From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Google-Smtp-Source: ACJfBouSBVC2czlpsrBzLMmg2hVNl3mIPT6Kvk1XsV4APMPU2sCOvOB/l589UcvJsipd3qPHhkHa ARC-Seal: i=1; a=rsa-sha256; t=1516378138; cv=none; d=google.com; s=arc-20160816; b=QagMuqWQnHuaUbn5bW9aCmolvE+TCZSD/42B1z1daTFRluIydg0s7Ym4Xiz4TBrajV LQhCbOxNqTR4LvaoWk2M5iCY/HM0z5bLX6rgsLwhQaNt0hv61radanPU26Opk97joOBS K0JfktJN54vu27WGAHDJBapVunFtX8bu9ZbiyQ/XT3yZN85F5FvXDMLBACP1yW/o3eCb ckzsFKYypT6hZerdSN8VPpkNBTb2yRHsp15vQ1u5llK52NMRdkzyFRdFck2KgRJaYE78 ALW8QVCtBd9p0jHaRYL6E/RzWwxP54JeMLkZbBUPkwA6PKWBPYcWrjd6/CpBaOF5nYIs z0xQ== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=mime-version:date:face:references:in-reply-to:cc:to:from:subject :message-id:dkim-signature:arc-authentication-results; bh=zddE9V3350qyVAdcjHyuLYtxvx6/GsrMKmNrWic1FwU=; b=y6y0wmJqjeD7B+9RQIYEusMvAVx8iDI4NkW4U9RY6r0ykIwD8nFTRVkGobwWjbWcnx sf38U2M39+I2dDJDeC2R4XigAjq5aVmweH3aaoONRLsGWQ3kFgvy0h3il57xdQCWZnjd jDIQ6v9uoqOzR2wVEM9IhWHACuMzHijepvRO1QvmNwnBZEXuigmNorCYob+O1vPN3701 OopKxuXYLy3aa+BRTSC4bY12mSSLim7afgJiwtlu64sWMGVmONWZ3swFCv9ipzvNKudX p5EmGAgLcxvIFmaY7m4PiG1FK37ohHHF9rbs7CeeCp8wBzas8fELJaEPjJujrZDTeUS6 bPCg== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@infradead.org header.s=twosheds.20170209 header.b=nH6yv1hI; spf=pass (google.com: best guess record for domain of batv+552516ad27b1608f30ae+5262+infradead.org+dwmw2@twosheds.srs.infradead.org designates 90.155.92.209 as permitted sender) smtp.mailfrom=BATV+552516ad27b1608f30ae+5262+infradead.org+dwmw2@twosheds.srs.infradead.org Authentication-Results: mx.google.com; dkim=pass header.i=@infradead.org header.s=twosheds.20170209 header.b=nH6yv1hI; spf=pass (google.com: best guess record for domain of batv+552516ad27b1608f30ae+5262+infradead.org+dwmw2@twosheds.srs.infradead.org designates 90.155.92.209 as permitted sender) smtp.mailfrom=BATV+552516ad27b1608f30ae+5262+infradead.org+dwmw2@twosheds.srs.infradead.org Message-ID: <1516378093.5087.30.camel@infradead.org> Subject: Re: [PATCH 34/35] x86/kvm: Add IBPB support From: David Woodhouse To: Paolo Bonzini , Peter Zijlstra , Thomas Gleixner , Josh Poimboeuf Cc: linux-kernel@vger.kernel.org, Dave Hansen , Ashok Raj , Tim Chen , Andy Lutomirski , Linus Torvalds , Greg KH , Andrea Arcangeli , Andi Kleen , Arjan Van De Ven , Dan Williams , Jun Nakajima , Asit Mallick , Jason Baron In-Reply-To: References: <20180118134800.711245485@infradead.org> <20180118140153.498071980@infradead.org> Face: 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 Content-Type: multipart/signed; micalg="sha-256"; protocol="application/x-pkcs7-signature"; boundary="=-e/aU6hAC3YsyM6j37nH9" Date: Fri, 19 Jan 2018 17:08:13 +0100 Mime-Version: 1.0 X-Mailer: Evolution 3.18.5.2-0ubuntu3.2 X-SRS-Rewrite: SMTP reverse-path rewritten from by twosheds.infradead.org. See http://www.infradead.org/rpr.html X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-LABELS: =?utf-8?b?IlxcSW1wb3J0YW50Ig==?= X-GMAIL-THRID: =?utf-8?q?1589944833614136394?= X-GMAIL-MSGID: =?utf-8?q?1590037723164814461?= X-Mailing-List: linux-kernel@vger.kernel.org List-ID: --=-e/aU6hAC3YsyM6j37nH9 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Fri, 2018-01-19 at 16:25 +0100, Paolo Bonzini wrote: > Without retpolines, KVM userspace is not protected from the guest > poisoning the BTB, because there is no IBRS-barrier on the vmexit > path. > So there are two more IBPBs that are needed if retpolines are > enabled: >=20 > 1) in kvm_sched_out >=20 > 2) at the end of vcpu_run Hm, yes. That does seem reasonable. Can we make it conditional so it only happens *if* we end up back in userspace, and not for a VM- >kernel->VM transition? And can I have a patch against http://git.infradead.org/users/dwmw2/linux-retpoline.git/shortlog/refs/head= s/ibpb-upstream please (see the XX in that top commit too). I'm still putting that together, and the IBRS bits on top; getting on an airplane to spend some more quality time with it now... --=-e/aU6hAC3YsyM6j37nH9 Content-Type: application/x-pkcs7-signature; name="smime.p7s" Content-Disposition: attachment; filename="smime.p7s" Content-Transfer-Encoding: base64 MIAGCSqGSIb3DQEHAqCAMIACAQExDzANBglghkgBZQMEAgEFADCABgkqhkiG9w0BBwEAAKCCEFQw ggUxMIIEGaADAgECAhBNRhEyk/HZ7naOeTHWrzuAMA0GCSqGSIb3DQEBCwUAMIGXMQswCQYDVQQG EwJHQjEbMBkGA1UECBMSR3JlYXRlciBNYW5jaGVzdGVyMRAwDgYDVQQHEwdTYWxmb3JkMRowGAYD VQQKExFDT01PRE8gQ0EgTGltaXRlZDE9MDsGA1UEAxM0Q09NT0RPIFJTQSBDbGllbnQgQXV0aGVu dGljYXRpb24gYW5kIFNlY3VyZSBFbWFpbCBDQTAeFw0xNzEyMjEwMDAwMDBaFw0xODEyMjEyMzU5 NTlaMCQxIjAgBgkqhkiG9w0BCQEWE2R3bXcyQGluZnJhZGVhZC5vcmcwggEiMA0GCSqGSIb3DQEB AQUAA4IBDwAwggEKAoIBAQDgzLNWa18DNpGUj/ZeH0Sgz53ESIbzdPw3OJeuNP6jZhxZojbyfxbM hETscxI/Hj6UZ4a7sHm5BkVjlsB1Af2Za/PXUt8MmLAcPMHkMPGunvkUibEvblDvpqMkQZlaZM+t 5PqFmWkbehLaEvbpNY7dmEAAeKh4klTzJzrr5AAzaCQ32cA2e3+DEIv5O5l9ViMIjy/JM+xMQrfX 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