Re: [PATCH 2/2] xen/grant-table: remove support for V2 tables

[Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>]

On Wed, Jul 02, 2014 at 11:25:29AM +0100, David Vrabel wrote:
> Since 11c7ff17c9b6dbf3a4e4f36be30ad531a6cf0ec9 (xen/grant-table: Force
> to use v1 of grants.) the code for V2 grant tables is not used.

.. and if we ever need it we can resurrect it.

Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
> 
> Signed-off-by: David Vrabel <david.vrabel@citrix.com>
> ---
>  arch/arm/xen/grant-table.c |    9 +-
>  arch/x86/xen/grant-table.c |   60 +--------
>  drivers/xen/grant-table.c  |  309 +-------------------------------------------
>  include/xen/grant_table.h  |   30 +----
>  4 files changed, 13 insertions(+), 395 deletions(-)
> 
> diff --git a/arch/arm/xen/grant-table.c b/arch/arm/xen/grant-table.c
> index 91cf08b..e437918 100644
> --- a/arch/arm/xen/grant-table.c
> +++ b/arch/arm/xen/grant-table.c
> @@ -45,14 +45,7 @@ void arch_gnttab_unmap(void *shared, unsigned long nr_gframes)
>  	return;
>  }
>  
> -int arch_gnttab_map_status(uint64_t *frames, unsigned long nr_gframes,
> -			   unsigned long max_nr_gframes,
> -			   grant_status_t **__shared)
> -{
> -	return -ENOSYS;
> -}
> -
> -int arch_gnttab_init(unsigned long nr_shared, unsigned long nr_status)
> +int arch_gnttab_init(unsigned long nr_shared)
>  {
>  	return 0;
>  }
> diff --git a/arch/x86/xen/grant-table.c b/arch/x86/xen/grant-table.c
> index 27301df..c1ef6b2 100644
> --- a/arch/x86/xen/grant-table.c
> +++ b/arch/x86/xen/grant-table.c
> @@ -48,7 +48,7 @@
>  static struct gnttab_vm_area {
>  	struct vm_struct *area;
>  	pte_t **ptes;
> -} gnttab_shared_vm_area, gnttab_status_vm_area;
> +} gnttab_shared_vm_area;
>  
>  int arch_gnttab_map_shared(unsigned long *frames, unsigned long nr_gframes,
>  			   unsigned long max_nr_gframes,
> @@ -72,43 +72,16 @@ int arch_gnttab_map_shared(unsigned long *frames, unsigned long nr_gframes,
>  	return 0;
>  }
>  
> -int arch_gnttab_map_status(uint64_t *frames, unsigned long nr_gframes,
> -			   unsigned long max_nr_gframes,
> -			   grant_status_t **__shared)
> -{
> -	grant_status_t *shared = *__shared;
> -	unsigned long addr;
> -	unsigned long i;
> -
> -	if (shared == NULL)
> -		*__shared = shared = gnttab_status_vm_area.area->addr;
> -
> -	addr = (unsigned long)shared;
> -
> -	for (i = 0; i < nr_gframes; i++) {
> -		set_pte_at(&init_mm, addr, gnttab_status_vm_area.ptes[i],
> -			   mfn_pte(frames[i], PAGE_KERNEL));
> -		addr += PAGE_SIZE;
> -	}
> -
> -	return 0;
> -}
> -
>  void arch_gnttab_unmap(void *shared, unsigned long nr_gframes)
>  {
> -	pte_t **ptes;
>  	unsigned long addr;
>  	unsigned long i;
>  
> -	if (shared == gnttab_status_vm_area.area->addr)
> -		ptes = gnttab_status_vm_area.ptes;
> -	else
> -		ptes = gnttab_shared_vm_area.ptes;
> -
>  	addr = (unsigned long)shared;
>  
>  	for (i = 0; i < nr_gframes; i++) {
> -		set_pte_at(&init_mm, addr, ptes[i], __pte(0));
> +		set_pte_at(&init_mm, addr, gnttab_shared_vm_area.ptes[i],
> +			   __pte(0));
>  		addr += PAGE_SIZE;
>  	}
>  }
> @@ -129,35 +102,12 @@ static int __init arch_gnttab_valloc(struct gnttab_vm_area *area,
>  	return 0;
>  }
>  
> -static void __init arch_gnttab_vfree(struct gnttab_vm_area *area)
> +int __init arch_gnttab_init(unsigned long nr_shared)
>  {
> -	free_vm_area(area->area);
> -	kfree(area->ptes);
> -}
> -
> -int __init arch_gnttab_init(unsigned long nr_shared, unsigned long nr_status)
> -{
> -	int ret;
> -
>  	if (!xen_pv_domain())
>  		return 0;
>  
> -	ret = arch_gnttab_valloc(&gnttab_shared_vm_area, nr_shared);
> -	if (ret < 0)
> -		return ret;
> -
> -	/*
> -	 * Always allocate the space for the status frames in case
> -	 * we're migrated to a host with V2 support.
