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[124.171.83.152]) by smtp.gmail.com with ESMTPSA id a1sm4636057pfd.65.2020.09.03.18.00.28 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 03 Sep 2020 18:00:33 -0700 (PDT) Subject: Re: [PATCH v1 09/10] powerpc/pseries/iommu: Make use of DDW even if it does not map the partition To: Leonardo Bras , Michael Ellerman , Benjamin Herrenschmidt , Paul Mackerras , Christophe Leroy , Joel Stanley , Thiago Jung Bauermann , Ram Pai , Brian King , Murilo Fossa Vicentini , David Dai Cc: linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org References: <20200817234033.442511-1-leobras.c@gmail.com> <20200817234033.442511-10-leobras.c@gmail.com> From: Alexey Kardashevskiy Message-ID: Date: Fri, 4 Sep 2020 11:00:25 +1000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.11.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 02/09/2020 16:11, Leonardo Bras wrote: > On Mon, 2020-08-31 at 14:35 +1000, Alexey Kardashevskiy wrote: >> >> On 29/08/2020 04:36, Leonardo Bras wrote: >>> On Mon, 2020-08-24 at 15:17 +1000, Alexey Kardashevskiy wrote: >>>> On 18/08/2020 09:40, Leonardo Bras wrote: >>>>> As of today, if the biggest DDW that can be created can't map the whole >>>>> partition, it's creation is skipped and the default DMA window >>>>> "ibm,dma-window" is used instead. >>>>> >>>>> DDW is 16x bigger than the default DMA window, >>>> >>>> 16x only under very specific circumstances which are >>>> 1. phyp >>>> 2. sriov >>>> 3. device class in hmc (or what that priority number is in the lpar config). >>> >>> Yeah, missing details. >>> >>>>> having the same amount of >>>>> pages, but increasing the page size to 64k. >>>>> Besides larger DMA window, >>>> >>>> "Besides being larger"? >>> >>> You are right there. >>> >>>>> it performs better for allocations over 4k, >>>> >>>> Better how? >>> >>> I was thinking for allocations larger than (512 * 4k), since >2 >>> hypercalls are needed here, and for 64k pages would still be just 1 >>> hypercall up to (512 * 64k). >>> But yeah, not the usual case anyway. >> >> Yup. >> >> >>>>> so it would be nice to use it instead. >>>> >>>> I'd rather say something like: >>>> === >>>> So far we assumed we can map the guest RAM 1:1 to the bus which worked >>>> with a small number of devices. SRIOV changes it as the user can >>>> configure hundreds VFs and since phyp preallocates TCEs and does not >>>> allow IOMMU pages bigger than 64K, it has to limit the number of TCEs >>>> per a PE to limit waste of physical pages. >>>> === >>> >>> I mixed this in my commit message, it looks like this: >>> >>> === >>> powerpc/pseries/iommu: Make use of DDW for indirect mapping >>> >>> So far it's assumed possible to map the guest RAM 1:1 to the bus, which >>> works with a small number of devices. SRIOV changes it as the user can >>> configure hundreds VFs and since phyp preallocates TCEs and does not >>> allow IOMMU pages bigger than 64K, it has to limit the number of TCEs >>> per a PE to limit waste of physical pages. >>> >>> As of today, if the assumed direct mapping is not possible, DDW >>> creation is skipped and the default DMA window "ibm,dma-window" is used >>> instead. >>> >>> The default DMA window uses 4k pages instead of 64k pages, and since >>> the amount of pages is the same, >> >> Is the amount really the same? I thought you can prioritize some VFs >> over others (== allocate different number of TCEs). Does it really >> matter if it is the same? > > On a conversation with Travis Pizel, he explained how it's supposed to > work, and I understood this: > > When a VF is created, it will be assigned a capacity, like 4%, 20%, and > so on. The number of 'TCE entries' that are available to that partition > are proportional to that capacity. > > If we use the default DMA window, the IOMMU pagesize/entry will be 