From: Jan Beulich <jbeulich@suse.com>
To: "xen-devel@lists.xenproject.org" <xen-devel@lists.xenproject.org>
Cc: "Andrew Cooper" <andrew.cooper3@citrix.com>,
"Ian Jackson" <ian.jackson@eu.citrix.com>, "Wei Liu" <wl@xen.org>,
"Roger Pau Monné" <roger.pau@citrix.com>
Subject: [Xen-devel] [PATCH] libxc/x86: correct overflow avoidance check in AMD CPUID handling
Date: Wed, 25 Sep 2019 10:34:04 +0200 [thread overview]
Message-ID: <c15e735a-089a-8c9e-5bb4-f2edd781819e@suse.com> (raw)
Commit df29d03f1d ("libxc/x86: avoid certain overflows in CPUID APIC ID
adjustments" introduced a one bit too narrow mask when checking whether
multiplying by 1 (in particular in leaf 1) would result in overflow.
Reported-by: Andrew Cooper <andrew.cooper3@citrix.com>
Signed-off-by: Jan Beulich <jbeulich@suse.com>
--- a/tools/libxc/xc_cpuid_x86.c
+++ b/tools/libxc/xc_cpuid_x86.c
@@ -403,7 +403,7 @@ static void amd_xc_cpuid_policy(const st
* - incrementing ApicIdCoreSize when it's zero (which changes the
* meaning of bits 7:0).
*/
- if ( (regs[2] & 0x7fu) < 0x7fu )
+ if ( (regs[2] & 0xffu) < 0x7fu )
{
if ( (regs[2] & 0xf000u) && (regs[2] & 0xf000u) != 0xf000u )
regs[2] = ((regs[2] + 0x1000u) & 0xf000u) | (regs[2] & 0xffu);
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next reply other threads:[~2019-09-25 8:35 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-25 8:34 Jan Beulich [this message]
2019-09-25 11:33 ` [Xen-devel] [PATCH] libxc/x86: correct overflow avoidance check in AMD CPUID handling Andrew Cooper
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