> -	 */
> -	ret = arch_gnttab_valloc(&gnttab_status_vm_area, nr_status);
> -	if (ret < 0)
> -		goto err;
> -
> -	return 0;
> -  err:
> -	arch_gnttab_vfree(&gnttab_shared_vm_area);
> -	return -ENOMEM;
> +	return arch_gnttab_valloc(&gnttab_shared_vm_area, nr_shared);
>  }
>  
>  #ifdef CONFIG_XEN_PVH
> diff --git a/drivers/xen/grant-table.c b/drivers/xen/grant-table.c
> index eeba754..c254ae0 100644
> --- a/drivers/xen/grant-table.c
> +++ b/drivers/xen/grant-table.c
> @@ -69,7 +69,6 @@ struct grant_frames xen_auto_xlat_grant_frames;
>  
>  static union {
>  	struct grant_entry_v1 *v1;
> -	union grant_entry_v2 *v2;
>  	void *addr;
>  } gnttab_shared;
>  
> @@ -120,36 +119,10 @@ struct gnttab_ops {
>  	 * by bit operations.
>  	 */
>  	int (*query_foreign_access)(grant_ref_t ref);
> -	/*
> -	 * Grant a domain to access a range of bytes within the page referred by
> -	 * an available grant entry. Ref parameter is reference of a grant entry
> -	 * which will be sub-page accessed, domid is id of grantee domain, frame
> -	 * is frame address of subpage grant, flags is grant type and flag
> -	 * information, page_off is offset of the range of bytes, and length is
> -	 * length of bytes to be accessed.
> -	 */
> -	void (*update_subpage_entry)(grant_ref_t ref, domid_t domid,
> -				     unsigned long frame, int flags,
> -				     unsigned page_off, unsigned length);
> -	/*
> -	 * Redirect an available grant entry on domain A to another grant
> -	 * reference of domain B, then allow domain C to use grant reference
> -	 * of domain B transitively. Ref parameter is an available grant entry
> -	 * reference on domain A, domid is id of domain C which accesses grant
> -	 * entry transitively, flags is grant type and flag information,
> -	 * trans_domid is id of domain B whose grant entry is finally accessed
> -	 * transitively, trans_gref is grant entry transitive reference of
> -	 * domain B.
> -	 */
> -	void (*update_trans_entry)(grant_ref_t ref, domid_t domid, int flags,
> -				   domid_t trans_domid, grant_ref_t trans_gref);
>  };
>  
>  static struct gnttab_ops *gnttab_interface;
>  
> -/*This reflects status of grant entries, so act as a global value*/
> -static grant_status_t *grstatus;
> -
>  static int grant_table_version;
>  static int grefs_per_grant_frame;
>  
> @@ -231,7 +204,7 @@ static void put_free_entry(grant_ref_t ref)
>  }
>  
>  /*
> - * Following applies to gnttab_update_entry_v1 and gnttab_update_entry_v2.
> + * Following applies to gnttab_update_entry_v1.
>   * Introducing a valid entry into the grant table:
>   *  1. Write ent->domid.
