From: Michael Kelley <mhklinux@outlook.com>
To: Christoph Hellwig <hch@infradead.org>
Cc: "tglx@linutronix.de" <tglx@linutronix.de>,
"mingo@redhat.com" <mingo@redhat.com>,
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Subject: RE: [PATCH v2 3/8] x86/mm: Remove "static" from vmap_pages_range()
Date: Mon, 27 Nov 2023 01:06:06 +0000 [thread overview]
Message-ID: <SN6PR02MB4157CF2A7C5064889843D79CD4BDA@SN6PR02MB4157.namprd02.prod.outlook.com> (raw)
In-Reply-To: <ZV7//Yjx6ngKSf0M@infradead.org>
From: Christoph Hellwig <hch@infradead.org> Sent: Wednesday, November 22, 2023 11:32 PM
>
> On Thu, Nov 23, 2023 at 12:24:49AM +0000, Michael Kelley wrote:
> > > I really do not want to expose vmap_pages_range. Please try to come up
> > > with a good way to encapsulate your map at a certain address primitive
> > > and implement it in vmalloc.c.
> >
> > To clarify, is your concern narrowly about vmap_pages_range()
> > specifically?
>
> The prime concern is that it took a lot of effort to make
> vmap_pages_range static and remove all the abuses. I absolutely
> object to undoing that.
OK, so I assume that means a new variant of vmap_pages_range(),
such as one that always sets the page_shift parameter to PAGE_SIZE,
is also disallowed because of the same potential for abuse.
So the only way to map a system memory page to a vmalloc
vaddr is via vmap() or some vmap() variant, which always
creates a new vmalloc area via get_vm_area(). I've done the
perf measurements, and that approach won't work for this use
case. Independent of the alignment requirements, the churn in
creating and removing a lot of vmalloc areas has too much perf
impact. The use case needs to create a single vmalloc area, and
then repeatedly map/unmap a page in that existing area.
I'll have to handle the top-level problem in this patch set in
a completely different way.
Michael
next prev parent reply other threads:[~2023-11-27 1:06 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-11-21 21:20 [PATCH v2 0/8] x86/coco: Mark CoCo VM pages not present when changing encrypted state mhkelley58
2023-11-21 21:20 ` [PATCH v2 1/8] x86/coco: Use slow_virt_to_phys() in page transition hypervisor callbacks mhkelley58
2023-11-21 21:20 ` [PATCH v2 2/8] x86/mm: Don't do a TLB flush if changing a PTE that isn't marked present mhkelley58
2023-11-27 22:21 ` Edgecombe, Rick P
2023-11-28 17:34 ` Michael Kelley
2023-11-21 21:20 ` [PATCH v2 3/8] x86/mm: Remove "static" from vmap_pages_range() mhkelley58
2023-11-22 6:26 ` Christoph Hellwig
2023-11-23 0:24 ` Michael Kelley
2023-11-23 7:32 ` Christoph Hellwig
2023-11-27 1:06 ` Michael Kelley [this message]
2023-11-21 21:20 ` [PATCH v2 4/8] x86/sev: Enable PVALIDATE for PFNs without a valid virtual address mhkelley58
2023-11-27 21:38 ` Edgecombe, Rick P
2023-11-28 18:08 ` Michael Kelley
2023-11-28 18:59 ` Edgecombe, Rick P
2023-12-12 18:35 ` Michael Kelley
2023-11-21 21:20 ` [PATCH v2 5/8] x86/mm: Mark CoCo VM pages not present while changing encrypted state mhkelley58
2023-11-21 21:20 ` [PATCH v2 6/8] x86/mm: Merge CoCo prepare and finish hypervisor callbacks mhkelley58
2023-11-21 21:20 ` [PATCH v2 7/8] x86/mm: Remove unnecessary call layer for __set_memory_enc_pgtable() mhkelley58
2023-11-21 21:20 ` [PATCH v2 8/8] x86/mm: Add comments about errors in set_memory_decrypted()/encrypted() mhkelley58
2023-11-24 10:06 ` [PATCH v2 0/8] x86/coco: Mark CoCo VM pages not present when changing encrypted state kirill.shutemov
2023-11-28 19:12 ` Michael Kelley
2023-11-29 15:10 ` kirill.shutemov
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