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SubjectRe: Can't boot as Xen dom0 due to commit fe055896
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On 16/12/16 11:45, Borislav Petkov wrote:
> On Fri, Dec 16, 2016 at 11:00:29AM +0100, Juergen Gross wrote:
>> Should work. I'm happy to test any patch. :-)
>
> I'm happy that you're happy to! :-)

That makes me happy. :-D

> Let's try this below.

Okay. Results:

Xen HVM domain is working.
Xen dom0 is working.
Bare metal is working, microcode has been loaded.

So you can add my:

Tested-by: Juergen Gross <jgross@suse.com>
Acked-by: Juergen Gross <jgross@suse.com>


Juergen

>
> Thanks!
>
> ---
> diff --git a/arch/x86/kernel/cpu/microcode/core.c b/arch/x86/kernel/cpu/microcode/core.c
> index 6996413c78c3..c4bb2f7169f6 100644
> --- a/arch/x86/kernel/cpu/microcode/core.c
> +++ b/arch/x86/kernel/cpu/microcode/core.c
> @@ -44,7 +44,7 @@
> #define DRIVER_VERSION "2.2"
>
> static struct microcode_ops *microcode_ops;
> -static bool dis_ucode_ldr;
> +static bool dis_ucode_ldr = true;
>
> LIST_HEAD(microcode_cache);
>
> @@ -76,6 +76,7 @@ struct cpu_info_ctx {
> static bool __init check_loader_disabled_bsp(void)
> {
> static const char *__dis_opt_str = "dis_ucode_ldr";
> + u32 a, b, c, d;
>
> #ifdef CONFIG_X86_32
> const char *cmdline = (const char *)__pa_nodebug(boot_command_line);
> @@ -88,8 +89,23 @@ static bool __init check_loader_disabled_bsp(void)
> bool *res = &dis_ucode_ldr;
> #endif
>
> - if (cmdline_find_option_bool(cmdline, option))
> - *res = true;
> + if (!have_cpuid_p())
> + return *res;
> +
> + a = 1;
> + c = 0;
> + native_cpuid(&a, &b, &c, &d);
> +
> + /*
> + * CPUID(1).ECX[31]: reserved for hypervisor use. This is still not
> + * completely accurate as xen pv guests don't see that CPUID bit set but
> + * that's good enough as they don't land on the BSP path anyway.
> + */
> + if (c & BIT(31))
> + return *res;
> +
> + if (cmdline_find_option_bool(cmdline, option) <= 0)
> + *res = false;
>
> return *res;
> }
> @@ -121,9 +137,6 @@ void __init load_ucode_bsp(void)
> if (check_loader_disabled_bsp())
> return;
>
> - if (!have_cpuid_p())
> - return;
> -
> vendor = x86_cpuid_vendor();
> family = x86_cpuid_family();
>
> @@ -157,9 +170,6 @@ void load_ucode_ap(void)
> if (check_loader_disabled_ap())
> return;
>
> - if (!have_cpuid_p())
> - return;
> -
> vendor = x86_cpuid_vendor();
> family = x86_cpuid_family();
>
>

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