| Message ID | 20180525153331.31188-4-andr2000@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On 05/25/2018 11:33 AM, Oleksandr Andrushchenko wrote: > From: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com> > > Extend grant table module API to allow allocating buffers that can > be used for DMA operations and mapping foreign grant references > on top of those. > The resulting buffer is similar to the one allocated by the balloon > driver in terms that proper memory reservation is made > ({increase|decrease}_reservation and VA mappings updated if needed). > This is useful for sharing foreign buffers with HW drivers which > cannot work with scattered buffers provided by the balloon driver, > but require DMAable memory instead. > > Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com> > --- > drivers/xen/Kconfig | 13 ++++ > drivers/xen/grant-table.c | 124 ++++++++++++++++++++++++++++++++++++++ > include/xen/grant_table.h | 25 ++++++++ > 3 files changed, 162 insertions(+) > > diff --git a/drivers/xen/Kconfig b/drivers/xen/Kconfig > index e5d0c28372ea..3431fe210624 100644 > --- a/drivers/xen/Kconfig > +++ b/drivers/xen/Kconfig > @@ -161,6 +161,19 @@ config XEN_GRANT_DEV_ALLOC > to other domains. This can be used to implement frontend drivers > or as part of an inter-domain shared memory channel. > > +config XEN_GRANT_DMA_ALLOC > + bool "Allow allocating DMA capable buffers with grant reference module" > + depends on XEN Should it depend on anything from DMA? CONFIG_HAS_DMA for example? > + help > + Extends grant table module API to allow allocating DMA capable > + buffers and mapping foreign grant references on top of it. > + The resulting buffer is similar to one allocated by the balloon > + driver in terms that proper memory reservation is made > + ({increase|decrease}_reservation and VA mappings updated if needed). > + This is useful for sharing foreign buffers with HW drivers which > + cannot work with scattered buffers provided by the balloon driver, > + but require DMAable memory instead. > + > config SWIOTLB_XEN > def_bool y > select SWIOTLB > diff --git a/drivers/xen/grant-table.c b/drivers/xen/grant-table.c > index d7488226e1f2..06fe6e7f639c 100644 > --- a/drivers/xen/grant-table.c > +++ b/drivers/xen/grant-table.c > @@ -45,6 +45,9 @@ > #include <linux/workqueue.h> > #include <linux/ratelimit.h> > #include <linux/moduleparam.h> > +#ifdef CONFIG_XEN_GRANT_DMA_ALLOC > +#include <linux/dma-mapping.h> > +#endif > > #include <xen/xen.h> > #include <xen/interface/xen.h> > @@ -57,6 +60,7 @@ > #ifdef CONFIG_X86 > #include <asm/xen/cpuid.h> > #endif > +#include <xen/mem_reservation.h> > #include <asm/xen/hypercall.h> > #include <asm/xen/interface.h> > > @@ -811,6 +815,82 @@ int gnttab_alloc_pages(int nr_pages, struct page **pages) > } > EXPORT_SYMBOL(gnttab_alloc_pages); > > +#ifdef CONFIG_XEN_GRANT_DMA_ALLOC > +/** > + * gnttab_dma_alloc_pages - alloc DMAable pages suitable for grant mapping into > + * @args: arguments to the function > + */ > +int gnttab_dma_alloc_pages(struct gnttab_dma_alloc_args *args) > +{ > + unsigned long pfn, start_pfn; > + xen_pfn_t *frames; > + size_t size; > + int i, ret; > + > + frames = kcalloc(args->nr_pages, sizeof(*frames), GFP_KERNEL); > + if (!frames) > + return -ENOMEM; > + > + size = args->nr_pages << PAGE_SHIFT; > + if (args->coherent) > + args->vaddr = dma_alloc_coherent(args->dev, size, > + &args->dev_bus_addr, > + GFP_KERNEL | __GFP_NOWARN); > + else > + args->vaddr = dma_alloc_wc(args->dev, size, > + &args->dev_bus_addr, > + GFP_KERNEL | __GFP_NOWARN); > + if (!args->vaddr) { > + pr_err("Failed to allocate DMA buffer of size %zu\n", size); > + ret = -ENOMEM; > + goto fail_free_frames; > + } > + > + start_pfn = __phys_to_pfn(args->dev_bus_addr); > + for (pfn = start_pfn, i = 0; pfn < start_pfn + args->nr_pages; > + pfn++, i++) { > + struct page *page = pfn_to_page(pfn); > + > + args->pages[i] = page; > + frames[i] = xen_page_to_gfn(page); > + xenmem_reservation_scrub_page(page); > + } > + > + xenmem_reservation_va_mapping_reset(args->nr_pages, args->pages); > + > + ret = xenmem_reservation_decrease(args->nr_pages, frames); > + if (ret != args->nr_pages) { > + pr_err("Failed to decrease reservation for DMA buffer\n"); > + xenmem_reservation_increase(ret, frames); > + ret = -EFAULT; > + goto fail_free_dma; > + } > + > + ret = gnttab_pages_set_private(args->nr_pages, args->pages); > + if (ret < 0) > + goto fail_clear_private; > + > + kfree(frames); > + return 0; > + > +fail_clear_private: > + gnttab_pages_clear_private(args->nr_pages, args->pages); > +fail_free_dma: Do you need to xenmem_reservation_increase()? > + xenmem_reservation_va_mapping_update(args->nr_pages, args->pages, > + frames); > + if (args->coherent) > + dma_free_coherent(args->dev, size, > + args->vaddr, args->dev_bus_addr); > + else > + dma_free_wc(args->dev, size, > + args->vaddr, args->dev_bus_addr); > +fail_free_frames: > + kfree(frames); > + return ret; > +} > +EXPORT_SYMBOL(gnttab_dma_alloc_pages); > +#endif > + > void gnttab_pages_clear_private(int nr_pages, struct page **pages) > { > int i; > @@ -838,6 +918,50 @@ void gnttab_free_pages(int nr_pages, struct page **pages) > } > EXPORT_SYMBOL(gnttab_free_pages); > > +#ifdef CONFIG_XEN_GRANT_DMA_ALLOC > +/** > + * gnttab_dma_free_pages - free DMAable pages > + * @args: arguments to the function > + */ > +int gnttab_dma_free_pages(struct gnttab_dma_alloc_args *args) > +{ > + xen_pfn_t *frames; > + size_t size; > + int i, ret; > + > + gnttab_pages_clear_private(args->nr_pages, args->pages); > + > + frames = kcalloc(args->nr_pages, sizeof(*frames), GFP_KERNEL); Any way you can do it without allocating memory? One possibility is to keep allocated frames from gnttab_dma_alloc_pages(). (Not sure I like that either but it's the only thing I can think of). > + if (!frames) > + return -ENOMEM; > + > + for (i = 0; i < args->nr_pages; i++) > + frames[i] = page_to_xen_pfn(args->pages[i]); Not xen_page_to_gfn()? > + > + ret = xenmem_reservation_increase(args->nr_pages, frames); > + if (ret != args->nr_pages) { > + pr_err("Failed to decrease reservation for DMA buffer\n"); > + ret = -EFAULT; > + } else { > + ret = 0; > + } > + > + xenmem_reservation_va_mapping_update(args->nr_pages, args->pages, > + frames); > + > + size = args->nr_pages << PAGE_SHIFT; > + if (args->coherent) > + dma_free_coherent(args->dev, size, > + args->vaddr, args->dev_bus_addr); > + else > + dma_free_wc(args->dev, size, > + args->vaddr, args->dev_bus_addr); > + kfree(frames); > + return ret; > +} > +EXPORT_SYMBOL(gnttab_dma_free_pages); > +#endif > + > /* Handling of paged out grant targets (GNTST_eagain) */ > #define MAX_DELAY 256 > static inline void > diff --git a/include/xen/grant_table.h b/include/xen/grant_table.h > index de03f2542bb7..982e34242b9c 100644 > --- a/include/xen/grant_table.h > +++ b/include/xen/grant_table.h > @@ -198,6 +198,31 @@ void gnttab_free_auto_xlat_frames(void); > int gnttab_alloc_pages(int nr_pages, struct page **pages); > void gnttab_free_pages(int nr_pages, struct page **pages); > > +#ifdef CONFIG_XEN_GRANT_DMA_ALLOC > +struct gnttab_dma_alloc_args { > + /* Device for which DMA memory will be/was allocated. */ > + struct device *dev; > + /* > + * If set then DMA buffer is coherent and write-combine otherwise. > + */ Single-line comment > + bool coherent; > + /* > + * Number of entries in the @pages array, defines the size > + * of the DMA buffer. > + */ This can be made into single line