From: Jan Beulich <email@example.com> To: Juergen Gross <firstname.lastname@example.org> Cc: "email@example.com" <firstname.lastname@example.org>, Boris Ostrovsky <email@example.com> Subject: Re: [PATCH] x86/Xen: swap NX determination and GDT setup on BSP Date: Fri, 21 May 2021 09:26:08 +0200 [thread overview] Message-ID: <firstname.lastname@example.org> (raw) In-Reply-To: <email@example.com> On 21.05.2021 09:18, Juergen Gross wrote: > On 20.05.21 14:08, Jan Beulich wrote: >> On 20.05.2021 13:57, Juergen Gross wrote: >>> On 20.05.21 13:42, Jan Beulich wrote: >>>> xen_setup_gdt(), via xen_load_gdt_boot(), wants to adjust page tables. >>>> For this to work when NX is not available, x86_configure_nx() needs to >>>> be called first. >>>> >>>> Reported-by: Olaf Hering <firstname.lastname@example.org> >>>> Signed-off-by: Jan Beulich <email@example.com> >>> >>> Reviewed-by: Juergen Gross <firstname.lastname@example.org> >> >> Thanks. I guess I forgot >> >> Cc: email@example.com >> >> If you agree, can you please add this before pushing to Linus? > > Uh, just had a look why x86_configure_nx() was called after > xen_setup_gdt(). > > Upstream your patch will be fine, but before kernel 5.9 it will > break running as 32-bit PV guest (see commit 36104cb9012a82e7). Oh, indeed. That commit then actually introduced the issue here, and hence a Fixes: tag may be warranted. > So I will take your patch as is, but for kernels 5.8 and older I > recommend a different approach by directly setting the NX > capability after checking the cpuid bit instead of letting that > do get_cpu_cap(). Right - perhaps the only halfway viable option. 64-bit kernels predating 4f277295e54c may then also need that one, but perhaps all stable ones already have it because it was tagged for stable. Jan
next prev parent reply other threads:[~2021-05-21 7:26 UTC|newest] Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-05-20 11:42 Jan Beulich 2021-05-20 11:57 ` Juergen Gross 2021-05-20 12:08 ` Jan Beulich 2021-05-20 12:18 ` Juergen Gross 2021-05-21 7:18 ` Juergen Gross 2021-05-21 7:26 ` Jan Beulich [this message] 2021-05-21 7:45 ` Juergen Gross 2021-05-21 13:12 ` Boris Ostrovsky 2021-05-21 13:15 ` Jan Beulich 2021-05-21 13:17 ` Boris Ostrovsky 2021-05-21 8:30 ` Juergen Gross
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