From: Thomas Gleixner <tglx@linutronix.de> To: Fenghua Yu <fenghua.yu@intel.com> Cc: Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>, H Peter Anvin <hpa@zytor.com>, David Woodhouse <dwmw2@infradead.org>, Lu Baolu <baolu.lu@linux.intel.com>, Dave Hansen <dave.hansen@intel.com>, Tony Luck <tony.luck@intel.com>, Ashok Raj <ashok.raj@intel.com>, Jacob Jun Pan <jacob.jun.pan@intel.com>, Dave Jiang <dave.jiang@intel.com>, Sohil Mehta <sohil.mehta@intel.com>, Ravi V Shankar <ravi.v.shankar@intel.com>, linux-kernel <linux-kernel@vger.kernel.org>, x86 <x86@kernel.org>, iommu@lists.linux-foundation.org Subject: Re: [PATCH 6/7] x86/traps: Fix up invalid PASID Date: Tue, 28 Apr 2020 02:13:11 +0200 [thread overview] Message-ID: <87a72wpiw8.fsf@nanos.tec.linutronix.de> (raw) In-Reply-To: <20200427201141.GA242333@romley-ivt3.sc.intel.com> Fenghua Yu <fenghua.yu@intel.com> writes: > On Sun, Apr 26, 2020 at 05:25:06PM +0200, Thomas Gleixner wrote: >> > @@ -499,6 +510,12 @@ dotraplinkage void do_general_protection(struct pt_regs *regs, long error_code) >> > int ret; >> > >> > RCU_LOCKDEP_WARN(!rcu_is_watching(), "entry code didn't wake RCU"); >> > + >> > + if (user_mode(regs) && fixup_pasid_exception()) { >> > + cond_local_irq_enable(regs); >> >> The point of this conditional irq enable _AFTER_ calling into the fixup >> function is? Also what's the reason for keeping interrupts disabled >> while calling into that function? Comments exist for a reason. > > irq needs to be disabled because the fixup function requires to disable > preempt in order to update the PASID MSR on the faulting CPU. No, that's just wrong. It's not about the update itself. > Will add comments here. Factual ones and not some fairy tales please. >> > +bool __fixup_pasid_exception(void) >> > +{ >> > + struct mm_struct *mm; >> > + bool ret = true; >> > + u64 pasid_msr; >> > + int pasid; >> > + >> > + mm = get_task_mm(current); >> >> Why do you need a reference to current->mm ? > > The PASID for the address space is per mm and is stored in mm. > To get the PASID, we need to get the mm and the > pasid=mm->context.pasid. It's obvious that you need to access current-mm in order to check current->mm->context.pasid. Let me rephrase the question: Why do you need to take a reference on current->mm ? Thanks, tglx
WARNING: multiple messages have this Message-ID (diff)
From: Thomas Gleixner <tglx@linutronix.de> To: Fenghua Yu <fenghua.yu@intel.com> Cc: Ravi V Shankar <ravi.v.shankar@intel.com>, Tony Luck <tony.luck@intel.com>, Dave Jiang <dave.jiang@intel.com>, Ashok Raj <ashok.raj@intel.com>, x86 <x86@kernel.org>, linux-kernel <linux-kernel@vger.kernel.org>, Dave Hansen <dave.hansen@intel.com>, iommu@lists.linux-foundation.org, Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>, Jacob Jun Pan <jacob.jun.pan@intel.com>, H Peter Anvin <hpa@zytor.com>, David Woodhouse <dwmw2@infradead.org> Subject: Re: [PATCH 6/7] x86/traps: Fix up invalid PASID Date: Tue, 28 Apr 2020 02:13:11 +0200 [thread overview] Message-ID: <87a72wpiw8.fsf@nanos.tec.linutronix.de> (raw) In-Reply-To: <20200427201141.GA242333@romley-ivt3.sc.intel.com> Fenghua Yu <fenghua.yu@intel.com> writes: > On Sun, Apr 26, 2020 at 05:25:06PM +0200, Thomas Gleixner wrote: >> > @@ -499,6 +510,12 @@ dotraplinkage void do_general_protection(struct pt_regs *regs, long error_code) >> > int ret; >> > >> > RCU_LOCKDEP_WARN(!rcu_is_watching(), "entry code didn't wake RCU"); >> > + >> > + if (user_mode(regs) && fixup_pasid_exception()) { >> > + cond_local_irq_enable(regs); >> >> The point of this conditional irq enable _AFTER_ calling into the fixup >> function is? Also what's the reason for keeping interrupts disabled >> while calling into that function? Comments exist for a reason. > > irq needs to be disabled because the fixup function requires to disable > preempt in order to update the PASID MSR