linux-kernel - [PATCH] x86/kvm/nVMX: tweak shadow fields

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Message-Id: <20181019141603.15995-1-vkuznets@redhat.com>
Date:   Fri, 19 Oct 2018 16:16:03 +0200
From:   Vitaly Kuznetsov <vkuznets@...hat.com>
To:     kvm@...r.kernel.org
Cc:     Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Jim Mattson <jmattson@...gle.com>,
        Liran Alon <liran.alon@...cle.com>,
        linux-kernel@...r.kernel.org
Subject: [PATCH] x86/kvm/nVMX: tweak shadow fields

It seems we have some leftovers from times when 'unrestricted guest'
wasn't exposed to L1. Stop shadowing GUEST_CS_{BASE,LIMIT,AR_SELECTOR}
and GUEST_ES_BASE, shadow GUEST_SS_AR_BYTES as it was found that some
hypervisors (e.g. Hyper-V without Enlightened VMCS) access it pretty
often.

Suggested-by: Paolo Bonzini <pbonzini@...hat.com>
Signed-off-by: Vitaly Kuznetsov <vkuznets@...hat.com>
---
 arch/x86/kvm/vmx.c               | 10 +++++-----
 arch/x86/kvm/vmx_shadow_fields.h |  5 +----
 2 files changed, 6 insertions(+), 9 deletions(-)

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index abeeb45d1c33..641a65b30685 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -12715,6 +12715,7 @@ static void prepare_vmcs02_full(struct vcpu_vmx *vmx, struct vmcs12 *vmcs12)
 	if (!hv_evmcs || !(hv_evmcs->hv_clean_fields &
 			   HV_VMX_ENLIGHTENED_CLEAN_FIELD_GUEST_GRP2)) {
 		vmcs_write16(GUEST_ES_SELECTOR, vmcs12->guest_es_selector);
+		vmcs_write16(GUEST_CS_SELECTOR, vmcs12->guest_cs_selector);
 		vmcs_write16(GUEST_SS_SELECTOR, vmcs12->guest_ss_selector);
 		vmcs_write16(GUEST_DS_SELECTOR, vmcs12->guest_ds_selector);
 		vmcs_write16(GUEST_FS_SELECTOR, vmcs12->guest_fs_selector);
@@ -12722,6 +12723,7 @@ static void prepare_vmcs02_full(struct vcpu_vmx *vmx, struct vmcs12 *vmcs12)
 		vmcs_write16(GUEST_LDTR_SELECTOR, vmcs12->guest_ldtr_selector);
 		vmcs_write16(GUEST_TR_SELECTOR, vmcs12->guest_tr_selector);
 		vmcs_write32(GUEST_ES_LIMIT, vmcs12->guest_es_limit);
+		vmcs_write32(GUEST_CS_LIMIT, vmcs12->guest_cs_limit);
 		vmcs_write32(GUEST_SS_LIMIT, vmcs12->guest_ss_limit);
 		vmcs_write32(GUEST_DS_LIMIT, vmcs12->guest_ds_limit);
 		vmcs_write32(GUEST_FS_LIMIT, vmcs12->guest_fs_limit);
@@ -12731,12 +12733,13 @@ static void prepare_vmcs02_full(struct vcpu_vmx *vmx, struct vmcs12 *vmcs12)
 		vmcs_write32(GUEST_GDTR_LIMIT, vmcs12->guest_gdtr_limit);
 		vmcs_write32(GUEST_IDTR_LIMIT, vmcs12->guest_idtr_limit);
 		vmcs_write32(GUEST_ES_AR_BYTES, vmcs12->guest_es_ar_bytes);
-		vmcs_write32(GUEST_SS_AR_BYTES, vmcs12->guest_ss_ar_bytes);
 		vmcs_write32(GUEST_DS_AR_BYTES, vmcs12->guest_ds_ar_bytes);
 		vmcs_write32(GUEST_FS_AR_BYTES, vmcs12->guest_fs_ar_bytes);
 		vmcs_write32(GUEST_GS_AR_BYTES, vmcs12->guest_gs_ar_bytes);
 		vmcs_write32(GUEST_LDTR_AR_BYTES, vmcs12->guest_ldtr_ar_bytes);
 		vmcs_write32(GUEST_TR_AR_BYTES, vmcs12->guest_tr_ar_bytes);
+		vmcs_writel(GUEST_ES_BASE, vmcs12->guest_es_base);
+		vmcs_writel(GUEST_CS_BASE, vmcs12->guest_cs_base);
 		vmcs_writel(GUEST_SS_BASE, vmcs12->guest_ss_base);
 		vmcs_writel(GUEST_DS_BASE, vmcs12->guest_ds_base);
 		vmcs_writel(GUEST_FS_BASE, vmcs12->guest_fs_base);
@@ -12838,11 +12841,8 @@ static int prepare_vmcs02(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12,
 	 */
 	if (!hv_evmcs || !(hv_evmcs->hv_clean_fields &
 			   HV_VMX_ENLIGHTENED_CLEAN_FIELD_GUEST_GRP2)) {
-		vmcs_write16(GUEST_CS_SELECTOR, vmcs12->guest_cs_selector);
-		vmcs_write32(GUEST_CS_LIMIT, vmcs12->guest_cs_limit);
 		vmcs_write32(GUEST_CS_AR_BYTES, vmcs12->guest_cs_ar_bytes);
-		vmcs_writel(GUEST_ES_BASE, vmcs12->guest_es_base);
-		vmcs_writel(GUEST_CS_BASE, vmcs12->guest_cs_base);
+		vmcs_write32(GUEST_SS_AR_BYTES, vmcs12->guest_ss_ar_bytes);
 	}
 
