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From: Thomas Gleixner <tglx@linutronix.de>
To: Junaid Shahid <junaids@google.com>, linux-kernel@vger.kernel.org
Cc: kvm@vger.kernel.org, pbonzini@redhat.com, jmattson@google.com,
	pjt@google.com, oweisse@google.com, alexandre.chartre@oracle.com,
	rppt@linux.ibm.com, dave.hansen@linux.intel.com,
	peterz@infradead.org, luto@kernel.org, linux-mm@kvack.org
Subject: Re: [RFC PATCH 04/47] mm: asi: ASI support in interrupts/exceptions
Date: Tue, 15 Mar 2022 13:55:39 +0100	[thread overview]
Message-ID: <877d8v74tw.ffs@tglx> (raw)
In-Reply-To: <9f2f1226-f398-f132-06f4-c21a2a2d1033@google.com>

Junaid,

On Mon, Mar 14 2022 at 19:01, Junaid Shahid wrote:
> On 3/14/22 08:50, Thomas Gleixner wrote:
>> On Tue, Feb 22 2022 at 21:21, Junaid Shahid wrote:
>>>   #define DEFINE_IDTENTRY_RAW(func)					\
>>> -__visible noinstr void func(struct pt_regs *regs)
>>> +static __always_inline void __##func(struct pt_regs *regs);		\
>>> +									\
>>> +__visible noinstr void func(struct pt_regs *regs)			\
>>> +{									\
>>> +	asi_intr_enter();						\
>> 
>> This is wrong. You cannot invoke arbitrary code within a noinstr
>> section.
>> 
>> Please enable CONFIG_VMLINUX_VALIDATION and watch the build result with
>> and without your patches.
>> 
> Thank you for the pointer. It seems that marking asi_intr_enter/exit
> and asi_enter/exit, and the few functions that they in turn call, as
> noinstr would fix this, correct? (Along with removing the VM_BUG_ONs
> from those functions and using notrace/nodebug variants of a couple of
> functions).

you can keep the BUG_ON()s. If such a bug happens the noinstr
correctness is the least of your worries, but it's important to get the
information out, right?

Vs. adding noinstr. Yes, making the full callchain noinstr is going to
cure it, but you really want to think hard whether these calls need to
be in this section of the exception handlers.

These code sections have other constraints aside of being excluded from
instrumentation, the main one being that you cannot use RCU there.

I'm not yet convinced that asi_intr_enter()/exit() need to be invoked in
exactly the places you put it. The changelog does not give any clue
about the why...

Thanks,

        tglx




  reply	other threads:[~2022-03-15 12:55 UTC|newest]

