From: Alexandre Chartre <alexandre.chartre@oracle.com>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: pbonzini@redhat.com, rkrcmar@redhat.com, mingo@redhat.com,
bp@alien8.de, hpa@zytor.com, dave.hansen@linux.intel.com,
luto@kernel.org, peterz@infradead.org, kvm@vger.kernel.org,
x86@kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org,
konrad.wilk@oracle.com, jan.setjeeilers@oracle.com,
liran.alon@oracle.com, jwadams@google.com, graf@amazon.de,
rppt@linux.vnet.ibm.com
Subject: Re: [RFC v2 01/26] mm/x86: Introduce kernel address space isolation
Date: Fri, 12 Jul 2019 09:43:59 +0200 [thread overview]
Message-ID: <42eac268-9b3a-b444-8288-76d57faf0826@oracle.com> (raw)
In-Reply-To: <alpine.DEB.2.21.1907112321570.1782@nanos.tec.linutronix.de>
On 7/11/19 11:33 PM, Thomas Gleixner wrote:
> On Thu, 11 Jul 2019, Alexandre Chartre wrote:
>> +/*
>> + * When isolation is active, the address space doesn't necessarily map
>> + * the percpu offset value (this_cpu_off) which is used to get pointers
>> + * to percpu variables. So functions which can be invoked while isolation
>> + * is active shouldn't be getting pointers to percpu variables (i.e. with
>> + * get_cpu_var() or this_cpu_ptr()). Instead percpu variable should be
>> + * directly read or written to (i.e. with this_cpu_read() or
>> + * this_cpu_write()).
>> + */
>> +
>> +int asi_enter(struct asi *asi)
>> +{
>> + enum asi_session_state state;
>> + struct asi *current_asi;
>> + struct asi_session *asi_session;
>> +
>> + state = this_cpu_read(cpu_asi_session.state);
>> + /*
>> + * We can re-enter isolation, but only with the same ASI (we don't
>> + * support nesting isolation). Also, if isolation is still active,
>> + * then we should be re-entering with the same task.
>> + */
>> + if (state == ASI_SESSION_STATE_ACTIVE) {
>> + current_asi = this_cpu_read(cpu_asi_session.asi);
>> + if (current_asi != asi) {
>> + WARN_ON(1);
>> + return -EBUSY;
>> + }
>> + WARN_ON(this_cpu_read(cpu_asi_session.task) != current);
>> + return 0;
>> + }
>> +
>> + /* isolation is not active so we can safely access the percpu pointer */
>> + asi_session = &get_cpu_var(cpu_asi_session);
>
> get_cpu_var()?? Where is the matching put_cpu_var() ? get_cpu_var()
> contains a preempt_disable ...
>
> What's wrong with a simple this_cpu_ptr() here?
>
Oups, my mistake, I should be using this_cpu_ptr(). I will replace all get_cpu_var()
with this_cpu_ptr().
>> +void asi_exit(struct asi *asi)
>> +{
>> + struct asi_session *asi_session;
>> + enum asi_session_state asi_state;
>> + unsigned long original_cr3;
>> +
>> + asi_state = this_cpu_read(cpu_asi_session.state);
>> + if (asi_state == ASI_SESSION_STATE_INACTIVE)
>> + return;
>> +
>> + /* TODO: Kick sibling hyperthread before switching to kernel cr3 */
>> + original_cr3 = this_cpu_read(cpu_asi_session.original_cr3);
>> + if (original_cr3)
>
> Why would this be 0 if the session is active?
>
Correct, original_cr3 won't be 0. I think this is a remain from a previous version
where original_cr3 was handled differently.
>> + write_cr3(original_cr3);
>> +
>> + /* page-table was switched, we can now access the percpu pointer */
>> + asi_session = &get_cpu_var(cpu_asi_session);
>
> See above.
>
Will fix that.
Thanks,
alex.
