[PATCH v3 2/8] s390/cio: introduce DMA pools to cio

Michael Mueller
2019-05-29T12:26:51Z

From: Halil Pasic <pasic@linux.ibm.com>

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>
Signed-off-by: Michael Mueller <mimu@linux.ibm.com>
---
arch/s390/Kconfig | 1 +
arch/s390/include/asm/cio.h | 11 ++++
drivers/s390/cio/css.c | 120 ++++++++++++++++++++++++++++++++++++++++++--
3 files changed, 128 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..43c007d2775a 100644
--- a/arch/s390/include/asm/cio.h
+++ b/arch/s390/include/asm/cio.h
@@ -328,6 +328,17 @@ 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);
+
+struct gen_pool;
+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..b97618497848 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 +226,8 @@ 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);
+ sch->dev.coherent_dma_mask = DMA_BIT_MASK(31);
+ sch->dev.dma_mask = &sch->dev.coherent_dma_mask;
return sch;

err:
@@ -899,6 +903,8 @@ 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;
+ 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 +1024,109 @@ 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 qite 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;
+
+ 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 +1168,19 @@ 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_rn;
css_init_done = 1;

/* Enable default isc for I/O subchannels. */
isc_register(IO_SCH_ISC);

return 0;
+out_unregister_rn:
+ unregister_reboot_notifier(&css_reboot_notifier);
out_unregister:
while (i-- > 0) {
struct channel_subsystem *css = channel_subsystems[i];
--
2.13.4