From: "Bae, Chang Seok" <chang.seok.bae@intel.com>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: "bp@suse.de" <bp@suse.de>, "Lutomirski, Andy" <luto@kernel.org>,
"mingo@kernel.org" <mingo@kernel.org>,
"x86@kernel.org" <x86@kernel.org>,
"Brown, Len" <len.brown@intel.com>,
"lenb@kernel.org" <lenb@kernel.org>,
"Hansen, Dave" <dave.hansen@intel.com>,
"Macieira, Thiago" <thiago.macieira@intel.com>,
"Liu, Jing2" <jing2.liu@intel.com>,
"Shankar, Ravi V" <ravi.v.shankar@intel.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v10 13/28] x86/fpu/xstate: Use feature disable (XFD) to protect dynamic user state
Date: Sun, 3 Oct 2021 22:38:29 +0000 [thread overview]
Message-ID: <E5C66E6E-8AB8-4258-814D-C8E94446E2C4@intel.com> (raw)
In-Reply-To: <87wnmw4w80.ffs@tglx>
On Oct 1, 2021, at 08:10, Thomas Gleixner <tglx@linutronix.de> wrote:
> On Fri, Oct 01 2021 at 17:02, Thomas Gleixner wrote:
>> On Wed, Aug 25 2021 at 08:53, Chang S. Bae wrote:
>>> DEFINE_IDTENTRY(exc_device_not_available)
>>> {
>>> unsigned long cr0 = read_cr0();
>>
>>> + if (handle_xfd_event(¤t->thread.fpu, regs))
>>> + return;
>>
>> As I said before, this is wrong because at that point interrupts are disabled.
>
> So you want something like this:
>
> static bool handle_xfd_event(struct pt_regs *regs)
> {
> u64 xfd_err, xfd_event, xfd, mask;
> struct fpu *fpu;
>
> if (!cpu_feature_enabled(X86_FEATURE_XFD))
> return false;
>
> rdmsrl_safe(MSR_IA32_XFD_ERR, &xfd_err);
> if (!xfd_err)
> return false;
>
> wrmsrl_safe(MSR_IA32_XFD_ERR, 0);
>
> xfd_event = xfd_err & xfeatures_mask_user_dynamic;
>
> /* Die if a non-handled feature raised the exception */
> if (WARN_ON(!xfd_event))
> return true;
>
> /* Die if that happens in kernel space */
> if (WARN_ON(!user_mode(regs)))
> return false;
>
> local_irq_enable();
v1 had some similar ones (not the same though) [1]. FWIW, I think Andy’s point
is worth to be noted here:
First, you can't just enable IRQs here. If IRQs are off, they're off for a
reason. Secondly, if they're *on*, you just forgot that fact.
> /* Make sure that dynamic buffer expansion is permitted. */
> if (dynamic_state_permitted(current, xfd_event) &&
> !realloc_xstate_buffer(current, xfd_event)) {
> mask = xfeatures_mask_user_dynamic;
> fpu = ¤t->thread.fpu;
> xfd_write((fpu->state_mask & mask) ^ mask);
> } else {
> force_sig_fault(SIGILL, ILL_ILLOPC, error_get_trap_addr(regs));
> }
>
> local_irq_disable();
> return true;
> }
>
> Along with a correct implementation of realloc_xstate_buffer().
Thanks,
Chang
[1] https://lore.kernel.org/lkml/CALCETrWjOYd4wM0Mn7fY+t4ztU99GNP77A6skNwjTViJYUEZYQ@mail.gmail.com/
next prev parent reply other threads:[~2021-10-03 22:38 UTC|newest]
Thread overview: 61+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-25 15:53 [PATCH v10 00/28] x86: Support Intel Advanced Matrix Extensions Chang S. Bae
2021-08-25 15:53 ` [PATCH v10 01/28] x86/fpu/xstate: Fix the state copy function to the XSTATE buffer Chang S. Bae
2021-10-01 12:44 ` Thomas Gleixner
2021-10-03 22:34 ` Bae, Chang Seok
2021-08-25 15:53 ` [PATCH v10 02/28] x86/fpu/xstate: Modify the initialization helper to handle both static and dynamic buffers Chang S. Bae
2021-10-01 12:45 ` Thomas Gleixner
2021-10-03 22:35 ` Bae, Chang Seok
2021-08-25 15:53 ` [PATCH v10 03/28] x86/fpu/xstate: Modify state copy helpers " Chang S. Bae
2021-10-01 12:47 ` Thomas Gleixner
2021-10-03 22:42 ` Bae, Chang Seok
2021-08-25 15:53 ` [PATCH v10 04/28] x86/fpu/xstate: Modify address finders " Chang S. Bae
2021-10-01 13:15 ` Thomas Gleixner
2021-10-03 22:35 ` Bae, Chang Seok
2021-10-04 12:54 ` Thomas Gleixner
2021-08-25 15:53 ` [PATCH v10 05/28] x86/fpu/xstate: Add a new variable to indicate dynamic user states Chang S. Bae
