Re: [Qemu-devel] [PATCH qemu v10 14/14] spapr_pci/spapr_pci_vfio: Support Dynamic DMA Windows (DDW)

[Alexey Kardashevskiy <aik@ozlabs.ru>]

On 07/07/2015 07:33 PM, Thomas Huth wrote:
> On Mon,  6 Jul 2015 12:11:10 +1000
> Alexey Kardashevskiy <aik@ozlabs.ru> wrote:
>
>> This adds support for Dynamic DMA Windows (DDW) option defined by
>> the SPAPR specification which allows to have additional DMA window(s)
>>
>> This implements DDW for emulated and VFIO devices. As all TCE root regions
>> are mapped at 0 and 64bit long (and actual tables are child regions),
>> this replaces memory_region_add_subregion() with _overlap() to make
>> QEMU memory API happy.
>>
>> This reserves RTAS token numbers for DDW calls.
>>
>> This implements helpers to interact with VFIO kernel interface.
>>
>> This changes the TCE table migration descriptor to support dynamic
>> tables as from now on, PHB will create as many stub TCE table objects
>> as PHB can possibly support but not all of them might be initialized at
>> the time of migration because DDW might or might not be requested by
>> the guest.
>>
>> The "ddw" property is enabled by default on a PHB but for compatibility
>> the pseries-2.3 machine and older disable it.
>>
>> This implements DDW for VFIO. The host kernel support is required.
>> This adds a "levels" property to PHB to control the number of levels
>> in the actual TCE table allocated by the host kernel, 0 is the default
>> value to tell QEMU to calculate the correct value. Current hardware
>> supports up to 5 levels.
>>
>> The existing linux guests try creating one additional huge DMA window
>> with 64K or 16MB pages and map the entire guest RAM to. If succeeded,
>> the guest switches to dma_direct_ops and never calls TCE hypercalls
>> (H_PUT_TCE,...) again. This enables VFIO devices to use the entire RAM
>> and not waste time on map/unmap later. This adds a "dma64_win_addr"
>> property which is a bus address for the 64bit window and by default
>> set to 0x800.0000.0000.0000 as this is what the modern POWER8 hardware
>> uses and this allows having emulated and VFIO devices on the same bus.
>>
>> This adds 4 RTAS handlers:
>> * ibm,query-pe-dma-window
>> * ibm,create-pe-dma-window
>> * ibm,remove-pe-dma-window
>> * ibm,reset-pe-dma-window
>> These are registered from type_init() callback.
>>
>> These RTAS handlers are implemented in a separate file to avoid polluting
>> spapr_iommu.c with PCI.
>>
>> Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
>> ---
> ...
>> diff --git a/hw/ppc/spapr_rtas_ddw.c b/hw/ppc/spapr_rtas_ddw.c
>> new file mode 100644
>> index 0000000..7539c6a
>> --- /dev/null
>> +++ b/hw/ppc/spapr_rtas_ddw.c
>> @@ -0,0 +1,300 @@
>> +/*
>> + * QEMU sPAPR Dynamic DMA windows support
>> + *
>> + * Copyright (c) 2014 Alexey Kardashevskiy, IBM Corporation.
>
> Happy new year?
>
>> + *  This program is free software; you can redistribute it and/or modify
>> + *  it under the terms of the GNU General Public License as published by
>> + *  the Free Software Foundation; either version 2 of the License,
>> + *  or (at your option) any later version.
>> + *
>> + *  This program is distributed in the hope that it will be useful,
>> + *  but WITHOUT ANY WARRANTY; without even the implied warranty of
>> + *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
>> + *  GNU General Public License for more details.
>> + *
>> + *  You should have received a copy of the GNU General Public License
>> + *  along with this program; if not, see <http://www.gnu.org/licenses/>.
