From: Borislav Petkov <bp@alien8.de>
To: Yu-cheng Yu <yu-cheng.yu@intel.com>
Cc: x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>,
linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org,
linux-mm@kvack.org, linux-arch@vger.kernel.org,
linux-api@vger.kernel.org, Arnd Bergmann <arnd@arndb.de>,
Andy Lutomirski <luto@amacapital.net>,
Balbir Singh <bsingharora@gmail.com>,
Cyrill Gorcunov <gorcunov@gmail.com>,
Dave Hansen <dave.hansen@linux.intel.com>,
Florian Weimer <fweimer@redhat.com>,
"H.J. Lu" <hjl.tools@gmail.com>, Jann Horn <jannh@google.com>,
Jonathan Corbet <corbet@lwn.net>,
Kees Cook <keescook@chromium.org>,
Mike Kravetz <mike.kravetz@oracle.com>,
Nadav Amit <nadav.amit@gmail.com>,
Oleg Nesterov <oleg@redhat.com>, Pavel Machek <pavel@ucw.cz>,
Peter Zijlstra <peterz@infradead.org>,
Randy Dunlap <rdunlap@infradead.org>,
"Ravi V. Shankar" <ravi.v.shankar@intel.com>,
Vedvyas Shanbhogue <vedvyas.shanbhogue@intel.com>
Subject: Re: [RFC PATCH v4 03/27] x86/fpu/xstate: Enable XSAVES system states
Date: Tue, 2 Oct 2018 19:15:54 +0200 [thread overview]
Message-ID: <20181002171554.GE29601@zn.tnic> (raw)
Message-ID: <20181002171554.fPij5TErghaBFBwkqVbtYG-2ocMaFgVfXi3HOWewrkY@z> (raw)
In-Reply-To: <20180921150351.20898-4-yu-cheng.yu@intel.com>
On Fri, Sep 21, 2018 at 08:03:27AM -0700, Yu-cheng Yu wrote:
> XSAVES saves both system and user states. The Linux kernel
> currently does not save/restore any system states. This patch
> creates the framework for supporting system states.
... and needs a lot more text explaining *why* it is doing that.
>
> Signed-off-by: Yu-cheng Yu <yu-cheng.yu@intel.com>
> ---
> arch/x86/include/asm/fpu/internal.h | 3 +-
> arch/x86/include/asm/fpu/xstate.h | 9 ++-
> arch/x86/kernel/fpu/core.c | 7 +-
> arch/x86/kernel/fpu/init.c | 10 ---
> arch/x86/kernel/fpu/xstate.c | 112 +++++++++++++++++-----------
> 5 files changed, 80 insertions(+), 61 deletions(-)
>
> diff --git a/arch/x86/include/asm/fpu/internal.h b/arch/x86/include/asm/fpu/internal.h
> index f1f9bf91a0ab..1f447865db3a 100644
> --- a/arch/x86/include/asm/fpu/internal.h
> +++ b/arch/x86/include/asm/fpu/internal.h
> @@ -45,7 +45,6 @@ extern void fpu__init_cpu_xstate(void);
> extern void fpu__init_system(struct cpuinfo_x86 *c);
> extern void fpu__init_check_bugs(void);
> extern void fpu__resume_cpu(void);
> -extern u64 fpu__get_supported_xfeatures_mask(void);
>
> /*
> * Debugging facility:
> @@ -94,7 +93,7 @@ static inline void fpstate_init_xstate(struct xregs_state *xsave)
> * trigger #GP:
> */
> xsave->header.xcomp_bv = XCOMP_BV_COMPACTED_FORMAT |
> - xfeatures_mask_user;
> + xfeatures_mask_all;
> }
>
> static inline void fpstate_init_fxstate(struct fxregs_state *fx)
> diff --git a/arch/x86/include/asm/fpu/xstate.h b/arch/x86/include/asm/fpu/xstate.h
> index 9b382e5157ed..a32dc5f8c963 100644
> --- a/arch/x86/include/asm/fpu/xstate.h
> +++ b/arch/x86/include/asm/fpu/xstate.h
> @@ -19,10 +19,10 @@
> #define XSAVE_YMM_SIZE 256
> #define XSAVE_YMM_OFFSET (XSAVE_HDR_SIZE + XSAVE_HDR_OFFSET)
>
> -/* System features */
> -#define XFEATURE_MASK_SYSTEM (XFEATURE_MASK_PT)
Previous patch renames it, this patch deletes it. Why do we need all
that unnecessary churn?
Also, this patch is trying to do a couple of things at once and
reviewing it is not trivial. Please split the changes logically.
> diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c
> index 19f8df54c72a..dd2c561c4544 100644
> --- a/arch/x86/kernel/fpu/xstate.c
> +++ b/arch/x86/kernel/fpu/xstate.c
> @@ -51,13 +51,16 @@ static short xsave_cpuid_features[] __initdata = {
> };
>
> /*
> - * Mask of xstate features supported by the CPU and the kernel:
> + * Mask of xstate features supported by the CPU and the kernel.
> + * This is the result from CPUID query, SUPPORTED_XFEATURES_MASK,
> + * and boot_cpu_has().
> */
This needs to explain what both masks are - user and system. "CPU" and
"kernel" is not "user" and "all".
> u64 xfeatures_mask_user __read_mostly;
> +u64 xfeatures_mask_all __read_mostly;
> @@ -219,30 +222,31 @@ void fpstate_sanitize_xstate(struct fpu *fpu)
> */
> void fpu__init_cpu_xstate(void)
> {
> - if (!boot_cpu_has(X86_FEATURE_XSAVE) || !xfeatures_mask_user)
> + if (!boot_cpu_has(X86_FEATURE_XSAVE) || !xfeatures_mask_all)
> return;
> +
> + cr4_set_bits(X86_CR4_OSXSAVE);
> +
> /*
> - * Make it clear that XSAVES system states are not yet
> - * implemented should anyone expect it to work by changing
> - * bits in XFEATURE_MASK_* macros and XCR0.
> + * XCR_XFEATURE_ENABLED_MASK sets the features that are managed
> + * by XSAVE{C, OPT} and XRSTOR. Only XSAVE user states can be
> + * set here.
> */
> - WARN_ONCE((xfeatures_mask_user & XFEATURE_MASK_SYSTEM),
> - "x86/fpu: XSAVES system states are not yet implemented.\n");
> + xsetbv(XCR_XFEATURE_ENABLED_MASK,
> + xfeatures_mask_user);
No need to break the line here.
Also, you have a couple more places in your patches where you
unnecessarily break lines. Please don't do that, even if it exceeds 80
cols by a couple of chars.
>
> - xfeatures_mask_user &= ~XFEATURE_MASK_SYSTEM;
> -
> - cr4_set_bits(X86_CR4_OSXSAVE);
> - xsetbv(XCR_XFEATURE_ENABLED_MASK, xfeatures_mask_user);
> + /*
> + * MSR_IA32_XSS sets which XSAVES system states to be managed by
> + * XSAVES. Only XSAVES system states can be set here.
> + */
> + if (boot_cpu_has(X86_FEATURE_XSAVES))
> + wrmsrl(MSR_IA32_XSS,
> + xfeatures_mask_all & ~xfeatures_mask_user);
--
Regards/Gruss,
Boris.
Good mailing practices for 400: avoid top-posting and trim the reply.
next prev parent reply other threads:[~2018-10-03 0:00 UTC|newest]
Thread overview: 142+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-21 15:03 [RFC PATCH v4 00/27] Control Flow Enforcement: Shadow Stack Yu-cheng Yu
2018-09-21 15:03 ` Yu-cheng Yu
2018-09-21 15:03 ` [RFC PATCH v4 01/27] x86/cpufeatures: Add CPUIDs for Control-flow Enforcement Technology (CET) Yu-cheng Yu
2018-09-21 15:03 ` Yu-cheng Yu
2018-09-25 16:27 ` Peter Zijlstra
2018-09-25 16:27 ` Peter Zijlstra
2018-09-25 16:29 ` Yu-cheng Yu
2018-09-25 16:29 ` Yu-cheng Yu
2018-09-28 16:51 ` Borislav Petkov
2018-09-28 16:51 ` Borislav Petkov
2018-09-28 16:56 ` Yu-cheng Yu
2018-09-28 16:56 ` Yu-cheng Yu
2018-09-21 15:03 ` [RFC PATCH v4 02/27] x86/fpu/xstate: Change some names to separate XSAVES system and user states Yu-cheng Yu
2018-09-21 15:03 ` Yu-cheng Yu
