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[PATCH v2 3/7] x86/kvm/vmx: Get rid of segment_base() on 64-bit kernels

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It was a bit buggy (it didn't list all segment types that needed
64-bit fixups), but the bug was irrelevant because it wasn't called
in any interesting context on 64-bit kernels and was only used for
code and data segments on 32-bit kernels.

To avoid confusion, make it explicitly 32-bit only.

Cc: Thomas Garnier <thgarnie@google.com>
Cc: Jim Mattson <jmattson@google.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Andy Lutomirski <luto@kernel.org>
---
 arch/x86/kvm/vmx.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 46420aaf1684..b1810a0edec3 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -2059,6 +2059,12 @@ static bool update_transition_efer(struct vcpu_vmx *vmx, int efer_offset)
 	}
 }
 
+#ifdef CONFIG_X86_32
+/*
+ * On 32-bit kernels, VM exits still load the FS and GS bases from the
+ * VMCS rather than the segment table.  KVM uses this helper to figure
+ * out the current bases to poke them into the VMCS before entry.
+ */
 static unsigned long segment_base(u16 selector)
 {
 	struct desc_ptr *gdt = this_cpu_ptr(&host_gdt);
@@ -2081,12 +2087,9 @@ static unsigned long segment_base(u16 selector)
 	}
 	d = (struct desc_struct *)(table_base + (selector & ~7));
 	v = get_desc_base(d);
-#ifdef CONFIG_X86_64
-       if (d->s == 0 && (d->type == 2 || d->type == 9 || d->type == 11))
-               v |= ((unsigned long)((struct ldttss_desc64 *)d)->base3) << 32;
-#endif
 	return v;
 }
+#endif
 
 static void vmx_save_host_state(struct kvm_vcpu *vcpu)
 {
-- 
2.9.3

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[PATCH v2 3/7] x86/kvm/vmx: Get rid of segment_base() on 64-bit kernels Andy Lutomirski <luto@kernel.org> - 2017-02-21 20:20 +0100

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