Date: Fri, 12 Jan 2018 19:01:48 +0000 From: bugzilla-noreply@freebsd.org To: freebsd-bugs@FreeBSD.org Subject: [Bug 213155] possible kernel regression when running 11.x-RELEASE on KVM on AMD Opterons Message-ID: <bug-213155-8-mqrYxaE8zR@https.bugs.freebsd.org/bugzilla/> In-Reply-To: <bug-213155-8@https.bugs.freebsd.org/bugzilla/> References: <bug-213155-8@https.bugs.freebsd.org/bugzilla/>
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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D213155 --- Comment #25 from Bennett <FREEBSD@bfeitell.users.panix.com> --- Thank you all for continuing to chase this down. I expect that using QEMU6= 4 as the CPU type, and adding the additional features is the best stopgap fix un= til this bug is actually resolved. I have been reading through the Linux Kernel mailing list as they work out = the patches for Meltdown and Spectre, and suspect that misidentifying the CPU a= s an Intel Westmere device to gain AES support will cause problems once the new mitigation code goes live. There still might be a performance hit for Free= BSD guests with this solution in the future, as the QEMU64 cpu exposed by KVM w= ill probably not show the new MSRs of a microcode patched Opeteron 4 or Opteron= 5 (K8) CPU. This will cause the guest to default to the expensive "retpolin= e" mitigation for Spectre, rather than the more efficient microcode patched AMD specific "MFence" mitigation that is in the works. --=20 You are receiving this mail because: You are the assignee for the bug.=
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