>   *  2. Write ent->frame:
> @@ -250,15 +223,6 @@ static void gnttab_update_entry_v1(grant_ref_t ref, domid_t domid,
>  	gnttab_shared.v1[ref].flags = flags;
>  }
>  
> -static void gnttab_update_entry_v2(grant_ref_t ref, domid_t domid,
> -				   unsigned long frame, unsigned flags)
> -{
> -	gnttab_shared.v2[ref].hdr.domid = domid;
> -	gnttab_shared.v2[ref].full_page.frame = frame;
> -	wmb();
> -	gnttab_shared.v2[ref].hdr.flags = GTF_permit_access | flags;
> -}
> -
>  /*
>   * Public grant-issuing interface functions
>   */
> @@ -285,132 +249,11 @@ int gnttab_grant_foreign_access(domid_t domid, unsigned long frame,
>  }
>  EXPORT_SYMBOL_GPL(gnttab_grant_foreign_access);
>  
> -static void gnttab_update_subpage_entry_v2(grant_ref_t ref, domid_t domid,
> -					   unsigned long frame, int flags,
> -					   unsigned page_off, unsigned length)
> -{
> -	gnttab_shared.v2[ref].sub_page.frame = frame;
> -	gnttab_shared.v2[ref].sub_page.page_off = page_off;
> -	gnttab_shared.v2[ref].sub_page.length = length;
> -	gnttab_shared.v2[ref].hdr.domid = domid;
> -	wmb();
> -	gnttab_shared.v2[ref].hdr.flags =
> -				GTF_permit_access | GTF_sub_page | flags;
> -}
> -
> -int gnttab_grant_foreign_access_subpage_ref(grant_ref_t ref, domid_t domid,
> -					    unsigned long frame, int flags,
> -					    unsigned page_off,
> -					    unsigned length)
> -{
> -	if (flags & (GTF_accept_transfer | GTF_reading |
> -		     GTF_writing | GTF_transitive))
> -		return -EPERM;
> -
> -	if (gnttab_interface->update_subpage_entry == NULL)
> -		return -ENOSYS;
> -
> -	gnttab_interface->update_subpage_entry(ref, domid, frame, flags,
> -					       page_off, length);
> -
> -	return 0;
> -}
> -EXPORT_SYMBOL_GPL(gnttab_grant_foreign_access_subpage_ref);
> -
> -int gnttab_grant_foreign_access_subpage(domid_t domid, unsigned long frame,
> -					int flags, unsigned page_off,
> -					unsigned length)
> -{
> -	int ref, rc;
> -
> -	ref = get_free_entries(1);
> -	if (unlikely(ref < 0))
> -		return -ENOSPC;
> -
> -	rc = gnttab_grant_foreign_access_subpage_ref(ref, domid, frame, flags,
> -						     page_off, length);
> -	if (rc < 0) {
> -		put_free_entry(ref);
> -		return rc;
> -	}
> -
> -	return ref;
> -}
> -EXPORT_SYMBOL_GPL(gnttab_grant_foreign_access_subpage);
> -
> -bool gnttab_subpage_grants_available(void)
> -{
> -	return gnttab_interface->update_subpage_entry != NULL;
> -}
> -EXPORT_SYMBOL_GPL(gnttab_subpage_grants_available);
> -
> -static void gnttab_update_trans_entry_v2(grant_ref_t ref, domid_t domid,
> -					 int flags, domid_t trans_domid,
> -					 grant_ref_t trans_gref)
> -{
> -	gnttab_shared.v2[ref].transitive.trans_domid = trans_domid;
> -	gnttab_shared.v2[ref].transitive.gref = trans_gref;
> -	gnttab_shared.v2[ref].hdr.domid = domid;
> -	wmb();
> -	gnttab_shared.v2[ref].hdr.flags =
> -				GTF_permit_access | GTF_transitive | flags;
> -}
> -