Thread overview: 64+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-02-23  5:21 [RFC PATCH 00/47] Address Space Isolation for KVM Junaid Shahid
2022-02-23  5:21 ` [RFC PATCH 01/47] mm: asi: Introduce ASI core API Junaid Shahid
2022-02-23  5:21 ` [RFC PATCH 02/47] mm: asi: Add command-line parameter to enable/disable ASI Junaid Shahid
2022-02-23  5:21 ` [RFC PATCH 03/47] mm: asi: Switch to unrestricted address space when entering scheduler Junaid Shahid
2022-02-23  5:21 ` [RFC PATCH 04/47] mm: asi: ASI support in interrupts/exceptions Junaid Shahid
2022-03-14 15:50   ` Thomas Gleixner
2022-03-15  2:01     ` Junaid Shahid
2022-03-15 12:55       ` Thomas Gleixner [this message]
2022-03-15 22:41         ` Junaid Shahid
2022-02-23  5:21 ` [RFC PATCH 05/47] mm: asi: Make __get_current_cr3_fast() ASI-aware Junaid Shahid
2022-02-23  5:21 ` [RFC PATCH 06/47] mm: asi: ASI page table allocation and free functions Junaid Shahid
2022-02-23  5:21 ` [RFC PATCH 07/47] mm: asi: Functions to map/unmap a memory range into ASI page tables Junaid Shahid
2022-02-23  5:21 ` [RFC PATCH 08/47] mm: asi: Add basic infrastructure for global non-sensitive mappings Junaid Shahid
2022-02-23  5:21 ` [RFC PATCH 09/47] mm: Add __PAGEFLAG_FALSE Junaid Shahid
2022-02-23  5:21 ` [RFC PATCH 10/47] mm: asi: Support for global non-sensitive direct map allocations Junaid Shahid
2022-03-23 21:06   ` Matthew Wilcox
2022-03-23 23:48     ` Junaid Shahid
2022-03-24  1:54       ` Junaid Shahid
2022-02-23  5:21 ` [RFC PATCH 11/47] mm: asi: Global non-sensitive vmalloc/vmap support Junaid Shahid
2022-02-23  5:21 ` [RFC PATCH 12/47] mm: asi: Support for global non-sensitive slab caches Junaid Shahid
2022-02-23  5:21 ` [RFC PATCH 13/47] asi: Added ASI memory cgroup flag Junaid Shahid
2022-02-23  5:21 ` [RFC PATCH 14/47] mm: asi: Disable ASI API when ASI is not enabled for a process Junaid Shahid
2022-02-23  5:21 ` [RFC PATCH 15/47] kvm: asi: Restricted address space for VM execution Junaid Shahid
2022-02-23  5:21 ` [RFC PATCH 16/47] mm: asi: Support for mapping non-sensitive pcpu chunks Junaid Shahid
2022-02-23  5:21 ` [RFC PATCH 17/47] mm: asi: Aliased direct map for local non-sensitive allocations Junaid Shahid
2022-02-23  5:21 ` [RFC PATCH 18/47] mm: asi: Support for pre-ASI-init " Junaid Shahid
2022-02-23  5:21 ` [RFC PATCH 19/47] mm: asi: Support for locally nonsensitive page allocations Junaid Shahid
2022-02-23  5:21 ` [RFC PATCH 20/47] mm: asi: Support for locally non-sensitive vmalloc allocations Junaid Shahid
2022-02-23  5:21 ` [RFC PATCH 21/47] mm: asi: Add support for locally non-sensitive VM_USERMAP pages Junaid Shahid
2022-02-23  5:21 ` [RFC PATCH 22/47] mm: asi: Added refcounting when initilizing an asi Junaid Shahid
2022-02-23  5:21 ` [RFC PATCH 23/47] mm: asi: Add support for mapping all userspace memory into ASI Junaid Shahid
2022-02-23  5:22 ` [RFC PATCH 24/47] mm: asi: Support for local non-sensitive slab caches Junaid Shahid
2022-02-23  5:22 ` [RFC PATCH 25/47] mm: asi: Avoid warning from NMI userspace accesses in ASI context Junaid Shahid
2022-02-23  5:22 ` [RFC PATCH 26/47] mm: asi: Use separate PCIDs for restricted address spaces Junaid Shahid
2022-02-23  5:22 ` [RFC PATCH 27/47] mm: asi: Avoid TLB flushes during ASI CR3 switches when possible Junaid Shahid
2022-02-23  5:22 ` [RFC PATCH 28/47] mm: asi: Avoid TLB flush IPIs to CPUs not in ASI context Junaid Shahid
2022-02-23  5:22 ` [RFC PATCH 29/47] mm: asi: Reduce TLB flushes when freeing pages asynchronously Junaid Shahid
2022-02-23  5:22 ` [RFC PATCH 30/47] mm: asi: Add API for mapping userspace address ranges Junaid Shahid
2022-02-23  5:22 ` [RFC PATCH 31/47] mm: asi: Support for non-sensitive SLUB caches Junaid Shahid
2022-02-23  5:22 ` [RFC PATCH 32/47] x86: asi: Allocate FPU state separately when ASI is enabled Junaid Shahid
2022-02-23  5:22 ` [RFC PATCH 33/47] kvm: asi: Map guest memory into restricted ASI address space Junaid Shahid
2022-02-23  5:22 ` [RFC PATCH 34/47] kvm: asi: Unmap guest memory from ASI address space when using nested virt Junaid Shahid
2022-02-23  5:22 ` [RFC PATCH 35/47] mm: asi: asi_exit() on PF, skip handling if address is accessible Junaid Shahid
2022-02-23  5:22 ` [RFC PATCH 36/47] mm: asi: Adding support for dynamic percpu ASI allocations Junaid Shahid
2022-02-23  5:22 ` [RFC PATCH 37/47] mm: asi: ASI annotation support for static variables Junaid Shahid
2022-02-23  5:22 ` [RFC PATCH 38/47] mm: asi: ASI annotation support for dynamic modules Junaid Shahid
2022-02-23  5:22 ` [RFC PATCH 39/47] mm: asi: Skip conventional L1TF/MDS mitigations Junaid Shahid
2022-02-23  5:22 ` [RFC PATCH 40/47] mm: asi: support for static percpu DEFINE_PER_CPU*_ASI Junaid Shahid
2022-02-23  5:22 ` [RFC PATCH 41/47] mm: asi: Annotation of static variables to be nonsensitive Junaid Shahid
2022-02-23  5:22 ` [RFC PATCH 42/47] mm: asi: Annotation of PERCPU " Junaid Shahid
2022-02-23  5:22 ` [RFC PATCH 43/47] mm: asi: Annotation of dynamic " Junaid Shahid
2022-02-23  5:22 ` [RFC PATCH 44/47] kvm: asi: Splitting kvm_vcpu_arch into non/sensitive parts Junaid Shahid
2022-02-23  5:22 ` [RFC PATCH 45/47] mm: asi: Mapping global nonsensitive areas in asi_global_init Junaid Shahid
2022-02-23  5:22 ` [RFC PATCH 46/47] kvm: asi: Do asi_exit() in vcpu_run loop before returning to userspace Junaid Shahid
2022-02-23  5:22 ` [RFC PATCH 47/47] mm: asi: Properly un/mapping task stack from ASI + tlb flush Junaid Shahid
2022-03-05  3:39 ` [RFC PATCH 00/47] Address Space Isolation for KVM Hyeonggon Yoo
2022-03-16 21:34 ` Alexandre Chartre
2022-03-17 23:25   ` Junaid Shahid
2022-03-22  9:46     ` Alexandre Chartre
2022-03-23 19:35       ` Junaid Shahid
2022-04-08  8:52         ` Alexandre Chartre
2022-04-11  3:26           ` junaid_shahid
2022-03-16 22:49 ` Thomas Gleixner
2022-03-17 21:24   ` Junaid Shahid

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