[PATCH v2 3/7] KVM: SVM: prepare for making SPEC_CTRL switch common with VMX

Paolo Bonzini
2026-04-27T10:58:59Z

Remove the local labels and restrict RESTORE_*_BODY to just
the restore code itself. Since the alternatives are different
between VMX and SVM, having labels in the per-vendor file and
jumps in another would be too confusing.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
arch/x86/kvm/svm/vmenter.S | 54 +++++++++++++++++++++-----------------
1 file changed, 30 insertions(+), 24 deletions(-)

diff --git a/arch/x86/kvm/svm/vmenter.S b/arch/x86/kvm/svm/vmenter.S
index d47c5c93c991..aa655b519fe0 100644
--- a/arch/x86/kvm/svm/vmenter.S
+++ b/arch/x86/kvm/svm/vmenter.S
@@ -39,10 +39,8 @@
ALTERNATIVE_2 "", \
"jmp 800f", X86_FEATURE_MSR_SPEC_CTRL, \
"", X86_FEATURE_V_SPEC_CTRL
-801:
.endm
-.macro RESTORE_GUEST_SPEC_CTRL_BODY
-800:
+.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
@@ -53,24 +51,23 @@
* and vmentry.
*/
#ifdef CONFIG_X86_64
- mov SVM_spec_ctrl(%rdi), %rdx
+ mov \guest_spec_ctrl, %rdx
cmp PER_CPU_VAR(x86_spec_ctrl_current), %rdx
- je 801b
+ je \label
movl %edx, %eax
shr $32, %rdx
#else
- mov SVM_spec_ctrl(%edi), %eax
+ mov \guest_spec_ctrl, %eax
mov PER_CPU_VAR(x86_spec_ctrl_current), %ecx
xor %eax, %ecx
- mov SVM_spec_ctrl + 4(%edi), %edx
+ mov 4 + \guest_spec_ctrl, %edx
mov PER_CPU_VAR(x86_spec_ctrl_current + 4), %esi
xor %edx, %esi
or %esi, %ecx
- je 801b
+ je \label
#endif
mov $MSR_IA32_SPEC_CTRL, %ecx
wrmsr
- jmp 801b
.endm

.macro RESTORE_HOST_SPEC_CTRL
@@ -78,10 +75,8 @@
ALTERNATIVE_2 "", \
"jmp 900f", X86_FEATURE_MSR_SPEC_CTRL, \
"", X86_FEATURE_V_SPEC_CTRL
-901:
.endm
-.macro RESTORE_HOST_SPEC_CTRL_BODY spec_ctrl_intercepted:req
-900:
+.macro RESTORE_HOST_SPEC_CTRL_BODY guest_spec_ctrl:req, spec_ctrl_intercepted:req, label:req
/* Same for after vmexit. */
mov $MSR_IA32_SPEC_CTRL, %ecx

@@ -92,28 +87,27 @@
cmpb $0, \spec_ctrl_intercepted
jnz 998f
rdmsr
- movl %eax, SVM_spec_ctrl(%_ASM_DI)
- movl %edx, SVM_spec_ctrl + 4(%_ASM_DI)
+ 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 SVM_spec_ctrl(%rdi), %rdx
- je 901b
+ cmp \guest_spec_ctrl, %rdx
+ je \label
movl %edx, %eax
shr $32, %rdx
#else
mov PER_CPU_VAR(x86_spec_ctrl_current), %eax
- mov SVM_spec_ctrl(%edi), %esi
+ mov \guest_spec_ctrl, %esi
xor %eax, %esi
mov PER_CPU_VAR(x86_spec_ctrl_current + 4), %edx
- mov SVM_spec_ctrl + 4(%edi), %edi
+ mov 4 + \guest_spec_ctrl, %edi
xor %edx, %edi
or %edi, %esi
- je 901b
+ je \label
#endif
wrmsr
- jmp 901b
.endm

#define SVM_CLEAR_CPU_BUFFERS \
@@ -162,6 +156,7 @@ SYM_FUNC_START(__svm_vcpu_run)

/* Clobbers RAX, RCX, RDX (and ESI on 32-bit), consumes RDI (@svm). */
RESTORE_GUEST_SPEC_CTRL
+801:

/*
* Use a single vmcb (vmcb01 because it's always valid) for
@@ -242,6 +237,7 @@ SYM_FUNC_START(__svm_vcpu_run)
* and RSP (pointer to @spec_ctrl_intercepted).
*/
RESTORE_HOST_SPEC_CTRL
+901:

/*
* Mitigate RETBleed for AMD/Hygon Zen uarch. RET should be
@@ -295,8 +291,12 @@ SYM_FUNC_START(__svm_vcpu_run)
pop %_ASM_BP
RET

- RESTORE_GUEST_SPEC_CTRL_BODY
- RESTORE_HOST_SPEC_CTRL_BODY (%_ASM_SP)
+800:
+ RESTORE_GUEST_SPEC_CTRL_BODY SVM_spec_ctrl(%_ASM_DI), 801b
+ jmp 801b
+900:
+ RESTORE_HOST_SPEC_CTRL_BODY SVM_spec_ctrl(%_ASM_DI), (%_ASM_SP), 901b
+ jmp 901b

10: cmpb $0, _ASM_RIP(virt_rebooting)
jne 2b
@@ -362,6 +362,7 @@ SYM_FUNC_START(__svm_sev_es_vcpu_run)

/* Clobbers RAX, RCX, and RDX (@hostsa), consumes RDI (@svm). */
RESTORE_GUEST_SPEC_CTRL
+801:

/* Get svm->current_vmcb->pa into RAX. */
mov SVM_current_vmcb(%rdi), %rax
@@ -378,6 +379,7 @@ SYM_FUNC_START(__svm_sev_es_vcpu_run)

/* Clobbers RAX, RCX, RDX, consumes RDI (@svm) and RSI (@spec_ctrl_intercepted). */
RESTORE_HOST_SPEC_CTRL
+901:

/*
* Mitigate RETBleed for AMD/Hygon Zen uarch. RET should be
@@ -391,8 +393,12 @@ SYM_FUNC_START(__svm_sev_es_vcpu_run)
FRAME_END
RET

- RESTORE_GUEST_SPEC_CTRL_BODY
- RESTORE_HOST_SPEC_CTRL_BODY %sil
+800:
+ RESTORE_GUEST_SPEC_CTRL_BODY SVM_spec_ctrl(%_ASM_DI), 801b
+ jmp 801b
+900:
+ RESTORE_HOST_SPEC_CTRL_BODY SVM_spec_ctrl(%_ASM_DI), %sil, 901b
+ jmp 901b

3: cmpb $0, virt_rebooting(%rip)
jne 2b
--
2.52.0