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From: Paolo Bonzini <pbonzini@redhat.com>
To: linux-kernel@vger.kernel.org, kvm@vger.kernel.org
Cc: Binbin Wu <binbin.wu@linux.intel.com>,
	Uros Bizjak <ubizjak@gmail.com>,
	"Chang S. Bae" <chang.seok.bae@intel.com>,
	Sean Christopherson <seanjc@google.com>
Subject: [PATCH v2 5/7] KVM: SVM: extract RESTORE_*_SPEC_CTRL_BODY out of svm/vmenter.S
Date: Mon, 27 Apr 2026 06:58:46 -0400	[thread overview]
Message-ID: <20260427105848.44865-6-pbonzini@redhat.com> (raw)
In-Reply-To: <20260427105848.44865-1-pbonzini@redhat.com>

Pure code movement, in preparation for using these macros for
VMX as well.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 arch/x86/kvm/svm/vmenter.S | 62 ----------------------------------
 arch/x86/kvm/vmenter.h     | 68 +++++++++++++++++++++++++++++++++++++-
 2 files changed, 67 insertions(+), 63 deletions(-)

diff --git a/arch/x86/kvm/svm/vmenter.S b/arch/x86/kvm/svm/vmenter.S
index 2bc7ecb338a9..f523d9e49839 100644
--- a/arch/x86/kvm/svm/vmenter.S
+++ b/arch/x86/kvm/svm/vmenter.S
@@ -41,35 +41,6 @@
 		"jmp 800f", X86_FEATURE_MSR_SPEC_CTRL, \
 		"", X86_FEATURE_V_SPEC_CTRL
 .endm
-.macro RESTORE_GUEST_SPEC_CTRL_BODY guest_spec_ctrl:req, label:req
-	/*
-	 * SPEC_CTRL handling: if the guest's SPEC_CTRL value differs from the
-	 * host's, write the MSR.  This is kept out-of-line so that the common
-	 * case does not have to jump.
-	 *
-	 * IMPORTANT: To avoid RSB underflow attacks and any other nastiness,
-	 * there must not be any returns or indirect branches between this code
-	 * and vmentry.
-	 */
-#ifdef CONFIG_X86_64
-	mov \guest_spec_ctrl, %rdx
-	cmp PER_CPU_VAR(x86_spec_ctrl_current), %rdx
-	je \label
-	movl %edx, %eax
-	shr $32, %rdx
-#else
-	mov \guest_spec_ctrl, %eax
-	mov PER_CPU_VAR(x86_spec_ctrl_current), %ecx
-	xor %eax, %ecx
-	mov 4 + \guest_spec_ctrl, %edx
-	mov PER_CPU_VAR(x86_spec_ctrl_current + 4), %esi
-	xor %edx, %esi
-	or %esi, %ecx
-	je \label
-#endif
-	mov $MSR_IA32_SPEC_CTRL, %ecx
-	wrmsr
-.endm
 
 .macro RESTORE_HOST_SPEC_CTRL
 	/* No need to do anything if SPEC_CTRL is unset or V_SPEC_CTRL is set */
@@ -77,39 +48,6 @@
 		"jmp 900f", X86_FEATURE_MSR_SPEC_CTRL, \
 		"", X86_FEATURE_V_SPEC_CTRL
 .endm
-.macro RESTORE_HOST_SPEC_CTRL_BODY guest_spec_ctrl:req, enter_flags:req, label:req
-	/* Same for after vmexit.  */
-	mov $MSR_IA32_SPEC_CTRL, %ecx
-
-	/*
-	 * Load the value that the guest had written into MSR_IA32_SPEC_CTRL,
-	 * if it was not intercepted during guest execution.
-	 */
-	testl $KVM_ENTER_SAVE_SPEC_CTRL, \enter_flags
-	jz 998f
-	rdmsr
-	movl %eax, \guest_spec_ctrl
-	movl %edx, 4 + \guest_spec_ctrl
-998:
-	/* Now restore the host value of the MSR if different from the guest's.  */
-#ifdef CONFIG_X86_64
-	mov PER_CPU_VAR(x86_spec_ctrl_current), %rdx
-	cmp \guest_spec_ctrl, %rdx
-	je \label
-	movl %edx, %eax
-	shr $32, %rdx
-#else
-	mov PER_CPU_VAR(x86_spec_ctrl_current), %eax
-	mov \guest_spec_ctrl, %esi
-	xor %eax, %esi
-	mov PER_CPU_VAR(x86_spec_ctrl_current + 4), %edx
-	mov 4 + \guest_spec_ctrl, %edi
-	xor %edx, %edi
-	or %edi, %esi
-	je \label
-#endif
-	wrmsr
-.endm
 