2018-09-25 16:37 ` Peter Zijlstra
2018-09-25 16:37 ` Peter Zijlstra
2018-10-02 15:29 ` Borislav Petkov
2018-10-02 15:29 ` Borislav Petkov
2018-10-02 16:21 ` Yu-cheng Yu
2018-10-02 16:21 ` Yu-cheng Yu
2018-10-02 16:30 ` Dave Hansen
2018-10-02 16:30 ` Dave Hansen
2018-10-02 16:37 ` Borislav Petkov
2018-10-02 16:37 ` Borislav Petkov
2018-10-02 16:39 ` Dave Hansen
2018-10-02 16:39 ` Dave Hansen
2018-10-02 16:43 ` Yu-cheng Yu
2018-10-02 16:43 ` Yu-cheng Yu
2018-09-21 15:03 ` [RFC PATCH v4 03/27] x86/fpu/xstate: Enable XSAVES system states Yu-cheng Yu
2018-09-21 15:03 ` Yu-cheng Yu
2018-09-25 17:03 ` Peter Zijlstra
2018-09-25 17:03 ` Peter Zijlstra
2018-09-25 17:23 ` Yu-cheng Yu
2018-09-25 17:23 ` Yu-cheng Yu
2018-10-02 17:15 ` Borislav Petkov [this message]
2018-10-02 17:15 ` Borislav Petkov
2018-10-04 15:47 ` Yu-cheng Yu
2018-10-04 15:47 ` Yu-cheng Yu
2018-09-21 15:03 ` [RFC PATCH v4 04/27] x86/fpu/xstate: Add XSAVES system states for shadow stack Yu-cheng Yu
2018-09-21 15:03 ` Yu-cheng Yu
2018-09-21 15:03 ` [RFC PATCH v4 05/27] Documentation/x86: Add CET description Yu-cheng Yu
2018-09-21 15:03 ` Yu-cheng Yu
2018-09-21 15:03 ` [RFC PATCH v4 06/27] x86/cet: Control protection exception handler Yu-cheng Yu
2018-09-21 15:03 ` Yu-cheng Yu
2018-10-03 10:39 ` Eugene Syromiatnikov
2018-10-03 10:39 ` Eugene Syromiatnikov
2018-10-03 16:11 ` Yu-cheng Yu
2018-10-03 16:11 ` Yu-cheng Yu
2018-09-21 15:03 ` [RFC PATCH v4 07/27] x86/cet/shstk: Add Kconfig option for user-mode shadow stack Yu-cheng Yu
2018-09-21 15:03 ` Yu-cheng Yu
2018-09-21 15:03 ` [RFC PATCH v4 08/27] mm: Introduce VM_SHSTK for shadow stack memory Yu-cheng Yu
2018-09-21 15:03 ` Yu-cheng Yu
2018-09-21 15:03 ` [RFC PATCH v4 09/27] x86/mm: Change _PAGE_DIRTY to _PAGE_DIRTY_HW Yu-cheng Yu
2018-09-21 15:03 ` Yu-cheng Yu
2018-10-03 13:38 ` Matthew Wilcox
2018-10-03 13:38 ` Matthew Wilcox
2018-10-03 14:05 ` Dave Hansen
2018-10-03 14:05 ` Dave Hansen
2018-10-03 16:07 ` Yu-cheng Yu
2018-10-03 16:07 ` Yu-cheng Yu
2018-09-21 15:03 ` [RFC PATCH v4 10/27] drm/i915/gvt: Update _PAGE_DIRTY to _PAGE_DIRTY_BITS Yu-cheng Yu
2018-09-21 15:03 ` Yu-cheng Yu
2018-10-03 13:19 ` Eugene Syromiatnikov
2018-10-03 13:19 ` Eugene Syromiatnikov
2018-09-21 15:03 ` [RFC PATCH v4 11/27] x86/mm: Introduce _PAGE_DIRTY_SW Yu-cheng Yu
2018-09-21 15:03 ` Yu-cheng Yu
2018-09-21 15:03 ` [RFC PATCH v4 12/27] x86/mm: Modify ptep_set_wrprotect and pmdp_set_wrprotect for _PAGE_DIRTY_SW Yu-cheng Yu
2018-09-21 15:03 ` Yu-cheng Yu
2018-09-21 15:03 ` [RFC PATCH v4 13/27] x86/mm: Shadow stack page fault error checking Yu-cheng Yu
2018-09-21 15:03 ` Yu-cheng Yu
2018-09-21 15:03 ` [RFC PATCH v4 14/27] mm: Handle shadow stack page fault Yu-cheng Yu
2018-09-21 15:03 ` Yu-cheng Yu
2018-09-21 15:03 ` [RFC PATCH v4 15/27] mm: Handle THP/HugeTLB " Yu-cheng Yu
2018-09-21 15:03 ` Yu-cheng Yu
2018-09-21 15:03 ` [RFC PATCH v4 16/27] mm: Update can_follow_write_pte/pmd for shadow stack Yu-cheng Yu
2018-09-21 15:03 ` Yu-cheng Yu