> -int gnttab_grant_foreign_access_trans_ref(grant_ref_t ref, domid_t domid,
> -					  int flags, domid_t trans_domid,
> -					  grant_ref_t trans_gref)
> -{
> -	if (flags & (GTF_accept_transfer | GTF_reading |
> -		     GTF_writing | GTF_sub_page))
> -		return -EPERM;
> -
> -	if (gnttab_interface->update_trans_entry == NULL)
> -		return -ENOSYS;
> -
> -	gnttab_interface->update_trans_entry(ref, domid, flags, trans_domid,
> -					     trans_gref);
> -
> -	return 0;
> -}
> -EXPORT_SYMBOL_GPL(gnttab_grant_foreign_access_trans_ref);
> -
> -int gnttab_grant_foreign_access_trans(domid_t domid, int flags,
> -				      domid_t trans_domid,
> -				      grant_ref_t trans_gref)
> -{
> -	int ref, rc;
> -
> -	ref = get_free_entries(1);
> -	if (unlikely(ref < 0))
> -		return -ENOSPC;
> -
> -	rc = gnttab_grant_foreign_access_trans_ref(ref, domid, flags,
> -						   trans_domid, trans_gref);
> -	if (rc < 0) {
> -		put_free_entry(ref);
> -		return rc;
> -	}
> -
> -	return ref;
> -}
> -EXPORT_SYMBOL_GPL(gnttab_grant_foreign_access_trans);
> -
> -bool gnttab_trans_grants_available(void)
> -{
> -	return gnttab_interface->update_trans_entry != NULL;
> -}
> -EXPORT_SYMBOL_GPL(gnttab_trans_grants_available);
> -
>  static int gnttab_query_foreign_access_v1(grant_ref_t ref)
>  {
>  	return gnttab_shared.v1[ref].flags & (GTF_reading|GTF_writing);
>  }
>  
> -static int gnttab_query_foreign_access_v2(grant_ref_t ref)
> -{
> -	return grstatus[ref] & (GTF_reading|GTF_writing);
> -}
> -
>  int gnttab_query_foreign_access(grant_ref_t ref)
>  {
>  	return gnttab_interface->query_foreign_access(ref);
> @@ -433,29 +276,6 @@ static int gnttab_end_foreign_access_ref_v1(grant_ref_t ref, int readonly)
>  	return 1;
>  }
>  
> -static int gnttab_end_foreign_access_ref_v2(grant_ref_t ref, int readonly)
> -{
> -	gnttab_shared.v2[ref].hdr.flags = 0;
> -	mb();
> -	if (grstatus[ref] & (GTF_reading|GTF_writing)) {
> -		return 0;
> -	} else {
> -		/* The read of grstatus needs to have acquire
> -		semantics.  On x86, reads already have
> -		that, and we just need to protect against
> -		compiler reorderings.  On other
> -		architectures we may need a full
> -		barrier. */
> -#ifdef CONFIG_X86
> -		barrier();
> -#else
> -		mb();
> -#endif
> -	}
> -
> -	return 1;
> -}
> -
>  static inline int _gnttab_end_foreign_access_ref(grant_ref_t ref, int readonly)
>  {
>  	return gnttab_interface->end_foreign_access_ref(ref, readonly);
> @@ -616,37 +436,6 @@ static unsigned long gnttab_end_foreign_transfer_ref_v1(grant_ref_t ref)
>  	return frame;
>  }
>  
> -static unsigned long gnttab_end_foreign_transfer_ref_v2(grant_ref_t ref)
> -{
> -	unsigned long frame;
> -	u16           flags;
> -	u16          *pflags;
> -
> -	pflags = &gnttab_shared.v2[ref].hdr.flags;
> -
> -	/*
> -	 * If a transfer is not even yet started, try to reclaim the grant
> -	 * reference and return failure (== 0).
