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-rw-r--r--arch/x86/kvm/vmx/vmenter.S352
1 files changed, 352 insertions, 0 deletions
diff --git a/arch/x86/kvm/vmx/vmenter.S b/arch/x86/kvm/vmx/vmenter.S
new file mode 100644
index 000000000..0b5db4de4
--- /dev/null
+++ b/arch/x86/kvm/vmx/vmenter.S
@@ -0,0 +1,352 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#include <linux/linkage.h>
+#include <asm/asm.h>
+#include <asm/bitsperlong.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"
+
+#define WORD_SIZE (BITS_PER_LONG / 8)
+
+#define VCPU_RAX __VCPU_REGS_RAX * WORD_SIZE
+#define VCPU_RCX __VCPU_REGS_RCX * WORD_SIZE
+#define VCPU_RDX __VCPU_REGS_RDX * WORD_SIZE
+#define VCPU_RBX __VCPU_REGS_RBX * WORD_SIZE
+/* Intentionally omit RSP as it's context switched by hardware */
+#define VCPU_RBP __VCPU_REGS_RBP * WORD_SIZE
+#define VCPU_RSI __VCPU_REGS_RSI * WORD_SIZE
+#define VCPU_RDI __VCPU_REGS_RDI * WORD_SIZE
+
+#ifdef CONFIG_X86_64
+#define VCPU_R8 __VCPU_REGS_R8 * WORD_SIZE
+#define VCPU_R9 __VCPU_REGS_R9 * WORD_SIZE
+#define VCPU_R10 __VCPU_REGS_R10 * WORD_SIZE
+#define VCPU_R11 __VCPU_REGS_R11 * WORD_SIZE
+#define VCPU_R12 __VCPU_REGS_R12 * WORD_SIZE
+#define VCPU_R13 __VCPU_REGS_R13 * WORD_SIZE
+#define VCPU_R14 __VCPU_REGS_R14 * WORD_SIZE
+#define VCPU_R15 __VCPU_REGS_R15 * WORD_SIZE
+#endif
+
+.section .noinstr.text, "ax"
+
+/**
+ * __vmx_vcpu_run - Run a vCPU via a transition to VMX guest mode
+ * @vmx: struct vcpu_vmx *
+ * @regs: unsigned long * (to guest registers)
+ * @flags: VMX_RUN_VMRESUME: use VMRESUME instead of VMLAUNCH
+ * VMX_RUN_SAVE_SPEC_CTRL: save guest SPEC_CTRL into vmx->spec_ctrl
+ *
+ * Returns:
+ * 0 on VM-Exit, 1 on VM-Fail
+ */
+SYM_FUNC_START(__vmx_vcpu_run)
+ push %_ASM_BP
+ mov %_ASM_SP, %_ASM_BP
+#ifdef CONFIG_X86_64
+ push %r15
+ push %r14
+ push %r13
+ push %r12
+#else
+ push %edi
+ push %esi
+#endif
+ push %_ASM_BX
+
+ /* Save @vmx for SPEC_CTRL handling */
+ push %_ASM_ARG1
+
+ /* Save @flags for SPEC_CTRL handling */
+ push %_ASM_ARG3
+
+ /*
+ * Save @regs, _ASM_ARG2 may be modified by vmx_update_host_rsp() and
+ * @regs is needed after VM-Exit to save the guest's register values.
+ */
+ push %_ASM_ARG2
+
+ /* Copy @flags to BL, _ASM_ARG3 is volatile. */
+ mov %_ASM_ARG3B, %bl
+
+ lea (%_ASM_SP), %_ASM_ARG2
+ call vmx_update_host_rsp
+
+ ALTERNATIVE "jmp .Lspec_ctrl_done", "", X86_FEATURE_MSR_SPEC_CTRL
+
+ /*
+ * SPEC_CTRL handling: if the guest's SPEC_CTRL value differs from the
+ * host's, write the MSR.
+ *
+ * IMPORTANT: To avoid RSB underflow attacks and any other nastiness,
+ * there must not be any returns or indirect branches between this code
+ * and vmentry.
+ */
+ mov 2*WORD_SIZE(%_ASM_SP), %_ASM_DI
+ movl VMX_spec_ctrl(%_ASM_DI), %edi
+ movl PER_CPU_VAR(x86_spec_ctrl_current), %esi
+ cmp %edi, %esi
+ je .Lspec_ctrl_done
+ mov $MSR_IA32_SPEC_CTRL, %ecx
+ xor %edx, %edx
+ mov %edi, %eax
+ wrmsr
+
+.Lspec_ctrl_done:
+
+ /*
+ * Since vmentry is serializing on affected CPUs, there's no need for
+ * an LFENCE to stop speculation from skipping the wrmsr.
