Re: [PATCH v5 2/8] s390/cio: introduce DMA pools to cio

[Michael Mueller <mimu@linux.ibm.com>]

On 12.06.19 13:12, Halil Pasic 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 one global pool for cio.
> 
> Our DMA pools are implemented as a gen_pool backed with DMA pages. The
> idea is to avoid each allocation effectively wasting a page, as we
> typically allocate much less than PAGE_SIZE.
> 
> Signed-off-by: Halil Pasic <pasic@linux.ibm.com>
> Reviewed-by: Sebastian Ott <sebott@linux.ibm.com>
> Reviewed-by: Cornelia Huck <cohuck@redhat.com>
> ---
>   arch/s390/Kconfig           |   1 +
>   arch/s390/include/asm/cio.h |  11 +++
>   drivers/s390/cio/css.c      | 133 ++++++++++++++++++++++++++++++++++--
>   3 files changed, 141 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
> index 88d8355b7bf7..2a245b56db8b 100644
> --- a/arch/s390/Kconfig
> +++ b/arch/s390/Kconfig
> @@ -191,6 +191,7 @@ config S390
>   	select ARCH_HAS_SCALED_CPUTIME
>   	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..58e7db912c30 100644
> --- a/arch/s390/include/asm/cio.h
> +++ b/arch/s390/include/asm/cio.h
> @@ -7,6 +7,7 @@
>   
>   #include <linux/spinlock.h>
>   #include <linux/bitops.h>
> +#include <linux/genalloc.h>
>   #include <asm/types.h>
>   
>   #define LPM_ANYPATH 0xff
> @@ -328,6 +329,16 @@ 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);
> +extern struct device *cio_get_dma_css_dev(void);
> +
> +void *cio_gp_dma_zalloc(struct gen_pool *gp_dma, struct device *dma_dev,
> +			size_t size);
> +void cio_gp_dma_free(struct gen_pool *gp_dma, void *cpu_addr, size_t size);
> +void cio_gp_dma_destroy(struct gen_pool *gp_dma, struct device *dma_dev);
> +struct gen_pool *cio_gp_dma_create(struct device *dma_dev, int nr_pages);
> +
>   /* 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..e0f19f1e82a0 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>
>   
> @@ -224,6 +226,12 @@ struct subchannel *css_alloc_subchannel(struct subchannel_id schid,
>   	INIT_WORK(&sch->todo_work, css_sch_todo);
>   	sch->dev.release = &css_subchannel_release;
>   	device_initialize(&sch->dev);
> +	/*
> +	 * The physical addresses of some the dma structures that can
> +	 * belong to a subchannel need to fit 31 bit width (e.g. ccw).
> +	 */
> +	sch->dev.coherent_dma_mask = DMA_BIT_MASK(31);
> +	sch->dev.dma_mask = &sch->dev.coherent_dma_mask;
>   	return sch;
>   
>   err:
> @@ -899,6 +907,13 @@ 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;
> +	/*
> +	 * We currently allocate notifier bits with this (using
> +	 * css->device as the device argument with the DMA API)
> +	 * and are fine with 64 bit addresses.
> +	 */
> +	css->device.coherent_dma_mask = DMA_BIT_MASK(64);
> +	css->device.dma_mask = &css->device.coherent_dma_mask;
>   
>   	mutex_init(&css->mutex);
>   	css->cssid = chsc_get_cssid(nr);
> @@ -1018,6 +1033,111 @@ static struct notifier_block css_power_notifier = {
>   	.notifier_call = css_power_event,
>   };
>   
> +#define  CIO_DMA_GFP (GFP_KERNEL | __GFP_ZERO)
> +static struct gen_pool *cio_dma_pool;
> +
> +/* Currently cio supports only a single css */
> +struct device *cio_get_dma_css_dev(void)
> +{
> +	return &channel_subsystems[0]->device;
> +}
> +
> +struct gen_pool *cio_gp_dma_create(struct device *dma_dev, int nr_pages)
> +{
> +	struct gen_pool *gp_dma;
> +	void *cpu_addr;
> +	dma_addr_t dma_addr;
> +	int i;
> +
> +	gp_dma = gen_pool_create(3, -1);
> +	if (!gp_dma)
