Date: Fri, 9 Nov 2012 16:00:30 +0000 (UTC) From: Konstantin Belousov <kib@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r242828 - head/sys/amd64/amd64 Message-ID: <201211091600.qA9G0Umd005041@svn.freebsd.org>
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Author: kib Date: Fri Nov 9 16:00:30 2012 New Revision: 242828 URL: http://svnweb.freebsd.org/changeset/base/242828 Log: Do not try to enable new features in the %cr4 if running under hypervisor. Apparently, hypervisors failed to filter out 'Standard Extended Features' report from CPUID, but deliver #gp when corresponding bit in %cr4 is toggled. This shall be reconsidered later, after hypervisors correct the bug. Reported and tested by: joel Reviewed by: avg MFC after: 2 weeks Modified: head/sys/amd64/amd64/identcpu.c Modified: head/sys/amd64/amd64/identcpu.c ============================================================================== --- head/sys/amd64/amd64/identcpu.c Fri Nov 9 15:29:52 2012 (r242827) +++ head/sys/amd64/amd64/identcpu.c Fri Nov 9 16:00:30 2012 (r242828) @@ -481,7 +481,7 @@ SYSINIT(hook_tsc_freq, SI_SUB_CONFIGURE, void identify_cpu(void) { - u_int regs[4]; + u_int regs[4], cpu_stdext_disable; do_cpuid(0, regs); cpu_high = regs[0]; @@ -516,6 +516,20 @@ identify_cpu(void) if (cpu_high >= 7) { cpuid_count(7, 0, regs); cpu_stdext_feature = regs[1]; + + /* + * Some hypervisors fail to filter out unsupported + * extended features. For now, disable the + * extensions, activation of which requires setting a + * bit in CR4, and which VM monitors do not support. + */ + if (cpu_feature2 & CPUID2_HV) { + cpu_stdext_disable = CPUID_STDEXT_FSGSBASE | + CPUID_STDEXT_SMEP; + } else + cpu_stdext_disable = 0; + TUNABLE_INT_FETCH("hw.cpu_stdext_disable", &cpu_stdext_disable); + cpu_stdext_feature &= ~cpu_stdext_disable; } if (cpu_vendor_id == CPU_VENDOR_INTEL ||
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