comment as well. However, I am not sure this comment as well as those below are necessary. Fields names are self-describing IMO. -boris > + int nr_pages; > + /* Array of pages @pages filled with pages of the DMA buffer. */ > + struct page **pages; > + /* Virtual/CPU address of the DMA buffer. */ > + void *vaddr; > + /* Bus address of the DMA buffer. */ > + dma_addr_t dev_bus_addr; > +}; > + > +int gnttab_dma_alloc_pages(struct gnttab_dma_alloc_args *args); > +int gnttab_dma_free_pages(struct gnttab_dma_alloc_args *args); > +#endif > + > int gnttab_pages_set_private(int nr_pages, struct page **pages); > void gnttab_pages_clear_private(int nr_pages, struct page **pages); >
On 05/29/2018 10:10 PM, Boris Ostrovsky wrote: > On 05/25/2018 11:33 AM, Oleksandr Andrushchenko wrote: >> From: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com> >> >> Extend grant table module API to allow allocating buffers that can >> be used for DMA operations and mapping foreign grant references >> on top of those. >> The resulting buffer is similar to the one allocated by the balloon >> driver in terms that proper memory reservation is made >> ({increase|decrease}_reservation and VA mappings updated if needed). >> This is useful for sharing foreign buffers with HW drivers which >> cannot work with scattered buffers provided by the balloon driver, >> but require DMAable memory instead. >> >> Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com> >> --- >> drivers/xen/Kconfig | 13 ++++ >> drivers/xen/grant-table.c | 124 ++++++++++++++++++++++++++++++++++++++ >> include/xen/grant_table.h | 25 ++++++++ >> 3 files changed, 162 insertions(+) >> >> diff --git a/drivers/xen/Kconfig b/drivers/xen/Kconfig >> index e5d0c28372ea..3431fe210624 100644 >> --- a/drivers/xen/Kconfig >> +++ b/drivers/xen/Kconfig >> @@ -161,6 +161,19 @@ config XEN_GRANT_DEV_ALLOC >> to other domains. This can be used to implement frontend drivers >> or as part of an inter-domain shared memory channel. >> >> +config XEN_GRANT_DMA_ALLOC >> + bool "Allow allocating DMA capable buffers with grant reference module" >> + depends on XEN > > Should it depend on anything from DMA? CONFIG_HAS_DMA for example? Yes, it must be "depends on XEN && HAS_DMA", thank you > >> + help >> + Extends grant table module API to allow allocating DMA capable >> + buffers and mapping foreign grant references on top of it. >> + The resulting buffer is similar to one allocated by the balloon >> + driver in terms that proper memory reservation is made >> + ({increase|decrease}_reservation and VA mappings updated if needed). >> + This is useful for sharing foreign buffers with HW drivers which >> + cannot work with scattered buffers provided by the balloon driver, >> + but require DMAable memory instead. >> + >> config SWIOTLB_XEN >> def_bool y >> select SWIOTLB >> diff --git a/drivers/xen/grant-table.c b/drivers/xen/grant-table.c >> index d7488226e1f2..06fe6e7f639c 100644 >> --- a/drivers/xen/grant-table.c >> +++ b/drivers/xen/grant-table.c >> @@ -45,6 +45,9 @@ >> #include <linux/workqueue.h> >> #include <linux/ratelimit.h> >> #include <linux/moduleparam.h> >> +#ifdef CONFIG_XEN_GRANT_DMA_ALLOC >> +#include <linux/dma-mapping.h> >> +#endif >> >> #include <xen/xen.h> >> #include <xen/interface/xen.h> >> @@ -57,6 +60,7 @@ >> #ifdef CONFIG_X86 >> #include <asm/xen/cpuid.h> >> #endif >> +#include <xen/mem_reservation.h> >> #include <asm/xen/hypercall.h> >> #include <asm/xen/interface.h> >> >> @@ -811,6 +815,82 @@ int gnttab_alloc_pages(int nr_pages, struct page **pages) >> } >> EXPORT_SYMBOL(gnttab_alloc_pages); >> >> +#ifdef CONFIG_XEN_GRANT_DMA_ALLOC >> +/** >> + * gnttab_dma_alloc_pages - alloc DMAable pages suitable for grant mapping into >> + * @args: arguments