On Fri, 10 May 2019 00:11:12 +0200 Halil Pasic <pasic at linux.ibm.com> wrote:> On Thu, 9 May 2019 12:11:06 +0200 > Cornelia Huck <cohuck at redhat.com> wrote: > > > On Wed, 8 May 2019 23:22:10 +0200 > > Halil Pasic <pasic at linux.ibm.com> wrote: > > > > > On Wed, 8 May 2019 15:18:10 +0200 (CEST) > > > Sebastian Ott <sebott at linux.ibm.com> wrote: > > > > > > > @@ -1063,6 +1163,7 @@ static int __init css_bus_init(void) > > > > > unregister_reboot_notifier(&css_reboot_notifier); > > > > > goto out_unregister; > > > > > } > > > > > + cio_dma_pool_init(); > > > > > > > > This is too late for early devices (ccw console!). > > > > > > You have already raised concern about this last time (thanks). I think, > > > I've addressed this issue: tje cio_dma_pool is only used by the airq > > > stuff. I don't think the ccw console needs it. Please have an other look > > > at patch #6, and explain your concern in more detail if it persists. > > > > What about changing the naming/adding comments here, so that (1) folks > > aren't confused by the same thing in the future and (2) folks don't try > > to use that pool for something needed for the early ccw consoles? > > > > I'm all for clarity! Suggestions for better names?css_aiv_dma_pool, maybe? Or is there other cross-device stuff that may need it?
On Fri, 10 May 2019 16:10:13 +0200 Cornelia Huck <cohuck at redhat.com> wrote:> On Fri, 10 May 2019 00:11:12 +0200 > Halil Pasic <pasic at linux.ibm.com> wrote: > > > On Thu, 9 May 2019 12:11:06 +0200 > > Cornelia Huck <cohuck at redhat.com> wrote: > > > > > On Wed, 8 May 2019 23:22:10 +0200 > > > Halil Pasic <pasic at linux.ibm.com> wrote: > > > > > > > On Wed, 8 May 2019 15:18:10 +0200 (CEST) > > > > Sebastian Ott <sebott at linux.ibm.com> wrote: > > > > > > > > > @@ -1063,6 +1163,7 @@ static int __init css_bus_init(void) > > > > > > unregister_reboot_notifier(&css_reboot_notifier); > > > > > > goto out_unregister; > > > > > > } > > > > > > + cio_dma_pool_init(); > > > > > > > > > > This is too late for early devices (ccw console!). > > > > > > > > You have already raised concern about this last time (thanks). I think, > > > > I've addressed this issue: the cio_dma_pool is only used by the airq > > > > stuff. I don't think the ccw console needs it. Please have an other look > > > > at patch #6, and explain your concern in more detail if it persists. > > > > > > What about changing the naming/adding comments here, so that (1) folks > > > aren't confused by the same thing in the future and (2) folks don't try > > > to use that pool for something needed for the early ccw consoles? > > > > > > > I'm all for clarity! Suggestions for better names? > > css_aiv_dma_pool, maybe? Or is there other cross-device stuff that may > need it? >Ouch! I was considering to use cio_dma_zalloc() for the adapter interruption vectors but I ended up between the two chairs in the end. So with this series there are no uses for cio_dma pool. I don't feel strongly about this going one way the other. Against getting rid of the cio_dma_pool and sticking with the speaks dma_alloc_coherent() that we waste a DMA page per vector, which is a non obvious side effect. What speaks against cio_dma_pool is that it is slightly more code, and this currently can not be used for very early stuff, which I don't think is relevant. What also used to speak against it is that allocations asking for more than a page would just fail, but I addressed that in the patch I've hacked up on top of the series, and I'm going to paste below. While at it I addressed some other issues as well. I've also got code that deals with AIRQ_IV_CACHELINE by turning the kmem_cache into a dma_pool. Cornelia, Sebastian which approach do you prefer: 1) get rid of cio_dma_pool and AIRQ_IV_CACHELINE, and waste a page per vector, or 2) go with the approach taken by the patch below? Regards, Halil -----------------------8<--------------------------------------------- From: Halil Pasic <pasic at