Compared to an IDT stack frame, a FRED stack frame has extra 16 bytes of information pushed at the regular stack top and 8 bytes of error code _always_ pushed at the regular stack bottom, add VMX_DO_FRED_EVENT_IRQOFF to generate FRED stack frames with event type and vector properly set. Thus, IRQ/NMI can be handled with the existing approach when FRED is enabled. For IRQ handling, general purpose registers are pushed to the stack to form a pt_regs structure, which is then used to call external_interrupt(). As a result, IRQ handling no longer re-enters the noinstr code. Tested-by: Shan Kang <shan.kang@xxxxxxxxx> Signed-off-by: Xin Li <xin3.li@xxxxxxxxx> --- Changes since v8: * Add a new macro VMX_DO_FRED_EVENT_IRQOFF for FRED instead of refactoring VMX_DO_EVENT_IRQOFF (Sean Christopherson). * Do NOT use a trampoline, just LEA+PUSH the return RIP, PUSH the error code, and jump to the FRED kernel entry point for NMI or call external_interrupt() for IRQs (Sean Christopherson). * Call external_interrupt() only when FRED is enabled, and convert the non-FRED handling to external_interrupt() after FRED lands (Sean Christopherson). --- arch/x86/kvm/vmx/vmenter.S | 88 ++++++++++++++++++++++++++++++++++++++ arch/x86/kvm/vmx/vmx.c | 19 ++++++-- 2 files changed, 104 insertions(+), 3 deletions(-) diff --git a/arch/x86/kvm/vmx/vmenter.S b/arch/x86/kvm/vmx/vmenter.S index 07e927d4d099..5ee6a57b59a5 100644 --- a/arch/x86/kvm/vmx/vmenter.S +++ b/arch/x86/kvm/vmx/vmenter.S @@ -2,12 +2,14 @@ #include <linux/linkage.h> #include <asm/asm.h> #include <asm/bitsperlong.h> +#include <asm/fred.h> #include <asm/kvm_vcpu_regs.h> #include <asm/nospec-branch.h> #include <asm/percpu.h> #include <asm/segment.h> #include "kvm-asm-offsets.h" #include "run_flags.h" +#include "../../entry/calling.h" #define WORD_SIZE (BITS_PER_LONG / 8) @@ -31,6 +33,80 @@ #define VCPU_R15 __VCPU_REGS_R15 * WORD_SIZE #endif +#ifdef CONFIG_X86_FRED +.macro VMX_DO_FRED_EVENT_IRQOFF branch_insn branch_target nmi=0 + /* + * Unconditionally create a stack frame, getting the correct RSP on the + * stack (for x86-64) would take two instructions anyways, and RBP can + * be used to restore RSP to make objtool happy (see below). + */ + push %_ASM_BP + mov %_ASM_SP, %_ASM_BP + + /* + * Don't check the FRED stack level, the call stack leading to this + * helper is effectively constant and shallow (relatively speaking). + * + * Emulate the FRED-defined redzone and stack alignment. + */ + sub $(FRED_CONFIG_REDZONE_AMOUNT << 6), %rsp + and $FRED_STACK_FRAME_RSP_MASK, %rsp + + /* + * A FRED stack frame has extra 16 bytes of information pushed at the + * regular stack top compared to an IDT stack frame. + */ + push $0 /* Reserved by FRED, must be 0 */ + push $0 /* FRED event data, 0 for NMI and external interrupts */ + + shl $32, %rdi /* FRED event type and vector */ + .if \nmi + bts $FRED_SSX_NMI_BIT, %rdi /* Set the NMI bit */ + .endif + bts $FRED_SSX_64_BIT_MODE_BIT, %rdi /* Set the 64-bit mode */ + or $__KERNEL_DS, %rdi + push %rdi + push %rbp + pushf + mov $__KERNEL_CS, %rax + push %rax + + /* + * Unlike the IDT event delivery, FRED _always_ pushes an error code + * after pushing the return RIP, thus the CALL instruction CANNOT be + * used here to push the return RIP, otherwise there is no chance to + * push an error code before invoking the