[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

[Andrew Cooper]

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

[Jan Beulich]

>>> On 17.10.17 at 19:16, <andrew.cooper3@citrix.com> wrote:
> 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>

Reviewed-by: Jan Beulich <jbeulich@suse.com>



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

[Tian, Kevin]

> From: Andrew Cooper [mailto:andrew.cooper3@citrix.com]
> Sent: Wednesday, October 18, 2017 1:16 AM
> 
> 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>

Acked-by: Kevin Tian <kevin.tian@intel.com>

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