From: Peter Zijlstra <peterz@infradead.org>
To: Khalid Aziz <khalid.aziz@oracle.com>
Cc: juergh@gmail.com, tycho@tycho.ws, jsteckli@amazon.de,
ak@linux.intel.com, torvalds@linux-foundation.org,
liran.alon@oracle.com, keescook@google.com,
akpm@linux-foundation.org, mhocko@suse.com,
catalin.marinas@arm.com, will.deacon@arm.com, jmorris@namei.org,
konrad.wilk@oracle.com,
Juerg Haefliger <juerg.haefliger@canonical.com>,
deepa.srinivasan@oracle.com, chris.hyser@oracle.com,
tyhicks@canonical.com, dwmw@amazon.co.uk,
andrew.cooper3@citrix.com, jcm@redhat.com,
boris.ostrovsky@oracle.com, kanth.ghatraju@oracle.com,
oao.m.martins@oracle.com, jmattson@google.com,
pradeep.vincent@oracle.com, john.haxby@oracle.com,
tglx@linutronix.de, kirill.shutemov@linux.intel.com, hch@lst.de,
steven.sistare@oracle.com, labbott@redhat.com, luto@kernel.org,
dave.hansen@intel.com, kernel-hardening@lists.openwall.com,
linux-mm@kvack.org, x86@kernel.org,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, Tycho Andersen <tycho@docker.com>,
Marco Benatto <marco.antonio.780@gmail.com>
Subject: Re: [RFC PATCH v8 03/14] mm, x86: Add support for eXclusive Page Frame Ownership (XPFO)
Date: Thu, 14 Feb 2019 11:56:31 +0100 [thread overview]
Message-ID: <20190214105631.GJ32494@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <8275de2a7e6b72d19b1cd2ec5d71a42c2c7dd6c5.1550088114.git.khalid.aziz@oracle.com>
On Wed, Feb 13, 2019 at 05:01:26PM -0700, Khalid Aziz wrote:
> static inline void *kmap_atomic(struct page *page)
> {
> + void *kaddr;
> +
> preempt_disable();
> pagefault_disable();
> + kaddr = page_address(page);
> + xpfo_kmap(kaddr, page);
> + return kaddr;
> }
> #define kmap_atomic_prot(page, prot) kmap_atomic(page)
>
> static inline void __kunmap_atomic(void *addr)
> {
> + xpfo_kunmap(addr, virt_to_page(addr));
> pagefault_enable();
> preempt_enable();
> }
How is that supposed to work; IIRC kmap_atomic was supposed to be
IRQ-safe.
> +/* Per-page XPFO house-keeping data */
> +struct xpfo {
> + unsigned long flags; /* Page state */
> + bool inited; /* Map counter and lock initialized */
What's sizeof(_Bool) ? Why can't you use a bit in that flags word?
> + atomic_t mapcount; /* Counter for balancing map/unmap requests */
> + spinlock_t maplock; /* Lock to serialize map/unmap requests */
> +};
Without that bool, the structure would be 16 bytes on 64bit, which seems
like a good number.
> +void xpfo_kmap(void *kaddr, struct page *page)
> +{
> + struct xpfo *xpfo;
> +
> + if (!static_branch_unlikely(&xpfo_inited))
> + return;
> +
> + xpfo = lookup_xpfo(page);
> +
> + /*
> + * The page was allocated before page_ext was initialized (which means
> + * it's a kernel page) or it's allocated to the kernel, so nothing to
> + * do.
> + */
> + if (!xpfo || unlikely(!xpfo->inited) ||
> + !test_bit(XPFO_PAGE_USER, &xpfo->flags))
> + return;
> +
> + spin_lock(&xpfo->maplock);
> +
> + /*
> + * The page was previously allocated to user space, so map it back
> + * into the kernel. No TLB flush required.
> + */
> + if ((atomic_inc_return(&xpfo->mapcount) == 1) &&
> + test_and_clear_bit(XPFO_PAGE_UNMAPPED, &xpfo->flags))
> + set_kpte(kaddr, page, PAGE_KERNEL);
> +
> + spin_unlock(&xpfo->maplock);
> +}
> +EXPORT_SYMBOL(xpfo_kmap);
> +
> +void xpfo_kunmap(void *kaddr, struct page *page)
> +{
> + struct xpfo *xpfo;
> +
> + if (!static_branch_unlikely(&xpfo_inited))
> + return;
> +
> + xpfo = lookup_xpfo(page);
> +
> + /*
> + * The page was allocated before page_ext was initialized (which means
> + * it's a kernel page) or it's allocated to the kernel, so nothing to
> + * do.
