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=213155 --- Comment #25 from Bennett <FREEBSD@bfeitell.users.panix.com> --- Thank you all for continuing to chase this down. I expect that using QEMU64 as the CPU type, and adding the additional features is the best stopgap fix until 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 as 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 FreeBSD guests with this solution in the future, as the QEMU64 cpu exposed by KVM will 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 "retpoline" mitigation for Spectre, rather than the more efficient microcode patched AMD specific "MFence" mitigation that is in the works. -- You are receiving this mail because: You are the assignee for the bug.
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