to the function >> + */ >> +int gnttab_dma_alloc_pages(struct gnttab_dma_alloc_args *args) >> +{ >> + unsigned long pfn, start_pfn; >> + xen_pfn_t *frames; >> + size_t size; >> + int i, ret; >> + >> + frames = kcalloc(args->nr_pages, sizeof(*frames), GFP_KERNEL); >> + if (!frames) >> + return -ENOMEM; >> + >> + size = args->nr_pages << PAGE_SHIFT; >> + if (args->coherent) >> + args->vaddr = dma_alloc_coherent(args->dev, size, >> + &args->dev_bus_addr, >> + GFP_KERNEL | __GFP_NOWARN); >> + else >> + args->vaddr = dma_alloc_wc(args->dev, size, >> + &args->dev_bus_addr, >> + GFP_KERNEL | __GFP_NOWARN); >> + if (!args->vaddr) { >> + pr_err("Failed to allocate DMA buffer of size %zu\n", size); >> + ret = -ENOMEM; >> + goto fail_free_frames; >> + } >> + >> + start_pfn = __phys_to_pfn(args->dev_bus_addr); >> + for (pfn = start_pfn, i = 0; pfn < start_pfn + args->nr_pages; >> + pfn++, i++) { >> + struct page *page = pfn_to_page(pfn); >> + >> + args->pages[i] = page; >> + frames[i] = xen_page_to_gfn(page); >> + xenmem_reservation_scrub_page(page); >> + } >> + >> + xenmem_reservation_va_mapping_reset(args->nr_pages, args->pages); >> + >> + ret = xenmem_reservation_decrease(args->nr_pages, frames); >> + if (ret != args->nr_pages) { >> + pr_err("Failed to decrease reservation for DMA buffer\n"); >> + xenmem_reservation_increase(ret, frames); >> + ret = -EFAULT; >> + goto fail_free_dma; >> + } >> + >> + ret = gnttab_pages_set_private(args->nr_pages, args->pages); >> + if (ret < 0) >> + goto fail_clear_private; >> + >> + kfree(frames); >> + return 0; >> + >> +fail_clear_private: >> + gnttab_pages_clear_private(args->nr_pages, args->pages); >> +fail_free_dma: > > Do you need to xenmem_reservation_increase()? Yes, missed that on fail_clear_private error path, will fix > >> + xenmem_reservation_va_mapping_update(args->nr_pages, args->pages, >> + frames); >> + if (args->coherent) >> + dma_free_coherent(args->dev, size, >> + args->vaddr, args->dev_bus_addr); >> + else >> + dma_free_wc(args->dev, size, >> + args->vaddr, args->dev_bus_addr); >> +fail_free_frames: >> + kfree(frames); >> + return ret; >> +} >> +EXPORT_SYMBOL(gnttab_dma_alloc_pages); >> +#endif >> + >> void gnttab_pages_clear_private(int nr_pages, struct page **pages) >> { >> int i; >> @@ -838,6 +918,50 @@ void gnttab_free_pages(int nr_pages, struct page **pages) >> } >> EXPORT_SYMBOL(gnttab_free_pages); >> >> +#ifdef CONFIG_XEN_GRANT_DMA_ALLOC >> +/** >> + * gnttab_dma_free_pages - free DMAable pages >> + * @args: arguments to the function >> + */ >> +int gnttab_dma_free_pages(struct gnttab_dma_alloc_args *args) >> +{ >> + xen_pfn_t *frames; >> + size_t size; >> + int i, ret; >> + >> + gnttab_pages_clear_private(args->nr_pages, args->pages); >> + >> + frames = kcalloc(args->nr_pages, sizeof(*frames), GFP_KERNEL); > > Any way you can do it without allocating memory? One possibility is to > keep allocated frames from gnttab_dma_alloc_pages(). (Not sure I like > that either but it's the only thing I can think of). Yes, I was also thinking about storing the allocated frames array from gnttab_dma_alloc_pages(), but that seemed not to be clear enough as the caller of the gnttab_dma_alloc_pages will need to store those frames in some context, so we can pass them on free. But the caller doesn't really need the frames which might confuse, so I decided to make those allocations on the fly. But I can still rework that to store the frames if you insist: please let me know. > > >> + if (!frames) >> + return -ENOMEM; >> + >> + for (i = 0; i < args->nr_pages; i++) >> + frames[i] = page_to_xen_pfn(args->pages[i]); > > Not xen_page_to_gfn()? Well, according to [1] it should be : /* XENMEM_populate_physmap requires a PFN based on Xen * granularity. */ frame_list[i] = page_to_xen_pfn(page); > >> + >> + ret = xenmem_reservation_increase(args->nr_pages, frames); >> + if (ret != args->nr_pages) { >> + pr_err("Failed to decrease reservation for DMA buffer\n"); >> + ret = -EFAULT; >> + } else { >> + ret = 0; >> + } >> + >> + xenmem_reservation_va_mapping_update(args->nr_pages, args->pages, >> + frames); >> + >> + size = args->nr_pages << PAGE_SHIFT; >> + if (args->coherent) >> + dma_free_coherent(args->dev, size, >> + args->vaddr, args->dev_bus_addr); >> + else >> + dma_free_wc(args->dev, size, >> + args->vaddr, args->dev_bus_addr); >> + kfree(frames); >> + return ret; >> +} >> +EXPORT_SYMBOL(gnttab_dma_free_pages); >> +#endif >> + >> /* Handling of paged out grant targets (GNTST_eagain) */ >> #define MAX_DELAY 256 >> static inline void >> diff --git a/include/xen/grant_table.h b/include/xen/grant_table.h >> index de03f2542bb7..982e34242b9c 100644 >> --- a/include/xen/grant_table.h >> +++ b/include/xen/grant_table.h >> @@ -198,6 +198,31 @@ void gnttab_free_auto_xlat_frames(void); >> int gnttab_alloc_pages(int nr_pages, struct page **pages); >> void gnttab_free_pages(int nr_pages, struct page **pages); >> >> +#ifdef CONFIG_XEN_GRANT_DMA_ALLOC >> +struct gnttab_dma_alloc_args { >> + /* Device for which DMA memory will be/was allocated. */ >> + struct device *dev; >> + /* >> + * If set then DMA buffer is coherent and write-combine otherwise. >> + */ > Single-line comment will fix > >> + bool coherent; >> + /* >> + * Number of entries in the @pages array, defines the size >> + * of the DMA buffer. >> + */ > This can be made into single line comment as well. However, I am not > sure this comment as well as those below are necessary. Fields names are > self-describing IMO. will remove > > -boris Thank you, Oleksandr >> + int nr_pages; >> + /* Array of pages @pages filled with pages of the DMA buffer. */ >> + struct page **pages; >> + /* Virtual/CPU address of the DMA buffer. */ >> + void *vaddr; >> + /* Bus address of the DMA buffer. */ >> + dma_addr_t dev_bus_addr; >> +}; >> + >> +int gnttab_dma_alloc_pages(struct gnttab_dma_alloc_args *args); >> +int gnttab_dma_free_pages(struct gnttab_dma_alloc_args *args); >> +#endif >> + >> int gnttab_pages_set_private(int nr_pages, struct page **pages); >> void gnttab_pages_clear_private(int nr_pages, struct page **pages); >> [1] https://elixir.bootlin.com/linux/v4.17-rc7/source/drivers/xen/balloon.c#L485
On 05/30/2018 02:34 AM, Oleksandr Andrushchenko wrote: > On 05/29/2018 10:10 PM, Boris Ostrovsky wrote: >> On 05/25/2018 11:33 AM, Oleksandr Andrushchenko wrote: >> +/** >> + * gnttab_dma_free_pages - free DMAable pages >> + * @args: arguments to the function >> + */ >> +int gnttab_dma_free_pages(struct gnttab_dma_alloc_args *args) >> +{ >> + xen_pfn_t *frames; >> + size_t size; >> + int i, ret; >> + >> + gnttab_pages_clear_private(args->nr_pages, args->pages); >> + >> + frames = kcalloc(args->nr_pages, sizeof(*frames), GFP_KERNEL); >> >> Any way you can do it without allocating memory? One possibility is to >> keep allocated frames from gnttab_dma_alloc_pages(). (Not sure I like >> that either but it's the only thing I can think of). > Yes, I was also thinking about storing the allocated frames array from > gnttab_dma_alloc_pages(), but that seemed not to be clear enough as > the caller of the gnttab_dma_alloc_pages will need to store those frames > in some context, so we can pass them on free. But the caller doesn't > really > need the frames which might confuse, so I decided to make those > allocations > on the fly. > But I can still rework that to store the frames if you insist: please > let me know. I would prefer not to allocate anything in the release path. Yes, I realize that dragging