2021-10-01 13:16 ` Thomas Gleixner
2021-10-03 22:35 ` Bae, Chang Seok
2021-10-04 12:57 ` Thomas Gleixner
2021-08-25 15:53 ` [PATCH v10 06/28] x86/fpu/xstate: Add new variables to indicate dynamic XSTATE buffer size Chang S. Bae
2021-10-01 13:32 ` Thomas Gleixner
2021-10-03 22:36 ` Bae, Chang Seok
2021-08-25 15:53 ` [PATCH v10 07/28] x86/fpu/xstate: Calculate and remember dynamic XSTATE buffer sizes Chang S. Bae
2021-08-25 15:53 ` [PATCH v10 08/28] x86/fpu/xstate: Convert the struct fpu 'state' field to a pointer Chang S. Bae
2021-08-25 15:53 ` [PATCH v10 09/28] x86/fpu/xstate: Introduce helpers to manage the XSTATE buffer dynamically Chang S. Bae
2021-10-01 14:20 ` Thomas Gleixner
2021-10-03 22:36 ` Bae, Chang Seok
2021-08-25 15:53 ` [PATCH v10 10/28] x86/fpu/xstate: Update the XSTATE save function to support dynamic states Chang S. Bae
2021-10-01 15:41 ` Thomas Gleixner
2021-10-02 21:31 ` Thomas Gleixner
2021-10-02 22:54 ` Bae, Chang Seok
2021-10-05 8:16 ` Paolo Bonzini
2021-10-05 7:50 ` Paolo Bonzini
2021-10-05 9:55 ` Thomas Gleixner
2021-08-25 15:53 ` [PATCH v10 11/28] x86/fpu/xstate: Update the XSTATE buffer address finder " Chang S. Bae
2021-08-25 15:53 ` [PATCH v10 12/28] x86/fpu/xstate: Update the XSTATE context copy function " Chang S. Bae
2021-08-25 15:53 ` [PATCH v10 13/28] x86/fpu/xstate: Use feature disable (XFD) to protect dynamic user state Chang S. Bae
2021-10-01 15:02 ` Thomas Gleixner
2021-10-01 15:10 ` Thomas Gleixner
2021-10-03 22:38 ` Bae, Chang Seok [this message]
2021-10-04 12:35 ` Thomas Gleixner
2021-10-01 20:20 ` Thomas Gleixner
2021-10-03 22:39 ` Bae, Chang Seok
2021-10-04 19:03 ` Thomas Gleixner
2021-10-03 22:41 ` Bae, Chang Seok
2021-08-25 15:53 ` [PATCH v10 14/28] x86/fpu/xstate: Support ptracer-induced XSTATE buffer expansion Chang S. Bae
2021-08-25 15:54 ` [PATCH v10 15/28] x86/arch_prctl: Create ARCH_SET_STATE_ENABLE/ARCH_GET_STATE_ENABLE Chang S. Bae
2021-08-25 16:36 ` Bae, Chang Seok
2021-08-25 15:54 ` [PATCH v10 16/28] x86/fpu/xstate: Support both legacy and expanded signal XSTATE size Chang S. Bae
2021-08-25 15:54 ` [PATCH v10 17/28] x86/fpu/xstate: Adjust the XSAVE feature table to address gaps in state component numbers Chang S. Bae
2021-08-25 15:54 ` [PATCH v10 18/28] x86/fpu/xstate: Disable XSTATE support if an inconsistent state is detected Chang S. Bae
2021-08-25 15:54 ` [PATCH v10 19/28] x86/cpufeatures/amx: Enumerate Advanced Matrix Extension (AMX) feature bits Chang S. Bae
2021-08-25 15:54 ` [PATCH v10 20/28] x86/fpu/amx: Define AMX state components and have it used for boot-time checks Chang S. Bae
2021-08-25 15:54 ` [PATCH v10 21/28] x86/fpu/amx: Initialize child's AMX state Chang S. Bae
2021-08-25 15:54 ` [PATCH v10 22/28] x86/fpu/amx: Enable the AMX feature in 64-bit mode Chang S. Bae
2021-08-25 15:54 ` [PATCH v10 23/28] x86/fpu/xstate: Skip writing zeros to signal frame for dynamic user states if in INIT-state Chang S. Bae
2021-08-25 15:54 ` [PATCH v10 24/28] selftest/x86/amx: Test cases for the AMX state management Chang S. Bae
2021-08-25 15:54 ` [PATCH v10 25/28] x86/insn/amx: Add TILERELEASE instruction to the opcode map Chang S. Bae
2021-08-25 15:54 ` [PATCH v10 26/28] intel_idle/amx: Add SPR support with XTILEDATA capability Chang S. Bae
2021-08-25 15:54 ` [PATCH v10 27/28] x86/fpu/xstate: Add a sanity check for XFD state when saving XSTATE Chang S. Bae
2021-08-25 15:54 ` [PATCH v10 28/28] x86/arch_prctl: ARCH_GET_FEATURES_WITH_KERNEL_ASSISTANCE Chang S. Bae
2021-09-30 21:12 ` [PATCH v10 00/28] x86: Support Intel Advanced Matrix Extensions Len Brown
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