> +		return NULL;
> +	for (i = 0; i < nr_pages; ++i) {
> +		cpu_addr = dma_alloc_coherent(dma_dev, PAGE_SIZE, &dma_addr,
> +					      CIO_DMA_GFP);
> +		if (!cpu_addr)
> +			return gp_dma;
> +		gen_pool_add_virt(gp_dma, (unsigned long) cpu_addr,
> +				  dma_addr, PAGE_SIZE, -1);
> +	}
> +	return gp_dma;
> +}
> +
> +static void __gp_dma_free_dma(struct gen_pool *pool,
> +			      struct gen_pool_chunk *chunk, void *data)
> +{
> +	size_t chunk_size = chunk->end_addr - chunk->start_addr + 1;
> +
> +	dma_free_coherent((struct device *) data, chunk_size,
> +			 (void *) chunk->start_addr,
> +			 (dma_addr_t) chunk->phys_addr);
> +}
> +
> +void cio_gp_dma_destroy(struct gen_pool *gp_dma, struct device *dma_dev)
> +{
> +	if (!gp_dma)
> +		return;
> +	/* this is quite ugly but no better idea */
> +	gen_pool_for_each_chunk(gp_dma, __gp_dma_free_dma, dma_dev);
> +	gen_pool_destroy(gp_dma);
> +}
> +
> +static int cio_dma_pool_init(void)
> +{
> +	/* No need to free up the resources: compiled in */
> +	cio_dma_pool = cio_gp_dma_create(cio_get_dma_css_dev(), 1);
> +	if (!cio_dma_pool)
> +		return -ENOMEM;
> +	return 0;
> +}
> +
> +void *cio_gp_dma_zalloc(struct gen_pool *gp_dma, struct device *dma_dev,
> +			size_t size)
> +{
> +	dma_addr_t dma_addr;
> +	unsigned long addr;
> +	size_t chunk_size;
> +
> +	if (!cio_dma_pool)
> +		return NULL;
> +	addr = gen_pool_alloc(gp_dma, size);
> +	while (!addr) {
> +		chunk_size = round_up(size, PAGE_SIZE);
> +		addr = (unsigned long) dma_alloc_coherent(dma_dev,
> +					 chunk_size, &dma_addr, CIO_DMA_GFP);
> +		if (!addr)
> +			return NULL;
> +		gen_pool_add_virt(gp_dma, addr, dma_addr, chunk_size, -1);
> +		addr = gen_pool_alloc(gp_dma, size);
> +	}
> +	return (void *) addr;
> +}
> +
> +void cio_gp_dma_free(struct gen_pool *gp_dma, void *cpu_addr, size_t size)
> +{
> +	if (!cpu_addr)
> +		return;
> +	memset(cpu_addr, 0, size);
> +	gen_pool_free(gp_dma, (unsigned long) cpu_addr, size);
> +}
> +
> +/*
> + * Allocate dma memory from the css global pool. Intended for memory not
> + * specific to any single device within the css. The allocated memory
> + * is not guaranteed to be 31-bit addressable.
> + *
> + * Caution: Not suitable for early stuff like console.
> + */
> +void *cio_dma_zalloc(size_t size)
> +{
> +	return cio_gp_dma_zalloc(cio_dma_pool, cio_get_dma_css_dev(), size);
> +}
> +
> +void cio_dma_free(void *cpu_addr, size_t size)
> +{
> +	cio_gp_dma_free(cio_dma_pool, cpu_addr, size);
> +}
> +
>   /*
>    * Now that the driver core is running, we can setup our channel subsystem.
>    * The struct subchannel's are created during probing.
> @@ -1059,16 +1179,21 @@ static int __init css_bus_init(void)
>   	if (ret)
>   		goto out_unregister;
>   	ret = register_pm_notifier(&css_power_notifier);
> -	if (ret) {
> -		unregister_reboot_notifier(&css_reboot_notifier);
> -		goto out_unregister;
> -	}
> +	if (ret)
> +		goto out_unregister_rn;
> +	ret = cio_dma_pool_init();
> +	if (ret)
> +		goto out_unregister_pmn;
>   	css_init_done = 1;
>   
>   	/* Enable default isc for I/O subchannels. */
>   	isc_register(IO_SCH_ISC);
>   
>   	return 0;
> +out_unregister_pmn:
> +	unregister_pm_notifier(&css_power_notifier);
> +out_unregister_rn:
> +	unregister_reboot_notifier(&css_reboot_notifier);
>   out_unregister:
>   	while (i-- > 0) {
>   		struct channel_subsystem *css = channel_subsystems[i];
> 

Reviewed-by: Michael Mueller <mimu@linux.ibm.com>

Michael