[PATCH for-next] x86/VT-x: Don't rewrite HOST_TR_SELECTOR on every context switch

* [PATCH for-next] x86/VT-x: Don't rewrite HOST_TR_SELECTOR on every context switch
@ 2017-10-17 17:16 Andrew Cooper
  2017-10-18  9:40 ` Jan Beulich
  2017-10-23  6:10 ` Tian, Kevin
  0 siblings, 2 replies; 3+ messages in thread
From: Andrew Cooper @ 2017-10-17 17:16 UTC (permalink / raw)
  To: Xen-devel; +Cc: Andrew Cooper, Kevin Tian, Wei Liu, Jun Nakajima, Jan Beulich

TSS_ENTRY is a compile time constant, so HOST_TR_SELECTOR can be set up during
VMCS construction and left alone thereafter, rather than rewriting it on every
context switch.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
---
CC: Jan Beulich <JBeulich@suse.com>
CC: Wei Liu <wei.liu2@citrix.com>
CC: Jun Nakajima <jun.nakajima@intel.com>
CC: Kevin Tian <kevin.tian@intel.com>
---
 xen/arch/x86/hvm/vmx/vmcs.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/xen/arch/x86/hvm/vmx/vmcs.c b/xen/arch/x86/hvm/vmx/vmcs.c
index b5100b5..6042109 100644
--- a/xen/arch/x86/hvm/vmx/vmcs.c
+++ b/xen/arch/x86/hvm/vmx/vmcs.c
@@ -806,7 +806,6 @@ static void vmx_set_host_env(struct vcpu *v)
               (unsigned long)(this_cpu(gdt_table) - FIRST_RESERVED_GDT_ENTRY));
     __vmwrite(HOST_IDTR_BASE, (unsigned long)idt_tables[cpu]);
 
-    __vmwrite(HOST_TR_SELECTOR, TSS_ENTRY << 3);
     __vmwrite(HOST_TR_BASE, (unsigned long)&per_cpu(init_tss, cpu));
 
     __vmwrite(HOST_SYSENTER_ESP, get_stack_bottom());
@@ -1144,6 +1143,7 @@ static int construct_vmcs(struct vcpu *v)
     __vmwrite(HOST_GS_SELECTOR, 0);
     __vmwrite(HOST_FS_BASE, 0);
     __vmwrite(HOST_GS_BASE, 0);
+    __vmwrite(HOST_TR_SELECTOR, TSS_ENTRY << 3);
 
     /* Host control registers. */
     v->arch.hvm_vmx.host_cr0 = read_cr0() | X86_CR0_TS;
-- 
2.1.4


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