 #define SVM_CLEAR_CPU_BUFFERS \
 	ALTERNATIVE "", __CLEAR_CPU_BUFFERS, X86_FEATURE_CLEAR_CPU_BUF_VM
diff --git a/arch/x86/kvm/vmenter.h b/arch/x86/kvm/vmenter.h
index 29cdae650069..84951e186859 100644
--- a/arch/x86/kvm/vmenter.h
+++ b/arch/x86/kvm/vmenter.h
@@ -6,4 +6,70 @@
 #define KVM_ENTER_SAVE_SPEC_CTRL		BIT(1)
 #define KVM_ENTER_CLEAR_CPU_BUFFERS_FOR_MMIO	BIT(2)
 
-#endif /* __KVM_X86_VMENTER_H */
+#ifdef __ASSEMBLER__
+.macro RESTORE_GUEST_SPEC_CTRL_BODY guest_spec_ctrl:req, label:req
+	/*
+	 * SPEC_CTRL handling: if the guest's SPEC_CTRL value differs from the
+	 * host's, write the MSR.  This is kept out-of-line so that the common
+	 * case does not have to jump.
+	 *
+	 * IMPORTANT: To avoid RSB underflow attacks and any other nastiness,
+	 * there must not be any returns or indirect branches between this code
+	 * and vmentry.
+	 */
+#ifdef CONFIG_X86_64
+	mov \guest_spec_ctrl, %rdx
+	cmp PER_CPU_VAR(x86_spec_ctrl_current), %rdx
+	je \label
+	movl %edx, %eax
+	shr $32, %rdx
+#else
+	mov \guest_spec_ctrl, %eax
+	mov PER_CPU_VAR(x86_spec_ctrl_current), %ecx
+	xor %eax, %ecx
+	mov 4 + \guest_spec_ctrl, %edx
+	mov PER_CPU_VAR(x86_spec_ctrl_current + 4), %esi
+	xor %edx, %esi
+	or %esi, %ecx
+	je \label
+#endif
+	mov $MSR_IA32_SPEC_CTRL, %ecx
+	wrmsr
+.endm
+
+.macro RESTORE_HOST_SPEC_CTRL_BODY guest_spec_ctrl:req, enter_flags:req, label:req
+	/* Same for after vmexit.  */
+	mov $MSR_IA32_SPEC_CTRL, %ecx
+
+	/*
+	 * Load the value that the guest had written into MSR_IA32_SPEC_CTRL,
+	 * if it was not intercepted during guest execution.
+	 */
+	testl $KVM_ENTER_SAVE_SPEC_CTRL, \enter_flags
+	jz 998f
+	rdmsr
+	movl %eax, \guest_spec_ctrl
+	movl %edx, 4 + \guest_spec_ctrl
+998:
+	/* Now restore the host value of the MSR if different from the guest's.  */
+#ifdef CONFIG_X86_64
+	mov PER_CPU_VAR(x86_spec_ctrl_current), %rdx
+	cmp \guest_spec_ctrl, %rdx
+	je \label
+	movl %edx, %eax
+	shr $32, %rdx
+#else
+	mov PER_CPU_VAR(x86_spec_ctrl_current), %eax
+	mov \guest_spec_ctrl, %esi
+	xor %eax, %esi
+	mov PER_CPU_VAR(x86_spec_ctrl_current + 4), %edx
+	mov 4 + \guest_spec_ctrl, %edi
+	xor %edx, %edi
+	or %edi, %esi
+	je \label
+#endif
+	wrmsr
+.endm
+
+#endif /* __ASSEMBLER__ */
+#endif /* __KVM_X86_ENTER_FLAGS_H */
-- 
2.52.0



  parent reply	other threads:[~2026-04-27 10:59 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-04-27 10:58 [PATCH v2 0/7] KVM: VMX/SVM: use the same SPEC_CTRL assembly code Paolo Bonzini
2026-04-27 10:58 ` [PATCH v2 1/7] KVM: VMX: remove regs argument of __vmx_vcpu_run Paolo Bonzini
2026-04-27 10:58 ` [PATCH v2 2/7] KVM: VMX: more cleanups to __vmx_vcpu_run Paolo Bonzini
2026-04-27 10:58 ` [PATCH v2 3/7] KVM: SVM: prepare for making SPEC_CTRL switch common with VMX Paolo Bonzini
2026-04-27 10:58 ` [PATCH v2 4/7] KVM: SVM: adopt the same VMX_RUN_* flags as VMX Paolo Bonzini
2026-04-27 17:51   ` Chang S. Bae
2026-04-27 18:01     ` Paolo Bonzini
2026-04-27 10:58 ` Paolo Bonzini [this message]
2026-04-27 10:58 ` [PATCH v2 6/7] KVM: VMX: switch to RESTORE_GUEST_SPEC_CTRL_BODY Paolo Bonzini
2026-04-27 10:58 ` [PATCH v2 7/7] KVM: VMX: replace vmx_spec_ctrl_restore_host with RESTORE_HOST_SPEC_CTRL_BODY Paolo Bonzini
2026-04-27 17:51   ` Chang S. Bae

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