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Re: Can't boot as Xen dom0 due to commit fe055896

From Borislav Petkov <bp@suse.de>
Newsgroups linux.kernel
Subject Re: Can't boot as Xen dom0 due to commit fe055896
Date 2016-12-16 10:10 +0100
Message-ID <sOWGD-1t7-53@gated-at.bofh.it> (permalink)
References (2 earlier) <sOHxU-8ap-35@gated-at.bofh.it> <sOHRg-6q-21@gated-at.bofh.it> <sOI0W-9O-31@gated-at.bofh.it> <sOIaC-cX-17@gated-at.bofh.it> <sOV7P-oP-1@gated-at.bofh.it>
Organization linux.* mail to news gateway

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On Fri, Dec 16, 2016 at 08:28:46AM +0100, Juergen Gross wrote:
> Not trying to load ucode in _any_ guest is an optimization only.

Does the hunk below work too?

I don't want to do hypervisor-specific solutions.

---
diff --git a/arch/x86/kernel/cpu/microcode/core.c b/arch/x86/kernel/cpu/microcode/core.c
index 6996413c78c3..54219f619205 100644
--- a/arch/x86/kernel/cpu/microcode/core.c
+++ b/arch/x86/kernel/cpu/microcode/core.c
@@ -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);
@@ -91,6 +92,17 @@ static bool __init check_loader_disabled_bsp(void)
 	if (cmdline_find_option_bool(cmdline, option))
 		*res = true;
 
+	if (!have_cpuid_p())
+		*res = true;
+
+	a = 1;
+	c = 0;
+	native_cpuid(&a, &b, &c, &d);
+
+	/* CPUID(1).ECX[31]: reserved for hypervisor use */
+	if (c & BIT(31))
+		*res = true;
+
 	return *res;
 }
 
@@ -121,9 +133,6 @@ 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 +166,6 @@ void load_ucode_ap(void)
 	if (check_loader_disabled_ap())
 		return;
 
-	if (!have_cpuid_p())
-		return;
-
 	vendor = x86_cpuid_vendor();
 	family = x86_cpuid_family();
 

-- 
Regards/Gruss,
    Boris.

SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg)
-- 

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Thread

Can't boot as Xen dom0 due to commit fe055896 Juergen Gross <jgross@suse.com> - 2016-12-15 17:20 +0100
  Re: Can't boot as Xen dom0 due to commit fe055896 Borislav Petkov <bp@suse.de> - 2016-12-15 17:50 +0100
    Re: [Xen-devel] Can't boot as Xen dom0 due to commit fe055896 "Jan Beulich" <JBeulich@suse.com> - 2016-12-15 18:00 +0100
      Re: [Xen-devel] Can't boot as Xen dom0 due to commit fe055896 Andrew Cooper <andrew.cooper3@citrix.com> - 2016-12-15 18:10 +0100
        Re: [Xen-devel] Can't boot as Xen dom0 due to commit fe055896 Borislav Petkov <bp@suse.de> - 2016-12-15 18:40 +0100
    Re: Can't boot as Xen dom0 due to commit fe055896 Boris Ostrovsky <boris.ostrovsky@oracle.com> - 2016-12-15 18:00 +0100
      Re: Can't boot as Xen dom0 due to commit fe055896 Borislav Petkov <bp@suse.de> - 2016-12-15 18:20 +0100
        Re: Can't boot as Xen dom0 due to commit fe055896 Boris Ostrovsky <boris.ostrovsky@oracle.com> - 2016-12-15 18:30 +0100
          Re: Can't boot as Xen dom0 due to commit fe055896 Borislav Petkov <bp@suse.de> - 2016-12-15 18:40 +0100
            Re: Can't boot as Xen dom0 due to commit fe055896 Boris Ostrovsky <boris.ostrovsky@oracle.com> - 2016-12-15 20:10 +0100
              Re: Can't boot as Xen dom0 due to commit fe055896 Boris Ostrovsky <boris.ostrovsky@oracle.com> - 2016-12-15 20:40 +0100
                Re: Can't boot as Xen dom0 due to commit fe055896 Borislav Petkov <bp@suse.de> - 2016-12-15 21:10 +0100
                Re: Can't boot as Xen dom0 due to commit fe055896 Boris Ostrovsky <boris.ostrovsky@oracle.com> - 2016-12-16 00:00 +0100
                Re: Can't boot as Xen dom0 due to commit fe055896 Borislav Petkov <bp@suse.de> - 2016-12-16 00:10 +0100
                Re: Can't boot as Xen dom0 due to commit fe055896 Boris Ostrovsky <boris.ostrovsky@oracle.com> - 2016-12-16 05:40 +0100
                Re: Can't boot as Xen dom0 due to commit fe055896 Borislav Petkov <bp@suse.de> - 2016-12-16 10:10 +0100
                Re: [Xen-devel] Can't boot as Xen dom0 due to commit fe055896 Andrew Cooper <andrew.cooper3@citrix.com> - 2016-12-16 10:40 +0100
                Re: Can't boot as Xen dom0 due to commit fe055896 Henrique de Moraes Holschuh <hmh@hmh.eng.br> - 2016-12-16 05:40 +0100
              Re: Can't boot as Xen dom0 due to commit fe055896 Borislav Petkov <bp@suse.de> - 2016-12-15 20:50 +0100
            Re: Can't boot as Xen dom0 due to commit fe055896 Juergen Gross <jgross@suse.com> - 2016-12-16 08:30 +0100
              Re: Can't boot as Xen dom0 due to commit fe055896 Borislav Petkov <bp@suse.de> - 2016-12-16 10:10 +0100
                Re: Can't boot as Xen dom0 due to commit fe055896 Juergen Gross <jgross@suse.com> - 2016-12-16 10:30 +0100
                Re: Can't boot as Xen dom0 due to commit fe055896 Borislav Petkov <bp@suse.de> - 2016-12-16 10:50 +0100
                Re: Can't boot as Xen dom0 due to commit fe055896 Juergen Gross <jgross@suse.com> - 2016-12-16 11:10 +0100
                Re: Can't boot as Xen dom0 due to commit fe055896 Borislav Petkov <bp@suse.de> - 2016-12-16 12:10 +0100
                Re: Can't boot as Xen dom0 due to commit fe055896 Juergen Gross <jgross@suse.com> - 2016-12-16 13:20 +0100
                Re: Can't boot as Xen dom0 due to commit fe055896 Borislav Petkov <bp@suse.de> - 2016-12-16 13:50 +0100
                Re: Can't boot as Xen dom0 due to commit fe055896 Borislav Petkov <bp@suse.de> - 2016-12-16 14:10 +0100
                Re: Can't boot as Xen dom0 due to commit fe055896 Boris Ostrovsky <boris.ostrovsky@oracle.com> - 2016-12-16 15:40 +0100
                Re: Can't boot as Xen dom0 due to commit fe055896 Borislav Petkov <bp@suse.de> - 2016-12-16 16:20 +0100
    Re: Can't boot as Xen dom0 due to commit fe055896 Juergen Gross <jgross@suse.com> - 2016-12-15 18:30 +0100

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