> + */
> + if (!xpfo || unlikely(!xpfo->inited) ||
> + !test_bit(XPFO_PAGE_USER, &xpfo->flags))
> + return;
> +
> + spin_lock(&xpfo->maplock);
> +
> + /*
> + * The page is to be allocated back to user space, so unmap it from the
> + * kernel, flush the TLB and tag it as a user page.
> + */
> + if (atomic_dec_return(&xpfo->mapcount) == 0) {
> + WARN(test_bit(XPFO_PAGE_UNMAPPED, &xpfo->flags),
> + "xpfo: unmapping already unmapped page\n");
> + set_bit(XPFO_PAGE_UNMAPPED, &xpfo->flags);
> + set_kpte(kaddr, page, __pgprot(0));
> + xpfo_flush_kernel_tlb(page, 0);
> + }
> +
> + spin_unlock(&xpfo->maplock);
> +}
> +EXPORT_SYMBOL(xpfo_kunmap);
And these here things are most definitely not IRQ-safe.
next prev parent reply other threads:[~2019-02-14 10:56 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-02-14 0:01 [RFC PATCH v8 00/14] Add support for eXclusive Page Frame Ownership Khalid Aziz
2019-02-14 0:01 ` [RFC PATCH v8 01/14] mm: add MAP_HUGETLB support to vm_mmap Khalid Aziz
2019-02-14 0:01 ` [RFC PATCH v8 02/14] x86: always set IF before oopsing from page fault Khalid Aziz
2019-02-14 0:01 ` [RFC PATCH v8 03/14] mm, x86: Add support for eXclusive Page Frame Ownership (XPFO) Khalid Aziz
2019-02-14 10:56 ` Peter Zijlstra [this message]
2019-02-14 16:15 ` Borislav Petkov
2019-02-14 17:19 ` Khalid Aziz
2019-02-14 17:13 ` Khalid Aziz
2019-02-14 19:08 ` Peter Zijlstra
2019-02-14 19:58 ` Khalid Aziz
2019-02-14 0:01 ` [RFC PATCH v8 04/14] swiotlb: Map the buffer if it was unmapped by XPFO Khalid Aziz
2019-02-14 7:47 ` Christoph Hellwig
2019-02-14 16:56 ` Khalid Aziz
2019-02-14 17:44 ` Christoph Hellwig
2019-02-14 19:48 ` Khalid Aziz
2019-02-14 0:01 ` [RFC PATCH v8 05/14] arm64/mm: Add support for XPFO Khalid Aziz
2019-02-14 0:01 ` [RFC PATCH v8 06/14] xpfo: add primitives for mapping underlying memory Khalid Aziz
2019-02-14 0:01 ` [RFC PATCH v8 07/14] arm64/mm, xpfo: temporarily map dcache regions Khalid Aziz
2019-02-14 15:54 ` Tycho Andersen
2019-02-14 17:29 ` Khalid Aziz
2019-02-14 23:49 ` Tycho Andersen
2019-02-14 0:01 ` [RFC PATCH v8 08/14] arm64/mm: disable section/contiguous mappings if XPFO is enabled Khalid Aziz
2019-02-15 13:09 ` Mark Rutland
2019-02-15 14:47 ` Khalid Aziz
2019-02-14 0:01 ` [RFC PATCH v8 09/14] mm: add a user_virt_to_phys symbol Khalid Aziz
2019-02-14 0:01 ` [RFC PATCH v8 10/14] lkdtm: Add test for XPFO Khalid Aziz
2019-02-14 0:01 ` [RFC PATCH v8 11/14] xpfo, mm: remove dependency on CONFIG_PAGE_EXTENSION Khalid Aziz
2019-02-14 0:01 ` [RFC PATCH v8 12/14] xpfo, mm: optimize spinlock usage in xpfo_kunmap Khalid Aziz
2019-02-14 0:01 ` [RFC PATCH v8 13/14] xpfo, mm: Defer TLB flushes for non-current CPUs (x86 only) Khalid Aziz
2019-02-14 17:42 ` Dave Hansen
2019-02-14 19:57 ` Khalid Aziz
2019-02-14 0:01 ` [RFC PATCH v8 14/14] xpfo, mm: Optimize XPFO TLB flushes by batching them together Khalid Aziz
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