frames array around is not necessary but IMO it's better than potentially failing an allocation during a teardown. A comment in the struct definition could explain the reason for having this field. >> >> >>> + if (!frames) >>> + return -ENOMEM; >>> + >>> + for (i = 0; i < args->nr_pages; i++) >>> + frames[i] = page_to_xen_pfn(args->pages[i]); >> >> Not xen_page_to_gfn()? > Well, according to [1] it should be : > /* XENMEM_populate_physmap requires a PFN based on Xen > * granularity. > */ > frame_list[i] = page_to_xen_pfn(page); Ah, yes. I was looking at decrease_reservation and automatically assumed the same parameter type. -boris
On 05/30/2018 06:20 PM, Boris Ostrovsky wrote: > On 05/30/2018 02:34 AM, Oleksandr Andrushchenko wrote: >> On 05/29/2018 10:10 PM, Boris Ostrovsky wrote: >>> On 05/25/2018 11:33 AM, Oleksandr Andrushchenko wrote: >>> +/** >>> + * gnttab_dma_free_pages - free DMAable pages >>> + * @args: arguments to the function >>> + */ >>> +int gnttab_dma_free_pages(struct gnttab_dma_alloc_args *args) >>> +{ >>> + xen_pfn_t *frames; >>> + size_t size; >>> + int i, ret; >>> + >>> + gnttab_pages_clear_private(args->nr_pages, args->pages); >>> + >>> + frames = kcalloc(args->nr_pages, sizeof(*frames), GFP_KERNEL); >>> >>> Any way you can do it without allocating memory? One possibility is to >>> keep allocated frames from gnttab_dma_alloc_pages(). (Not sure I like >>> that either but it's the only thing I can think of). >> Yes, I was also thinking about storing the allocated frames array from >> gnttab_dma_alloc_pages(), but that seemed not to be clear enough as >> the caller of the gnttab_dma_alloc_pages will need to store those frames >> in some context, so we can pass them on free. But the caller doesn't >> really >> need the frames which might confuse, so I decided to make those >> allocations >> on the fly. >> But I can still rework that to store the frames if you insist: please >> let me know. > > I would prefer not to allocate anything in the release path. Yes, I > realize that dragging frames array around is not necessary but IMO it's > better than potentially failing an allocation during a teardown. A > comment in the struct definition could explain the reason for having > this field. Then I would suggest we have it this way: current API requires that struct page **pages are allocated from outside. So, let's allocate the frames from outside as well. This way the caller is responsible for both pages and frames arrays and API looks consistent. > >>> >>>> + if (!frames) >>>> + return -ENOMEM; >>>> + >>>> + for (i = 0; i < args->nr_pages; i++) >>>> + frames[i] = page_to_xen_pfn(args->pages[i]); >>> Not xen_page_to_gfn()? >> Well, according to [1] it should be : >> /* XENMEM_populate_physmap requires a PFN based on Xen >> * granularity. >> */ >> frame_list[i] = page_to_xen_pfn(page); > > Ah, yes. I was looking at decrease_reservation and automatically assumed > the same parameter type. Good, then this one is resolved > > -boris > > Thank you, Oleksandr
On 05/30/2018 01:49 PM, Oleksandr Andrushchenko wrote: > On 05/30/2018 06:20 PM, Boris Ostrovsky wrote: >> On 05/30/2018 02:34 AM, Oleksandr Andrushchenko wrote: >>> On 05/29/2018 10:10 PM, Boris Ostrovsky wrote: >>>> On 05/25/2018 11:33 AM, Oleksandr Andrushchenko wrote: >>>> +/** >>>> + * gnttab_dma_free_pages - free DMAable pages >>>> + * @args: arguments to the function >>>> + */ >>>> +int gnttab_dma_free_pages(struct gnttab_dma_alloc_args *args) >>>> +{ >>>> + xen_pfn_t *frames; >>>> + size_t size; >>>> + int i, ret; >>>> + >>>> + gnttab_pages_clear_private(args->nr_pages, args->pages); >>>> + >>>> + frames = kcalloc(args->nr_pages, sizeof(*frames), GFP_KERNEL); >>>> >>>> Any way you can do it without allocating