2018-09-21 15:03 ` [RFC PATCH v4 17/27] mm: Introduce do_mmap_locked() Yu-cheng Yu
2018-09-21 15:03 ` Yu-cheng Yu
2018-09-21 15:03 ` [RFC PATCH v4 18/27] x86/cet/shstk: User-mode shadow stack support Yu-cheng Yu
2018-09-21 15:03 ` Yu-cheng Yu
2018-10-03 15:08 ` Eugene Syromiatnikov
2018-10-03 15:08 ` Eugene Syromiatnikov
2018-10-03 15:12 ` Yu-cheng Yu
2018-10-03 15:12 ` Yu-cheng Yu
2018-09-21 15:03 ` [RFC PATCH v4 19/27] x86/cet/shstk: Introduce WRUSS instruction Yu-cheng Yu
2018-09-21 15:03 ` Yu-cheng Yu
2018-10-03 4:15 ` Eugene Syromiatnikov
2018-10-03 4:15 ` Eugene Syromiatnikov
2018-09-21 15:03 ` [RFC PATCH v4 20/27] x86/cet/shstk: Signal handling for shadow stack Yu-cheng Yu
2018-09-21 15:03 ` Yu-cheng Yu
2018-10-03 14:36 ` Eugene Syromiatnikov
2018-10-03 14:36 ` Eugene Syromiatnikov
2018-10-03 16:46 ` Jann Horn
2018-10-03 16:46 ` Jann Horn
2018-09-21 15:03 ` [RFC PATCH v4 21/27] x86/cet/shstk: ELF header parsing of Shadow Stack Yu-cheng Yu
2018-09-21 15:03 ` Yu-cheng Yu
2018-10-03 23:27 ` Eugene Syromiatnikov
2018-10-03 23:27 ` Eugene Syromiatnikov
2018-10-09 21:15 ` Yu-cheng Yu
2018-10-09 21:15 ` Yu-cheng Yu
2018-10-15 23:40 ` Kees Cook
2018-10-15 23:40 ` Kees Cook
2018-10-16 17:23 ` Yu-cheng Yu
2018-10-16 17:23 ` Yu-cheng Yu
2018-09-21 15:03 ` [RFC PATCH v4 22/27] x86/cet/shstk: Handle thread shadow stack Yu-cheng Yu
2018-09-21 15:03 ` Yu-cheng Yu
2018-09-21 15:03 ` [RFC PATCH v4 23/27] mm/map: Add Shadow stack pages to memory accounting Yu-cheng Yu
2018-09-21 15:03 ` Yu-cheng Yu
2018-09-21 16:55 ` Randy Dunlap
2018-09-21 16:55 ` Randy Dunlap
2018-09-21 17:21 ` Yu-cheng Yu
2018-09-21 17:21 ` Yu-cheng Yu
2018-09-21 15:03 ` [RFC PATCH v4 24/27] mm/mmap: Create a guard area between VMAs Yu-cheng Yu
2018-09-21 15:03 ` Yu-cheng Yu
2018-10-03 4:56 ` Eugene Syromiatnikov
2018-10-03 4:56 ` Eugene Syromiatnikov
2018-10-03 5:36 ` Andy Lutomirski
2018-10-03 5:36 ` Andy Lutomirski
2018-10-03 16:00 ` Yu-cheng Yu
2018-10-03 16:00 ` Yu-cheng Yu
2018-10-03 16:18 ` Andy Lutomirski
2018-10-03 16:18 ` Andy Lutomirski
2018-10-03 16:32 ` Eugene Syromiatnikov
2018-10-03 16:32 ` Eugene Syromiatnikov
2018-10-03 16:40 ` Yu-cheng Yu
2018-10-03 16:40 ` Yu-cheng Yu
2018-10-03 16:52 ` Jann Horn
2018-10-03 16:52 ` Jann Horn
2018-10-03 21:21 ` Eugene Syromiatnikov
2018-10-03 21:21 ` Eugene Syromiatnikov
2018-09-21 15:03 ` [RFC PATCH v4 25/27] mm/mmap: Prevent Shadow Stack VMA merges Yu-cheng Yu
2018-09-21 15:03 ` Yu-cheng Yu
2018-09-21 15:03 ` [RFC PATCH v4 26/27] x86/cet/shstk: Add arch_prctl functions for Shadow Stack Yu-cheng Yu
2018-09-21 15:03 ` Yu-cheng Yu
2018-10-03 17:57 ` Eugene Syromiatnikov
2018-10-03 17:57 ` Eugene Syromiatnikov
2018-09-21 15:03 ` [RFC PATCH v4 27/27] x86/cet/shstk: Add Shadow Stack instructions to opcode map Yu-cheng Yu
2018-09-21 15:03 ` Yu-cheng Yu
2018-09-21 22:53 ` [RFC PATCH v4 00/27] Control Flow Enforcement: Shadow Stack Dave Hansen
2018-09-21 22:53 ` Dave Hansen
2018-09-24 15:25 ` Yu-cheng Yu
2018-09-24 15:25 ` Yu-cheng Yu
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