linux-kernel - [PATCH v2 4/8] KVM: SVM: retrieve VMCB from assembly

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Message-Id: <20221108151532.1377783-5-pbonzini@redhat.com>
Date:   Tue,  8 Nov 2022 10:15:28 -0500
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc:     nathan@...nel.org, thomas.lendacky@....com,
        andrew.cooper3@...rix.com, peterz@...radead.org,
        jmattson@...gle.com, seanjc@...gle.com, stable@...r.kernel.org
Subject: [PATCH v2 4/8] KVM: SVM: retrieve VMCB from assembly

This is needed in order to keep the number of arguments to 3 or less,
after adding hsave_pa and spec_ctrl_intercepted.  32-bit builds only
support passing three arguments in registers, fortunately all other
data is reachable from the vcpu_svm struct.

It is not strictly necessary for __svm_sev_es_vcpu_run, but staying
consistent is a good idea since it makes __svm_sev_es_vcpu_run a
stripped version of _svm_vcpu_run.

No functional change intended.

Cc: stable@...r.kernel.org
Fixes: f14eec0a3203 ("KVM: SVM: move more vmentry code to assembly")
Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
---
 arch/x86/kvm/kvm-asm-offsets.c |  2 ++
 arch/x86/kvm/svm/svm.c         |  5 ++---
 arch/x86/kvm/svm/svm.h         |  4 ++--
 arch/x86/kvm/svm/vmenter.S     | 20 ++++++++++----------
 4 files changed, 16 insertions(+), 15 deletions(-)

diff --git a/arch/x86/kvm/kvm-asm-offsets.c b/arch/x86/kvm/kvm-asm-offsets.c
index 30db96852e2d..f1b694e431ae 100644
--- a/arch/x86/kvm/kvm-asm-offsets.c
+++ b/arch/x86/kvm/kvm-asm-offsets.c
@@ -15,6 +15,8 @@ static void __used common(void)
 	if (IS_ENABLED(CONFIG_KVM_AMD)) {
 		BLANK();
 		OFFSET(SVM_vcpu_arch_regs, vcpu_svm, vcpu.arch.regs);
+		OFFSET(SVM_current_vmcb, vcpu_svm, current_vmcb);
+		OFFSET(KVM_VMCB_pa, kvm_vmcb_info, pa);
 	}
 
 	if (IS_ENABLED(CONFIG_KVM_INTEL)) {
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index b412bc5773c5..0c86c435c51f 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -3914,12 +3914,11 @@ static fastpath_t svm_exit_handlers_fastpath(struct kvm_vcpu *vcpu)
 static noinstr void svm_vcpu_enter_exit(struct kvm_vcpu *vcpu)
 {
 	struct vcpu_svm *svm = to_svm(vcpu);
-	unsigned long vmcb_pa = svm->current_vmcb->pa;
 
 	guest_state_enter_irqoff();
 
 	if (sev_es_guest(vcpu->kvm)) {
-		__svm_sev_es_vcpu_run(vmcb_pa);
+		__svm_sev_es_vcpu_run(svm);
 	} else {
 		struct svm_cpu_data *sd = per_cpu(svm_data, vcpu->cpu);
 
@@ -3930,7 +3929,7 @@ static noinstr void svm_vcpu_enter_exit(struct kvm_vcpu *vcpu)
 		 * vmcb02 when switching vmcbs for nested virtualization.
 		 */
 		vmload(svm->vmcb01.pa);
-		__svm_vcpu_run(vmcb_pa, svm);
+		__svm_vcpu_run(svm);
 		vmsave(svm->vmcb01.pa);
 
 		vmload(__sme_page_pa(sd->save_area));
diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h
index 447e25c9101a..7ff1879e73c5 100644
--- a/arch/x86/kvm/svm/svm.h
+++ b/arch/x86/kvm/svm/svm.h
@@ -683,7 +683,7 @@ void sev_es_unmap_ghcb(struct vcpu_svm *svm);
 
 /* vmenter.S */
 
-void __svm_sev_es_vcpu_run(unsigned long vmcb_pa);
-void __svm_vcpu_run(unsigned long vmcb_pa, struct vcpu_svm *svm);
+void __svm_sev_es_vcpu_run(struct vcpu_svm *svm);
+void __svm_vcpu_run(struct vcpu_svm *svm);
 
 #endif
diff --git a/arch/x86/kvm/svm/vmenter.S b/arch/x86/kvm/svm/vmenter.S
index 531510ab6072..d07bac1952c5 100644
--- a/arch/x86/kvm/svm/vmenter.S
+++ b/arch/x86/kvm/svm/vmenter.S
@@ -32,7 +32,6 @@
 
 /**
  * __svm_vcpu_run - Run a vCPU via a transition to SVM guest mode
- * @vmcb_pa:	unsigned long
  * @svm:	struct vcpu_svm *
  */
 SYM_FUNC_START(__svm_vcpu_run)
@@ -49,16 +48,16 @@ SYM_FUNC_START(__svm_vcpu_run)
 	push %_ASM_BX
 
 	/* Save @svm. */
-	push %_ASM_ARG2
-
-	/* Save @vmcb. */
 	push %_ASM_ARG1
 
+.ifnc _ASM_ARG1, _ASM_DI
 	/* Move @svm to RDI. */
-	mov %_ASM_ARG2, %_ASM_DI
+	mov %_ASM_ARG1, %_ASM_DI
+.endif
 
-	/* "POP" @vmcb to RAX. */
-	pop %_ASM_AX
+	/* Get svm->current_vmcb->pa into RAX. */
+	mov SVM_current_vmcb(%_ASM_DI), %_ASM_AX
+	mov KVM_VMCB_pa(%_ASM_AX), %_ASM_AX
 
 	/* Load guest registers. */
 	mov VCPU_RCX(%_ASM_DI), %_ASM_CX
@@ -170,7 +169,7 @@ SYM_FUNC_END(__svm_vcpu_run)
 
 /**
  * __svm_sev_es_vcpu_run - Run a SEV-ES vCPU via a transition to SVM guest mode
- * @vmcb_pa:	unsigned long
+ * @svm:	struct vcpu_svm *
  */
 SYM_FUNC_START(__svm_sev_es_vcpu_run)
 	push %_ASM_BP
@@ -185,8 +184,9 @@ SYM_FUNC_START(__svm_sev_es_vcpu_run)
 #endif
 	push %_ASM_BX
 
-	/* Move @vmcb to RAX. */
-	mov %_ASM_ARG1, %_ASM_AX
+	/* Get svm->current_vmcb->pa into RAX. */
+	mov SVM_current_vmcb(%_ASM_ARG1), %_ASM_AX
+	mov KVM_VMCB_pa(%_ASM_AX), %_ASM_AX
 
 	/* Enter guest mode */
 	sti
-- 
2.31.1