memory? One possibility is to >>>> keep allocated frames from gnttab_dma_alloc_pages(). (Not sure I like >>>> that either but it's the only thing I can think of). >>> Yes, I was also thinking about storing the allocated frames array from >>> gnttab_dma_alloc_pages(), but that seemed not to be clear enough as >>> the caller of the gnttab_dma_alloc_pages will need to store those >>> frames >>> in some context, so we can pass them on free. But the caller doesn't >>> really >>> need the frames which might confuse, so I decided to make those >>> allocations >>> on the fly. >>> But I can still rework that to store the frames if you insist: please >>> let me know. >> >> I would prefer not to allocate anything in the release path. Yes, I >> realize that dragging frames array around is not necessary but IMO it's >> better than potentially failing an allocation during a teardown. A >> comment in the struct definition could explain the reason for having >> this field. > Then I would suggest we have it this way: current API requires that > struct page **pages are allocated from outside. So, let's allocate > the frames from outside as well. This way the caller is responsible for > both pages and frames arrays and API looks consistent. Yes, that works too. -boris
diff --git a/drivers/xen/Kconfig b/drivers/xen/Kconfig index e5d0c28372ea..3431fe210624 100644 --- a/drivers/xen/Kconfig +++ b/drivers/xen/Kconfig @@ -161,6 +161,19 @@ config XEN_GRANT_DEV_ALLOC to other domains. This can be used to implement frontend drivers or as part of an inter-domain shared memory channel. +config XEN_GRANT_DMA_ALLOC + bool "Allow allocating DMA capable buffers with grant reference module" + depends on XEN + help + Extends grant table module API to allow allocating DMA capable + buffers and mapping foreign grant references on top of it. + The resulting buffer is similar to one allocated by the balloon + driver in terms that proper memory reservation is made + ({increase|decrease}_reservation and VA mappings updated if needed). + This is useful for sharing foreign buffers with HW drivers which + cannot work with scattered buffers provided by the balloon driver, + but require DMAable memory instead. + config SWIOTLB_XEN def_bool y select SWIOTLB diff --git a/drivers/xen/grant-table.c b/drivers/xen/grant-table.c index d7488226e1f2..06fe6e7f639c 100644 --- a/drivers/xen/grant-table.c +++ b/drivers/xen/grant-table.c @@ -45,6 +45,9 @@ #include <linux/workqueue.h> #include <linux/ratelimit.h> #include <linux/moduleparam.h> +#ifdef CONFIG_XEN_GRANT_DMA_ALLOC +#include <linux/dma-mapping.h> +#endif #include <xen/xen.h> #include <xen/interface/xen.h> @@ -57,6 +60,7 @@ #ifdef CONFIG_X86 #include <asm/xen/cpuid.h> #endif +#include <xen/mem_reservation.h> #include <asm/xen/hypercall.h> #include <asm/xen/interface.h> @@ -811,6 +815,82 @@ int gnttab_alloc_pages(int nr_pages, struct page **pages) } EXPORT_SYMBOL(gnttab_alloc_pages); +#ifdef CONFIG_XEN_GRANT_DMA_ALLOC +/** + * gnttab_dma_alloc_pages - alloc DMAable pages suitable for grant mapping into + * @args: arguments to the function + */ +int gnttab_dma_alloc_pages(struct gnttab_dma_alloc_args *args) +{ + unsigned long pfn, start_pfn; + xen_pfn_t *frames; + size_t size; + int i, ret; + + frames = kcalloc(args->nr_pages, sizeof(*frames), GFP_KERNEL); + if (!frames) + return -ENOMEM; + + size = args->nr_pages << PAGE_SHIFT; + if (args->coherent) + args->vaddr = dma_alloc_coherent(args->dev, size, + &args->dev_bus_addr, + GFP_KERNEL | __GFP_NOWARN); + else + args->vaddr = dma_alloc_wc(args->dev, size, + &args->dev_bus_addr, + GFP_KERNEL | __GFP_NOWARN); + if (!args->vaddr) { + pr_err("Failed to allocate DMA buffer of size %zu\n", size); + ret = -ENOMEM; + goto