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RE: [PATCH 2/3] x86/boot: Don't enable EFER.SCE for !CONFIG_PV builds

  • To: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>
  • From: "Tian, Kevin" <kevin.tian@xxxxxxxxx>
  • Date: Wed, 22 Apr 2020 08:02:33 +0000
  • Accept-language: en-US
  • Cc: Wei Liu <wl@xxxxxxx>, Jan Beulich <JBeulich@xxxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>
  • Delivery-date: Wed, 22 Apr 2020 08:03:16 +0000
  • Dlp-product: dlpe-windows
  • Dlp-reaction: no-action
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  • List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
  • Thread-index: AQHWFyRLs5sm5DaTOEa1b2TGziQ7AqiEylaw
  • Thread-topic: [PATCH 2/3] x86/boot: Don't enable EFER.SCE for !CONFIG_PV builds

> From: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> Sent: Monday, April 20, 2020 10:59 PM
> This will cause all SYSCALL/SYSRET instructions to suffer #UD rather than
> following the MSR_{L,C}STAR pointers, allowing us to drop the star_enter()
> panic helper, allowing us to clean up the IST stacks in a subsequent patch.
> Drop the now-dead conditional SYSENTER logic in the middle of
> subarch_percpu_traps_init().
> In addition, vmx_restore_host_msrs() need not restore any host
> state.  (Regarding the asymmetric changes, VT-x automatically restores
> SYSENTER state on vmexit, and SVM restores both SYSCALL/SYSENTER state
> with
> the VMSAVE/VMLOAD instructions.)
> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>

Reviewed-by: Kevin Tian <kevin.tian@xxxxxxxxx>



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