From: Peter Zijlstra <peterz@infradead.org>
To: "Raj, Ashok" <ashok.raj@intel.com>
Cc: Ravi V Shankar <ravi.v.shankar@intel.com>,
Dave Hansen <dave.hansen@intel.com>,
H Peter Anvin <hpa@zytor.com>, Dave Jiang <dave.jiang@intel.com>,
x86 <x86@kernel.org>, amd-gfx <amd-gfx@lists.freedesktop.org>,
Ingo Molnar <mingo@redhat.com>, Fenghua Yu <fenghua.yu@intel.com>,
Yu-cheng Yu <yu-cheng.yu@intel.com>,
Andrew Donnellan <ajd@linux.ibm.com>,
Borislav Petkov <bp@alien8.de>,
Thomas Gleixner <tglx@linutronix.de>,
Tony Luck <tony.luck@intel.com>,
linuxppc-dev <linuxppc-dev@lists.ozlabs.org>,
Felix Kuehling <Felix.Kuehling@amd.com>,
linux-kernel <linux-kernel@vger.kernel.org>,
iommu@lists.linux-foundation.org,
Jacob Jun Pan <jacob.jun.pan@intel.com>,
Frederic Barrat <fbarrat@linux.ibm.com>,
David Woodhouse <dwmw2@infradead.org>
Subject: Re: [PATCH v2 12/12] x86/traps: Fix up invalid PASID
Date: Mon, 15 Jun 2020 20:32:04 +0200 [thread overview]
Message-ID: <20200615183204.GE2531@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20200615181921.GA33928@otc-nc-03>
On Mon, Jun 15, 2020 at 11:19:21AM -0700, Raj, Ashok wrote:
> On Mon, Jun 15, 2020 at 06:03:57PM +0200, Peter Zijlstra wrote:
> >
> > I don't get why you need a rdmsr here, or why not having one would
> > require a TIF flag. Is that because this MSR is XSAVE/XRSTOR managed?
> >
> > > > > + */
> > > > > + rdmsrl(MSR_IA32_PASID, pasid_msr);
> > > > > + if (pasid_msr & MSR_IA32_PASID_VALID)
> > > > > + return false;
> > > > > +
> > > > > + /* Fix up the MSR if the MSR doesn't have a valid PASID. */
> > > > > + wrmsrl(MSR_IA32_PASID, pasid | MSR_IA32_PASID_VALID);
> >
> > How much more expensive is the wrmsr over the rdmsr? Can't we just
> > unconditionally write the current PASID and call it a day?
>
> The reason to check the rdmsr() is because we are using a hueristic taking
> GP faults. If we already setup the MSR, but we get it a second time it
> means the reason is something other than PASID_MSR not being set.
>
> Ideally we should use the TIF_ to track this would be cheaper, but we were
> told those bits aren't easy to give out.
Why do you need a TIF flag? Why not any other random flag in current?
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next prev parent reply other threads:[~2020-06-15 18:32 UTC|newest]
Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-13 0:41 [PATCH v2 00/12] x86: tag application address space for devices Fenghua Yu
2020-06-13 0:41 ` [PATCH v2 01/12] iommu: Change type of pasid to unsigned int Fenghua Yu
2020-06-13 0:41 ` [PATCH v2 02/12] ocxl: " Fenghua Yu
2020-06-18 8:05 ` Frederic Barrat
2020-06-18 15:37 ` Fenghua Yu
2020-06-18 16:56 ` Frederic Barrat
2020-06-13 0:41 ` [PATCH v2 03/12] iommu/vt-d: Change flags type to unsigned int in binding mm Fenghua Yu
2020-06-13 0:41 ` [PATCH v2 04/12] docs: x86: Add documentation for SVA (Shared Virtual Addressing) Fenghua Yu
2020-06-13 12:17 ` Lu Baolu
2020-06-15 23:16 ` Fenghua Yu
2020-06-13 0:41 ` [PATCH v2 05/12] x86/cpufeatures: Enumerate ENQCMD and ENQCMDS instructions Fenghua Yu
2020-06-13 0:41 ` [PATCH v2 06/12] x86/fpu/xstate: Add supervisor PASID state for ENQCMD feature Fenghua Yu
2020-06-13 0:41 ` [PATCH v2 07/12] x86/msr-index: Define IA32_PASID MSR Fenghua Yu
2020-06-13 0:41 ` [PATCH v2 08/12] mm: Define pasid in mm Fenghua Yu
2020-06-16 8:28 ` Jean-Philippe Brucker
2020-06-16 15:11 ` Fenghua Yu
2020-06-13 0:41 ` [PATCH v2 09/12] fork: Clear PASID for new mm Fenghua Yu
2020-06-13 0:41 ` [PATCH v2 10/12] x86/process: Clear PASID state for a newly forked/cloned thread Fenghua Yu
2020-06-13 0:41 ` [PATCH v2 11/12] x86/mmu: Allocate/free PASID Fenghua Yu
2020-06-13 13:07 ` Lu Baolu
2020-06-15 2:13 ` Lu Baolu
2020-06-13 0:41 ` [PATCH v2 12/12] x86/traps: Fix up invalid PASID Fenghua Yu
2020-06-15 7:53 ` Peter Zijlstra
2020-06-15 7:56 ` Peter Zijlstra
2020-06-15 15:48 ` Fenghua Yu
2020-06-15 16:03 ` Peter Zijlstra
2020-06-15 17:11 ` Luck, Tony
2020-06-15 18:12 ` Fenghua Yu
2020-06-15 18:31 ` Peter Zijlstra
2020-06-15 18:55 ` Fenghua Yu
2020-06-15 19:09 ` Peter Zijlstra
2020-06-15 20:17 ` Fenghua Yu
2020-06-15 20:51 ` Andy Lutomirski
2020-06-15 20:56 ` Luck, Tony
2020-06-15 21:18 ` Andy Lutomirski
2020-06-15 21:24 ` Luck, Tony
2020-06-15 21:53 ` Peter Zijlstra
2020-06-16 23:23 ` Fenghua Yu
2020-06-17 8:31 ` Peter Zijlstra
2020-06-15 18:19 ` Raj, Ashok
2020-06-15 18:32 ` Peter Zijlstra [this message]
2020-06-15 7:52 ` [PATCH v2 00/12] x86: tag application address space for devices Peter Zijlstra
2020-06-15 14:53 ` Fenghua Yu
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