[PW_SID:1127876] RISC-V: KVM: fix vcpu vector context handling#2288
[PW_SID:1127876] RISC-V: KVM: fix vcpu vector context handling#2288linux-riscv-bot wants to merge 5 commits into
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setup_smp() calls set_cpu_possible() for CPUs 1..nr_cpu_ids-1 but never for CPU 0 (the boot CPU). x86 handles this via init_cpu_possible(cpumask_of(0)); RISC-V has no equivalent. Without CPU 0 in cpu_possible_mask, rcu_init_one()'s for_each_possible_cpu() loop skips it, leaving rdp->mynode=NULL. rcutree_prepare_cpu() then dereferences NULL and hangs. Exposed on Sophgo SG2042 (64-hart, 4-NUMA) with Linux 7.2-rc3. Cc: stable@vger.kernel.org Fixes: a4166ae ("riscv: Deduplicate code in setup_smp()") Signed-off-by: Paul Sherman <shermanpauldylan@gmail.com> Link: https://patch.msgid.link/20260714223301.5265-1-shermanpauldylan@gmail.com Signed-off-by: Paul Walmsley <pjw@kernel.org>
Refactor riscv_v_start_kernel_context() to drop `is_nested` variable and simplify the logic. This introduces no functional change and works as a preparatory patch for the kernel-mode vector fix. Signed-off-by: Andy Chiu <tchiu@tenstorrent.com> Signed-off-by: Linux RISC-V bot <linux.riscv.bot@gmail.com>
Similar to commit 7137a20 ("arm64/fpsimd: Permit kernel mode NEON with IRQs off"), we are upgrading get/put_cpu_vector_context such that kvm_arch_vcpu_load/put can be safely called under both irq off and regular process context. Also, export both symbols so kvm module can call into it. Signed-off-by: Andy Chiu <tchiu@tenstorrent.com> Signed-off-by: Linux RISC-V bot <linux.riscv.bot@gmail.com>
Running vector workloads like perf + mcf on KVM can result in an
unexpected termination due to a vtype corruption. This happens because
the kernel-mode vector (KMV) misattributes the guest's vcpu context as
the user's context and source from a wrong status.VS.
The simplified call chain that results in this problem is shown as
follow:
__riscv_sys_ioctl()
kvm_arch_vcpu_ioctl_run()
kvm_riscv_vcpu_exit()
kvm_riscv_vcpu_sbi_ecall()
kvm_riscv_vcpu_pmu_ctr_stop()
kvm_vcpu_write_guest()
__copy_to_user()
enter_vector_usercopy()
kernel_vector_begin()
kernel_vector_begin() should use the sstatus.VS from guest's vcpu
context instead of task_pt_reg(current). Also, it should not save
guest's v-reg into the user's context memory.
To resolve this, the vcpu context must be correctly saved when KMV is
serving a guest. However, invoking KVM functions directly from generic
RISC-V architecture code introduces a reverse dependency, breaking
builds when KVM is configured as N or M.
Address this by registering an RCU-protected callback for context
flushing. KVM registers this callback at module initialization and
unregisters it on exit. When KMV starts a kernel context, it can now
safely flush the vector context via the callback.
