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From: Thomas Gleixner <tglx@linutronix.de>
To: "Mika Penttilä" <mika.penttila@nextfour.com>,
	"Chang S. Bae" <chang.seok.bae@intel.com>,
	linux-kernel@vger.kernel.org
Cc: x86@kernel.org, dave.hansen@linux.intel.com,
	arjan@linux.intel.com, ravi.v.shankar@intel.com
Subject: Re: [PATCH 15/23] x86/fpu: Add sanity checks for XFD
Date: Mon, 25 Oct 2021 20:13:11 +0200	[thread overview]
Message-ID: <87o87dezwo.ffs@tglx> (raw)
In-Reply-To: <20d31ed9-be3d-dca6-ceef-ced35f80d131@nextfour.com>

On Mon, Oct 25 2021 at 11:33, Mika Penttilä wrote:
> On 22.10.2021 1.55, Chang S. Bae wrote:
>> +#ifdef CONFIG_X86_DEBUG_FPU
>> +/*
>> + * Ensure that a subsequent XSAVE* or XRSTOR* instruction with RFBM=@mask
>> + * can safely operate on the @fpstate buffer.
>> + */
>> +static bool xstate_op_valid(struct fpstate *fpstate, u64 mask, bool rstor)
>> +{
>> +	u64 xfd = __this_cpu_read(xfd_state);
>> +
>> +	if (fpstate->xfd == xfd)
>> +		return true;
>> +
>> +	/* For current's fpstate the XFD state must be correct. */
>> +	if (fpstate->xfd == current->thread.fpu.fpstate->xfd)
>> +		return false;
>> +
> Should this return true or is the comment confusing?

Comment might be confusing. The logic here is:

If fpstate->xfd equal xfd then it's valid.

So the next check is whether fpstate is the same as current's
fpstate. If that's the case then the result is invalid because for
current's fpstate the first condition should be true. But if it is not
true then the state is not valid.

Thanks,

        tglx

  reply	other threads:[~2021-10-25 18:13 UTC|newest]