+ */
+
+ /* Load @regs to RAX. */
+ mov (%_ASM_SP), %_ASM_AX
+
+ /* Check if vmlaunch or vmresume is needed */
+ testb $VMX_RUN_VMRESUME, %bl
+
+ /* Load guest registers. Don't clobber flags. */
+ mov VCPU_RCX(%_ASM_AX), %_ASM_CX
+ mov VCPU_RDX(%_ASM_AX), %_ASM_DX
+ mov VCPU_RBX(%_ASM_AX), %_ASM_BX
+ mov VCPU_RBP(%_ASM_AX), %_ASM_BP
+ mov VCPU_RSI(%_ASM_AX), %_ASM_SI
+ mov VCPU_RDI(%_ASM_AX), %_ASM_DI
+#ifdef CONFIG_X86_64
+ mov VCPU_R8 (%_ASM_AX), %r8
+ mov VCPU_R9 (%_ASM_AX), %r9
+ mov VCPU_R10(%_ASM_AX), %r10
+ mov VCPU_R11(%_ASM_AX), %r11
+ mov VCPU_R12(%_ASM_AX), %r12
+ mov VCPU_R13(%_ASM_AX), %r13
+ mov VCPU_R14(%_ASM_AX), %r14
+ mov VCPU_R15(%_ASM_AX), %r15
+#endif
+ /* Load guest RAX. This kills the @regs pointer! */
+ mov VCPU_RAX(%_ASM_AX), %_ASM_AX
+
+ /* Check EFLAGS.ZF from 'testb' above */
+ jz .Lvmlaunch
+
+ /*
+ * After a successful VMRESUME/VMLAUNCH, control flow "magically"
+ * resumes below at 'vmx_vmexit' due to the VMCS HOST_RIP setting.
+ * So this isn't a typical function and objtool needs to be told to
+ * save the unwind state here and restore it below.
+ */
+ UNWIND_HINT_SAVE
+
+/*
+ * If VMRESUME/VMLAUNCH and corresponding vmexit succeed, execution resumes at
+ * the 'vmx_vmexit' label below.
+ */
+.Lvmresume:
+ vmresume
+ jmp .Lvmfail
+
+.Lvmlaunch:
+ vmlaunch
+ jmp .Lvmfail
+
+ _ASM_EXTABLE(.Lvmresume, .Lfixup)
+ _ASM_EXTABLE(.Lvmlaunch, .Lfixup)
+
+SYM_INNER_LABEL(vmx_vmexit, SYM_L_GLOBAL)
+
+ /* Restore unwind state from before the VMRESUME/VMLAUNCH. */
+ UNWIND_HINT_RESTORE
+ ENDBR
+
+ /* Temporarily save guest's RAX. */
+ push %_ASM_AX
+
+ /* Reload @regs to RAX. */
+ mov WORD_SIZE(%_ASM_SP), %_ASM_AX
+
+ /* Save all guest registers, including RAX from the stack */
+ pop VCPU_RAX(%_ASM_AX)
+ mov %_ASM_CX, VCPU_RCX(%_ASM_AX)
+ mov %_ASM_DX, VCPU_RDX(%_ASM_AX)
+ mov %_ASM_BX, VCPU_RBX(%_ASM_AX)
+ mov %_ASM_BP, VCPU_RBP(%_ASM_AX)
+ mov %_ASM_SI, VCPU_RSI(%_ASM_AX)
+ mov %_ASM_DI, VCPU_RDI(%_ASM_AX)
+#ifdef CONFIG_X86_64
+ mov %r8, VCPU_R8 (%_ASM_AX)
+ mov %r9, VCPU_R9 (%_ASM_AX)
+ mov %r10, VCPU_R10(%_ASM_AX)
+ mov %r11, VCPU_R11(%_ASM_AX)
+ mov %r12, VCPU_R12(%_ASM_AX)
+ mov %r13, VCPU_R13(%_ASM_AX)
+ mov %r14, VCPU_R14(%_ASM_AX)
+ mov %r15, VCPU_R15(%_ASM_AX)
+#endif
+
+ /* Clear return value to indicate VM-Exit (as opposed to VM-Fail). */
+ xor %ebx, %ebx
+
+.Lclear_regs:
+ /* Discard @regs. The register is irrelevant, it just can't be RBX. */
+ pop %_ASM_AX
+
+ /*
+ * Clear all general purpose registers except RSP and RBX to prevent
+ * speculative use of the guest's values, even those that are reloaded
+ * via the stack. In theory, an L1 cache miss when restoring registers
+ * could lead to speculative execution with the guest's values.