on the faulting CPU. No, that's just wrong. It's not about the update itself. > Will add comments here. Factual ones and not some fairy tales please. >> > +bool __fixup_pasid_exception(void) >> > +{ >> > + struct mm_struct *mm; >> > + bool ret = true; >> > + u64 pasid_msr; >> > + int pasid; >> > + >> > + mm = get_task_mm(current); >> >> Why do you need a reference to current->mm ? > > The PASID for the address space is per mm and is stored in mm. > To get the PASID, we need to get the mm and the > pasid=mm->context.pasid. It's obvious that you need to access current-mm in order to check current->mm->context.pasid. Let me rephrase the question: Why do you need to take a reference on current->mm ? Thanks, tglx _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu
next prev parent reply other threads:[~2020-04-28 0:13 UTC|newest] Thread overview: 74+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-03-30 19:33 [PATCH 0/7] x86: tag application address space for devices Fenghua Yu 2020-03-30 19:33 ` Fenghua Yu 2020-03-30 19:33 ` [PATCH 1/7] docs: x86: Add a documentation for ENQCMD Fenghua Yu 2020-03-30 19:33 ` Fenghua Yu 2020-04-26 11:02 ` Thomas Gleixner 2020-04-26 11:02 ` Thomas Gleixner 2020-04-27 20:13 ` Fenghua Yu 2020-04-27 20:13 ` Fenghua Yu 2020-03-30 19:33 ` [PATCH 2/7] x86/cpufeatures: Enumerate ENQCMD and ENQCMDS instructions Fenghua Yu 2020-03-30 19:33 ` Fenghua Yu 2020-04-26 11:06 ` Thomas Gleixner 2020-04-26 11:06 ` Thomas Gleixner 2020-04-27 20:17 ` Fenghua Yu 2020-04-27 20:17 ` Fenghua Yu 2020-03-30 19:33 ` [PATCH 3/7] x86/fpu/xstate: Add supervisor PASID state for ENQCMD feature Fenghua Yu 2020-03-30 19:33 ` Fenghua Yu 2020-04-26 11:17 ` Thomas Gleixner 2020-04-26 11:17 ` Thomas Gleixner 2020-04-27 20:33 ` Fenghua Yu 2020-04-27 20:33 ` Fenghua Yu 2020-03-30 19:33 ` [PATCH 4/7] x86/msr-index: Define IA32_PASID MSR Fenghua Yu 2020-03-30 19:33 ` Fenghua Yu 2020-04-26 11:22 ` Thomas Gleixner 2020-04-26 11:22 ` Thomas Gleixner 2020-04-27 20:50 ` Fenghua Yu 2020-04-27 20:50 ` Fenghua Yu 2020-03-30 19:33 ` [PATCH 5/7] x86/mmu: Allocate/free PASID Fenghua Yu 2020-03-30 19:33 ` Fenghua Yu 2020-04-26 14:55 ` Thomas Gleixner 2020-04-26 14:55 ` Thomas Gleixner 2020-04-27 22:18 ` Fenghua Yu 2020-04-27 22:18 ` Fenghua Yu 2020-04-27 23:44 ` Thomas Gleixner 2020-04-27 23:44 ` Thomas Gleixner 2020-04-28 18:21 ` Jacob Pan (Jun) 2020-04-28 18:21 ` Jacob Pan (Jun) 2020-04-28 18:54 ` Thomas Gleixner 2020-04-28 18:54 ` Thomas Gleixner 2020-04-28 19:07 ` Luck, Tony 2020-04-28 19:07 ` Luck, Tony 2020-04-28 20:42 ` Jacob Pan (Jun) 2020-04-28 20:42 ` Jacob Pan (Jun) 2020-04-28 20:59 ` Luck, Tony 2020-04-28 20:59 ` Luck, Tony 2020-04-28 22:13 ` Jacob Pan (Jun) 2020-04-28 22:13 ` Jacob Pan (Jun) 2020-04-28 22:32 ` Luck, Tony 2020-04-28 22:32 ` Luck, Tony 2020-04-28 20:40 ` Jacob Pan (Jun) 2020-04-28 20:40 ` Jacob Pan (Jun) 2020-04-28 20:57 ` Fenghua Yu 2020-04-28 20:57 ` Fenghua Yu 2020-03-30 19:33 ` [PATCH 6/7] x86/traps: Fix up invalid PASID Fenghua Yu 2020-03-30 19:33 ` Fenghua Yu 2020-04-26 15:25 ` Thomas Gleixner 2020-04-26 15:25 ` Thomas Gleixner 2020-04-27 20:11 ` Fenghua Yu 2020-04-27 20:11 ` Fenghua Yu 2020-04-28 0:13 ` Thomas Gleixner [this message] 2020-04-28 0:13 ` Thomas Gleixner 2020-04-27 22:46 ` Raj, Ashok 2020-04-27 22:46 ` Raj, Ashok 2020-04-27 23:08 ` Luck, Tony 2020-04-27 23:08 ` Luck, Tony 2020-04-28 0:20 ` Thomas Gleixner 2020-04-28 0:20 ` Thomas Gleixner 2020-04-28 0:54 ` Thomas Gleixner 2020-04-28 0:54 ` Thomas Gleixner 2020-04-28 1:08 ` Raj, Ashok 2020-04-28 1:08 ` Raj, Ashok 2020-03-30 19:33 ` [PATCH 7/7] x86/process: Clear PASID state for a newly forked/cloned thread Fenghua Yu 2020-03-30 19:33 ` Fenghua Yu 2020-04-22 20:41 ` [PATCH 0/7] x86: tag application address space for devices Fenghua Yu 2020-04-22 20:41 ` Fenghua Yu
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