6.18-stable review patch. If anyone has any objections, please let me know.
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From: Fangyu Yu fangyu.yu@linux.alibaba.com
[ Upstream commit 974555d6e417974e63444266e495a06d06c23af5 ]
When executing HLV* instructions at the HS mode, a guest page fault may occur when a g-stage page table migration between triggering the virtual instruction exception and executing the HLV* instruction.
This may be a corner case, and one simpler way to handle this is to re-execute the instruction where the virtual instruction exception occurred, and the guest page fault will be automatically handled.
Fixes: b91f0e4cb8a3 ("RISC-V: KVM: Factor-out instruction emulation into separate sources") Signed-off-by: Fangyu Yu fangyu.yu@linux.alibaba.com Reviewed-by: Anup Patel anup@brainfault.org Link: https://lore.kernel.org/r/20251121133543.46822-1-fangyu.yu@linux.alibaba.com Signed-off-by: Anup Patel anup@brainfault.org Signed-off-by: Sasha Levin sashal@kernel.org --- arch/riscv/kvm/vcpu_insn.c | 22 ++++++++++++++++++++++ 1 file changed, 22 insertions(+)
diff --git a/arch/riscv/kvm/vcpu_insn.c b/arch/riscv/kvm/vcpu_insn.c index de1f96ea62251..4d89b94128aea 100644 --- a/arch/riscv/kvm/vcpu_insn.c +++ b/arch/riscv/kvm/vcpu_insn.c @@ -298,6 +298,22 @@ static int system_opcode_insn(struct kvm_vcpu *vcpu, struct kvm_run *run, return (rc <= 0) ? rc : 1; }
+static bool is_load_guest_page_fault(unsigned long scause) +{ + /** + * If a g-stage page fault occurs, the direct approach + * is to let the g-stage page fault handler handle it + * naturally, however, calling the g-stage page fault + * handler here seems rather strange. + * Considering this is a corner case, we can directly + * return to the guest and re-execute the same PC, this + * will trigger a g-stage page fault again and then the + * regular g-stage page fault handler will populate + * g-stage page table. + */ + return (scause == EXC_LOAD_GUEST_PAGE_FAULT); +} + /** * kvm_riscv_vcpu_virtual_insn -- Handle virtual instruction trap * @@ -323,6 +339,8 @@ int kvm_riscv_vcpu_virtual_insn(struct kvm_vcpu *vcpu, struct kvm_run *run, ct->sepc, &utrap); if (utrap.scause) { + if (is_load_guest_page_fault(utrap.scause)) + return 1; utrap.sepc = ct->sepc; kvm_riscv_vcpu_trap_redirect(vcpu, &utrap); return 1; @@ -378,6 +396,8 @@ int kvm_riscv_vcpu_mmio_load(struct kvm_vcpu *vcpu, struct kvm_run *run, insn = kvm_riscv_vcpu_unpriv_read(vcpu, true, ct->sepc, &utrap); if (utrap.scause) { + if (is_load_guest_page_fault(utrap.scause)) + return 1; /* Redirect trap if we failed to read instruction */ utrap.sepc = ct->sepc; kvm_riscv_vcpu_trap_redirect(vcpu, &utrap); @@ -504,6 +524,8 @@ int kvm_riscv_vcpu_mmio_store(struct kvm_vcpu *vcpu, struct kvm_run *run, insn = kvm_riscv_vcpu_unpriv_read(vcpu, true, ct->sepc, &utrap); if (utrap.scause) { + if (is_load_guest_page_fault(utrap.scause)) + return 1; /* Redirect trap if we failed to read instruction */ utrap.sepc = ct->sepc; kvm_riscv_vcpu_trap_redirect(vcpu, &utrap);