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Re: [PATCH] x86/amd: Drop allow_unsafe parameter, tune down XSA-9 mitigations
- To: Teddy Astie <teddy.astie@xxxxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Mon, 4 May 2026 12:37:42 +0200
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- Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Anthony PERARD <anthony.perard@xxxxxxxxxx>, Michal Orzel <michal.orzel@xxxxxxx>, Julien Grall <julien@xxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx
- Delivery-date: Mon, 04 May 2026 10:37:37 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 22.04.2026 18:58, Teddy Astie wrote:
> @@ -1205,19 +1201,12 @@ static void cf_check init_amd(struct cpuinfo_x86 *c)
> if (c->family == 0x10)
> __clear_bit(X86_FEATURE_MONITOR, c->x86_capability);
>
> - if (!cpu_has_amd_erratum(c, AMD_ERRATUM_121))
> - opt_allow_unsafe = 1;
> - else if (opt_allow_unsafe < 0)
> - panic("Xen will not boot on this CPU for security reasons"
> - "Pass \"allow_unsafe\" if you're trusting all your"
> - " (PV) guest kernels.\n");
> - else if (!opt_allow_unsafe && c == &boot_cpu_data)
> + if (cpu_has_amd_erratum(c, AMD_ERRATUM_121))
> + {
Nit: Misplaced brace (it's Linux style here). But really I don't see why
braces are added in the first place.
> printk(KERN_WARNING
> - "*** Xen will not allow creation of DomU-s on"
> - " this CPU for security reasons. ***\n"
> - KERN_WARNING
> - "*** Pass \"allow_unsafe\" if you're trusting"
> - " all your (PV) guest kernels. ***\n");
> + "*** This CPU is affected with erratum 121"
> + " 64-bits PV guests are able to cause a DoS (XSA-9)
> ***\n");
Why the change in indentation?
There's also punctuation missing between both parts of the log message.
Jan
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