Fixes: ecd2ada ("riscv: Add support for kernel mode vector")
Signed-off-by: Andy Chiu <tchiu@tenstorrent.com>
Signed-off-by: Linux RISC-V bot <linux.riscv.bot@gmail.com>
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Patch 1: "[v2,1/3] riscv: vector: refactor riscv_v_start_kernel_context" |
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Patch 1: "[v2,1/3] riscv: vector: refactor riscv_v_start_kernel_context" |
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Patch 1: "[v2,1/3] riscv: vector: refactor riscv_v_start_kernel_context" |
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Patch 1: "[v2,1/3] riscv: vector: refactor riscv_v_start_kernel_context" |
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Patch 1: "[v2,1/3] riscv: vector: refactor riscv_v_start_kernel_context" |
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Patch 1: "[v2,1/3] riscv: vector: refactor riscv_v_start_kernel_context" |
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Patch 1: "[v2,1/3] riscv: vector: refactor riscv_v_start_kernel_context" |
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Patch 1: "[v2,1/3] riscv: vector: refactor riscv_v_start_kernel_context" |
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Patch 1: "[v2,1/3] riscv: vector: refactor riscv_v_start_kernel_context" |
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Patch 1: "[v2,1/3] riscv: vector: refactor riscv_v_start_kernel_context" |
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Patch 1: "[v2,1/3] riscv: vector: refactor riscv_v_start_kernel_context" |
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Patch 1: "[v2,1/3] riscv: vector: refactor riscv_v_start_kernel_context" |
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Patch 2: "[v2,2/3] riscv: vector: allow non-preemptible kernel-mode vector with IRQs off" |
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Patch 2: "[v2,2/3] riscv: vector: allow non-preemptible kernel-mode vector with IRQs off" |
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Patch 2: "[v2,2/3] riscv: vector: allow non-preemptible kernel-mode vector with IRQs off" |
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Patch 2: "[v2,2/3] riscv: vector: allow non-preemptible kernel-mode vector with IRQs off" |
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Patch 2: "[v2,2/3] riscv: vector: allow non-preemptible kernel-mode vector with IRQs off" |
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Patch 2: "[v2,2/3] riscv: vector: allow non-preemptible kernel-mode vector with IRQs off" |
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Patch 2: "[v2,2/3] riscv: vector: allow non-preemptible kernel-mode vector with IRQs off" |
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Patch 2: "[v2,2/3] riscv: vector: allow non-preemptible kernel-mode vector with IRQs off" |
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Patch 2: "[v2,2/3] riscv: vector: allow non-preemptible kernel-mode vector with IRQs off" |
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Patch 2: "[v2,2/3] riscv: vector: allow non-preemptible kernel-mode vector with IRQs off" |
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Patch 2: "[v2,2/3] riscv: vector: allow non-preemptible kernel-mode vector with IRQs off" |
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Patch 2: "[v2,2/3] riscv: vector: allow non-preemptible kernel-mode vector with IRQs off" |
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Patch 3: "[v2,3/3] RISC-V: KVM: fix vcpu vector context handling for kernel-mode vector" |
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Patch 3: "[v2,3/3] RISC-V: KVM: fix vcpu vector context handling for kernel-mode vector" |
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Patch 3: "[v2,3/3] RISC-V: KVM: fix vcpu vector context handling for kernel-mode vector" |
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Patch 3: "[v2,3/3] RISC-V: KVM: fix vcpu vector context handling for kernel-mode vector" |
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Patch 3: "[v2,3/3] RISC-V: KVM: fix vcpu vector context handling for kernel-mode vector" |
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Patch 3: "[v2,3/3] RISC-V: KVM: fix vcpu vector context handling for kernel-mode vector" |
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Patch 3: "[v2,3/3] RISC-V: KVM: fix vcpu vector context handling for kernel-mode vector" |
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Patch 3: "[v2,3/3] RISC-V: KVM: fix vcpu vector context handling for kernel-mode vector" |
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Patch 3: "[v2,3/3] RISC-V: KVM: fix vcpu vector context handling for kernel-mode vector" |
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Patch 3: "[v2,3/3] RISC-V: KVM: fix vcpu vector context handling for kernel-mode vector" |
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Patch 3: "[v2,3/3] RISC-V: KVM: fix vcpu vector context handling for kernel-mode vector" |
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Patch 3: "[v2,3/3] RISC-V: KVM: fix vcpu vector context handling for kernel-mode vector" |
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PR for series 1127876 applied to workflow__riscv__fixes
Name: RISC-V: KVM: fix vcpu vector context handling
URL: https://patchwork.kernel.org/project/linux-riscv/list/?series=1127876
Version: 2