linux-kernel - [PATCH 14/28] KVM: nSVM: remove trailing padding for struct vmcb_control

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Message-Id: <20200526172308.111575-15-pbonzini@redhat.com>
Date:   Tue, 26 May 2020 13:22:54 -0400
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc:     vkuznets@...hat.com, mlevitsk@...hat.com,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Jim Mattson <jmattson@...gle.com>
Subject: [PATCH 14/28] KVM: nSVM: remove trailing padding for struct vmcb_control_area

Allow placing the VMCB structs on the stack or in other structs without
wasting too much space.  Add BUILD_BUG_ON as a quick safeguard against typos.

Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
---
 arch/x86/include/asm/svm.h | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/svm.h b/arch/x86/include/asm/svm.h
index 6ece8561ba66..8a1f5382a4ea 100644
--- a/arch/x86/include/asm/svm.h
+++ b/arch/x86/include/asm/svm.h
@@ -96,7 +96,6 @@ struct __attribute__ ((__packed__)) vmcb_control_area {
 	u8 reserved_6[8];	/* Offset 0xe8 */
 	u64 avic_logical_id;	/* Offset 0xf0 */
 	u64 avic_physical_id;	/* Offset 0xf8 */
-	u8 reserved_7[768];
 };
 
 
@@ -203,8 +202,16 @@ struct __attribute__ ((__packed__)) vmcb_save_area {
 	u64 last_excp_to;
 };
 
+
+static inline void __unused_size_checks(void)
+{
+	BUILD_BUG_ON(sizeof(struct vmcb_save_area) != 0x298);
+	BUILD_BUG_ON(sizeof(struct vmcb_control_area) != 256);
+}
+
 struct __attribute__ ((__packed__)) vmcb {
 	struct vmcb_control_area control;
+	u8 reserved_control[1024 - sizeof(struct vmcb_control_area)];
 	struct vmcb_save_area save;
 };
 
-- 
2.26.2