Messages in this thread | | | From | Thomas Gleixner <> | Subject | Re: [patch 02/38] x86/cpu: Use native_wrmsrl() in load_percpu_segment() | Date | Mon, 18 Jul 2022 10:55:29 +0200 |
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On Mon, Jul 18 2022 at 08:54, Thomas Gleixner wrote: > On Mon, Jul 18 2022 at 07:11, Juergen Gross wrote: >>> - switch_to_new_gdt(cpu); >>> + switch_to_real_gdt(cpu); >> >> ... can't you use the paravirt variant of load_gdt in switch_to_real_gdt() ? > > That does not solve the problem of having a disagreement between GDT and > GS_BASE. Let me dig into this some more.
Bah. The real problem is __loadsegment_simple(gs, 0). After that GS_BASE is 0. So any per CPU access before setting MSR_GS_BASE back to working state is going into lala land.
So it's not the GDT. It's the mov 0, %gs which makes stuff go south, but as %gs is already 0, we can keep the paravirt load_gdt() and use native_write_msr() and everything should be happy.
Thanks,
tglx
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