Messages in this thread | | | From | Thomas Gleixner <> | Subject | Re: [PATCH v8 24/33] x86/fred: disallow the swapgs instruction when FRED is enabled | Date | Mon, 05 Jun 2023 15:47:20 +0200 |
| |
On Mon, Apr 10 2023 at 01:14, Xin Li wrote: > From: "H. Peter Anvin (Intel)" <hpa@zytor.com> > > The FRED architecture establishes the full supervisor/user through: > 1) FRED event delivery swaps the value of the GS base address and > that of the IA32_KERNEL_GS_BASE MSR. > 2) ERETU swaps the value of the GS base address and that of the > IA32_KERNEL_GS_BASE MSR. > Thus, the swapgs instruction is disallowed when FRED is enabled, > otherwise it causes #UD.
Which does not explain why writing directly to the IA32_KERNEL_GS_BASE MSR is doing the right thing.
Thanks,
tglx
| |