linux-kernel - [PATCH 5/8] KVM: SVM: retrieve VMCB from assembly

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Message-Id: <20221107145436.276079-6-pbonzini@redhat.com>
Date:   Mon,  7 Nov 2022 09:54:33 -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 5/8] KVM: SVM: retrieve VMCB from assembly

This is needed in order to keep the number of arguments to 3 or less,
so that they are all passed in registers on either 32-bit or 64-bit
builds.

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/kernel/asm-offsets.c |  1 +
 arch/x86/kvm/svm/svm.c        |  5 ++---
 arch/x86/kvm/svm/svm.h        |  4 ++--
 arch/x86/kvm/svm/vmenter.S    | 20 ++++++++++----------
 4 files changed, 15 insertions(+), 15 deletions(-)

diff --git a/arch/x86/kernel/asm-offsets.c b/arch/x86/kernel/asm-offsets.c
index f01293a1e594..69d1fed51086 100644
--- a/arch/x86/kernel/asm-offsets.c
+++ b/arch/x86/kernel/asm-offsets.c
@@ -114,6 +114,7 @@ static void __used common(void)
 		BLANK();
 		OFFSET(SVM_vcpu_arch_regs, vcpu_svm, vcpu.arch.regs);
 		OFFSET(SVM_vmcb01, vcpu_svm, vmcb01);
+		OFFSET(SVM_current_vmcb, vcpu_svm, current_vmcb);
 		OFFSET(KVM_VMCB_pa, kvm_vmcb_info, pa);
 	}
 
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index ae65cdcab660..550a364be8d3 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -3915,16 +3915,15 @@ 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);
 
-		__svm_vcpu_run(vmcb_pa, svm);
+		__svm_vcpu_run(svm);
 		vmload(__sme_page_pa(sd->save_area));
 	}
 
diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h
index 5f8dfc9cd9a7..c5b8ec370108 100644
--- a/arch/x86/kvm/svm/svm.h
+++ b/arch/x86/kvm/svm/svm.h
@@ -483,7 +483,7 @@ 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 4709bc8868d7..9738ce41fac9 100644
--- a/arch/x86/kvm/svm/vmenter.S
+++ b/arch/x86/kvm/svm/vmenter.S
@@ -34,7 +34,6 @@
 
 /**
  * __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)
@@ -51,13 +50,12 @@ 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
 
 	/*
 	 * Use a single vmcb (vmcb01 because it's always valid) for
@@ -69,8 +67,9 @@ SYM_FUNC_START(__svm_vcpu_run)
 1:	vmload %_ASM_AX
 2:
 
-	/* "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
@@ -197,7 +196,7 @@ 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
@@ -212,8 +211,9 @@ 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