Commit 52a9fcbc authored by Sean Christopherson's avatar Sean Christopherson Committed by Paolo Bonzini
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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
3901336e, "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: default avatarPaolo Bonzini <pbonzini@redhat.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: default avatarSean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 4b526de5

arch/x86/kvm/vmx/ops.h

+40 −32
Original line number Diff line number Diff line
@@ -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)

arch/x86/kvm/vmx/vmx.c

+34 −0
Original line number Diff line number Diff line
@@ -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);

/*

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