linux-kernel - [PATCH 3.10 211/250] powerpc: Disable HFSCR[TM] if TM is not supported

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <1496876436-32402-212-git-send-email-w@1wt.eu>
Date:   Thu,  8 Jun 2017 00:59:57 +0200
From:   Willy Tarreau <w@....eu>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        linux@...ck-us.net
Cc:     Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Sam Bobroff <sam.bobroff@....ibm.com>, Willy Tarreau <w@....eu>
Subject: [PATCH 3.10 211/250] powerpc: Disable HFSCR[TM] if TM is not supported

From: Benjamin Herrenschmidt <benh@...nel.crashing.org>

commit 7ed23e1bae8bf7e37fd555066550a00b95a3a98b upstream.

On Power8 & Power9 the early CPU inititialisation in __init_HFSCR()
turns on HFSCR[TM] (Hypervisor Facility Status and Control Register
[Transactional Memory]), but that doesn't take into account that TM
might be disabled by CPU features, or disabled by the kernel being built
with CONFIG_PPC_TRANSACTIONAL_MEM=n.

So later in boot, when we have setup the CPU features, clear HSCR[TM] if
the TM CPU feature has been disabled. We use CPU_FTR_TM_COMP to account
for the CONFIG_PPC_TRANSACTIONAL_MEM=n case.

Without this a KVM guest might try use TM, even if told not to, and
cause an oops in the host kernel. Typically the oops is seen in
__kvmppc_vcore_entry() and may or may not be fatal to the host, but is
always bad news.

In practice all shipping CPU revisions do support TM, and all host
kernels we are aware of build with TM support enabled, so no one should
actually be able to hit this in the wild.

Fixes: 2a3563b023e5 ("powerpc: Setup in HFSCR for POWER8")
Signed-off-by: Benjamin Herrenschmidt <benh@...nel.crashing.org>
Tested-by: Sam Bobroff <sam.bobroff@....ibm.com>
[mpe: Rewrite change log with input from Sam, add Fixes/stable]
Signed-off-by: Michael Ellerman <mpe@...erman.id.au>
[sb: Backported to linux-4.4.y: adjusted context]
Signed-off-by: Sam Bobroff <sam.bobroff@....ibm.com>
Signed-off-by: Willy Tarreau <w@....eu>
---
 arch/powerpc/kernel/setup_64.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/arch/powerpc/kernel/setup_64.c b/arch/powerpc/kernel/setup_64.c
index 389fb807..1d3d3d6 100644
--- a/arch/powerpc/kernel/setup_64.c
+++ b/arch/powerpc/kernel/setup_64.c
@@ -142,6 +142,15 @@ static void check_smt_enabled(void)
 			of_node_put(dn);
 		}
 	}
+
+	/*
+	 * Fixup HFSCR:TM based on CPU features. The bit is set by our
+	 * early asm init because at that point we haven't updated our
+	 * CPU features from firmware and device-tree. Here we have,
+	 * so let's do it.
+	 */
+	if (cpu_has_feature(CPU_FTR_HVMODE) && !cpu_has_feature(CPU_FTR_TM_COMP))
+		mtspr(SPRN_HFSCR, mfspr(SPRN_HFSCR) & ~HFSCR_TM);
 }

 /* Look for smt-enabled= cmdline option */
-- 
2.8.0.rc2.1.gbe9624a