From 52a9fcbc73a30375cad8d9e7b519e1ad97b0880a Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Fri, 19 Jul 2019 13:41:07 -0700 Subject: [PATCH] KVM: VMX: Optimize VMX instruction error and fault handling Rework the VMX instruction helpers using asm-goto to branch directly to error/fault "handlers" in lieu of using __ex(), i.e. the generic ____kvm_handle_fault_on_reboot(). Branching directly to fault handling code during fixup avoids the extra JMP that is inserted after every VMX instruction when using the generic "fault on reboot" (see commit 3901336ed9887, "x86/kvm: Don't call kvm_spurious_fault() from .fixup"). Opportunistically clean up the helpers so that they all have consistent error handling and messages. Leave the usage of ____kvm_handle_fault_on_reboot() (via __ex()) in kvm_cpu_vmxoff() and nested_vmx_check_vmentry_hw() as is. The VMXOFF case is not a fast path, i.e. the cleanliness of __ex() is worth the JMP, and the extra JMP in nested_vmx_check_vmentry_hw() is unavoidable. Note, VMREAD cannot get the asm-goto treatment as output operands aren't compatible with GCC's asm-goto due to internal compiler restrictions. Acked-by: Paolo Bonzini Cc: Josh Poimboeuf Signed-off-by: Sean Christopherson Signed-off-by: Paolo Bonzini --- arch/x86/kvm/vmx/ops.h | 72 +++++++++++++++++++++++------------------- arch/x86/kvm/vmx/vmx.c | 34 ++++++++++++++++++++ 2 files changed, 74 insertions(+), 32 deletions(-) diff --git a/arch/x86/kvm/vmx/ops.h b/arch/x86/kvm/vmx/ops.h index 2200fb698dd0..79e25d49d4d9 100644 --- a/arch/x86/kvm/vmx/ops.h +++ b/arch/x86/kvm/vmx/ops.h @@ -14,6 +14,12 @@ #define __ex_clear(x, reg) \ ____kvm_handle_fault_on_reboot(x, "xor " reg ", " reg) +void vmwrite_error(unsigned long field, unsigned long value); +void vmclear_error(struct vmcs *vmcs, u64 phys_addr); +void vmptrld_error(struct vmcs *vmcs, u64 phys_addr); +void invvpid_error(unsigned long ext, u16 vpid, gva_t gva); +void invept_error(unsigned long ext, u64 eptp, gpa_t gpa); + static __always_inline void vmcs_check16(unsigned long field) { BUILD_BUG_ON_MSG(__builtin_constant_p(field) && ((field) & 0x6001) == 0x2000, @@ -103,21 +109,39 @@ static __always_inline unsigned long vmcs_readl(unsigned long field) return __vmcs_readl(field); } -static noinline void vmwrite_error(unsigned long field, unsigned long value) -{ - printk(KERN_ERR "vmwrite error: reg %lx value %lx (err %d)\n", - field, value, vmcs_read32(VM_INSTRUCTION_ERROR)); - dump_stack(); -} +#define vmx_asm1(insn, op1, error_args...) \ +do { \ + asm_volatile_goto("1: " __stringify(insn) " %0\n\t" \ + ".byte 0x2e\n\t" /* branch not taken hint */ \ + "jna %l[error]\n\t" \ + _ASM_EXTABLE(1b, %l[fault]) \ + : : op1 : "cc" : error, fault); \ + return; \ +error: \ + insn##_error(error_args); \ + return; \ +fault: \ + kvm_spurious_fault(); \ +} while (0) + +#define vmx_asm2(insn, op1, op2, error_args...) \ +do { \ + asm_volatile_goto("1: " __stringify(insn) " %1, %0\n\t" \ + ".byte 0x2e\n\t" /* branch not taken hint */ \ + "jna %l[error]\n\t" \ + _ASM_EXTABLE(1b, %l[fault]) \ + : : op1, op2 : "cc" : error, fault); \ + return; \ +error: \ + insn##_error(error_args); \ + return; \ +fault: \ + kvm_spurious_fault(); \ +} while (0) static __always_inline void __vmcs_writel(unsigned long field, unsigned long