 	if (vmx->nested.nested_run_pending &&
diff --git a/arch/x86/kvm/vmx_shadow_fields.h b/arch/x86/kvm/vmx_shadow_fields.h
index cd0c75f6d037..132432f375c2 100644
--- a/arch/x86/kvm/vmx_shadow_fields.h
+++ b/arch/x86/kvm/vmx_shadow_fields.h
@@ -28,7 +28,6 @@
  */
 
 /* 16-bits */
-SHADOW_FIELD_RW(GUEST_CS_SELECTOR)
 SHADOW_FIELD_RW(GUEST_INTR_STATUS)
 SHADOW_FIELD_RW(GUEST_PML_INDEX)
 SHADOW_FIELD_RW(HOST_FS_SELECTOR)
@@ -47,8 +46,8 @@ SHADOW_FIELD_RW(VM_ENTRY_EXCEPTION_ERROR_CODE)
 SHADOW_FIELD_RW(VM_ENTRY_INTR_INFO_FIELD)
 SHADOW_FIELD_RW(VM_ENTRY_INSTRUCTION_LEN)
 SHADOW_FIELD_RW(TPR_THRESHOLD)
-SHADOW_FIELD_RW(GUEST_CS_LIMIT)
 SHADOW_FIELD_RW(GUEST_CS_AR_BYTES)
+SHADOW_FIELD_RW(GUEST_SS_AR_BYTES)
 SHADOW_FIELD_RW(GUEST_INTERRUPTIBILITY_INFO)
 SHADOW_FIELD_RW(VMX_PREEMPTION_TIMER_VALUE)
 
@@ -61,8 +60,6 @@ SHADOW_FIELD_RW(GUEST_CR0)
 SHADOW_FIELD_RW(GUEST_CR3)
 SHADOW_FIELD_RW(GUEST_CR4)
 SHADOW_FIELD_RW(GUEST_RFLAGS)
-SHADOW_FIELD_RW(GUEST_CS_BASE)
-SHADOW_FIELD_RW(GUEST_ES_BASE)
 SHADOW_FIELD_RW(CR0_GUEST_HOST_MASK)
 SHADOW_FIELD_RW(CR0_READ_SHADOW)
 SHADOW_FIELD_RW(CR4_READ_SHADOW)
-- 
2.17.2