fail_free_frames; + } + + start_pfn = __phys_to_pfn(args->dev_bus_addr); + for (pfn = start_pfn, i = 0; pfn < start_pfn + args->nr_pages; + pfn++, i++) { + struct page *page = pfn_to_page(pfn); + + args->pages[i] = page; + frames[i] = xen_page_to_gfn(page); + xenmem_reservation_scrub_page(page); + } + + xenmem_reservation_va_mapping_reset(args->nr_pages, args->pages); + + ret = xenmem_reservation_decrease(args->nr_pages, frames); + if (ret != args->nr_pages) { + pr_err("Failed to decrease reservation for DMA buffer\n"); + xenmem_reservation_increase(ret, frames); + ret = -EFAULT; + goto fail_free_dma; + } + + ret = gnttab_pages_set_private(args->nr_pages, args->pages); + if (ret < 0) + goto fail_clear_private; + + kfree(frames); + return 0; + +fail_clear_private: + gnttab_pages_clear_private(args->nr_pages, args->pages); +fail_free_dma: + xenmem_reservation_va_mapping_update(args->nr_pages, args->pages, + frames); + if (args->coherent) + dma_free_coherent(args->dev, size, + args->vaddr, args->dev_bus_addr); + else + dma_free_wc(args->dev, size, + args->vaddr, args->dev_bus_addr); +fail_free_frames: + kfree(frames); + return ret; +} +EXPORT_SYMBOL(gnttab_dma_alloc_pages); +#endif + void gnttab_pages_clear_private(int nr_pages, struct page **pages) { int i; @@ -838,6 +918,50 @@ void gnttab_free_pages(int nr_pages, struct page **pages) } EXPORT_SYMBOL(gnttab_free_pages); +#ifdef CONFIG_XEN_GRANT_DMA_ALLOC +/** + * gnttab_dma_free_pages - free DMAable pages + * @args: arguments to the function + */ +int gnttab_dma_free_pages(struct gnttab_dma_alloc_args *args) +{ + xen_pfn_t *frames; + size_t size; + int i, ret; + + gnttab_pages_clear_private(args->nr_pages, args->pages); + + frames = kcalloc(args->nr_pages, sizeof(*frames), GFP_KERNEL); + if (!frames) + return -ENOMEM; + + for (i = 0; i < args->nr_pages; i++) + frames[i] = page_to_xen_pfn(args->pages[i]); + + ret = xenmem_reservation_increase(args->nr_pages, frames); + if (ret != args->nr_pages) { + pr_err("Failed to decrease reservation for DMA buffer\n"); + ret = -EFAULT; + } else { + ret = 0; + } + + xenmem_reservation_va_mapping_update(args->nr_pages, args->pages, + frames); + + size = args->nr_pages << PAGE_SHIFT; + if (args->coherent) + dma_free_coherent(args->dev, size, + args->vaddr, args->dev_bus_addr); + else + dma_free_wc(args->dev, size, + args->vaddr, args->dev_bus_addr); + kfree(frames); + return ret; +} +EXPORT_SYMBOL(gnttab_dma_free_pages); +#endif + /* Handling of paged out grant targets (GNTST_eagain) */ #define MAX_DELAY 256 static inline void diff --git a/include/xen/grant_table.h b/include/xen/grant_table.h index de03f2542bb7..982e34242b9c 100644 --- a/include/xen/grant_table.h +++ b/include/xen/grant_table.h @@ -198,6 +198,31 @@ void gnttab_free_auto_xlat_frames(void); int gnttab_alloc_pages(int nr_pages, struct page **pages); void gnttab_free_pages(int nr_pages, struct page **pages); +#ifdef CONFIG_XEN_GRANT_DMA_ALLOC +struct gnttab_dma_alloc_args { + /* Device for which DMA memory will be/was allocated. */ + struct device *dev; + /* + * If set then DMA buffer is coherent and write-combine otherwise. + */ + bool coherent; + /* + * Number of entries in the @pages array, defines the size + * of the DMA buffer. + */ + int nr_pages; + /* Array of pages @pages filled with pages of the DMA buffer. */ + struct page **pages; + /* Virtual/CPU address of the DMA buffer. */ + void *vaddr; + /* Bus address of the DMA buffer. */ + dma_addr_t dev_bus_addr; +}; + +int gnttab_dma_alloc_pages(struct gnttab_dma_alloc_args *args); +int gnttab_dma_free_pages(struct gnttab_dma_alloc_args *args); +#endif + int gnttab_pages_set_private(int nr_pages, struct page **pages); void gnttab_pages_clear_private(int nr_pages, struct page **pages);