On Fri, 5 Apr 2019 01:16:14 +0200 Halil Pasic <[email protected]> wrote:
> To support protected virtualization cio will need to make sure the > memory used for communication with the hypervisor is DMA memory. > > Let us introduce a DMA pool to cio that will help us in allocating missing 'and' > deallocating those chunks of memory. > > We use a gen_pool backed with DMA pages to avoid each allocation > effectively wasting a page, as we typically allocate much less > than PAGE_SIZE. > > Signed-off-by: Halil Pasic <[email protected]> > --- > arch/s390/Kconfig | 1 + > arch/s390/include/asm/cio.h | 3 +++ > drivers/s390/cio/css.c | 57 > +++++++++++++++++++++++++++++++++++++++++++++ > 3 files changed, 61 insertions(+) > > diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig > index 46c69283a67b..e8099ab47368 100644 > --- a/arch/s390/Kconfig > +++ b/arch/s390/Kconfig > @@ -194,6 +194,7 @@ config S390 > select VIRT_TO_BUS > select HAVE_NMI > select SWIOTLB > + select GENERIC_ALLOCATOR > > > config SCHED_OMIT_FRAME_POINTER > diff --git a/arch/s390/include/asm/cio.h b/arch/s390/include/asm/cio.h > index 1727180e8ca1..4510e418614a 100644 > --- a/arch/s390/include/asm/cio.h > +++ b/arch/s390/include/asm/cio.h > @@ -328,6 +328,9 @@ static inline u8 pathmask_to_pos(u8 mask) > void channel_subsystem_reinit(void); > extern void css_schedule_reprobe(void); > > +extern void *cio_dma_zalloc(size_t size); > +extern void cio_dma_free(void *cpu_addr, size_t size); > + > /* Function from drivers/s390/cio/chsc.c */ > int chsc_sstpc(void *page, unsigned int op, u16 ctrl, u64 *clock_delta); > int chsc_sstpi(void *page, void *result, size_t size); > diff --git a/drivers/s390/cio/css.c b/drivers/s390/cio/css.c > index aea502922646..72629d99d8e4 100644 > --- a/drivers/s390/cio/css.c > +++ b/drivers/s390/cio/css.c > @@ -20,6 +20,8 @@ > #include <linux/reboot.h> > #include <linux/suspend.h> > #include <linux/proc_fs.h> > +#include <linux/genalloc.h> > +#include <linux/dma-mapping.h> > #include <asm/isc.h> > #include <asm/crw.h> > > @@ -886,6 +888,8 @@ static const struct attribute_group *cssdev_attr_groups[] > = { > NULL, > }; > > +static u64 css_dev_dma_mask = DMA_BIT_MASK(31); > + > static int __init setup_css(int nr) > { > struct channel_subsystem *css; > @@ -899,6 +903,9 @@ static int __init setup_css(int nr) > dev_set_name(&css->device, "css%x", nr); > css->device.groups = cssdev_attr_groups; > css->device.release = channel_subsystem_release; > + /* some cio DMA memory needs to be 31 bit addressable */ > + css->device.coherent_dma_mask = DMA_BIT_MASK(31), > + css->device.dma_mask = &css_dev_dma_mask; Question: Does this percolate down to the child devices eventually? E.g., you have a ccw_device getting the mask from its parent subchannel, which gets it from its parent css? If so, does that clash with the the mask you used for the virtio_ccw_device in a previous patch? Or are they two really different things? > > mutex_init(&css->mutex); > css->cssid = chsc_get_cssid(nr); > @@ -1018,6 +1025,55 @@ static struct notifier_block css_power_notifier = { > .notifier_call = css_power_event, > }; > > +#define POOL_INIT_PAGES 1 > +static struct gen_pool *cio_dma_pool; > +/* Currently cio supports only a single css */ > +static struct device *cio_dma_css; That global variable feels wrong, especially if you plan to support MCSS-E in the future. (Do you? :) If yes, should the dma pool be global or per-css? As css0 currently is the root device for the channel subsystem stuff, you'd either need a new parent to hang this off from or size this with the number of css images.) For now, just grab channel_subsystems[0]->device directly? > +static gfp_t cio_dma_flags; > + > +static void __init cio_dma_pool_init(void) > +{ > + void *cpu_addr; > + dma_addr_t dma_addr; > + int i; > + > + cio_dma_css = &channel_subsystems[0]->device; > + cio_dma_flags = GFP_DMA | GFP_KERNEL | __GFP_ZERO; > + cio_dma_pool = gen_pool_create(3, -1); > + /* No need to free up the resources: compiled in */ > + for (i = 0; i < POOL_INIT_PAGES; ++i) { > + cpu_addr = dma_alloc_coherent(cio_dma_css, PAGE_SIZE, &dma_addr, > + cio_dma_flags); > + if (!cpu_addr) > + return; > + gen_pool_add_virt(cio_dma_pool, (unsigned long) cpu_addr, > + dma_addr, PAGE_SIZE, -1); > + } > + > +} > + > +void *cio_dma_zalloc(size_t size) > +{ > + dma_addr_t dma_addr; > + unsigned long addr = gen_pool_alloc(cio_dma_pool, size); > + > + if (!addr) { > + addr = (unsigned long) dma_alloc_coherent(cio_dma_css, > + PAGE_SIZE, &dma_addr, cio_dma_flags); > + if (!addr) > + return NULL; > + gen_pool_add_virt(cio_dma_pool, addr, dma_addr, PAGE_SIZE, -1); > + addr = gen_pool_alloc(cio_dma_pool, size); > + } > + return (void *) addr; At this point, you're always going via the css0 device. I'm wondering whether you should pass in the cssid here and use css_by_id(cssid) to make this future proof. But then, I'm not quite clear from which context this will be called. > +} > + > +void cio_dma_free(void *cpu_addr, size_t size) > +{ > + memset(cpu_addr, 0, size); > + gen_pool_free(cio_dma_pool, (unsigned long) cpu_addr, size); > +} > + > /* > * Now that the driver core is running, we can setup our channel subsystem. > * The struct subchannel's are created during probing. > @@ -1063,6 +1119,7 @@ static int __init css_bus_init(void) > unregister_reboot_notifier(&css_reboot_notifier); > goto out_unregister; > } > + cio_dma_pool_init(); > css_init_done = 1; > > /* Enable default isc for I/O subchannels. */ _______________________________________________ Virtualization mailing list [email protected] https://lists.linuxfoundation.org/mailman/listinfo/virtualization
