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Date: Wed, 9 Oct 2019 18:59:21 +0200
From: Borislav Petkov <bp@...en8.de>
To: Yu-cheng Yu <yu-cheng.yu@...el.com>
Cc: linux-kernel@...r.kernel.org, x86@...nel.org,
"H. Peter Anvin" <hpa@...or.com>,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>,
Dave Hansen <dave.hansen@...ux.intel.com>,
Tony Luck <tony.luck@...el.com>,
Andy Lutomirski <luto@...nel.org>,
Rik van Riel <riel@...riel.com>,
"Ravi V. Shankar" <ravi.v.shankar@...el.com>,
Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
Fenghua Yu <fenghua.yu@...el.com>,
Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH 3/6] x86/fpu/xstate: Separate user and supervisor
xfeatures mask
On Wed, Sep 25, 2019 at 08:10:19AM -0700, Yu-cheng Yu wrote:
> Before the introduction of XSAVES supervisor states, 'xfeatures_mask' is
> used at various places to determine XSAVE buffer components and XCR0 bits.
> It contains only user xstates. To support supervisor xstates, it is
> necessary to separate user and supervisor xstates:
>
> - First, change 'xfeatures_mask' to 'xfeatures_mask_all', which represents
> the full set of bits that should ever be set in a kernel XSAVE buffer.
> - Introduce xfeature_mask_supervisor() and xfeatures_mask_user() to
xfeatures_mask_supervisor()
^
's' is missing.
> extract relevant xfeatures from xfeatures_mask_all.
>
> Signed-off-by: Yu-cheng Yu <yu-cheng.yu@...el.com>
> Signed-off-by: Fenghua Yu <fenghua.yu@...el.com>
Similar problem here. Fenghua's SOB means what exactly?
You're probably trying to say that he co-developed it but then it needs
to state that this way:
Signed-off-by: Fenghua Yu <fenghua.yu@...el.com>
Co-developed-by: Yu-cheng Yu <yu-cheng.yu@...el.com>
Signed-off-by: Yu-cheng Yu <yu-cheng.yu@...el.com>
> Reviewed-by: Dave Hansen <dave.hansen@...ux.intel.com>
> Reviewed-by: Tony Luck <tony.luck@...el.com>
> ---
> arch/x86/include/asm/fpu/internal.h | 2 +-
> arch/x86/include/asm/fpu/xstate.h | 8 ++-
> arch/x86/kernel/fpu/signal.c | 15 ++++--
> arch/x86/kernel/fpu/xstate.c | 78 +++++++++++++++++------------
> 4 files changed, 65 insertions(+), 38 deletions(-)
>
> diff --git a/arch/x86/include/asm/fpu/internal.h b/arch/x86/include/asm/fpu/internal.h
> index 4c95c365058a..f56ad1248b5d 100644
> --- a/arch/x86/include/asm/fpu/internal.h
> +++ b/arch/x86/include/asm/fpu/internal.h
> @@ -92,7 +92,7 @@ static inline void fpstate_init_xstate(struct xregs_state *xsave)
> * XRSTORS requires these bits set in xcomp_bv, or it will
> * trigger #GP:
> */
> - xsave->header.xcomp_bv = XCOMP_BV_COMPACTED_FORMAT | xfeatures_mask;
> + xsave->header.xcomp_bv = XCOMP_BV_COMPACTED_FORMAT | 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 014c386deaa3..5954bd97da16 100644
> --- a/arch/x86/include/asm/fpu/xstate.h
> +++ b/arch/x86/include/asm/fpu/xstate.h
> @@ -51,7 +51,13 @@
> #define REX_PREFIX
> #endif
>
> -extern u64 xfeatures_mask;
> +extern u64 xfeatures_mask_all;
> +
> +static inline u64 xfeatures_mask_user(void)
> +{
> + return xfeatures_mask_all & SUPPORTED_XFEATURES_MASK_USER;
> +}
Please group this function along with xfeature_is_user(),
xfeature_is_supervisor() and xfeature_mask_supervisor() in the xstate.h
header as they're very similar in what they do.
> +
> extern u64 xstate_fx_sw_bytes[USER_XSTATE_FX_SW_WORDS];
>
> extern void __init update_regset_xstate_info(unsigned int size,
...
> @@ -731,16 +742,22 @@ void __init fpu__init_system_xstate(void)
> return;
> }
>
> + /*
> + * Find user xstates supported by the processor.
> + */
> cpuid_count(XSTATE_CPUID, 0, &eax, &ebx, &ecx, &edx);
> - xfeatures_mask = eax + ((u64)edx << 32);
> + xfeatures_mask_all = eax + ((u64)edx << 32);
> +
> + /* Place supervisor features in xfeatures_mask_all here */
>
Remove that newline.
> - if ((xfeatures_mask & XFEATURE_MASK_FPSSE) != XFEATURE_MASK_FPSSE) {
> + if ((xfeatures_mask_user() & XFEATURE_MASK_FPSSE) != XFEATURE_MASK_FPSSE) {
> /*
> * This indicates that something really unexpected happened
> * with the enumeration. Disable XSAVE and try to continue
> * booting without it. This is too early to BUG().
> */
> - pr_err("x86/fpu: FP/SSE not present amongst the CPU's xstate features: 0x%llx.\n", xfeatures_mask);
> + pr_err("x86/fpu: FP/SSE not present amongst the CPU's xstate features: 0x%llx.\n",
> + xfeatures_mask_all);
> goto out_disable;
> }
>
> @@ -749,10 +766,10 @@ void __init fpu__init_system_xstate(void)
> */
> for (i = 0; i < ARRAY_SIZE(xsave_cpuid_features); i++) {
> if (!boot_cpu_has(xsave_cpuid_features[i]))
> - xfeatures_mask &= ~BIT(i);
> + xfeatures_mask_all &= ~BIT_ULL(i);
> }
>
> - xfeatures_mask &= fpu__get_supported_xfeatures_mask();
> + xfeatures_mask_all &= fpu__get_supported_xfeatures_mask();
>
> /* Enable xstate instructions to be able to continue with initialization: */
> fpu__init_cpu_xstate();
> @@ -764,16 +781,16 @@ void __init fpu__init_system_xstate(void)
> * Update info used for ptrace frames; use standard-format size and no
> * supervisor xstates:
> */
> - update_regset_xstate_info(fpu_user_xstate_size,
> - xfeatures_mask & SUPPORTED_XFEATURES_MASK_USER);
> + update_regset_xstate_info(fpu_user_xstate_size, xfeatures_mask_user());
>
> fpu__init_prepare_fx_sw_frame();
> setup_init_fpu_buf();
> setup_xstate_comp();
> print_xstate_offset_size();
>
> - pr_info("x86/fpu: Enabled xstate features 0x%llx, context size is %d bytes, using '%s' format.\n",
> - xfeatures_mask,
> + pr_info("x86/fpu: Enabled xstate features 0x%llx: user 0x%llx, context size is %d bytes, using '%s' format.\n",
> + xfeatures_mask_all,
> + xfeatures_mask_user(),
Why do we need to dump the user features separately?
> fpu_kernel_xstate_size,
> boot_cpu_has(X86_FEATURE_XSAVES) ? "compacted" : "standard");
> return;
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
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