linux-kernel - [PATCH 05/23] KVM: nSVM: do not copy vmcb01->control blindly to vmcb02->control

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Date:   Tue,  2 Mar 2021 14:33:25 -0500
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc:     seanjc@...gle.com
Subject: [PATCH 05/23] KVM: nSVM: do not copy vmcb01->control blindly to vmcb02->control

Most fields were going to be overwritten by vmcb12 control fields, or
do not matter at all because they are filled by the processor on vmexit.
Therefore, we need not copy them from vmcb01 to vmcb02 on vmentry.

Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
---
 arch/x86/kvm/svm/nested.c | 23 +++++++++++++++++++++--
 arch/x86/kvm/svm/svm.h    |  2 +-
 2 files changed, 22 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c
index 4d136465dee1..f88d0614d9b8 100644
--- a/arch/x86/kvm/svm/nested.c
+++ b/arch/x86/kvm/svm/nested.c
@@ -428,9 +428,28 @@ static void nested_vmcb02_prepare_control(struct vcpu_svm *svm)
 {
 	const u32 mask = V_INTR_MASKING_MASK | V_GIF_ENABLE_MASK | V_GIF_MASK;
 
-	/* FIXME: go through each field one by one.  */
-	svm->nested.vmcb02.ptr->control = svm->vmcb01.ptr->control;
+	/*
+	 * Filled at exit: exit_code, exit_code_hi, exit_info_1, exit_info_2,
+	 * exit_int_info, exit_int_info_err, next_rip, insn_len, insn_bytes.
+	 */
+
+	/*
+	 * Also covers avic_vapic_bar, avic_backing_page, avic_logical_id,
+	 * avic_physical_id.
+	 */
+	WARN_ON(svm->vmcb01.ptr->control.int_ctl & AVIC_ENABLE_MASK);
+
+	/* Copied from vmcb01.  msrpm_base can be overwritten later.  */
+	svm->vmcb->control.nested_ctl = svm->vmcb01.ptr->control.nested_ctl;
+	svm->vmcb->control.iopm_base_pa = svm->vmcb01.ptr->control.iopm_base_pa;
+	svm->vmcb->control.msrpm_base_pa = svm->vmcb01.ptr->control.msrpm_base_pa;
+
+	/* Done at vmrun: asid.  */
+
+	/* Also overwritten later if necessary.  */
+	svm->vmcb->control.tlb_ctl = TLB_CONTROL_DO_NOTHING;
 
+	/* nested_cr3.  */
 	if (nested_npt_enabled(svm))
 		nested_svm_init_mmu_context(&svm->vcpu);
 
-- 
2.26.2