4k, > and if we use DDW, we will get 64k pagesize. As the number of entries > will be the same (for the same capacity), the total space that can be > addressed by the IOMMU will be 16 times bigger. This sometimes enable > direct mapping, but sometimes it's still not enough. Good to know. This is still an implementation detail, QEMU does not allocate TCEs like this. > > On Travis words : > "A low capacity VF, with less resources available, will certainly have > less DMA window capability than a high capacity VF. But, an 8GB DMA > window (with 64k pages) is still 16x larger than an 512MB window (with > 4K pages). > A high capacity VF - for example, one that Leonardo has in his scenario > - will go from 8GB (using 4K pages) to 128GB (using 64K pages) - again, > 16x larger - but it's obviously still possible to create a partition > that exceeds 128GB of memory in size." Right except the default dma window is not 8GB, it is <=2GB. > >> >> >>> making use of DDW instead of the >>> default DMA window for indirect mapping will expand in 16x the amount >>> of memory that can be mapped on DMA. >> >> Stop saying "16x", it is not guaranteed by anything :) >> >> >>> The DDW created will be used for direct mapping by default. [...] >>> === >>> >>> What do you think? >>> >>>>> The DDW created will be used for direct mapping by default. >>>>> If it's not available, indirect mapping will be used instead. >>>>> >>>>> For indirect mapping, it's necessary to update the iommu_table so >>>>> iommu_alloc() can use the DDW created. For this, >>>>> iommu_table_update_window() is called when everything else succeeds >>>>> at enable_ddw(). >>>>> >>>>> Removing the default DMA window for using DDW with indirect mapping >>>>> is only allowed if there is no current IOMMU memory allocated in >>>>> the iommu_table. enable_ddw() is aborted otherwise. >>>>> >>>>> As there will never have both direct and indirect mappings at the same >>>>> time, the same property name can be used for the created DDW. >>>>> >>>>> So renaming >>>>> define DIRECT64_PROPNAME "linux,direct64-ddr-window-info" >>>>> to >>>>> define DMA64_PROPNAME "linux,dma64-ddr-window-info" >>>>> looks the right thing to do. >>>> >>>> I know I suggested this but this does not look so good anymore as I >>>> suspect it breaks kexec (from older kernel to this one) so you either >>>> need to check for both DT names or just keep the old one. Changing the >>>> macro name is fine. >>>> >>> >>> Yeah, having 'direct' in the name don't really makes sense if it's used >>> for indirect mapping. I will just add this new define instead of >>> replacing the old one, and check for both. >>> Is that ok? >> >> No, having two of these does not seem right or useful. It is pseries >> which does not use petitboot (relies on grub instead so until the target >> kernel is started, there will be no ddw) so realistically we need this >> property for kexec/kdump which uses the same kernel but different >> initramdisk so for that purpose we need the same property name. >> >> But I can see myself annoyed when I try petitboot in the hacked pseries >> qemu and things may crash :) On this basis I'd suggest keeping the name >> and adding a comment next to it that it is not always "direct" anymore. >> > > Keeping the same name should bring more problems than solve. > If we have indirect mapping and kexec() to an older kernel, it will > think direct mapping is enabled, and trying to use a DMA address > without doing H_PUT_* first may cause a crash. > > I tested with a new property name, and it doesn't crash. > As the property is not found, it does try to create a new DDW, which > fails and it falls back to using the default DMA window. > The device that need the IOMMU don't work well, but when iommu_map() > fails, it doesn't try to use the DMA address as valid. Right, as discussed on