> -	 */
> -	while (!((flags = *pflags) & GTF_transfer_committed)) {
> -		if (sync_cmpxchg(pflags, flags, 0) == flags)
> -			return 0;
> -		cpu_relax();
> -	}
> -
> -	/* If a transfer is in progress then wait until it is completed. */
> -	while (!(flags & GTF_transfer_completed)) {
> -		flags = *pflags;
> -		cpu_relax();
> -	}
> -
> -	rmb();  /* Read the frame number /after/ reading completion status. */
> -	frame = gnttab_shared.v2[ref].full_page.frame;
> -	BUG_ON(frame == 0);
> -
> -	return frame;
> -}
> -
>  unsigned long gnttab_end_foreign_transfer_ref(grant_ref_t ref)
>  {
>  	return gnttab_interface->end_foreign_transfer_ref(ref);
> @@ -962,12 +751,6 @@ int gnttab_unmap_refs(struct gnttab_unmap_grant_ref *unmap_ops,
>  }
>  EXPORT_SYMBOL_GPL(gnttab_unmap_refs);
>  
> -static unsigned nr_status_frames(unsigned nr_grant_frames)
> -{
> -	BUG_ON(grefs_per_grant_frame == 0);
> -	return (nr_grant_frames * grefs_per_grant_frame + SPP - 1) / SPP;
> -}
> -
>  static int gnttab_map_frames_v1(xen_pfn_t *frames, unsigned int nr_gframes)
>  {
>  	int rc;
> @@ -985,55 +768,6 @@ static void gnttab_unmap_frames_v1(void)
>  	arch_gnttab_unmap(gnttab_shared.addr, nr_grant_frames);
>  }
>  
> -static int gnttab_map_frames_v2(xen_pfn_t *frames, unsigned int nr_gframes)
> -{
> -	uint64_t *sframes;
> -	unsigned int nr_sframes;
> -	struct gnttab_get_status_frames getframes;
> -	int rc;
> -
> -	nr_sframes = nr_status_frames(nr_gframes);
> -
> -	/* No need for kzalloc as it is initialized in following hypercall
> -	 * GNTTABOP_get_status_frames.
> -	 */
> -	sframes = kmalloc(nr_sframes  * sizeof(uint64_t), GFP_ATOMIC);
> -	if (!sframes)
> -		return -ENOMEM;
> -
> -	getframes.dom        = DOMID_SELF;
> -	getframes.nr_frames  = nr_sframes;
> -	set_xen_guest_handle(getframes.frame_list, sframes);
> -
> -	rc = HYPERVISOR_grant_table_op(GNTTABOP_get_status_frames,
> -				       &getframes, 1);
> -	if (rc == -ENOSYS) {
> -		kfree(sframes);
> -		return -ENOSYS;
> -	}
> -
> -	BUG_ON(rc || getframes.status);
> -
> -	rc = arch_gnttab_map_status(sframes, nr_sframes,
> -				    nr_status_frames(gnttab_max_grant_frames()),
> -				    &grstatus);
> -	BUG_ON(rc);
> -	kfree(sframes);
> -
> -	rc = arch_gnttab_map_shared(frames, nr_gframes,
> -				    gnttab_max_grant_frames(),
> -				    &gnttab_shared.addr);
> -	BUG_ON(rc);
> -
> -	return 0;
> -}
> -
> -static void gnttab_unmap_frames_v2(void)
> -{
> -	arch_gnttab_unmap(gnttab_shared.addr, nr_grant_frames);
> -	arch_gnttab_unmap(grstatus, nr_status_frames(nr_grant_frames));
> -}
> -
>  static int gnttab_map(unsigned int start_idx, unsigned int end_idx)
>  {
>  	struct gnttab_setup_table setup;
> @@ -1101,43 +835,13 @@ static struct gnttab_ops gnttab_v1_ops = {
>  	.query_foreign_access		= gnttab_query_foreign_access_v1,
>  };
>  
> -static struct gnttab_ops gnttab_v2_ops = {
> -	.map_frames			= gnttab_map_frames_v2,
> -	.unmap_frames			= gnttab_unmap_frames_v2,
> -	.update_entry			= gnttab_update_entry_v2,
> -	.end_foreign_access_ref		= gnttab_end_foreign_access_ref_v2,
> -	.end_foreign_transfer_ref	= gnttab_end_foreign_transfer_ref_v2,
> -	.query_foreign_access		= gnttab_query_foreign_access_v2,
> -	.update_subpage_entry		= gnttab_update_subpage_entry_v2,
> -	.update_trans_entry		= gnttab_update_trans_entry_v2,
> -};
> -
>  static void gnttab_request_version(void)
>  {
> -	int rc;
> -	struct gnttab_set_version gsv;
> +	/* Only version 1 is used, which will always be available. */
> +	grant_table_version = 1;
> +	grefs_per_grant_frame = PAGE_SIZE / sizeof(struct grant_entry_v1);
> +	gnttab_interface = &gnttab_v1_ops;
>  
> -	gsv.version = 1;
> -
> -	rc = HYPERVISOR_grant_table_op(GNTTABOP_set_version, &gsv, 1);
> -	if (rc == 0 && gsv.version == 2) {
> -		grant_table_version = 2;
> -		grefs_per_grant_frame = PAGE_SIZE / sizeof(union grant_entry_v2);
> -		gnttab_interface = &gnttab_v2_ops;
> -	} else if (grant_table_version == 2) {
> -		/*
> -		 * If we've already used version 2 features,
> -		 * but then suddenly discover that they're not
> -		 * available (e.g. migrating to an older
> -		 * version of Xen), almost unbounded badness
> -		 * can happen.
