linux-kernel - Re: [RFC PATCH v7 04/16] swiotlb: Map the buffer if it was unmapped by XPFO

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Date:   Wed, 23 Jan 2019 09:16:35 -0500
From:   Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
To:     Khalid Aziz <khalid.aziz@...cle.com>
Cc:     juergh@...il.com, tycho@...ho.ws, jsteckli@...zon.de,
        ak@...ux.intel.com, torvalds@...ux-foundation.org,
        liran.alon@...cle.com, keescook@...gle.com,
        Juerg Haefliger <juerg.haefliger@...onical.com>,
        deepa.srinivasan@...cle.com, chris.hyser@...cle.com,
        tyhicks@...onical.com, dwmw@...zon.co.uk,
        andrew.cooper3@...rix.com, jcm@...hat.com,
        boris.ostrovsky@...cle.com, kanth.ghatraju@...cle.com,
        joao.m.martins@...cle.com, jmattson@...gle.com,
        pradeep.vincent@...cle.com, john.haxby@...cle.com,
        tglx@...utronix.de, kirill.shutemov@...ux.intel.com, hch@....de,
        steven.sistare@...cle.com, kernel-hardening@...ts.openwall.com,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Tycho Andersen <tycho@...ker.com>
Subject: Re: [RFC PATCH v7 04/16] swiotlb: Map the buffer if it was unmapped
 by XPFO

On Thu, Jan 10, 2019 at 02:09:36PM -0700, Khalid Aziz wrote:
> From: Juerg Haefliger <juerg.haefliger@...onical.com>
> 
> v6: * guard against lookup_xpfo() returning NULL
> 
> CC: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
> Signed-off-by: Juerg Haefliger <juerg.haefliger@...onical.com>
> Signed-off-by: Tycho Andersen <tycho@...ker.com>
> Signed-off-by: Khalid Aziz <khalid.aziz@...cle.com>

Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>

> ---
>  include/linux/xpfo.h |  4 ++++
>  kernel/dma/swiotlb.c |  3 ++-
>  mm/xpfo.c            | 15 +++++++++++++++
>  3 files changed, 21 insertions(+), 1 deletion(-)
> 
> diff --git a/include/linux/xpfo.h b/include/linux/xpfo.h
> index a39259ce0174..e38b823f44e3 100644
> --- a/include/linux/xpfo.h
> +++ b/include/linux/xpfo.h
> @@ -35,6 +35,8 @@ void xpfo_kunmap(void *kaddr, struct page *page);
>  void xpfo_alloc_pages(struct page *page, int order, gfp_t gfp);
>  void xpfo_free_pages(struct page *page, int order);
>  
> +bool xpfo_page_is_unmapped(struct page *page);
> +
>  #else /* !CONFIG_XPFO */
>  
>  static inline void xpfo_kmap(void *kaddr, struct page *page) { }
> @@ -42,6 +44,8 @@ static inline void xpfo_kunmap(void *kaddr, struct page *page) { }
>  static inline void xpfo_alloc_pages(struct page *page, int order, gfp_t gfp) { }
>  static inline void xpfo_free_pages(struct page *page, int order) { }
>  
> +static inline bool xpfo_page_is_unmapped(struct page *page) { return false; }
> +
>  #endif /* CONFIG_XPFO */
>  
>  #endif /* _LINUX_XPFO_H */
> diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
> index 045930e32c0e..820a54b57491 100644
> --- a/kernel/dma/swiotlb.c
> +++ b/kernel/dma/swiotlb.c
> @@ -396,8 +396,9 @@ static void swiotlb_bounce(phys_addr_t orig_addr, phys_addr_t tlb_addr,
>  {
>  	unsigned long pfn = PFN_DOWN(orig_addr);
>  	unsigned char *vaddr = phys_to_virt(tlb_addr);
> +	struct page *page = pfn_to_page(pfn);
>  
> -	if (PageHighMem(pfn_to_page(pfn))) {
> +	if (PageHighMem(page) || xpfo_page_is_unmapped(page)) {
>  		/* The buffer does not have a mapping.  Map it in and copy */
>  		unsigned int offset = orig_addr & ~PAGE_MASK;
>  		char *buffer;
> diff --git a/mm/xpfo.c b/mm/xpfo.c
> index bff24afcaa2e..cdbcbac582d5 100644
> --- a/mm/xpfo.c
> +++ b/mm/xpfo.c
> @@ -220,3 +220,18 @@ void xpfo_kunmap(void *kaddr, struct page *page)
>  	spin_unlock(&xpfo->maplock);
>  }
>  EXPORT_SYMBOL(xpfo_kunmap);
> +
> +bool xpfo_page_is_unmapped(struct page *page)
> +{
> +	struct xpfo *xpfo;
> +
> +	if (!static_branch_unlikely(&xpfo_inited))
> +		return false;
> +
> +	xpfo = lookup_xpfo(page);
> +	if (unlikely(!xpfo) && !xpfo->inited)
> +		return false;
> +
> +	return test_bit(XPFO_PAGE_UNMAPPED, &xpfo->flags);
> +}
> +EXPORT_SYMBOL(xpfo_page_is_unmapped);
> -- 
> 2.17.1
>