From: Josh Poimboeuf <jpoimboe@kernel.org>
Date: Tue, 14 Jun 2022 23:16:12 +0200
Subject: KVM: VMX: Convert launched argument to flags
Git-commit: bb06650634d3552c0f8557e9d16aa1a408040e28
Patch-mainline: v5.19-rc7
References: bsc#1199657 CVE-2022-29900 CVE-2022-29901

Convert __vmx_vcpu_run()'s 'launched' argument to 'flags', in
preparation for doing SPEC_CTRL handling immediately after vmexit, which
will need another flag.

This is much easier than adding a fourth argument, because this code
supports both 32-bit and 64-bit, and the fourth argument on 32-bit would
have to be pushed on the stack.

Note that __vmx_vcpu_run_flags() is called outside of the noinstr
critical section because it will soon start calling potentially
traceable functions.

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/nested.c    |    2 +-
 arch/x86/kvm/vmx/run_flags.h |    7 +++++++
 arch/x86/kvm/vmx/vmenter.S   |    9 +++++----
 arch/x86/kvm/vmx/vmx.c       |   17 ++++++++++++++---
 arch/x86/kvm/vmx/vmx.h       |    5 ++++-
 5 files changed, 31 insertions(+), 9 deletions(-)

--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -3056,7 +3056,7 @@ static int nested_vmx_check_vmentry_hw(s
 	}
 
 	vm_fail = __vmx_vcpu_run(vmx, (unsigned long *)&vcpu->arch.regs,
-				 vmx->loaded_vmcs->launched);
+				 __vmx_vcpu_run_flags(vmx));
 
 	if (vmx->msr_autoload.host.nr)
 		vmcs_write32(VM_EXIT_MSR_LOAD_COUNT, vmx->msr_autoload.host.nr);
--- /dev/null
+++ b/arch/x86/kvm/vmx/run_flags.h
@@ -0,0 +1,7 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __KVM_X86_VMX_RUN_FLAGS_H
+#define __KVM_X86_VMX_RUN_FLAGS_H
+
+#define VMX_RUN_VMRESUME	(1 << 0)
+
+#endif /* __KVM_X86_VMX_RUN_FLAGS_H */
--- a/arch/x86/kvm/vmx/vmenter.S
+++ b/arch/x86/kvm/vmx/vmenter.S
@@ -5,6 +5,7 @@
 #include <asm/kvm_vcpu_regs.h>
 #include <asm/nospec-branch.h>
 #include <asm/segment.h>
+#include "run_flags.h"
 
 #define WORD_SIZE (BITS_PER_LONG / 8)
 
@@ -34,7 +35,7 @@
  * __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)
- * @launched:	%true if the VMCS has been launched
+ * @flags:	VMX_RUN_VMRESUME: use VMRESUME instead of VMLAUNCH
  *
  * Returns:
  *	0 on VM-Exit, 1 on VM-Fail
@@ -59,7 +60,7 @@ SYM_FUNC_START(__vmx_vcpu_run)
 	 */
 	push %_ASM_ARG2
 
-	/* Copy @launched to BL, _ASM_ARG3 is volatile. */
+	/* Copy @flags to BL, _ASM_ARG3 is volatile. */
 	mov %_ASM_ARG3B, %bl
 
 	lea (%_ASM_SP), %_ASM_ARG2
@@ -69,7 +70,7 @@ SYM_FUNC_START(__vmx_vcpu_run)
 	mov (%_ASM_SP), %_ASM_AX
 
 	/* Check if vmlaunch or vmresume is needed */
-	testb %bl, %bl
+	testb $VMX_RUN_VMRESUME, %bl
 
 	/* Load guest registers.  Don't clobber flags. */
 	mov VCPU_RCX(%_ASM_AX), %_ASM_CX
@@ -92,7 +93,7 @@ SYM_FUNC_START(__vmx_vcpu_run)
 	mov VCPU_RAX(%_ASM_AX), %_ASM_AX
 
 	/* Check EFLAGS.ZF from 'testb' above */
-	je .Lvmlaunch
+	jz .Lvmlaunch
 
 	/*
 	 * After a successful VMRESUME/VMLAUNCH, control flow "magically"
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -835,6 +835,16 @@ static bool msr_write_intercepted(struct
 					 MSR_IA32_SPEC_CTRL);
 }
 
+unsigned int __vmx_vcpu_run_flags(struct vcpu_vmx *vmx)
+{
+	unsigned int flags = 0;
+
+	if (vmx->loaded_vmcs->launched)
+		flags |= VMX_RUN_VMRESUME;
+
+	return flags;
+}
+
 static void clear_atomic_switch_msr_special(struct vcpu_vmx *vmx,
 		unsigned long entry, unsigned long exit)
 {
@@ -6638,7 +6648,8 @@ static fastpath_t vmx_exit_handlers_fast
 }
 
 static noinstr void vmx_vcpu_enter_exit(struct kvm_vcpu *vcpu,
-					struct vcpu_vmx *vmx)
+					struct vcpu_vmx *vmx,
+					unsigned long flags)
 {
 	kvm_guest_enter_irqoff();
 
@@ -6657,7 +6668,7 @@ static noinstr void vmx_vcpu_enter_exit(
 		native_write_cr2(vcpu->arch.cr2);
 
 	vmx->fail = __vmx_vcpu_run(vmx, (unsigned long *)&vcpu->arch.regs,
-				   vmx->loaded_vmcs->launched);
+				   flags);
 
 	vcpu->arch.cr2 = native_read_cr2();
 
@@ -6741,7 +6752,7 @@ static fastpath_t vmx_vcpu_run(struct kv
 	x86_spec_ctrl_set_guest(vmx->spec_ctrl, 0);
 
 	/* The actual VMENTER/EXIT is in the .noinstr.text section. */
-	vmx_vcpu_enter_exit(vcpu, vmx);
+	vmx_vcpu_enter_exit(vcpu, vmx, __vmx_vcpu_run_flags(vmx));
 
 	/*
 	 * We do not use IBRS in the kernel. If this vCPU has used the
--- a/arch/x86/kvm/vmx/vmx.h
+++ b/arch/x86/kvm/vmx/vmx.h
@@ -13,6 +13,7 @@
 #include "vmcs.h"
 #include "vmx_ops.h"
 #include "cpuid.h"
+#include "run_flags.h"
 
 #define MSR_TYPE_R	1
 #define MSR_TYPE_W	2
@@ -383,7 +384,9 @@ void vmx_set_virtual_apic_mode(struct kv
 struct vmx_uret_msr *vmx_find_uret_msr(struct vcpu_vmx *vmx, u32 msr);
 void pt_update_intercept_for_msr(struct kvm_vcpu *vcpu);
 void vmx_update_host_rsp(struct vcpu_vmx *vmx, unsigned long host_rsp);
-bool __vmx_vcpu_run(struct vcpu_vmx *vmx, unsigned long *regs, bool launched);
+unsigned int __vmx_vcpu_run_flags(struct vcpu_vmx *vmx);
+bool __vmx_vcpu_run(struct vcpu_vmx *vmx, unsigned long *regs,
+		    unsigned int flags);
 int vmx_find_loadstore_msr_slot(struct vmx_msrs *m, u32 msr);
 void vmx_ept_load_pdptrs(struct kvm_vcpu *vcpu);