linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: linux-kernel@vger.kernel.org
Cc: x86@kernel.org, "Andy Lutomirski" <luto@kernel.org>,
	"Paolo Bonzini" <pbonzini@redhat.com>,
	"Radim Krčmář" <rkrcmar@redhat.com>,
	kvm@vger.kernel.org, "Jason A. Donenfeld" <Jason@zx2c4.com>,
	"Rik van Riel" <riel@surriel.com>,
	"Dave Hansen" <dave.hansen@linux.intel.com>,
	"Sebastian Andrzej Siewior" <bigeasy@linutronix.de>
Subject: [PATCH 05/11] x86/fpu: set PKRU state for kernel threads
Date: Thu,  4 Oct 2018 16:05:41 +0200	[thread overview]
Message-ID: <20181004140547.13014-6-bigeasy@linutronix.de> (raw)
In-Reply-To: <20181004140547.13014-1-bigeasy@linutronix.de>

The PKRU value is not set for kernel threads because they do not have
the ->initialized value set. As a result the kernel thread has a random
PKRU value set which it inherits from the previous task.
It has been suggested by Paolo Bonzini to set it for kernel threads, too
because it might be a fix.
I *think* this is not required because the kernel threads don't copy
data to/from userland and don't have access to any userspace mm in
general.
However there is this use_mm(). If we gain a mm by use_mm() we don't
have a matching PKRU value because those are per thread. It has been
suggested to use 0 as the PKRU value but this would bypass PKRU.

Set the initial (default) PKRU value for kernel threads.

Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
 arch/x86/include/asm/fpu/internal.h | 20 ++++++++++++--------
 1 file changed, 12 insertions(+), 8 deletions(-)

diff --git a/arch/x86/include/asm/fpu/internal.h b/arch/x86/include/asm/fpu/internal.h
index 956d967ca824a..4ecaf4d22954e 100644
--- a/arch/x86/include/asm/fpu/internal.h
+++ b/arch/x86/include/asm/fpu/internal.h
@@ -14,6 +14,7 @@
 #include <linux/compat.h>
 #include <linux/sched.h>
 #include <linux/slab.h>
+#include <linux/pkeys.h>
 
 #include <asm/user.h>
 #include <asm/fpu/api.h>
@@ -573,20 +574,23 @@ static inline void switch_fpu_finish(struct fpu *new_fpu, int cpu)
 	bool load_fpu;
 
 	load_fpu = static_cpu_has(X86_FEATURE_FPU) && new_fpu->initialized;
-	if (!load_fpu)
-		return;
-
-	__fpregs_load_activate(new_fpu, cpu);
-
 #ifdef CONFIG_X86_INTEL_MEMORY_PROTECTION_KEYS
 	if (static_cpu_has(X86_FEATURE_OSPKE)) {
 		struct pkru_state *pk;
 
-		pk = __raw_xsave_addr(&new_fpu->state.xsave, XFEATURE_PKRU);
-		if (pk->pkru != __read_pkru())
-			__write_pkru(pk->pkru);
+		if (!load_fpu) {
+			pkru_set_init_value();
+		} else {
+			pk = __raw_xsave_addr(&new_fpu->state.xsave,
+					      XFEATURE_PKRU);
+			if (pk->pkru != __read_pkru())
+				__write_pkru(pk->pkru);
+		}
 	}
 #endif
+	if (!load_fpu)
+		return;
+	__fpregs_load_activate(new_fpu, cpu);
 }
 
 /*
-- 
2.19.0


  parent reply	other threads:[~2018-10-04 14:06 UTC|newest]

