From owner-freebsd-bugs@freebsd.org Wed Feb 10 00:26:24 2016 Return-Path: Delivered-To: freebsd-bugs@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id 5738EAA12DB for ; Wed, 10 Feb 2016 00:26:24 +0000 (UTC) (envelope-from bugzilla-noreply@freebsd.org) Received: from kenobi.freebsd.org (kenobi.freebsd.org [IPv6:2001:1900:2254:206a::16:76]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id 2E280E0E for ; Wed, 10 Feb 2016 00:26:24 +0000 (UTC) (envelope-from bugzilla-noreply@freebsd.org) Received: from bugs.freebsd.org ([127.0.1.118]) by kenobi.freebsd.org (8.15.2/8.15.2) with ESMTP id u1A0QNCb097136 for ; Wed, 10 Feb 2016 00:26:24 GMT (envelope-from bugzilla-noreply@freebsd.org) From: bugzilla-noreply@freebsd.org To: freebsd-bugs@FreeBSD.org Subject: [Bug 207068] hwpmc wrap around/sign extension Date: Wed, 10 Feb 2016 00:26:24 +0000 X-Bugzilla-Reason: AssignedTo X-Bugzilla-Type: new X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: Base System X-Bugzilla-Component: kern X-Bugzilla-Version: 10.2-STABLE X-Bugzilla-Keywords: hwpmc X-Bugzilla-Severity: Affects Some People X-Bugzilla-Who: joss.upton@yahoo.com X-Bugzilla-Status: New X-Bugzilla-Resolution: X-Bugzilla-Priority: --- X-Bugzilla-Assigned-To: freebsd-bugs@FreeBSD.org X-Bugzilla-Flags: X-Bugzilla-Changed-Fields: bug_id short_desc product version rep_platform op_sys bug_status keywords bug_severity priority component assigned_to reporter cc Message-ID: Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Bugzilla-URL: https://bugs.freebsd.org/bugzilla/ Auto-Submitted: auto-generated MIME-Version: 1.0 X-BeenThere: freebsd-bugs@freebsd.org X-Mailman-Version: 2.1.20 Precedence: list List-Id: Bug reports List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 10 Feb 2016 00:26:24 -0000 https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D207068 Bug ID: 207068 Summary: hwpmc wrap around/sign extension Product: Base System Version: 10.2-STABLE Hardware: amd64 OS: Any Status: New Keywords: hwpmc Severity: Affects Some People Priority: --- Component: kern Assignee: freebsd-bugs@FreeBSD.org Reporter: joss.upton@yahoo.com CC: freebsd-amd64@FreeBSD.org, joss.upton@yahoo.com CC: freebsd-amd64@FreeBSD.org hwpmc_intel writes the old value of a counter back to the counter value register during a context switch in. However, those registers ignore the u= pper 32 bits (EDX) and instead sign extended to the register width based on EAX[= 31]. This is the behavior on all machines not supporting "full width writes" (indicated by CPUID2_PDCM being set && and IA32_PERF_CAPABILITIES(0x345) & FW_WRITE(bit 13) being set). If full width writes are supported, full-width aliases for IA32_PMCn exist 0x400 MSRs higher (e.g. IA32_PMC0 =3D=3D 0xC1 and IA32_A_PMC0 =3D 0x4C1). This affects processes monitoring CPU_CLK for processes running more than a second or two. Using this counter quickly runs into a "negative increment" assertion in hwpmc_mod.c because of the sign extension. Attached is the le= ast invasive patch I could come up with and it's against 10.2-R. It also fixes a few debugging PMCDBGs and adjusts the size of PMC_DEFAULT_DEBUG_FLAGS to match the size of the structure. --=20 You are receiving this mail because: You are the assignee for the bug.=