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From:   Vitaly Kuznetsov <vkuznets@redhat.com>
To:     kvm@vger.kernel.org
Cc:     Paolo Bonzini <pbonzini@redhat.com>,
        =?UTF-8?q?Radim=20Kr=C4=8Dm=C3=A1=C5=99?= <rkrcmar@redhat.com>,
        linux-kernel@vger.kernel.org, Roman Kagan <rkagan@virtuozzo.com>,
        "K. Y. Srinivasan" <kys@microsoft.com>,
        Haiyang Zhang <haiyangz@microsoft.com>,
        Stephen Hemminger <sthemmin@microsoft.com>, x86@kernel.org,
        "Michael Kelley (EOSG)" <Michael.H.Kelley@microsoft.com>,
        Nadav Amit <nadav.amit@gmail.com>,
        Thomas Gleixner <tglx@linutronix.de>
Subject: [PATCH] x86/hyper-v: define structures from TLFS as packed
Date:   Fri, 30 Nov 2018 13:15:11 +0100
Message-Id: <20181130121511.12331-1-vkuznets@redhat.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

Without 'packed' compiler is free to add optimization paddings and re-order
structure fields for randomization/optimization. And structures from
hyperv-tlfs.h are used for hypervisor-guest communication, we need to
ultimately forbid such practices.

Suggested-by: Nadav Amit <nadav.amit@gmail.com>
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
---
- This is a follow-up to my "[PATCH v2 0/4] x86/kvm/hyper-v: Implement
 Direct Mode for synthetic timers" series, as suggested by Thomas I'm
 routing it to KVM tree to avoid merge conflicts.
---
 arch/x86/include/asm/hyperv-tlfs.h | 50 +++++++++++++++---------------
 1 file changed, 25 insertions(+), 25 deletions(-)

diff --git a/arch/x86/include/asm/hyperv-tlfs.h b/arch/x86/include/asm/hyperv-tlfs.h
index ebfed56976d2..6a60fa17f6f2 100644
--- a/arch/x86/include/asm/hyperv-tlfs.h
+++ b/arch/x86/include/asm/hyperv-tlfs.h
@@ -271,7 +271,7 @@ union hv_x64_msr_hypercall_contents {
 		u64 enable:1;
 		u64 reserved:11;
 		u64 guest_physical_address:52;
-	};
+	} __packed;
 };
 
 /*
@@ -283,7 +283,7 @@ struct ms_hyperv_tsc_page {
 	volatile u64 tsc_scale;
 	volatile s64 tsc_offset;
 	u64 reserved2[509];
-};
+}  __packed;
 
 /*
  * The guest OS needs to register the guest ID with the hypervisor.
@@ -324,7 +324,7 @@ struct hv_reenlightenment_control {
 	__u64 enabled:1;
 	__u64 reserved2:15;
 	__u64 target_vp:32;
-};
+}  __packed;
 
 #define HV_X64_MSR_TSC_EMULATION_CONTROL	0x40000107
 #define HV_X64_MSR_TSC_EMULATION_STATUS		0x40000108
@@ -332,12 +332,12 @@ struct hv_reenlightenment_control {
 struct hv_tsc_emulation_control {
 	__u64 enabled:1;
 	__u64 reserved:63;
-};
+} __packed;
 
 struct hv_tsc_emulation_status {
 	__u64 inprogress:1;
 	__u64 reserved:63;
-};
+} __packed;
 
 #define HV_X64_MSR_HYPERCALL_ENABLE		0x00000001
 #define HV_X64_MSR_HYPERCALL_PAGE_ADDRESS_SHIFT	12
@@ -409,7 +409,7 @@ typedef struct _HV_REFERENCE_TSC_PAGE {
 	__u32 res1;
 	__u64 tsc_scale;
 	__s64 tsc_offset;
-} HV_REFERENCE_TSC_PAGE, *PHV_REFERENCE_TSC_PAGE;
+}  __packed HV_REFERENCE_TSC_PAGE, *PHV_REFERENCE_TSC_PAGE;
 
 /* Define the number of synthetic interrupt sources. */
 #define HV_SYNIC_SINT_COUNT		(16)
@@ -466,7 +466,7 @@ union hv_message_flags {
 	struct {
 		__u8 msg_pending:1;
 		__u8 reserved:7;
-	};
+	} __packed;
 };
 
 /* Define port identifier type. */
@@ -488,7 +488,7 @@ struct hv_message_header {
 		__u64 sender;
 		union hv_port_id port;
 	};
-};
+} __packed;
 