linux.ibm.com> Date: Sun, 12 May 2019 18:08:05 +0200 Subject: [PATCH] WIP: use cio dma pool for airqs Let's not waste a DMA page per adapter interrupt bit vector. --- Lightly tested... --- arch/s390/include/asm/airq.h | 1 - drivers/s390/cio/airq.c | 10 +++------- drivers/s390/cio/css.c | 18 +++++++++++++++--- 3 files changed, 18 insertions(+), 11 deletions(-) diff --git a/arch/s390/include/asm/airq.h b/arch/s390/include/asm/airq.h index 1492d48..981a3eb 100644 --- a/arch/s390/include/asm/airq.h +++ b/arch/s390/include/asm/airq.h @@ -30,7 +30,6 @@ void unregister_adapter_interrupt(struct airq_struct *airq); /* Adapter interrupt bit vector */ struct airq_iv { unsigned long *vector; /* Adapter interrupt bit vector */ - dma_addr_t vector_dma; /* Adapter interrupt bit vector dma */ unsigned long *avail; /* Allocation bit mask for the bit vector */ unsigned long *bitlock; /* Lock bit mask for the bit vector */ unsigned long *ptr; /* Pointer associated with each bit */ diff --git a/drivers/s390/cio/airq.c b/drivers/s390/cio/airq.c index 7a5c0a0..f11f437 100644 --- a/drivers/s390/cio/airq.c +++ b/drivers/s390/cio/airq.c @@ -136,8 +136,7 @@ struct airq_iv *airq_iv_create(unsigned long bits, unsigned long flags) goto out; iv->bits = bits; size = iv_size(bits); - iv->vector = dma_alloc_coherent(cio_get_dma_css_dev(), size, - &iv->vector_dma, GFP_KERNEL); + iv->vector = cio_dma_zalloc(size); if (!iv->vector) goto out_free; if (flags & AIRQ_IV_ALLOC) { @@ -172,8 +171,7 @@ struct airq_iv *airq_iv_create(unsigned long bits, unsigned long flags) kfree(iv->ptr); kfree(iv->bitlock); kfree(iv->avail); - dma_free_coherent(cio_get_dma_css_dev(), size, iv->vector, - iv->vector_dma); + cio_dma_free(iv->vector, size); kfree(iv); out: return NULL; @@ -189,9 +187,7 @@ void airq_iv_release(struct airq_iv *iv) kfree(iv->data); kfree(iv->ptr); kfree(iv->bitlock); - kfree(iv->vector); - dma_free_coherent(cio_get_dma_css_dev(), iv_size(iv->bits), - iv->vector, iv->vector_dma); + cio_dma_free(iv->vector, iv_size(iv->bits)); kfree(iv->avail); kfree(iv); } diff --git a/drivers/s390/cio/css.c b/drivers/s390/cio/css.c index 7087cc3..88d9c92 100644 --- a/drivers/s390/cio/css.c +++ b/drivers/s390/cio/css.c @@ -1063,7 +1063,10 @@ struct gen_pool *cio_gp_dma_create(struct device *dma_dev, int nr_pages) static void __gp_dma_free_dma(struct gen_pool *pool, struct gen_pool_chunk *chunk, void *data) { - dma_free_coherent((struct device *) data, PAGE_SIZE, + + 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); } @@ -1088,13 +1091,15 @@ void *cio_gp_dma_zalloc(struct gen_pool *gp_dma, struct device *dma_dev, { dma_addr_t dma_addr; unsigned long addr = gen_pool_alloc(gp_dma, size); + size_t chunk_size; if (!addr) { + chunk_size = round_up(size, PAGE_SIZE); addr = (unsigned long) dma_alloc_coherent(dma_dev, - PAGE_SIZE, &dma_addr, CIO_DMA_GFP); + chunk_size, &dma_addr, CIO_DMA_GFP); if (!addr) return NULL; - gen_pool_add_virt(gp_dma, addr, dma_addr, PAGE_SIZE, -1); + gen_pool_add_virt(gp_dma, addr, dma_addr, chunk_size, -1); addr = gen_pool_alloc(gp_dma, size); } return (void *) addr; @@ -1108,6 +1113,13 @@ void cio_gp_dma_free(struct gen_pool *gp_dma, void *cpu_addr, size_t 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. + * + * 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); -- 2.5.5
On Sun, 12 May 2019 20:22:56 +0200 Halil Pasic <pasic at linux.ibm.com> wrote:> On Fri, 10 May 2019 16:10:13 +0200 > Cornelia Huck <cohuck at redhat.com> wrote: > > > On Fri, 10 May 2019 00:11:12 +0200 > > Halil Pasic <pasic at linux.ibm.com> wrote: > > > > > On Thu, 9 May 2019 12:11:06 +0200 > > > Cornelia Huck <cohuck at redhat.com> wrote: > > > > > > > On Wed, 8 May 2019 23:22:10 +0200 > > > > Halil Pasic <pasic at linux.ibm.com> wrote: > > > > > > > > > On Wed, 8 May 2019 15:18:10 +0200 (CEST) > > > > > Sebastian Ott <sebott at linux.ibm.com> wrote: > > > > > > > > > > > @@ -1063,6 +1163,7 @@ static int __init