[PATCH v2 1/7] KVM: VMX: remove regs argument of __vmx_vcpu_run

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

Registers are reachable through vcpu_vmx, no need to pass
a separate pointer to the regs[] array.

No functional change intended.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
arch/x86/kvm/kvm-asm-offsets.c | 1 +
arch/x86/kvm/vmx/vmenter.S | 58 +++++++++++++++-------------------
arch/x86/kvm/vmx/vmx.c | 3 +-
arch/x86/kvm/vmx/vmx.h | 3 +-
4 files changed, 28 insertions(+), 37 deletions(-)

diff --git a/arch/x86/kvm/kvm-asm-offsets.c b/arch/x86/kvm/kvm-asm-offsets.c
index 24a710d37323..36ac61724dd7 100644
--- a/arch/x86/kvm/kvm-asm-offsets.c
+++ b/arch/x86/kvm/kvm-asm-offsets.c
@@ -24,6 +24,7 @@ static void __used common(void)

if (IS_ENABLED(CONFIG_KVM_INTEL)) {
BLANK();
+ OFFSET(VMX_vcpu_arch_regs, vcpu_vmx, vcpu.arch.regs);
OFFSET(VMX_spec_ctrl, vcpu_vmx, spec_ctrl);
}
}
diff --git a/arch/x86/kvm/vmx/vmenter.S b/arch/x86/kvm/vmx/vmenter.S
index 8a481dae9cae..0a09288a8d29 100644
--- a/arch/x86/kvm/vmx/vmenter.S
+++ b/arch/x86/kvm/vmx/vmenter.S
@@ -11,24 +11,24 @@

#define WORD_SIZE (BITS_PER_LONG / 8)

-#define VCPU_RAX __VCPU_REGS_RAX * WORD_SIZE
-#define VCPU_RCX __VCPU_REGS_RCX * WORD_SIZE
-#define VCPU_RDX __VCPU_REGS_RDX * WORD_SIZE
-#define VCPU_RBX __VCPU_REGS_RBX * WORD_SIZE
+#define VCPU_RAX (VMX_vcpu_arch_regs + __VCPU_REGS_RAX * WORD_SIZE)
+#define VCPU_RCX (VMX_vcpu_arch_regs + __VCPU_REGS_RCX * WORD_SIZE)
+#define VCPU_RDX (VMX_vcpu_arch_regs + __VCPU_REGS_RDX * WORD_SIZE)
+#define VCPU_RBX (VMX_vcpu_arch_regs + __VCPU_REGS_RBX * WORD_SIZE)
/* Intentionally omit RSP as it's context switched by hardware */
-#define VCPU_RBP __VCPU_REGS_RBP * WORD_SIZE
-#define VCPU_RSI __VCPU_REGS_RSI * WORD_SIZE
-#define VCPU_RDI __VCPU_REGS_RDI * WORD_SIZE
+#define VCPU_RBP (VMX_vcpu_arch_regs + __VCPU_REGS_RBP * WORD_SIZE)
+#define VCPU_RSI (VMX_vcpu_arch_regs + __VCPU_REGS_RSI * WORD_SIZE)
+#define VCPU_RDI (VMX_vcpu_arch_regs + __VCPU_REGS_RDI * WORD_SIZE)