slack. > >> >>>>> To make sure the property differentiates both cases, a new u32 for flags >>>>> was added at the end of the property, where BIT(0) set means direct >>>>> mapping. >>>>> >>>>> Signed-off-by: Leonardo Bras >>>>> --- >>>>> arch/powerpc/platforms/pseries/iommu.c | 108 +++++++++++++++++++------ >>>>> 1 file changed, 84 insertions(+), 24 deletions(-) >>>>> >>>>> diff --git a/arch/powerpc/platforms/pseries/iommu.c b/arch/powerpc/platforms/pseries/iommu.c >>>>> index 3a1ef02ad9d5..9544e3c91ced 100644 >>>>> --- a/arch/powerpc/platforms/pseries/iommu.c >>>>> +++ b/arch/powerpc/platforms/pseries/iommu.c >>>>> @@ -350,8 +350,11 @@ struct dynamic_dma_window_prop { >>>>> __be64 dma_base; /* address hi,lo */ >>>>> __be32 tce_shift; /* ilog2(tce_page_size) */ >>>>> __be32 window_shift; /* ilog2(tce_window_size) */ >>>>> + __be32 flags; /* DDW properties, see bellow */ >>>>> }; >>>>> >>>>> +#define DDW_FLAGS_DIRECT 0x01 >>>> >>>> This is set if ((1<= ddw_memory_hotplug_max()), you >>>> could simply check window_shift and drop the flags. >>>> >>> >>> Yeah, it's better this way, I will revert this. >>> >>>>> + >>>>> struct direct_window { >>>>> struct device_node *device; >>>>> const struct dynamic_dma_window_prop *prop; >>>>> @@ -377,7 +380,7 @@ static LIST_HEAD(direct_window_list); >>>>> static DEFINE_SPINLOCK(direct_window_list_lock); >>>>> /* protects initializing window twice for same device */ >>>>> static DEFINE_MUTEX(direct_window_init_mutex); >>>>> -#define DIRECT64_PROPNAME "linux,direct64-ddr-window-info" >>>>> +#define DMA64_PROPNAME "linux,dma64-ddr-window-info" >>>>> >>>>> static int tce_clearrange_multi_pSeriesLP(unsigned long start_pfn, >>>>> unsigned long num_pfn, const void *arg) >>>>> @@ -836,7 +839,7 @@ static void remove_ddw(struct device_node *np, bool remove_prop) >>>>> if (ret) >>>>> return; >>>>> >>>>> - win = of_find_property(np, DIRECT64_PROPNAME, NULL); >>>>> + win = of_find_property(np, DMA64_PROPNAME, NULL); >>>>> if (!win) >>>>> return; >>>>> >>>>> @@ -852,7 +855,7 @@ static void remove_ddw(struct device_node *np, bool remove_prop) >>>>> np, ret); >>>>> } >>>>> >>>>> -static bool find_existing_ddw(struct device_node *pdn, u64 *dma_addr) >>>>> +static bool find_existing_ddw(struct device_node *pdn, u64 *dma_addr, bool *direct_mapping) >>>>> { >>>>> struct direct_window *window; >>>>> const struct dynamic_dma_window_prop *direct64; >>>>> @@ -864,6 +867,7 @@ static bool find_existing_ddw(struct device_node *pdn, u64 *dma_addr) >>>>> if (window->device == pdn) { >>>>> direct64 = window->prop; >>>>> *dma_addr = be64_to_cpu(direct64->dma_base); >>>>> + *direct_mapping = be32_to_cpu(direct64->flags) & DDW_FLAGS_DIRECT; >>>>> found = true; >>>>> break; >>>>> } >>>>> @@ -901,8 +905,8 @@ static int find_existing_ddw_windows(void) >>>>> if (!firmware_has_feature(FW_FEATURE_LPAR)) >>>>> return 0; >>>>> >>>>> - for_each_node_with_property(pdn, DIRECT64_PROPNAME) { >>>>> - direct64 = of_get_property(pdn, DIRECT64_PROPNAME, &len); >>>>> + for_each_node_with_property(pdn, DMA64_PROPNAME) { >>>>> + direct64 = of_get_property(pdn, DMA64_PROPNAME, &len); >>>>> if (!direct64) >>>>> continue; >>>>> >>>>> @@ -1124,7 +1128,8 @@ static void reset_dma_window(struct pci_dev *dev, struct device_node *par_dn) >>>>> } >>>>> >>>>> static int ddw_property_create(struct property **ddw_win, const char *propname, >>>>> - u32 liobn, u64 dma_addr, u32 page_shift, u32 window_shift) >>>>> + u32 liobn, u64 dma_addr, u32 page_shift, >>>>> + u32 window_shift, bool direct_mapping) >>>>> { >>>>> struct dynamic_dma_window_prop *ddwprop; >>>>> struct property *win64; >>>>> @@ -1144,6 +1149,36 @@ static int ddw_property_create(struct property **ddw_win, const char *propname, >>>>> ddwprop->dma_base = cpu_to_be64(dma_addr); >>>>> ddwprop->tce_shift = cpu_to_be32(page_shift); >>>>> ddwprop->window_shift = cpu_to_be32(window_shift); >>>>> + if (direct_mapping) >>>>> + ddwprop->flags = cpu_to_be32(DDW_FLAGS_DIRECT); >>>>> + >>>>> + return 0; >>>>> +} >>>>> + >>>>> +static int iommu_table_update_window(struct iommu_table **tbl, int nid, unsigned long liobn, >>>>> + unsigned long win_addr, unsigned long page_shift, >>>>> + unsigned long window_size) >>>> >>>> Rather strange helper imho. I'd extract the most of >>>> iommu_table_setparms_lpar() into iommu_table_setparms() (except >>>> of_parse_dma_window) and call new helper from where you call >>>> iommu_table_update_window; and do >>>> iommu_pseries_alloc_table/iommu_tce_table_put there. >>>> >>> >>> I don't see how to extract iommu_table_setparms_lpar() into >>> iommu_table_setparms(), they look to be used for different machine >>> types. >>> >>> Do mean you extracting most of iommu_table_setparms_lpar() (and maybe >>> iommu_table_setparms() ) into a new helper, which is called in both >>> functions and use it instead of iommu_table_update_window() ? >> >> Yes, this. > > I will do that then, seems better. :) > >> >> >>>>> +{ >>>>> + struct iommu_table *new_tbl, *old_tbl; >>>>> + >>>>> + new_tbl = iommu_pseries_alloc_table(nid); >>>>> + if (!new_tbl) >>>>> + return -ENOMEM; >>>>> + >>>>> + old_tbl = *tbl; >>>>> + new_tbl->it_index = liobn; >>>>> + new_tbl->it_offset = win_addr >> page_shift; >>>>> + new_tbl->it_page_shift = page_shift; >>>>> + new_tbl->it_size = window_size >> page_shift; >>>>> + new_tbl->it_base = old_tbl->it_base; >>>> >>>> Should not be used in pseries. >>>> >>> >>> The point here is to migrate the values from the older tbl to the >> >> The actual window/table is new (on the hypervisor side), you are not >> migrating a single TCE, you deleted one whole window and created another >> whole window, calling it "migration" is confusing, especially when PAPR >> actually defines TCE migration. > > Ok, I understand it's confusing now. I will avoid using this term from > now on. > >> >> >>> newer. I Would like to understand why this is bad, if it will still be >>> 'unused' as the older tbl. >> >> Having explicit values is more readable imho. > > Ok, I understand why it should be improved.! > > Alexey, thank you for reviewing, and for helping me with my questions! Thanks for doing this all! > > Best regards, > >> >> >>>>> + new_tbl->it_busno = old_tbl->it_busno; >>>>> + new_tbl->it_blocksize = old_tbl->it_blocksize; >>>> >>>> 16 for pseries and does not change (may be even make it a macro). >>>> >>>>> + new_tbl->it_type = old_tbl->it_type; >>>> >>>> TCE_PCI. >>>> >>> >>> Same as above. >>> >>>>> + new_tbl->it_ops = old_tbl->it_ops; >>>>> + >>>>> + iommu_init_table(new_tbl, nid, old_tbl->it_reserved_start, old_tbl->it_reserved_end); >>>>> + iommu_tce_table_put(old_tbl); >>>>> + *tbl = new_tbl; >>>>> >>>>> return 0; >>>>> } >>>>> @@ -1171,12 +1206,16 @@ static bool enable_ddw(struct pci_dev *dev, struct device_node *pdn) >>>>> struct direct_window *window; >>>>> struct property *win64 = NULL; >>>>> struct failed_ddw_pdn *fpdn; >>>>> - bool default_win_removed = false; >>>>> + bool default_win_removed = false, maps_whole_partition = false; >>>> >>>> s/maps_whole_partition/direct_mapping/ >>>> >>> >>> Sure, I will get it replaced. >>> >>>>> + struct pci_dn *pci = PCI_DN(pdn); >>>>> + struct iommu_table *tbl = pci->table_group->tables[0]; >>>>> >>>>> mutex_lock(&direct_window_init_mutex); >>>>> >>>>> - if (find_existing_ddw(pdn, &dev->dev.archdata.dma_offset)) >>>>> - goto out_unlock; >>>>> + if (find_existing_ddw(pdn, &dev->dev.archdata.dma_offset, &maps_whole_partition)) { >>>>> + mutex_unlock(&direct_window_init_mutex); >>>>> + return maps_whole_partition; >>>>> + } >>>>> >>>>> /* >>>>> * If we already went through this for a previous function of >>>>> @@ -1258,16 +1297,24 @@ static bool enable_ddw(struct pci_dev *dev, struct device_node *pdn) >>>>> query.page_size); >>>>> goto out_failed; >>>>> } >>>>> + >>>>> /* verify the window * number of ptes will map the partition */ >>>>> - /* check largest block * page size > max memory hotplug addr */ >>>>> max_addr = ddw_memory_hotplug_max(); >>>>> if (query.largest_available_block < (max_addr >> page_shift)) { >>>>> - dev_dbg(&dev->dev, "can't map partition max 0x%llx with %llu " >>>>> - "%llu-sized pages\n", max_addr, query.largest_available_block, >>>>> - 1ULL << page_shift); >>>>> - goto out_failed; >>>>> + dev_dbg(&dev->dev, "can't map partition max 0x%llx with %llu %llu-sized pages\n", >>>>> + max_addr, query.largest_available_block, >>>>> + 1ULL << page_shift); >>>>> + >>>>> + len = order_base_2(query.largest_available_block << page_shift); >>>>> + } else { >>>>> + maps_whole_partition = true; >>>>> + len = order_base_2(max_addr); >>>>> } >>>>> - len = order_base_2(max_addr); >>>>> + >>>>> + /* DDW + IOMMU on single window may fail if there is any allocation */ >>>>> + if (default_win_removed && !maps_whole_partition && >>>>> + iommu_table_in_use(tbl)) >>>>> + goto out_failed; >>>>> >>>>> ret = create_ddw(dev, ddw_avail, &create, page_shift, len); >>>>> if (ret != 0) >>>>> @@ -1277,8 +1324,8 @@ static bool enable_ddw(struct pci_dev *dev, struct device_node *pdn) >>>>> create.liobn, dn); >>>>> >>>>> win_addr = ((u64)create.addr_hi << 32) | create.addr_lo; >>>>> - ret = ddw_property_create(&win64, DIRECT64_PROPNAME, create.liobn, win_addr, >>>>> - page_shift, len); >>>>> + ret = ddw_property_create(&win64, DMA64_PROPNAME, create.liobn, win_addr, >>>>> + page_shift, len, maps_whole_partition); >>>>> if (ret) { >>>>> dev_info(&dev->dev, >>>>> "couldn't allocate property, property name, or value\n"); >>>>> @@ -1297,12 +1344,25 @@ static bool enable_ddw(struct pci_dev *dev, struct device_node *pdn) >>>>> if (!window) >>>>> goto out_prop_del; >>>>> >>>>> - ret = walk_system_ram_range(0, memblock_end_of_DRAM() >> PAGE_SHIFT, >>>>> - win64->value, tce_setrange_multi_pSeriesLP_walk); >>>>> - if (ret) { >>>>> - dev_info(&dev->dev, "failed to map direct window for %pOF: %d\n", >>>>> - dn, ret); >>>>> - goto out_free_window; >>>>> + if (maps_whole_partition) { >>>>> + /* DDW maps the whole partition, so enable direct DMA mapping */ >>>>> + ret = walk_system_ram_range(0, memblock_end_of_DRAM() >> PAGE_SHIFT, >>>>> + win64->value, tce_setrange_multi_pSeriesLP_walk); >>>>> + if (ret) { >>>>> + dev_info(&dev->dev, "failed to map direct window for %pOF: %d\n", >>>>> + dn, ret); >>>>> + goto out_free_window; >>>>> + } >>>>> + } else { >>>>> + /* New table for using DDW instead of the default DMA window */ >>>>> + if (iommu_table_update_window(&tbl, pci->phb->node, create.liobn, >>>>> + win_addr, page_shift, 1UL << len)) >>>>> + goto out_free_window; >>>>> + >>>>> + set_iommu_table_base(&dev->dev, tbl); >>>>> + WARN_ON(dev->dev.archdata.dma_offset >= SZ_4G); >>>> >>>> What is this check for exactly? Why 4G, not >= 0, for example? >>> >>> I am not really sure, you suggested adding it here: >>> http://patchwork.ozlabs.org/project/linuxppc-dev/patch/20200716071658.467820-6-leobras.c@gmail.com/#2488874 >> >> Ah right I did suggest this :) My bad. I think I suggested it before >> suggesting to keep the reserved area boundaries checked/adjusted to the >> window boundaries, may as well drop this. Thanks, >> >> >>> I can remove it if it's ok. >>> >>>>> + goto out_unlock; >>>>> + >>>>> } >>>>> >>>>> dev->dev.archdata.dma_offset = win_addr; >>>>> @@ -1340,7 +1400,7 @@ static bool enable_ddw(struct pci_dev *dev, struct device_node *pdn) >>>>> >>>>> out_unlock: >>>>> mutex_unlock(&direct_window_init_mutex); >>>>> - return win64; >>>>> + return win64 && maps_whole_partition; >>>>> } >>>>> >>>>> static void pci_dma_dev_setup_pSeriesLP(struct pci_dev *dev) >>>>> > -- Alexey