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Message-Id: <20220720011350.1024134-20-sashal@kernel.org>
Date: Tue, 19 Jul 2022 21:13:28 -0400
From: Sasha Levin <sashal@...nel.org>
To: linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc: Josh Poimboeuf <jpoimboe@...nel.org>,
Peter Zijlstra <peterz@...radead.org>,
Borislav Petkov <bp@...e.de>, Sasha Levin <sashal@...nel.org>,
seanjc@...gle.com, pbonzini@...hat.com, tglx@...utronix.de,
mingo@...hat.com, bp@...en8.de, dave.hansen@...ux.intel.com,
x86@...nel.org, kvm@...r.kernel.org
Subject: [PATCH AUTOSEL 5.15 20/42] KVM: VMX: Flatten __vmx_vcpu_run()
From: Josh Poimboeuf <jpoimboe@...nel.org>
[ Upstream commit 8bd200d23ec42d66ccd517a72dd0b9cc6132d2fd ]
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@...nel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Signed-off-by: Borislav Petkov <bp@...e.de>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
arch/x86/kvm/vmx/vmenter.S | 119 ++++++++++++++-----------------------
1 file changed, 46 insertions(+), 73 deletions(-)
diff --git a/arch/x86/kvm/vmx/vmenter.S b/arch/x86/kvm/vmx/vmenter.S
index 435c187927c4..c83163fb2e9c 100644
--- a/arch/x86/kvm/vmx/vmenter.S
+++ b/arch/x86/kvm/vmx/vmenter.S
@@ -30,68 +30,6 @@
.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)
@@ -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 +91,37 @@ 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
+ ENDBR
/* Temporarily save guest's RAX. */
push %_ASM_AX
@@ -185,9 +148,13 @@ 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 +164,7 @@ 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 +183,8 @@ 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 +197,15 @@ 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)
--
2.35.1
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