>> + WARN_ON(asi_session->task != current);
>> + asi_session->state = ASI_SESSION_STATE_INACTIVE;
>> + asi_session->asi = NULL;
>> + asi_session->task = NULL;
>> + asi_session->original_cr3 = 0;
>> +}
>
> Thanks,
>
> tglx
>
next prev parent reply other threads:[~2019-07-12 7:45 UTC|newest]
Thread overview: 68+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-11 14:25 [RFC v2 00/27] Kernel Address Space Isolation Alexandre Chartre
2019-07-11 14:25 ` [RFC v2 01/26] mm/x86: Introduce kernel address space isolation Alexandre Chartre
2019-07-11 21:33 ` Thomas Gleixner
2019-07-12 7:43 ` Alexandre Chartre [this message]
2019-07-11 14:25 ` [RFC v2 02/26] mm/asi: Abort isolation on interrupt, exception and context switch Alexandre Chartre
2019-07-11 20:11 ` Andi Kleen
2019-07-11 20:17 ` Mike Rapoport
2019-07-11 20:41 ` Alexandre Chartre
2019-07-12 0:05 ` Andy Lutomirski
2019-07-12 7:50 ` Alexandre Chartre
2019-07-11 14:25 ` [RFC v2 03/26] mm/asi: Handle page fault due to address space isolation Alexandre Chartre
2019-07-11 14:25 ` [RFC v2 04/26] mm/asi: Functions to track buffers allocated for an ASI page-table Alexandre Chartre
2019-07-11 14:25 ` [RFC v2 05/26] mm/asi: Add ASI page-table entry offset functions Alexandre Chartre
2019-07-11 14:25 ` [RFC v2 06/26] mm/asi: Add ASI page-table entry allocation functions Alexandre Chartre
2019-07-11 14:25 ` [RFC v2 07/26] mm/asi: Add ASI page-table entry set functions Alexandre Chartre
2019-07-11 14:25 ` [RFC v2 08/26] mm/asi: Functions to populate an ASI page-table from a VA range Alexandre Chartre
2019-07-11 14:25 ` [RFC v2 09/26] mm/asi: Helper functions to map module into ASI Alexandre Chartre
2019-07-11 14:25 ` [RFC v2 10/26] mm/asi: Keep track of VA ranges mapped in ASI page-table Alexandre Chartre
2019-07-11 14:25 ` [RFC v2 11/26] mm/asi: Functions to clear ASI page-table entries for a VA range Alexandre Chartre
2019-07-11 14:25 ` [RFC v2 12/26] mm/asi: Function to copy page-table entries for percpu buffer Alexandre Chartre
2019-07-11 14:25 ` [RFC v2 13/26] mm/asi: Add asi_remap() function Alexandre Chartre
2019-07-11 14:25 ` [RFC v2 14/26] mm/asi: Handle ASI mapped range leaks and overlaps Alexandre Chartre
2019-07-11 14:25 ` [RFC v2 15/26] mm/asi: Initialize the ASI page-table with core mappings Alexandre Chartre
2019-07-11 14:25 ` [RFC v2 16/26] mm/asi: Option to map current task into ASI Alexandre Chartre
2019-07-11 14:25 ` [RFC v2 17/26] rcu: Move tree.h static forward declarations to tree.c Alexandre Chartre
2019-07-11 14:25 ` [RFC v2 18/26] rcu: Make percpu rcu_data non-static Alexandre Chartre
2019-07-11 14:25 ` [RFC v2 19/26] mm/asi: Add option to map RCU data Alexandre Chartre
2019-07-11 14:25 ` [RFC v2 20/26] mm/asi: Add option to map cpu_hw_events Alexandre Chartre
2019-07-11 14:25 ` [RFC v2 21/26] mm/asi: Make functions to read cr3/cr4 ASI aware Alexandre Chartre
2019-07-11 14:25 ` [RFC v2 22/26] KVM: x86/asi: Introduce address_space_isolation module parameter Alexandre Chartre
2019-07-11 14:25 ` [RFC v2 23/26] KVM: x86/asi: Introduce KVM address space isolation Alexandre Chartre
2019-07-11 14:25 ` [RFC v2 24/26] KVM: x86/asi: Populate the KVM ASI page-table Alexandre Chartre
2019-07-11 14:25 ` [RFC v2 25/26] KVM: x86/asi: Switch to KVM address space on entry to guest Alexandre Chartre
2019-07-11 14:25 ` [RFC v2 26/26] KVM: x86/asi: Map KVM memslots and IO buses into KVM ASI Alexandre Chartre
2019-07-11 14:40 ` [RFC v2 00/27] Kernel Address Space Isolation Alexandre Chartre
2019-07-11 22:38 ` Dave Hansen
2019-07-12 8:09 ` Alexandre Chartre
2019-07-12 13:51 ` Dave Hansen
2019-07-12 14:06 ` Alexandre Chartre
2019-07-12 15:23 ` Thomas Gleixner
2019-07-12 10:44 ` Thomas Gleixner
2019-07-12 11:56 ` Alexandre Chartre
2019-07-12 12:50 ` Peter Zijlstra
2019-07-12 13:43 ` Alexandre Chartre
2019-07-12 13:58 ` Dave Hansen
2019-07-12 14:36 ` Andy Lutomirski
2019-07-14 18:17 ` Alexander Graf
2019-07-12 13:54 ` Dave Hansen
2019-07-12 15:20 ` Peter Zijlstra
2019-07-12 15:16 ` Thomas Gleixner
2019-07-12 16:37 ` Alexandre Chartre
2019-07-12 16:45 ` Andy Lutomirski
2019-07-14 17:11 ` Mike Rapoport
2019-07-12 19:06 ` Peter Zijlstra
2019-07-14 15:06 ` Andy Lutomirski
2019-07-15 10:33 ` Peter Zijlstra
2019-07-12 19:48 ` Thomas Gleixner
2019-07-15 8:23 ` Alexandre Chartre
2019-07-15 8:28 ` Thomas Gleixner
2019-07-12 16:00 ` Thomas Gleixner
2019-07-12 11:44 ` Peter Zijlstra
2019-07-12 12:17 ` Alexandre Chartre
2019-07-12 12:36 ` Peter Zijlstra
2019-07-12 12:47 ` Alexandre Chartre
2019-07-12 13:07 ` Peter Zijlstra
2019-07-12 13:46 ` Alexandre Chartre
2019-07-31 16:31 ` Dario Faggioli
2019-08-22 12:31 ` Alexandre Chartre
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