css_bus_init(void) > > > > > > > unregister_reboot_notifier(&css_reboot_notifier); > > > > > > > goto out_unregister; > > > > > > > } > > > > > > > + cio_dma_pool_init(); > > > > > > > > > > > > This is too late for early devices (ccw console!). > > > > > > > > > > You have already raised concern about this last time (thanks). I think, > > > > > I've addressed this issue: the cio_dma_pool is only used by the airq > > > > > stuff. I don't think the ccw console needs it. Please have an other look > > > > > at patch #6, and explain your concern in more detail if it persists. > > > > > > > > What about changing the naming/adding comments here, so that (1) folks > > > > aren't confused by the same thing in the future and (2) folks don't try > > > > to use that pool for something needed for the early ccw consoles? > > > > > > > > > > I'm all for clarity! Suggestions for better names? > > > > css_aiv_dma_pool, maybe? Or is there other cross-device stuff that may > > need it? > > > > Ouch! I was considering to use cio_dma_zalloc() for the adapter > interruption vectors but I ended up between the two chairs in the end. > So with this series there are no uses for cio_dma pool. > > I don't feel strongly about this going one way the other. > > Against getting rid of the cio_dma_pool and sticking with the speaks > dma_alloc_coherent() that we waste a DMA page per vector, which is a > non obvious side effect.That would basically mean one DMA page per virtio-ccw device, right? For single queue devices, this seems like quite a bit of overhead. Are we expecting many devices in use per guest?> > What speaks against cio_dma_pool is that it is slightly more code, and > this currently can not be used for very early stuff, which I don't > think is relevant.Unless properly documented, it feels like something you can easily trip over, however. I assume that the "very early stuff" is basically only ccw consoles. Not sure if we can use virtio-serial as an early ccw console -- IIRC that was only about 3215/3270? While QEMU guests are able to use a 3270 console, this is experimental and I would not count that as a use case. Anyway, 3215/3270 don't use adapter interrupts, and probably not anything cross-device, either; so unless early virtio-serial is a thing, this restriction is fine if properly documented.> What also used to speak against it is that > allocations asking for more than a page would just fail, but I addressed > that in the patch I've hacked up on top of the series, and I'm going to > paste below. While at it I addressed some other issues as well.Hm, which "other issues"?> > I've also got code that deals with AIRQ_IV_CACHELINE by turning the > kmem_cache into a dma_pool.Isn't that percolating to other airq users again? Or maybe I just don't understand what you're proposing here...> > Cornelia, Sebastian which approach do you prefer: > 1) get rid of cio_dma_pool and AIRQ_IV_CACHELINE, and waste a page per > vector, or > 2) go with the approach taken by the patch below?I'm not sure that I properly understand this (yeah, you probably guessed); so I'm not sure I can make a good call here.> > > Regards, > Halil > -----------------------8<--------------------------------------------- > From: Halil Pasic <pasic at linux.ibm.com> > Date: Sun, 12 May 2019 18:08:05 +0200 > Subject: [PATCH] WIP: use cio dma pool for airqs > > Let's not waste a DMA page per adapter interrupt bit vector. > --- > Lightly tested... > --- > arch/s390/include/asm/airq.h | 1 - > drivers/s390/cio/airq.c | 10 +++------- > drivers/s390/cio/css.c | 18 +++++++++++++++--- > 3 files changed, 18 insertions(+), 11 deletions(-) > > diff --git a/arch/s390/include/asm/airq.h b/arch/s390/include/asm/airq.h > index 1492d48..981a3eb 100644 > --- a/arch/s390/include/asm/airq.h > +++ b/arch/s390/include/asm/airq.h > @@ -30,7 +30,6 @@ void unregister_adapter_interrupt(struct airq_struct *airq); > /* Adapter interrupt bit vector */ > struct airq_iv { > unsigned long *vector; /* Adapter interrupt bit vector */ > - dma_addr_t