> -		 */
> -		panic("we need grant tables version 2, but only version 1 is available");
> -	} else {
> -		grant_table_version = 1;
> -		grefs_per_grant_frame = PAGE_SIZE / sizeof(struct grant_entry_v1);
> -		gnttab_interface = &gnttab_v1_ops;
> -	}
>  	pr_info("Grant tables using version %d layout\n", grant_table_version);
>  }
>  
> @@ -1225,8 +929,7 @@ int gnttab_init(void)
>  		}
>  	}
>  
> -	ret = arch_gnttab_init(max_nr_grant_frames,
> -			       nr_status_frames(max_nr_grant_frames));
> +	ret = arch_gnttab_init(max_nr_grant_frames);
>  	if (ret < 0)
>  		goto ini_nomem;
>  
> diff --git a/include/xen/grant_table.h b/include/xen/grant_table.h
> index 5c1aba1..3387465 100644
> --- a/include/xen/grant_table.h
> +++ b/include/xen/grant_table.h
> @@ -64,24 +64,6 @@ int gnttab_resume(void);
>  
>  int gnttab_grant_foreign_access(domid_t domid, unsigned long frame,
>  				int readonly);
> -int gnttab_grant_foreign_access_subpage(domid_t domid, unsigned long frame,
> -					int flags, unsigned page_off,
> -					unsigned length);
> -int gnttab_grant_foreign_access_trans(domid_t domid, int flags,
> -				      domid_t trans_domid,
> -				      grant_ref_t trans_gref);
> -
> -/*
> - * Are sub-page grants available on this version of Xen?  Returns true if they
> - * are, and false if they're not.
> - */
> -bool gnttab_subpage_grants_available(void);
> -
> -/*
> - * Are transitive grants available on this version of Xen?  Returns true if they
> - * are, and false if they're not.
> - */
> -bool gnttab_trans_grants_available(void);
>  
>  /*
>   * End access through the given grant reference, iff the grant entry is no
> @@ -128,13 +110,6 @@ void gnttab_cancel_free_callback(struct gnttab_free_callback *callback);
>  
>  void gnttab_grant_foreign_access_ref(grant_ref_t ref, domid_t domid,
>  				     unsigned long frame, int readonly);
> -int gnttab_grant_foreign_access_subpage_ref(grant_ref_t ref, domid_t domid,
> -					    unsigned long frame, int flags,
> -					    unsigned page_off,
> -					    unsigned length);
> -int gnttab_grant_foreign_access_trans_ref(grant_ref_t ref, domid_t domid,
> -					  int flags, domid_t trans_domid,
> -					  grant_ref_t trans_gref);
>  
>  void gnttab_grant_foreign_transfer_ref(grant_ref_t, domid_t domid,
>  				       unsigned long pfn);
> @@ -170,13 +145,10 @@ gnttab_set_unmap_op(struct gnttab_unmap_grant_ref *unmap, phys_addr_t addr,
>  	unmap->dev_bus_addr = 0;
>  }
>  
> -int arch_gnttab_init(unsigned long nr_shared, unsigned long nr_status);
> +int arch_gnttab_init(unsigned long nr_shared);
>  int arch_gnttab_map_shared(xen_pfn_t *frames, unsigned long nr_gframes,
>  			   unsigned long max_nr_gframes,
>  			   void **__shared);
> -int arch_gnttab_map_status(uint64_t *frames, unsigned long nr_gframes,
> -			   unsigned long max_nr_gframes,
> -			   grant_status_t **__shared);
>  void arch_gnttab_unmap(void *shared, unsigned long nr_gframes);
>  
>  struct grant_frames {
> -- 
> 1.7.10.4
>