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From: Junaid Shahid <junaids@google.com>
To: Matthew Wilcox <willy@infradead.org>
Cc: linux-kernel@vger.kernel.org, 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, tglx@linutronix.de, luto@kernel.org,
	linux-mm@kvack.org
Subject: Re: [RFC PATCH 10/47] mm: asi: Support for global non-sensitive direct map allocations
Date: Wed, 23 Mar 2022 18:54:37 -0700	[thread overview]
Message-ID: <ec6e5c54-2ff8-9af5-a25d-d99921a3da06@google.com> (raw)
In-Reply-To: <3a7c3a71-0be7-261e-20b7-54b4864eedb5@google.com>

On 3/23/22 16:48, Junaid Shahid wrote:
> Hi Matthew,
> 
> On 3/23/22 14:06, Matthew Wilcox wrote:
>> On Tue, Feb 22, 2022 at 09:21:46PM -0800, Junaid Shahid wrote:
>>> standard ASI instances. A new page flag is also added so that when
>>> these pages are freed, they can also be unmapped from the ASI page
>>> tables.
>>
>> It's cute how you just throw this in as an aside.  Page flags are
>> in high demand and just adding them is not to be done lightly.  Is
>> there any other way of accomplishing what you want?
>>
> 
> I suppose we may be able to use page_ext instead. That certainly should be 
> feasible for the PG_local_nonsensitive flag introduced in a later patch, 
> although I am not completely sure about the PG_global_nonsensitive flag. That 
> could get slightly tricky (though likely still possible to do) in case we need 
> to allocate any non-sensitive memory before page_ext is initialized. One concern 
> with using page_ext could be the extra memory usage on large machines.
> 
> BTW is page flag scarcity an issue on 64-bit systems as well, or only 32-bit 
> systems? ASI is only supported on 64-bit systems (at least currently).
> 

One other thing that we could do to remove the need for the 
PG_global_nonsensitive flag altogether (though not the PG_local_nonsensitive 
flag) would be to always try to unmap pages from the asi_global_nonsensitive_pgd 
in free_pages(). Basically, that would mean adding a page table walk to every 
free_pages() rather than just non-sensitive free_pages(). Do you think that may 
be a better trade-off in order to avoid the flag?

Thanks,
Junaid


  reply	other threads:[~2022-03-24  1:54 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
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 [this message]
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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