KVM: VMX: Flatten __vmx_vcpu_run()

commit 8bd200d23ec42d66ccd517a72dd0b9cc6132d2fd upstream.

Move the vmx_vm{enter,exit}() functionality into __vmx_vcpu_run().  This
will make it easier to do the spec_ctrl handling before the first RET.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
[cascardo: remove ENDBR]
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/x86/kvm/vmx/vmenter.S b/arch/x86/kvm/vmx/vmenter.S
index 435c187..cd1cd51 100644 (file)
--- a/arch/x86/kvm/vmx/vmenter.S
+++ b/arch/x86/kvm/vmx/vmenter.S
@@ -31,68 +31,6 @@
 .section .noinstr.text, "ax"
 
 /**
- * vmx_vmenter - VM-Enter the current loaded VMCS
- *
- * %RFLAGS.ZF: !VMCS.LAUNCHED, i.e. controls VMLAUNCH vs. VMRESUME
- *
- * Returns:
- *     %RFLAGS.CF is set on VM-Fail Invalid
- *     %RFLAGS.ZF is set on VM-Fail Valid
- *     %RFLAGS.{CF,ZF} are cleared on VM-Success, i.e. VM-Exit
- *
- * Note that VMRESUME/VMLAUNCH fall-through and return directly if
- * they VM-Fail, whereas a successful VM-Enter + VM-Exit will jump
- * to vmx_vmexit.
- */
-SYM_FUNC_START_LOCAL(vmx_vmenter)
-       /* EFLAGS.ZF is set if VMCS.LAUNCHED == 0 */
-       je 2f
-
-1:     vmresume
-       RET
-
-2:     vmlaunch
-       RET
-
-3:     cmpb $0, kvm_rebooting
-       je 4f
-       RET
-4:     ud2
-
-       _ASM_EXTABLE(1b, 3b)
-       _ASM_EXTABLE(2b, 3b)
-
-SYM_FUNC_END(vmx_vmenter)
-
-/**
- * vmx_vmexit - Handle a VMX VM-Exit
- *
- * Returns:
- *     %RFLAGS.{CF,ZF} are cleared on VM-Success, i.e. VM-Exit
- *
- * This is vmx_vmenter's partner in crime.  On a VM-Exit, control will jump
- * here after hardware loads the host's state, i.e. this is the destination
- * referred to by VMCS.HOST_RIP.
- */
-SYM_FUNC_START(vmx_vmexit)
-#ifdef CONFIG_RETPOLINE
-       ALTERNATIVE "jmp .Lvmexit_skip_rsb", "", X86_FEATURE_RETPOLINE
-       /* Preserve guest's RAX, it's used to stuff the RSB. */
-       push %_ASM_AX
-
-       /* IMPORTANT: Stuff the RSB immediately after VM-Exit, before RET! */
-       FILL_RETURN_BUFFER %_ASM_AX, RSB_CLEAR_LOOPS, X86_FEATURE_RETPOLINE
-
-       /* Clear RFLAGS.CF and RFLAGS.ZF to preserve VM-Exit, i.e. !VM-Fail. */
-       or $1, %_ASM_AX
-
-       pop %_ASM_AX
-.Lvmexit_skip_rsb:
-#endif
-       RET
-SYM_FUNC_END(vmx_vmexit)
-
-/**
  * __vmx_vcpu_run - Run a vCPU via a transition to VMX guest mode
  * @vmx:       struct vcpu_vmx * (forwarded to vmx_update_host_rsp)
  * @regs:      unsigned long * (to guest registers)
@@ -124,8 +62,7 @@ SYM_FUNC_START(__vmx_vcpu_run)
        /* Copy @launched to BL, _ASM_ARG3 is volatile. */
        mov %_ASM_ARG3B, %bl
 
-       /* Adjust RSP to account for the CALL to vmx_vmenter(). */
-       lea -WORD_SIZE(%_ASM_SP), %_ASM_ARG2
+       lea (%_ASM_SP), %_ASM_ARG2
        call vmx_update_host_rsp
 
        /* Load @regs to RAX. */
@@ -154,11 +91,36 @@ SYM_FUNC_START(__vmx_vcpu_run)
        /* Load guest RAX.  This kills the @regs pointer! */
        mov VCPU_RAX(%_ASM_AX), %_ASM_AX
 
-       /* Enter guest mode */
-       call vmx_vmenter
+       /* Check EFLAGS.ZF from 'testb' above */
+       je .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)
 
-       /* Jump on VM-Fail. */
-       jbe 2f
+SYM_INNER_LABEL(vmx_vmexit, SYM_L_GLOBAL)
+
+       /* Restore unwind state from before the VMRESUME/VMLAUNCH. */
+       UNWIND_HINT_RESTORE
 
        /* Temporarily save guest's RAX. */
        push %_ASM_AX
@@ -185,9 +147,13 @@ SYM_FUNC_START(__vmx_vcpu_run)
        mov %r15, VCPU_R15(%_ASM_AX)
 #endif
 
+       /* IMPORTANT: RSB must be stuffed before the first return. */
+       FILL_RETURN_BUFFER %_ASM_BX, RSB_CLEAR_LOOPS, X86_FEATURE_RETPOLINE
+
        /* Clear RAX to indicate VM-Exit (as opposed to VM-Fail). */
        xor %eax, %eax
 
+.Lclear_regs:
        /*
         * Clear all general purpose registers except RSP and RAX to prevent
         * speculative use of the guest's values, even those that are reloaded
@@ -197,7 +163,7 @@ SYM_FUNC_START(__vmx_vcpu_run)
         * free.  RSP and RAX are exempt as RSP is restored by hardware during
         * VM-Exit and RAX is explicitly loaded with 0 or 1 to return VM-Fail.
         */
-1:     xor %ecx, %ecx
+       xor %ecx, %ecx
        xor %edx, %edx
        xor %ebx, %ebx
        xor %ebp, %ebp
@@ -216,8 +182,8 @@ SYM_FUNC_START(__vmx_vcpu_run)
 
        /* "POP" @regs. */
        add $WORD_SIZE, %_ASM_SP
-       pop %_ASM_BX
 
+       pop %_ASM_BX
 #ifdef CONFIG_X86_64
        pop %r12
        pop %r13
@@ -230,9 +196,15 @@ SYM_FUNC_START(__vmx_vcpu_run)
        pop %_ASM_BP
        RET
 
-       /* VM-Fail.  Out-of-line to avoid a taken Jcc after VM-Exit. */
-2:     mov $1, %eax
-       jmp 1b
+.Lfixup:
+       cmpb $0, kvm_rebooting
+       jne .Lvmfail
+       ud2
+.Lvmfail:
+       /* VM-Fail: set return value to 1 */
+       mov $1, %eax
+       jmp .Lclear_regs
+
 SYM_FUNC_END(__vmx_vcpu_run)