value) { - bool error; - - asm volatile (__ex("vmwrite %2, %1") CC_SET(na) - : CC_OUT(na) (error) : "r"(field), "rm"(value)); - if (unlikely(error)) - vmwrite_error(field, value); + vmx_asm2(vmwrite, "r"(field), "rm"(value), field, value); } static __always_inline void vmcs_write16(unsigned long field, u16 value) @@ -182,28 +206,18 @@ static __always_inline void vmcs_set_bits(unsigned long field, u32 mask) static inline void vmcs_clear(struct vmcs *vmcs) { u64 phys_addr = __pa(vmcs); - bool error; - asm volatile (__ex("vmclear %1") CC_SET(na) - : CC_OUT(na) (error) : "m"(phys_addr)); - if (unlikely(error)) - printk(KERN_ERR "kvm: vmclear fail: %p/%llx\n", - vmcs, phys_addr); + vmx_asm1(vmclear, "m"(phys_addr), vmcs, phys_addr); } static inline void vmcs_load(struct vmcs *vmcs) { u64 phys_addr = __pa(vmcs); - bool error; if (static_branch_unlikely(&enable_evmcs)) return evmcs_load(phys_addr); - asm volatile (__ex("vmptrld %1") CC_SET(na) - : CC_OUT(na) (error) : "m"(phys_addr)); - if (unlikely(error)) - printk(KERN_ERR "kvm: vmptrld %p/%llx failed\n", - vmcs, phys_addr); + vmx_asm1(vmptrld, "m"(phys_addr), vmcs, phys_addr); } static inline void __invvpid(unsigned long ext, u16 vpid, gva_t gva) @@ -213,11 +227,8 @@ static inline void __invvpid(unsigned long ext, u16 vpid, gva_t gva) u64 rsvd : 48; u64 gva; } operand = { vpid, 0, gva }; - bool error; - asm volatile (__ex("invvpid %2, %1") CC_SET(na) - : CC_OUT(na) (error) : "r"(ext), "m"(operand)); - BUG_ON(error); + vmx_asm2(invvpid, "r"(ext), "m"(operand), ext, vpid, gva); } static inline void __invept(unsigned long ext, u64 eptp, gpa_t gpa) @@ -225,11 +236,8 @@ static inline void __invept(unsigned long ext, u64 eptp, gpa_t gpa) struct { u64 eptp, gpa; } operand = {eptp, gpa}; - bool error; - asm volatile (__ex("invept %2, %1") CC_SET(na) - : CC_OUT(na) (error) : "r"(ext), "m"(operand)); - BUG_ON(error); + vmx_asm2(invept, "r"(ext), "m"(operand), ext, eptp, gpa); } static inline bool vpid_sync_vcpu_addr(int vpid, gva_t addr) diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index a7c9922e3905..52c7614b5ecd 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -343,6 +343,40 @@ static __always_inline void vmx_disable_intercept_for_msr(unsigned long *msr_bit void vmx_vmexit(void); +#define vmx_insn_failed(fmt...) \ +do { \ + WARN_ONCE(1, fmt); \ + pr_warn_ratelimited(fmt); \ +} while (0) + +noinline void vmwrite_error(unsigned long field, unsigned long value) +{ + vmx_insn_failed("kvm: vmwrite failed: field=%lx val=%lx err=%d\n", + field, value, vmcs_read32(VM_INSTRUCTION_ERROR)); +} + +noinline void vmclear_error(struct vmcs *vmcs, u64 phys_addr) +{ + vmx_insn_failed("kvm: vmclear failed: %p/%llx\n", vmcs, phys_addr); +} + +noinline void vmptrld_error(struct vmcs *vmcs, u64 phys_addr) +{ + vmx_insn_failed("kvm: vmptrld failed: %p/%llx\n", vmcs, phys_addr); +} + +noinline void invvpid_error(unsigned long ext, u16 vpid, gva_t gva) +{ + vmx_insn_failed("kvm: invvpid failed: ext=0x%lx vpid=%u gva=0x%lx\n", + ext, vpid, gva); +} + +noinline void invept_error(unsigned long ext, u64 eptp, gpa_t gpa) +{ + vmx_insn_failed("kvm: invept failed: ext=0x%lx eptp=%llx gpa=0x%llx\n", + ext, eptp, gpa); +} + static DEFINE_PER_CPU(struct vmcs *, vmxarea); DEFINE_PER_CPU(struct vmcs *, current_vmcs); /*