vector_dma; /* Adapter interrupt bit vector dma */ > unsigned long *avail; /* Allocation bit mask for the bit vector */ > unsigned long *bitlock; /* Lock bit mask for the bit vector */ > unsigned long *ptr; /* Pointer associated with each bit */ > diff --git a/drivers/s390/cio/airq.c b/drivers/s390/cio/airq.c > index 7a5c0a0..f11f437 100644 > --- a/drivers/s390/cio/airq.c > +++ b/drivers/s390/cio/airq.c > @@ -136,8 +136,7 @@ struct airq_iv *airq_iv_create(unsigned long bits, unsigned long flags) > goto out; > iv->bits = bits; > size = iv_size(bits); > - iv->vector = dma_alloc_coherent(cio_get_dma_css_dev(), size, > - &iv->vector_dma, GFP_KERNEL); > + iv->vector = cio_dma_zalloc(size); > if (!iv->vector) > goto out_free; > if (flags & AIRQ_IV_ALLOC) { > @@ -172,8 +171,7 @@ struct airq_iv *airq_iv_create(unsigned long bits, unsigned long flags) > kfree(iv->ptr); > kfree(iv->bitlock); > kfree(iv->avail); > - dma_free_coherent(cio_get_dma_css_dev(), size, iv->vector, > - iv->vector_dma); > + cio_dma_free(iv->vector, size); > kfree(iv); > out: > return NULL; > @@ -189,9 +187,7 @@ void airq_iv_release(struct airq_iv *iv) > kfree(iv->data); > kfree(iv->ptr); > kfree(iv->bitlock); > - kfree(iv->vector); > - dma_free_coherent(cio_get_dma_css_dev(), iv_size(iv->bits), > - iv->vector, iv->vector_dma); > + cio_dma_free(iv->vector, iv_size(iv->bits)); > kfree(iv->avail); > kfree(iv); > } > diff --git a/drivers/s390/cio/css.c b/drivers/s390/cio/css.c > index 7087cc3..88d9c92 100644 > --- a/drivers/s390/cio/css.c > +++ b/drivers/s390/cio/css.c > @@ -1063,7 +1063,10 @@ struct gen_pool *cio_gp_dma_create(struct device *dma_dev, int nr_pages) > static void __gp_dma_free_dma(struct gen_pool *pool, > struct gen_pool_chunk *chunk, void *data) > { > - dma_free_coherent((struct device *) data, PAGE_SIZE, > + > + 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); > } > @@ -1088,13 +1091,15 @@ void *cio_gp_dma_zalloc(struct gen_pool *gp_dma, struct device *dma_dev, > { > dma_addr_t dma_addr; > unsigned long addr = gen_pool_alloc(gp_dma, size); > + size_t chunk_size; > > if (!addr) { > + chunk_size = round_up(size, PAGE_SIZE);Doesn't that mean that we still go up to chunks of at least PAGE_SIZE? Or can vectors now share the same chunk?> addr = (unsigned long) dma_alloc_coherent(dma_dev, > - PAGE_SIZE, &dma_addr, CIO_DMA_GFP); > + chunk_size, &dma_addr, CIO_DMA_GFP); > if (!addr) > return NULL; > - gen_pool_add_virt(gp_dma, addr, dma_addr, PAGE_SIZE, -1); > + gen_pool_add_virt(gp_dma, addr, dma_addr, chunk_size, -1); > addr = gen_pool_alloc(gp_dma, size); > } > return (void *) addr; > @@ -1108,6 +1113,13 @@ void cio_gp_dma_free(struct gen_pool *gp_dma, void *cpu_addr, size_t 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. > + * > + * Caution: Not suitable for early stuff like console.Maybe add "Do not use prior to <point in startup>"?> + * > + */ > void *cio_dma_zalloc(size_t size) > { > return cio_gp_dma_zalloc(cio_dma_pool, cio_get_dma_css_dev(), size);
On Sun, 12 May 2019, Halil Pasic wrote:> I've also got code that deals with AIRQ_IV_CACHELINE by turning the > kmem_cache into a dma_pool. > > Cornelia, Sebastian which approach do you prefer: > 1) get rid of cio_dma_pool and AIRQ_IV_CACHELINE, and waste a page per > vector, or > 2) go with the approach taken by the patch below?We only have a couple of users for airq_iv: virtio_ccw.c: 2K bits pci with floating IRQs: <= 2K (for the per-function bit vectors) 1..4K (for the summary bit vector) pci with CPU directed IRQs: 2K (for the per-CPU bit vectors) 1..nr_cpu (for the summary bit vector) The options are: * page allocations for everything * dma_pool for AIRQ_IV_CACHELINE ,gen_pool for others * dma_pool for everything I think we should do option 3 and use a dma_pool with cachesize alignment for everything (as a prerequisite we have to limit config PCI_NR_FUNCTIONS to 2K - but that is not a real constraint). Sebastian
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