 /* Define synthetic interrupt controller message format. */
 struct hv_message {
@@ -496,12 +496,12 @@ struct hv_message {
 	union {
 		__u64 payload[HV_MESSAGE_PAYLOAD_QWORD_COUNT];
 	} u;
-};
+} __packed;
 
 /* Define the synthetic interrupt message page layout. */
 struct hv_message_page {
 	struct hv_message sint_message[HV_SYNIC_SINT_COUNT];
-};
+} __packed;
 
 /* Define timer message payload structure. */
 struct hv_timer_message_payload {
@@ -509,7 +509,7 @@ struct hv_timer_message_payload {
 	__u32 reserved;
 	__u64 expiration_time;	/* When the timer expired */
 	__u64 delivery_time;	/* When the message was delivered */
-};
+} __packed;
 
 /* Define virtual processor assist page structure. */
 struct hv_vp_assist_page {
@@ -519,7 +519,7 @@ struct hv_vp_assist_page {
 	__u64 nested_enlightenments_control[2];
 	__u32 enlighten_vmentry;
 	__u64 current_nested_vmcs;
-};
+} __packed;
 
 struct hv_enlightened_vmcs {
 	u32 revision_id;
@@ -693,7 +693,7 @@ struct hv_enlightened_vmcs {
 		u32 nested_flush_hypercall:1;
 		u32 msr_bitmap:1;
 		u32 reserved:30;
-	} hv_enlightenments_control;
+	}  __packed hv_enlightenments_control;
 	u32 hv_vp_id;
 
 	u64 hv_vm_id;
@@ -703,7 +703,7 @@ struct hv_enlightened_vmcs {
 	u64 padding64_5[7];
 	u64 xss_exit_bitmap;
 	u64 padding64_6[7];
-};
+} __packed;
 
 #define HV_VMX_ENLIGHTENED_CLEAN_FIELD_NONE			0
 #define HV_VMX_ENLIGHTENED_CLEAN_FIELD_IO_BITMAP		BIT(0)
@@ -744,7 +744,7 @@ union hv_stimer_config {
 		u64 reserved_z0:3;
 		u64 sintx:4;
 		u64 reserved_z1:44;
-	};
+	} __packed;
 };
 
 
@@ -759,7 +759,7 @@ union hv_synic_scontrol {
 	struct {
 		u64 enable:1;
 		u64 reserved:63;
-	};
+	} __packed;
 };
 
 /* Define synthetic interrupt source. */
@@ -771,7 +771,7 @@ union hv_synic_sint {
 		u64 masked:1;
 		u64 auto_eoi:1;
 		u64 reserved2:46;
-	};
+	} __packed;
 };
 
 /* Define the format of the SIMP register */
@@ -781,7 +781,7 @@ union hv_synic_simp {
 		u64 simp_enabled:1;
 		u64 preserved:11;
 		u64 base_simp_gpa:52;
-	};
+	} __packed;
 };
 
 /* Define the format of the SIEFP register */
@@ -791,34 +791,34 @@ union hv_synic_siefp {
 		u64 siefp_enabled:1;
 		u64 preserved:11;
 		u64 base_siefp_gpa:52;
-	};
+	} __packed;
 };
 
 struct hv_vpset {
 	u64 format;
 	u64 valid_bank_mask;
 	u64 bank_contents[];
-};
+} __packed;
 
 /* HvCallSendSyntheticClusterIpi hypercall */
 struct hv_send_ipi {
 	u32 vector;
 	u32 reserved;
 	u64 cpu_mask;
-};
+} __packed;
 
 /* HvCallSendSyntheticClusterIpiEx hypercall */
 struct hv_send_ipi_ex {
 	u32 vector;
 	u32 reserved;
 	struct hv_vpset vp_set;
-};
+} __packed;
 
 /* HvFlushGuestPhysicalAddressSpace hypercalls */
 struct hv_guest_mapping_flush {
 	u64 address_space;
 	u64 flags;
-};
+} __packed;
 
 /* HvFlushVirtualAddressSpace, HvFlushVirtualAddressList hypercalls */
 struct hv_tlb_flush {
@@ -826,7 +826,7 @@ struct hv_tlb_flush {
 	u64 flags;
 	u64 processor_mask;
 	u64 gva_list[];
-};
+} __packed;
 
 /* HvFlushVirtualAddressSpaceEx, HvFlushVirtualAddressListEx hypercalls */
 struct hv_tlb_flush_ex {
@@ -834,6 +834,6 @@ struct hv_tlb_flush_ex {
 	u64 flags;
 	struct hv_vpset hv_vp_set;
 	u64 gva_list[];
-};
+} __packed;
 
 #endif
-- 
2.19.2