+ * Zeroing XORs are dirt cheap, i.e. the extra paranoia is essentially
+ * free. RSP and RBX are exempt as RSP is restored by hardware during
+ * VM-Exit and RBX is explicitly loaded with 0 or 1 to hold the return
+ * value.
+ */
+ xor %eax, %eax
+ xor %ecx, %ecx
+ xor %edx, %edx
+ xor %ebp, %ebp
+ xor %esi, %esi
+ xor %edi, %edi
+#ifdef CONFIG_X86_64
+ xor %r8d, %r8d
+ xor %r9d, %r9d
+ xor %r10d, %r10d
+ xor %r11d, %r11d
+ xor %r12d, %r12d
+ xor %r13d, %r13d
+ xor %r14d, %r14d
+ xor %r15d, %r15d
+#endif
+
+ /*
+ * IMPORTANT: RSB filling and SPEC_CTRL handling must be done before
+ * the first unbalanced RET after vmexit!
+ *
+ * For retpoline or IBRS, RSB filling is needed to prevent poisoned RSB
+ * entries and (in some cases) RSB underflow.
+ *
+ * eIBRS has its own protection against poisoned RSB, so it doesn't
+ * need the RSB filling sequence. But it does need to be enabled, and a
+ * single call to retire, before the first unbalanced RET.
+ */
+
+ FILL_RETURN_BUFFER %_ASM_CX, RSB_CLEAR_LOOPS, X86_FEATURE_RSB_VMEXIT,\
+ X86_FEATURE_RSB_VMEXIT_LITE
+
+ pop %_ASM_ARG2 /* @flags */
+ pop %_ASM_ARG1 /* @vmx */
+
+ call vmx_spec_ctrl_restore_host
+
+ /* Put return value in AX */
+ mov %_ASM_BX, %_ASM_AX
+
+ pop %_ASM_BX
+#ifdef CONFIG_X86_64
+ pop %r12
+ pop %r13
+ pop %r14
+ pop %r15
+#else
+ pop %esi
+ pop %edi
+#endif
+ pop %_ASM_BP
+ RET
+
+.Lfixup:
+ cmpb $0, kvm_rebooting
+ jne .Lvmfail
+ ud2
+.Lvmfail:
+ /* VM-Fail: set return value to 1 */
+ mov $1, %_ASM_BX
+ jmp .Lclear_regs
+
+SYM_FUNC_END(__vmx_vcpu_run)
+
+
+.section .text, "ax"
+
+/**
+ * vmread_error_trampoline - Trampoline from inline asm to vmread_error()
+ * @field: VMCS field encoding that failed
+ * @fault: %true if the VMREAD faulted, %false if it failed
+
+ * Save and restore volatile registers across a call to vmread_error(). Note,
+ * all parameters are passed on the stack.
+ */
+SYM_FUNC_START(vmread_error_trampoline)
+ push %_ASM_BP
+ mov %_ASM_SP, %_ASM_BP
+
+ push %_ASM_AX
+ push %_ASM_CX
+ push %_ASM_DX
+#ifdef CONFIG_X86_64
+ push %rdi
+ push %rsi
+ push %r8
+ push %r9
+ push %r10
+ push %r11
+#endif
+
+ /* Load @field and @fault to arg1 and arg2 respectively. */
+ mov 3*WORD_SIZE(%_ASM_BP), %_ASM_ARG2
+ mov 2*WORD_SIZE(%_ASM_BP), %_ASM_ARG1
+
+ call vmread_error
+
+ /* Zero out @fault, which will be popped into the result register. */
+ _ASM_MOV $0, 3*WORD_SIZE(%_ASM_BP)
+
+#ifdef CONFIG_X86_64
+ pop %r11
+ pop %r10
+ pop %r9
+ pop %r8
+ pop %rsi
+ pop %rdi
+#endif
+ pop %_ASM_DX
+ pop %_ASM_CX
+ pop %_ASM_AX
+ pop %_ASM_BP
+
+ RET
+SYM_FUNC_END(vmread_error_trampoline)
+
+SYM_FUNC_START(vmx_do_interrupt_nmi_irqoff)
+ /*
+ * 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
+
+#ifdef CONFIG_X86_64
+ /*
+ * Align RSP to a 16-byte boundary (to emulate CPU behavior) before
+ * creating the synthetic interrupt stack frame for the IRQ/NMI.
+ */
+ and $-16, %rsp
+ push $__KERNEL_DS
+ push %rbp
+#endif
+ pushf
+ push $__KERNEL_CS
+ CALL_NOSPEC _ASM_ARG1
+
+ /*
+ * "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
+SYM_FUNC_END(vmx_do_interrupt_nmi_irqoff)