#ifdef CONFIG_X86_64
-#define VCPU_R8 __VCPU_REGS_R8 * WORD_SIZE
-#define VCPU_R9 __VCPU_REGS_R9 * WORD_SIZE
-#define VCPU_R10 __VCPU_REGS_R10 * WORD_SIZE
-#define VCPU_R11 __VCPU_REGS_R11 * WORD_SIZE
-#define VCPU_R12 __VCPU_REGS_R12 * WORD_SIZE
-#define VCPU_R13 __VCPU_REGS_R13 * WORD_SIZE
-#define VCPU_R14 __VCPU_REGS_R14 * WORD_SIZE
-#define VCPU_R15 __VCPU_REGS_R15 * WORD_SIZE
+#define VCPU_R8 (VMX_vcpu_arch_regs + __VCPU_REGS_R8 * WORD_SIZE)
+#define VCPU_R9 (VMX_vcpu_arch_regs + __VCPU_REGS_R9 * WORD_SIZE)
+#define VCPU_R10 (VMX_vcpu_arch_regs + __VCPU_REGS_R10 * WORD_SIZE)
+#define VCPU_R11 (VMX_vcpu_arch_regs + __VCPU_REGS_R11 * WORD_SIZE)
+#define VCPU_R12 (VMX_vcpu_arch_regs + __VCPU_REGS_R12 * WORD_SIZE)
+#define VCPU_R13 (VMX_vcpu_arch_regs + __VCPU_REGS_R13 * WORD_SIZE)
+#define VCPU_R14 (VMX_vcpu_arch_regs + __VCPU_REGS_R14 * WORD_SIZE)
+#define VCPU_R15 (VMX_vcpu_arch_regs + __VCPU_REGS_R15 * WORD_SIZE)
#endif

.macro VMX_DO_EVENT_IRQOFF call_insn call_target
@@ -68,7 +68,6 @@
/**
* __vmx_vcpu_run - Run a vCPU via a transition to VMX guest mode
* @vmx: struct vcpu_vmx *
- * @regs: unsigned long * (to guest registers)
* @flags: VMX_RUN_VMRESUME: use VMRESUME instead of VMLAUNCH
* VMX_RUN_SAVE_SPEC_CTRL: save guest SPEC_CTRL into vmx->spec_ctrl
* VMX_RUN_CLEAR_CPU_BUFFERS_FOR_MMIO: vCPU can access host MMIO
@@ -94,12 +93,6 @@ SYM_FUNC_START(__vmx_vcpu_run)
push %_ASM_ARG1

/* Save @flags (used for VMLAUNCH vs. VMRESUME and mitigations). */
- push %_ASM_ARG3
-
- /*
- * Save @regs, _ASM_ARG2 may be modified by vmx_update_host_rsp() and
- * @regs is needed after VM-Exit to save the guest's register values.
- */
push %_ASM_ARG2

lea (%_ASM_SP), %_ASM_ARG2
@@ -107,6 +100,9 @@ SYM_FUNC_START(__vmx_vcpu_run)

ALTERNATIVE "jmp .Lspec_ctrl_done", "", X86_FEATURE_MSR_SPEC_CTRL

+ /* Reload @vmx, _ASM_ARG1 may be modified by vmx_update_host_rsp(). */
+ mov WORD_SIZE(%_ASM_SP), %_ASM_DI
+
/*
* SPEC_CTRL handling: if the guest's SPEC_CTRL value differs from the
* host's, write the MSR.
@@ -115,7 +111,6 @@ SYM_FUNC_START(__vmx_vcpu_run)
* there must not be any returns or indirect branches between this code
* and vmentry.
*/
- mov 2*WORD_SIZE(%_ASM_SP), %_ASM_DI
#ifdef CONFIG_X86_64
mov VMX_spec_ctrl(%rdi), %rdx
cmp PER_CPU_VAR(x86_spec_ctrl_current), %rdx
@@ -142,8 +137,8 @@ SYM_FUNC_START(__vmx_vcpu_run)
* an LFENCE to stop speculation from skipping the wrmsr.
*/

- /* Load @regs to RAX. */
- mov (%_ASM_SP), %_ASM_AX
+ /* Load @vmx to RAX. */
+ mov WORD_SIZE(%_ASM_SP), %_ASM_AX

/* Load guest registers. Don't clobber flags. */
mov VCPU_RCX(%_ASM_AX), %_ASM_CX
@@ -162,7 +157,7 @@ SYM_FUNC_START(__vmx_vcpu_run)
mov VCPU_R14(%_ASM_AX), %r14
mov VCPU_R15(%_ASM_AX), %r15
#endif
- /* Load guest RAX. This kills the @regs pointer! */
+ /* Load guest RAX. This kills the @vmx pointer! */
mov VCPU_RAX(%_ASM_AX), %_ASM_AX