Thread overview: 57+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-10-04 14:05 [PATCH 00/11 v3] x86: load FPU registers on return to userland Sebastian Andrzej Siewior
2018-10-04 14:05 ` [PATCH 01/11] x86/entry: remove _TIF_ALLWORK_MASK Sebastian Andrzej Siewior
2018-10-11 16:27   ` Borislav Petkov
2018-10-04 14:05 ` [PATCH 02/11] x86/fpu: add (__)make_fpregs_active helpers Sebastian Andrzej Siewior
2018-10-04 14:05 ` [PATCH 03/11] x86/fpu: make __raw_xsave_addr() use feature number instead of mask Sebastian Andrzej Siewior
2018-10-11 17:30   ` Christophe de Dinechin
2018-10-18 11:19     ` Sebastian Andrzej Siewior
2018-10-12 15:52   ` Dave Hansen
2018-10-18 11:17     ` Sebastian Andrzej Siewior
2018-10-18 11:21       ` Sebastian Andrzej Siewior
2018-10-17 10:01   ` Borislav Petkov
2018-10-18 11:48     ` Sebastian Andrzej Siewior
2018-10-04 14:05 ` [PATCH 04/11] x86/fpu: eager switch PKRU state Sebastian Andrzej Siewior
2018-10-12 17:51   ` Dave Hansen
2018-10-12 18:09     ` Andy Lutomirski
2018-10-12 19:44       ` Dave Hansen
2018-10-18 16:13     ` Sebastian Andrzej Siewior
2018-10-18 17:50       ` Dave Hansen
2018-10-04 14:05 ` Sebastian Andrzej Siewior [this message]
2018-10-12 17:54   ` [PATCH 05/11] x86/fpu: set PKRU state for kernel threads Dave Hansen
2018-10-12 18:02     ` Andy Lutomirski
2018-10-18 16:26       ` Sebastian Andrzej Siewior
2018-10-18 16:48         ` Andy Lutomirski
2018-10-18 17:47           ` Dave Hansen
2018-10-18 18:25           ` Sebastian Andrzej Siewior
2018-10-18 20:46             ` Andy Lutomirski
2018-10-18 20:56               ` Dave Hansen
2018-10-18 21:24                 ` Sebastian Andrzej Siewior
2018-10-18 21:58                   ` Andy Lutomirski
2018-10-19  7:44               ` Paolo Bonzini
2018-10-19 16:59                 ` Andy Lutomirski
2018-10-19 17:01                   ` Dave Hansen
2018-10-19 17:37                     ` Andy Lutomirski
2018-10-19 18:26                       ` Dave Hansen
2018-10-04 14:05 ` [PATCH 06/11] x86/pkeys: make init_pkru_value static Sebastian Andrzej Siewior
2018-10-12 17:55   ` Dave Hansen
2018-10-04 14:05 ` [PATCH 07/11] x86/pkeys: Drop the preempt-disable section Sebastian Andrzej Siewior
2018-10-12 17:58   ` Dave Hansen
2018-10-12 18:07     ` Andy Lutomirski
2018-10-12 20:26       ` Sebastian Andrzej Siewior
2018-10-04 14:05 ` [PATCH 08/11] x86/fpu: Always store the registers in copy_fpstate_to_sigframe() Sebastian Andrzej Siewior
2018-10-11 17:50   ` Christophe de Dinechin
2018-10-11 21:18     ` Andy Lutomirski
2018-10-12 18:15   ` Dave Hansen
2018-11-02 14:42     ` Sebastian Andrzej Siewior
2018-10-04 14:05 ` [PATCH 09/11] x86/entry: add TIF_LOAD_FPU Sebastian Andrzej Siewior
2018-10-04 14:05 ` [PATCH 10/11] x86/fpu: prepare copy_fpstate_to_sigframe for TIF_LOAD_FPU Sebastian Andrzej Siewior
2018-10-12 19:40   ` Dave Hansen
2018-10-15 15:24     ` Borislav Petkov
2018-11-02 15:44       ` Sebastian Andrzej Siewior
2018-11-02 22:55     ` Sebastian Andrzej Siewior
2018-10-04 14:05 ` [PATCH 11/11] x86/fpu: defer FPU state load until return to userspace Sebastian Andrzej Siewior
2018-10-04 16:14   ` Andy Lutomirski
2018-10-12 20:25     ` Sebastian Andrzej Siewior
2018-10-04 16:45 ` [PATCH 00/11 v3] x86: load FPU registers on return to userland Rik van Riel
2018-10-04 16:50   ` Andy Lutomirski
2018-10-05 11:55   ` Sebastian Andrzej Siewior

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20181004140547.13014-6-bigeasy@linutronix.de \
    --to=bigeasy@linutronix.de \
    --cc=Jason@zx2c4.com \
    --cc=dave.hansen@linux.intel.com \
    --cc=kvm@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=luto@kernel.org \
    --cc=pbonzini@redhat.com \
    --cc=riel@surriel.com \
    --cc=rkrcmar@redhat.com \
    --cc=x86@kernel.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).