In IRQ/NMI induced VM exits, KVM VMX needs to execute the respective handlers, which requires the software to create a FRED stack frame, and use it to invoke the handlers. Add fred_irq_entry_from_kvm() for this job. Export fred_entry_from_kvm() because VMX can be compiled as a module. Suggested-by: Sean Christopherson <seanjc@xxxxxxxxxx> Tested-by: Shan Kang <shan.kang@xxxxxxxxx> Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Signed-off-by: Xin Li <xin3.li@xxxxxxxxx> --- Changes since v10: * Better explain the reason why no need to check current stack level (Paolo Bonzini). Changes since v9: * Shove the whole thing into arch/x86/entry/entry_64_fred.S for invoking external_interrupt() and fred_exc_nmi() (Sean Christopherson). * Correct and improve a few comments (Sean Christopherson). * Merge the two IRQ/NMI asm entries into one as it's fine to invoke noinstr code from regular code (Thomas Gleixner). * Setup the long mode and NMI flags in the augmented SS field of FRED stack frame in C instead of asm (Thomas Gleixner). * Add UNWIND_HINT_{SAVE,RESTORE} to get rid of the warning: "objtool: asm_fred_entry_from_kvm+0x0: unreachable instruction" (Peter Zijlstra). 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/entry/entry_64_fred.S | 76 ++++++++++++++++++++++++++++++++++ arch/x86/entry/entry_fred.c | 14 +++++++ arch/x86/include/asm/fred.h | 18 ++++++++ 3 files changed, 108 insertions(+) diff --git a/arch/x86/entry/entry_64_fred.S b/arch/x86/entry/entry_64_fred.S index d1c2fc4af8ae..9917b4ea1543 100644 --- a/arch/x86/entry/entry_64_fred.S +++ b/arch/x86/entry/entry_64_fred.S @@ -4,7 +4,9 @@ */ #include <asm/asm.h> +#include <asm/export.h> #include <asm/fred.h> +#include <asm/segment.h> #include "calling.h" @@ -54,3 +56,77 @@ SYM_CODE_START_NOALIGN(asm_fred_entrypoint_kernel) FRED_EXIT ERETS SYM_CODE_END(asm_fred_entrypoint_kernel) + +#if IS_ENABLED(CONFIG_KVM_INTEL) +SYM_FUNC_START(asm_fred_entry_from_kvm) + push %rbp + mov %rsp, %rbp + + UNWIND_HINT_SAVE + + /* + * Both IRQ and NMI from VMX can be handled on current task stack + * because there is no need to protect from reentrancy and the call + * stack leading to this helper is effectively constant and shallow + * (relatively speaking). Do the same when FRED is active, i.e., no + * need to check current stack level for a stack switch. + * + * Emulate the FRED-defined redzone and stack alignment. + */ + sub $(FRED_CONFIG_REDZONE_AMOUNT << 6), %rsp + and $FRED_STACK_FRAME_RSP_MASK, %rsp + + /* + * Start to push a FRED stack frame, which is always 64 bytes: + * + * +--------+-----------------+ + * | Bytes | Usage | + * +--------+-----------------+ + * | 63:56 | Reserved | + * | 55:48 | Event Data | + * | 47:40 | SS + Event Info | + * | 39:32 | RSP | + * | 31:24 | RFLAGS | + * | 23:16 | CS + Aux Info | + * | 15:8 | RIP | + * | 7:0 | Error Code | + * +--------+-----------------+ + */ + push $0 /* Reserved, must be 0 */ + push $0 /* Event data, 0 for IRQ/NMI */ + push %rdi /* fred_ss handed in by the caller */ + 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 /* Return RIP */ + push $0 /* Error code, 0 for IRQ/NMI */ + + PUSH_AND_CLEAR_REGS clear_bp=0 unwind_hint=0 + movq %rsp, %rdi /* %rdi -> pt_regs */ + call __fred_entry_from_kvm /* Call the C entry point */ + POP_REGS + ERETS +1: + /* + * Objtool doesn't understand what ERETS does, this hint tells it that + * yes, we'll reach here and with what stack state. A save/restore pair + * isn't strictly needed, but it's the simplest form. + */ + UNWIND_HINT_RESTORE + pop %rbp + RET + +SYM_FUNC_END(asm_fred_entry_from_kvm) +EXPORT_SYMBOL_GPL(asm_fred_entry_from_kvm); +#endif diff --git a/arch/x86/entry/entry_fred.c b/arch/x86/entry/entry_fred.c index 97e2552d6951..4c0398010e04 100644 --- a/arch/x86/entry/entry_fred.c +++ b/arch/x86/entry/entry_fred.c @@ -242,3 +242,17 @@ __visible noinstr void fred_entry_from_kernel(struct pt_regs *regs) return fred_bad_type(regs, error_code); } } + +#if IS_ENABLED(CONFIG_KVM_INTEL) +__visible noinstr void __fred_entry_from_kvm(struct pt_regs *regs) +{ + switch (regs->fred_ss.type) { + case EVENT_TYPE_EXTINT: + return fred_extint(regs); + case EVENT_TYPE_NMI: + return fred_exc_nmi(regs); + default: + WARN_ON_ONCE(1); + } +} +#endif diff --git a/arch/x86/include/asm/fred.h b/arch/x86/include/asm/fred.h index 16a64ffecbf8..2fa9f34e5c95 100644 --- a/arch/x86/include/asm/fred.h +++ b/arch/x86/include/asm/fred.h @@ -9,6 +9,7 @@ #include <linux/const.h> #include <asm/asm.h> +#include <asm/trapnr.h> /* * FRED event return instruction opcodes for ERET{S,U}; supported in @@ -62,12 +63,29 @@ static __always_inline unsigned long fred_event_data(struct pt_regs *regs) void asm_fred_entrypoint_user(void); void asm_fred_entrypoint_kernel(void); +void asm_fred_entry_from_kvm(struct fred_ss); __visible void fred_entry_from_user(struct pt_regs *regs); __visible void fred_entry_from_kernel(struct pt_regs *regs); +__visible void __fred_entry_from_kvm(struct pt_regs *regs); + +/* Can be called from noinstr code, thus __always_inline */ +static __always_inline void fred_entry_from_kvm(unsigned int type, unsigned int vector) +{ + struct fred_ss ss = { + .ss =__KERNEL_DS, + .type = type, + .vector = vector, + .nmi = type == EVENT_TYPE_NMI, + .lm = 1, + }; + + asm_fred_entry_from_kvm(ss); +} #else /* CONFIG_X86_FRED */ static __always_inline unsigned long fred_event_data(struct pt_regs *regs) { return 0; } +static __always_inline void fred_entry_from_kvm(unsigned int type, unsigned int vector) { } #endif /* CONFIG_X86_FRED */ #endif /* !__ASSEMBLY__ */ -- 2.34.1