/*
@@ -172,7 +167,7 @@ SYM_FUNC_START(__vmx_vcpu_run)
* do VERW. Else, do nothing (no mitigations needed/enabled).
*/
ALTERNATIVE_2 "", \
- __stringify(testl $VMX_RUN_CLEAR_CPU_BUFFERS_FOR_MMIO, WORD_SIZE(%_ASM_SP); \
+ __stringify(testl $VMX_RUN_CLEAR_CPU_BUFFERS_FOR_MMIO, (%_ASM_SP); \
jz .Lskip_mmio_verw; \
VERW; \
.Lskip_mmio_verw:), \
@@ -180,7 +175,7 @@ SYM_FUNC_START(__vmx_vcpu_run)
__stringify(VERW), X86_FEATURE_CLEAR_CPU_BUF_VM

/* Check @flags to see if VMLAUNCH or VMRESUME is needed. */
- testl $VMX_RUN_VMRESUME, WORD_SIZE(%_ASM_SP)
+ testl $VMX_RUN_VMRESUME, (%_ASM_SP)
jz .Lvmlaunch

/*
@@ -215,8 +210,8 @@ SYM_INNER_LABEL_ALIGN(vmx_vmexit, SYM_L_GLOBAL)
/* Temporarily save guest's RAX. */
push %_ASM_AX

- /* Reload @regs to RAX. */
- mov WORD_SIZE(%_ASM_SP), %_ASM_AX
+ /* Reload @vmx to RAX. */
+ mov 2*WORD_SIZE(%_ASM_SP), %_ASM_AX

/* Save all guest registers, including RAX from the stack */
pop VCPU_RAX(%_ASM_AX)
@@ -241,9 +236,6 @@ SYM_INNER_LABEL_ALIGN(vmx_vmexit, SYM_L_GLOBAL)
xor %ebx, %ebx

.Lclear_regs:
- /* Discard @regs. The register is irrelevant, it just can't be RBX. */
- pop %_ASM_AX
-
/*
* Clear all general purpose registers except RSP and RBX to prevent
* speculative use of the guest's values, even those that are reloaded
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index a29896a9ef14..7dd4aff29026 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -7468,8 +7468,7 @@ static noinstr void vmx_vcpu_enter_exit(struct kvm_vcpu *vcpu,
if (vcpu->arch.cr2 != native_read_cr2())
native_write_cr2(vcpu->arch.cr2);

- vmx->fail = __vmx_vcpu_run(vmx, (unsigned long *)&vcpu->arch.regs,
- flags);
+ vmx->fail = __vmx_vcpu_run(vmx, flags);

vcpu->arch.cr2 = native_read_cr2();
vcpu->arch.regs_avail &= ~VMX_REGS_LAZY_LOAD_SET;
diff --git a/arch/x86/kvm/vmx/vmx.h b/arch/x86/kvm/vmx/vmx.h
index db84e8001da5..53793d530a69 100644
--- a/arch/x86/kvm/vmx/vmx.h
+++ b/arch/x86/kvm/vmx/vmx.h
@@ -370,8 +370,7 @@ void pt_update_intercept_for_msr(struct kvm_vcpu *vcpu);
void vmx_update_host_rsp(struct vcpu_vmx *vmx, unsigned long host_rsp);
void vmx_spec_ctrl_restore_host(struct vcpu_vmx *vmx, unsigned int flags);
unsigned int __vmx_vcpu_run_flags(struct vcpu_vmx *vmx);
-bool __vmx_vcpu_run(struct vcpu_vmx *vmx, unsigned long *regs,
- unsigned int flags);
+bool __vmx_vcpu_run(struct vcpu_vmx *vmx, unsigned int flags);
void vmx_ept_load_pdptrs(struct kvm_vcpu *vcpu);

void vmx_set_intercept_for_msr(struct kvm_vcpu *vcpu, u32 msr, int type, bool set);
--
2.52.0