Thread overview: 60+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-10-21 22:55 [PATCH 00/23] x86: Support Intel Advanced Matrix Extensions (part 4) Chang S. Bae
2021-10-21 22:55 ` [PATCH 01/23] signal: Add an optional check for altstack size Chang S. Bae
2021-10-22  0:06   ` Bae, Chang Seok
2021-10-22 15:20   ` Eric W. Biederman
2021-10-22 20:58     ` Bae, Chang Seok
2021-10-22 22:51     ` Dave Hansen
2021-10-26 16:16   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-10-21 22:55 ` [PATCH 02/23] x86/signal: Implement sigaltstack size validation Chang S. Bae
2021-10-26 16:16   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-10-21 22:55 ` [PATCH 03/23] x86/fpu/xstate: Provide xstate_calculate_size() Chang S. Bae
2021-10-26 16:16   ` [tip: x86/fpu] " tip-bot2 for Chang S. Bae
2021-10-21 22:55 ` [PATCH 04/23] x86/fpu: Add members to struct fpu to cache permission information Chang S. Bae
2021-10-26 16:16   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-10-21 22:55 ` [PATCH 05/23] x86/fpu: Add fpu_state_config::legacy_features Chang S. Bae
2021-10-26 16:16   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-10-21 22:55 ` [PATCH 06/23] x86/arch_prctl: Add controls for dynamic XSTATE components Chang S. Bae
2021-10-24 21:17   ` Borislav Petkov
2021-10-26  9:11     ` [PATCH] Documentation/x86: Add documentation for using dynamic XSTATE features Chang S. Bae
2021-10-26 16:16       ` [tip: x86/fpu] " tip-bot2 for Chang S. Bae
2021-10-28 13:10       ` tip-bot2 for Chang S. Bae
2021-10-26 16:16   ` [tip: x86/fpu] x86/arch_prctl: Add controls for dynamic XSTATE components tip-bot2 for Chang S. Bae
2021-10-21 22:55 ` [PATCH 07/23] x86/fpu: Add basic helpers for dynamically enabled features Chang S. Bae
2021-10-26 16:16   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-10-21 22:55 ` [PATCH 08/23] x86/signal: Use fpu::__state_user_size for sigalt stack validation Chang S. Bae
2021-10-26 16:16   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-10-21 22:55 ` [PATCH 09/23] x86/fpu/signal: Prepare for variable sigframe length Chang S. Bae
2021-10-26 16:16   ` [tip: x86/fpu] " tip-bot2 for Chang S. Bae
2021-10-21 22:55 ` [PATCH 10/23] x86/fpu: Prepare fpu_clone() for dynamically enabled features Chang S. Bae
2021-10-26 16:16   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-10-21 22:55 ` [PATCH 11/23] x86/fpu: Reset permission and fpstate on exec() Chang S. Bae
2021-10-26 16:16   ` [tip: x86/fpu] " tip-bot2 for Chang S. Bae
2021-10-21 22:55 ` [PATCH 12/23] x86/cpufeatures: Add eXtended Feature Disabling (XFD) feature bit Chang S. Bae
2021-10-26 16:16   ` [tip: x86/fpu] " tip-bot2 for Chang S. Bae
2021-10-21 22:55 ` [PATCH 13/23] x86/msr-index: Add MSRs for XFD Chang S. Bae
2021-10-26 16:16   ` [tip: x86/fpu] " tip-bot2 for Chang S. Bae
2021-10-21 22:55 ` [PATCH 14/23] x86/fpu: Add XFD state to fpstate Chang S. Bae
2021-10-26 16:16   ` [tip: x86/fpu] " tip-bot2 for Chang S. Bae
2021-10-21 22:55 ` [PATCH 15/23] x86/fpu: Add sanity checks for XFD Chang S. Bae
2021-10-25  8:11   ` Borislav Petkov
2021-10-25 20:15     ` Thomas Gleixner
2021-10-25  8:33   ` Mika Penttilä
2021-10-25 18:13     ` Thomas Gleixner [this message]
2021-10-25 19:57       ` Dave Hansen
2021-10-26 16:16   ` [tip: x86/fpu] " tip-bot2 for Thomas Gleixner
2021-10-21 22:55 ` [PATCH 16/23] x86/fpu: Update XFD state where required Chang S. Bae
2021-10-26 16:16   ` [tip: x86/fpu] " tip-bot2 for Chang S. Bae
2021-10-21 22:55 ` [PATCH 17/23] x86/fpu/xstate: Add XFD #NM handler Chang S. Bae
2021-10-26 16:16   ` [tip: x86/fpu] " tip-bot2 for Chang S. Bae
2021-10-21 22:55 ` [PATCH 18/23] x86/fpu/xstate: Add fpstate_realloc()/free() Chang S. Bae
2021-10-26 16:16   ` [tip: x86/fpu] " tip-bot2 for Chang S. Bae
2021-10-21 22:55 ` [PATCH 19/23] x86/fpu/xstate: Prepare XSAVE feature table for gaps in state component numbers Chang S. Bae
2021-10-26 16:16   ` [tip: x86/fpu] " tip-bot2 for Chang S. Bae
2021-10-21 22:55 ` [PATCH 20/23] x86/fpu/amx: Define AMX state components and have it used for boot-time checks Chang S. Bae
2021-10-26 16:16   ` [tip: x86/fpu] " tip-bot2 for Chang S. Bae
2021-10-21 22:55 ` [PATCH 21/23] x86/fpu: Calculate the default sizes independently Chang S. Bae
2021-10-26 16:16   ` [tip: x86/fpu] " tip-bot2 for Chang S. Bae
2021-10-21 22:55 ` [PATCH 22/23] x86/fpu: Add XFD handling for dynamic states Chang S. Bae
2021-10-26 16:16   ` [tip: x86/fpu] " tip-bot2 for Chang S. Bae
2021-10-21 22:55 ` [PATCH 23/23] x86/fpu/amx: Enable the AMX feature in 64-bit mode Chang S. Bae
2021-10-26 16:16   ` [tip: x86/fpu] " tip-bot2 for Chang S. Bae

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