Date: Mon, 20 May 2019 19:55:32 -0700 From: Mel Pilgrim <list_freebsd@bluerosetech.com> To: Tim Daneliuk <tundra@tundraware.com>, freebsd-questions@freebsd.org Subject: Re: Unclear On The New MDS Patch Message-ID: <17c04ae2-9b32-3cbe-93c9-819af21b4ff8@bluerosetech.com> In-Reply-To: <ab6a8ca9-9c5a-251d-85df-74e8a5bb7410@tundraware.com> References: <db4ca28f-feed-5c71-b178-d3a750f1ed28@tundraware.com> <20190519230343.4340af09@gumby.homeunix.com> <ab6a8ca9-9c5a-251d-85df-74e8a5bb7410@tundraware.com>
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On 2019-05-20 11:11, Tim Daneliuk wrote: > What about cloud based servers like Digital Ocean FreeBSD droplets? Does > microcode updating even make sense in that context since the underlying > system is actually what touches the hardware? Short answer: no. Longer answer: Microcode updates use the WRMSR (WRite Model Specific Register) instruction, which requires ring 0. Intel and AMD virtualization both emulate ring 0 for guests by pushing the physical ring 0 into a layer only accessible by the VMM and faking it for guests so they can operate without paravirtualization. This is visible with software like msr-tools, where the rdmsr tool works fine but wrmsr appears to have no effect when run on a guest.
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