From: Josh Poimboeuf <jpoimboe@kernel.org>
Date: Tue, 14 Jun 2022 23:16:11 +0200
Subject: KVM: VMX: Flatten __vmx_vcpu_run()
Git-commit: 8bd200d23ec42d66ccd517a72dd0b9cc6132d2fd
Patch-mainline: v5.19-rc7
References: bsc#1199657 CVE-2022-29900 CVE-2022-29901
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>
---
arch/x86/kvm/vmx/vmenter.S | 110 +++++++++++++--------------------------------
1 file changed, 33 insertions(+), 77 deletions(-)
--- a/arch/x86/kvm/vmx/vmenter.S
+++ b/arch/x86/kvm/vmx/vmenter.S
@@ -30,72 +30,6 @@
.text
/**
- * 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.
- */
-ENTRY(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
-
- .pushsection .fixup, "ax"
-5: jmp 3b
- .popsection
-
- _ASM_EXTABLE(1b, 5b)
- _ASM_EXTABLE(2b, 5b)
-
-ENDPROC(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.
- */
-ENTRY(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
-ENDPROC(vmx_vmexit)
-
-/**
* __vmx_vcpu_run - Run a vCPU via a transition to VMX guest mode
* @vmx: struct vcpu_vmx *
* @regs: unsigned long * (to guest registers)
@@ -127,8 +61,7 @@ ENTRY(__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. */
@@ -157,11 +90,25 @@ ENTRY(__vmx_vcpu_run)
/* Load guest RAX. This kills the vmx_vcpu pointer! */
mov VCPU_RAX(%_ASM_AX), %_ASM_AX
- /* Enter guest mode */
- call vmx_vmenter
+ /* Check EFLAGS.ZF from 'testb' above */
+ je .Lvmlaunch
+
+/*
+ * 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)
/* Temporarily save guest's RAX. */
push %_ASM_AX
@@ -188,9 +135,13 @@ ENTRY(__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
@@ -200,7 +151,7 @@ ENTRY(__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 %ebx, %ebx
+ xor %ebx, %ebx
xor %ecx, %ecx
xor %edx, %edx
xor %esi, %esi
@@ -219,8 +170,8 @@ ENTRY(__vmx_vcpu_run)
/* "POP" @regs. */
add $WORD_SIZE, %_ASM_SP
- pop %_ASM_BX
+ pop %_ASM_BX
#ifdef CONFIG_X86_64
pop %r12
pop %r13
@@ -233,7 +184,12 @@ ENTRY(__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
ENDPROC(__vmx_vcpu_run)