); vmid_bits = (vmid_bits & HGATP_VMID) >> HGATP_VMID_SHIFT; vmid_bits = fls_long(vmid_bits); - csr_write(CSR_HGATP, old); + csr_write(CSR_HGATP, 0); /* We polluted local TLB so flush all guest TLB */ kvm_riscv_local_hfence_gvma_all();