Date: Fri, 18 Jan 2019 17:08:44 -0800 (PST) From: "Rodney W. Grimes" <freebsd@pdx.rh.CN85.dnsmgr.net> To: Conrad Meyer <cem@freebsd.org> Cc: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: Re: svn commit: r343166 - head/sys/amd64/vmm Message-ID: <201901190108.x0J18isQ058215@pdx.rh.CN85.dnsmgr.net> In-Reply-To: <201901182354.x0INspeZ015766@repo.freebsd.org>
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> Author: cem > Date: Fri Jan 18 23:54:51 2019 > New Revision: 343166 > URL: https://svnweb.freebsd.org/changeset/base/343166 > > Log: > vmm(4): Mask Spectre feature bits on AMD hosts > > For parity with Intel hosts, which already mask out the CPUID feature > bits that indicate the presence of the SPEC_CTRL MSR, do the same on > AMD. > > Eventually we may want to have a better support story for guests, but > for now, limit the damage of incorrectly indicating an MSR we do not yet > support. > > Eventually, we may want a generic CPUID override system for > administrators, or for minimum supported feature set in heterogenous > environments with failover. That is a much larger scope effort than > this bug fix. This area has a MAINTAINERS line, could you please respect it. > PR: 235010 > Reported by: Rys Sommefeldt <rys AT sommefeldt.com> > Sponsored by: Dell EMC Isilon > > Modified: > head/sys/amd64/vmm/x86.c > > Modified: head/sys/amd64/vmm/x86.c > ============================================================================== > --- head/sys/amd64/vmm/x86.c Fri Jan 18 23:26:31 2019 (r343165) > +++ head/sys/amd64/vmm/x86.c Fri Jan 18 23:54:51 2019 (r343166) > @@ -136,6 +136,14 @@ x86_emulate_cpuid(struct vm *vm, int vcpu_id, > case CPUID_8000_0008: > cpuid_count(*eax, *ecx, regs); > if (vmm_is_amd()) { > + /* > + * As on Intel (0000_0007:0, EDX), mask out > + * unsupported or unsafe AMD extended features > + * (8000_0008 EBX). > + */ > + regs[1] &= (AMDFEID_CLZERO | AMDFEID_IRPERF | > + AMDFEID_XSAVEERPTR); > + > vm_get_topology(vm, &sockets, &cores, &threads, > &maxcpus); > /* > > -- Rod Grimes rgrimes@freebsd.org
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