From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linutronix.de (193.142.43.55:993) by crypto-ml.lab.linutronix.de with IMAP4-SSL for ; 12 Mar 2020 16:02:30 -0000 Received: from mga12.intel.com ([192.55.52.136]) by Galois.linutronix.de with esmtps (TLS1.2:DHE_RSA_AES_256_CBC_SHA256:256) (Exim 4.80) (envelope-from ) id 1jCQI1-0005od-Hm for speck@linutronix.de; Thu, 12 Mar 2020 17:02:29 +0100 Date: Thu, 12 Mar 2020 09:02:24 -0700 From: "Luck, Tony" Subject: [MODERATED] Re: [PATCH 1/2] v3 more sampling fun 1 Message-ID: <20200312160224.GA17609@agluck-desk2.amr.corp.intel.com> References: <7509b1c6-1324-5763-36b4-83d306da7979@citrix.com> <20200311231819.GB78230@mtg-dev.jf.intel.com> <20200312002521.GA32316@agluck-desk2.amr.corp.intel.com> <20200312152501.GA16899@agluck-desk2.amr.corp.intel.com> MIME-Version: 1.0 In-Reply-To: <20200312152501.GA16899@agluck-desk2.amr.corp.intel.com> Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit To: speck@linutronix.de List-ID: On Thu, Mar 12, 2020 at 08:25:01AM -0700, speck for Luck, Tony wrote: > On Thu, Mar 12, 2020 at 01:34:50AM +0000, speck for Andrew Cooper wrote: > > Particularly with this issue where it seems that no hypervisor is > > interested in offering the knob to guest kernels (so could at least > > infer based on SRBDS_CTRL), nor is there an ARCH_CAPS_$FOO_NO bit which > > could be filled in by a hypervisor on unaffected or mitigated hardware. > > Maybe that is the solution? We allocated a s/w (VMM) bit in > ARCH_CAPABILITIES for the TLB DoS issue for the nested hypervisor case. > Should we do that again for this issue? Bah, memory fail. I was actually thinking of bit 3 SKIP_L1DFL_VMENTRY that told a nested VMM it didn't need to flush L1D again for L1TF as an outer VMM was already handling that. > If you think so, then we can take this discussion to Keybase so > that the other VMM vendors who hang out there can chime in. > > [Note that it isn't my call to allocate a bit in ARCH_CAPABILITIES, > but I can campaign for it if folks want it]. > > -Tony