Re: x86: Meltdown/Spectre_v2 status

From: "Woodhouse, David" <dwmw@amazon.co.uk>
To: "tglx@linutronix.de" <tglx@linutronix.de>,
	"jpoimboe@redhat.com" <jpoimboe@redhat.com>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"peterz@infradead.org" <peterz@infradead.org>,
	"arjan@linux.intel.com" <arjan@linux.intel.com>,
	"mingo@kernel.org" <mingo@kernel.org>,
	"torvalds@linux-foundation.org" <torvalds@linux-foundation.org>,
	"tim.c.chen@linux.intel.com" <tim.c.chen@linux.intel.com>,
	"ak@linux.intel.com" <ak@linux.intel.com>,
	"pjt@google.com" <pjt@google.com>, "bp@alien8.de" <bp@alien8.de>,
	"dave.hansen@intel.com" <dave.hansen@intel.com>,
	"jikos@kernel.org" <jikos@kernel.org>,
	"thomas.lendacky@amd.com" <thomas.lendacky@amd.com>,
	"gregkh@linux-foundation.org" <gregkh@linux-foundation.org>
Subject: Re: x86: Meltdown/Spectre_v2 status
Date: Sat, 13 Jan 2018 11:55:17 +0000	[thread overview]
Message-ID: <1515844512.22302.543.camel@amazon.co.uk> (raw)
In-Reply-To: <20180112224814.q722naei5qs76bam@treble>

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On Fri, 2018-01-12 at 16:48 -0600, Josh Poimboeuf wrote:
> >   1) Meltdown is addressed
> >   2) Retpoline mostly covered if we have working compilers some day 
> >   3) RSB after vmexit and on context switch (pending)
> > 
> > plus the infrastructure and basic building blocks are in place.
> > 
> > That's what is going to be in 4.15 (unless Linus goes berserk on the pull
> > requests)

To be clear: This doesn't include IBPB and thus userspace processes
(and VM guests) are not protected from each other.

But the attacks there are extremely hard to pull off, and I think we
can live with that in the short term. IBPB does need to be next, but I
think we're entirely correct to proceed without it for now. I just want
to make sure we're clear about the status.

> And for those who are curious (I was) it looks like the BPF variant 1
> fix has already been merged into Linus' tree.

Great. I was going to check on that too.

> Thomas, amazing job distilling some sanity out of the pandemonium.

Indeed. Thank you, Thomas.

FWIW we've done a backport of the sysfs/vulnerability and retpoline
parts to 4.9, including cherry-picking a few earlier needed commits:
http://git.infradead.org/retpoline-stable.git/shortlog/refs/heads/linux-4.9.y

Josh, I'd very much appreciate your eyes on my objtool-related
backports — both your retpoline-specific patches, as well as the
.discard.* bits they depended on. Thanks.

Bringing ASM_CALL_CONSTRAINT in as-is seemed like the same thing to do
too.

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