IRQ/NMI handler. + * + * Use LEA to get the return RIP and push it, then push an error code. + */ + lea 1f(%rip), %rax + push %rax + push $0 /* FRED error code, 0 for NMI and external interrupts */ + + .if \nmi == 0 + PUSH_REGS + mov %rsp, %rdi + .endif + + \branch_insn \branch_target + + .if \nmi == 0 + POP_REGS + .endif + +1: + /* + * "Restore" RSP from RBP, even though IRET has already unwound RSP to + * the correct value. objtool doesn't know the callee will IRET and, + * without the explicit restore, thinks the stack is getting walloped. + * Using an unwind hint is problematic due to x86-64's dynamic alignment. + */ + mov %_ASM_BP, %_ASM_SP + pop %_ASM_BP + RET +.endm +#endif + .macro VMX_DO_EVENT_IRQOFF call_insn call_target /* * Unconditionally create a stack frame, getting the correct RSP on the @@ -299,6 +375,12 @@ SYM_INNER_LABEL_ALIGN(vmx_vmexit, SYM_L_GLOBAL) SYM_FUNC_END(__vmx_vcpu_run) +#ifdef CONFIG_X86_FRED +SYM_FUNC_START(vmx_do_fred_nmi_irqoff) + VMX_DO_FRED_EVENT_IRQOFF jmp fred_entrypoint_kernel nmi=1 +SYM_FUNC_END(vmx_do_fred_nmi_irqoff) +#endif + SYM_FUNC_START(vmx_do_nmi_irqoff) VMX_DO_EVENT_IRQOFF call asm_exc_nmi_kvm_vmx SYM_FUNC_END(vmx_do_nmi_irqoff) @@ -357,6 +439,12 @@ SYM_FUNC_START(vmread_error_trampoline) SYM_FUNC_END(vmread_error_trampoline) #endif +#ifdef CONFIG_X86_FRED +SYM_FUNC_START(vmx_do_fred_interrupt_irqoff) + VMX_DO_FRED_EVENT_IRQOFF call external_interrupt +SYM_FUNC_END(vmx_do_fred_interrupt_irqoff) +#endif + SYM_FUNC_START(vmx_do_interrupt_irqoff) VMX_DO_EVENT_IRQOFF CALL_NOSPEC _ASM_ARG1 SYM_FUNC_END(vmx_do_interrupt_irqoff) diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index 0ecf4be2c6af..4e90c69a92bf 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -6890,6 +6890,14 @@ static void vmx_apicv_post_state_restore(struct kvm_vcpu *vcpu) memset(vmx->pi_desc.pir, 0, sizeof(vmx->pi_desc.pir)); } +#ifdef CONFIG_X86_FRED +void vmx_do_fred_interrupt_irqoff(unsigned int vector); +void vmx_do_fred_nmi_irqoff(unsigned int vector); +#else +#define vmx_do_fred_interrupt_irqoff(x) BUG() +#define vmx_do_fred_nmi_irqoff(x) BUG() +#endif + void vmx_do_interrupt_irqoff(unsigned long entry); void vmx_do_nmi_irqoff(void); @@ -6932,14 +6940,16 @@ static void handle_external_interrupt_irqoff(struct kvm_vcpu *vcpu) { u32 intr_info = vmx_get_intr_info(vcpu); unsigned int vector = intr_info & INTR_INFO_VECTOR_MASK; - gate_desc *desc = (gate_desc *)host_idt_base + vector; if (KVM_BUG(!is_external_intr(intr_info), vcpu->kvm, "unexpected VM-Exit interrupt info: 0x%x", intr_info)) return; kvm_before_interrupt(vcpu, KVM_HANDLING_IRQ); - vmx_do_interrupt_irqoff(gate_offset(desc)); + if (cpu_feature_enabled(X86_FEATURE_FRED)) + vmx_do_fred_interrupt_irqoff(vector); /* Event type is 0 */ + else + vmx_do_interrupt_irqoff(gate_offset((gate_desc *)host_idt_base + vector)); kvm_after_interrupt(vcpu); vcpu->arch.at_instruction_boundary = true; @@ -7225,7 +7235,10 @@ static noinstr void vmx_vcpu_enter_exit(struct kvm_vcpu *vcpu, if ((u16)vmx->exit_reason.basic == EXIT_REASON_EXCEPTION_NMI && is_nmi(vmx_get_intr_info(vcpu))) { kvm_before_interrupt(vcpu, KVM_HANDLING_NMI); - vmx_do_nmi_irqoff(); + if (cpu_feature_enabled(X86_FEATURE_FRED)) + vmx_do_fred_nmi_irqoff((EVENT_TYPE_NMI << 16) | NMI_VECTOR); + else + vmx_do_nmi_irqoff(); kvm_after_interrupt(vcpu); } -- 2.34.1