>> + */
>> +
>> +#include "qemu/error-report.h"
>> +#include "hw/ppc/spapr.h"
>> +#include "hw/pci-host/spapr.h"
>> +#include "trace.h"
>> +
>> +static int spapr_phb_get_active_win_num_cb(Object *child, void *opaque)
>> +{
>> +    sPAPRTCETable *tcet;
>> +
>> +    tcet = (sPAPRTCETable *) object_dynamic_cast(child, TYPE_SPAPR_TCE_TABLE);
>> +    if (tcet && tcet->enabled) {
>> +        ++*(unsigned *)opaque;
>> +    }
>> +    return 0;
>> +}
>> +
>> +static unsigned spapr_phb_get_active_win_num(sPAPRPHBState *sphb)
>> +{
>> +    unsigned ret = 0;
>> +
>> +    object_child_foreach(OBJECT(sphb), spapr_phb_get_active_win_num_cb, &ret);
>> +
>> +    return ret;
>> +}
>> +
>> +static int spapr_phb_get_free_liobn_cb(Object *child, void *opaque)
>> +{
>> +    sPAPRTCETable *tcet;
>> +
>> +    tcet = (sPAPRTCETable *) object_dynamic_cast(child, TYPE_SPAPR_TCE_TABLE);
>> +    if (tcet && !tcet->enabled) {
>> +        *(uint32_t *)opaque = tcet->liobn;
>> +        return 1;
>> +    }
>> +    return 0;
>> +}
>> +
>> +static unsigned spapr_phb_get_free_liobn(sPAPRPHBState *sphb)
>> +{
>> +    uint32_t liobn = 0;
>> +
>> +    object_child_foreach(OBJECT(sphb), spapr_phb_get_free_liobn_cb, &liobn);
>> +
>> +    return liobn;
>> +}
>> +
>> +static uint32_t spapr_query_mask(struct ppc_one_seg_page_size *sps,
>> +                                 uint64_t page_mask)
>> +{
>> +    int i, j;
>> +    uint32_t mask = 0;
>> +    const struct { int shift; uint32_t mask; } masks[] = {
>> +        { 12, RTAS_DDW_PGSIZE_4K },
>> +        { 16, RTAS_DDW_PGSIZE_64K },
>> +        { 24, RTAS_DDW_PGSIZE_16M },
>> +        { 25, RTAS_DDW_PGSIZE_32M },
>> +        { 26, RTAS_DDW_PGSIZE_64M },
>> +        { 27, RTAS_DDW_PGSIZE_128M },
>> +        { 28, RTAS_DDW_PGSIZE_256M },
>> +        { 34, RTAS_DDW_PGSIZE_16G },
>> +    };
>> +
>> +    for (i = 0; i < PPC_PAGE_SIZES_MAX_SZ; i++) {
>> +        for (j = 0; j < ARRAY_SIZE(masks); ++j) {
>> +            if ((sps[i].page_shift == masks[j].shift) &&
>> +                    (page_mask & (1ULL << masks[j].shift))) {
>> +                mask |= masks[j].mask;
>> +            }
>> +        }
>> +    }
>> +
>> +    return mask;
>> +}
>> +
>> +static void rtas_ibm_query_pe_dma_window(PowerPCCPU *cpu,
>> +                                         sPAPRMachineState *spapr,
>> +                                         uint32_t token, uint32_t nargs,
>> +                                         target_ulong args,
>> +                                         uint32_t nret, target_ulong rets)
>> +{
>> +    CPUPPCState *env = &cpu->env;
>> +    sPAPRPHBState *sphb;
>> +    uint64_t buid;
>> +    uint32_t avail, addr, pgmask = 0;
>> +    unsigned current;
>> +
>> +    if ((nargs != 3) || (nret != 5)) {
>> +        goto param_error_exit;
>> +    }
>> +
>> +    buid = ((uint64_t)rtas_ld(args, 1) << 32) | rtas_ld(args, 2);
>> +    addr = rtas_ld(args, 0);
>> +    sphb = spapr_pci_find_phb(spapr, buid);
>> +    if (!sphb || !sphb->ddw_enabled) {
>> +        goto param_error_exit;
>> +    }
>> +
>> +    current = spapr_phb_get_active_win_num(sphb);
>> +    avail = (sphb->windows_supported > current) ?
>> +            (sphb->windows_supported - current) : 0;
>> +
>> +    /* Work out supported page masks */
>> +    pgmask = spapr_query_mask(env->sps.sps, sphb->page_size_mask);
>> +
>> +    rtas_st(rets, 0, RTAS_OUT_SUCCESS);
>> +    rtas_st(rets, 1, avail);
>> +
>> +    /*
>> +     * This is "Largest contiguous block of TCEs allocated specifically
>> +     * for (that is, are reserved for) this PE".
>> +     * Return the maximum number as all RAM was in 4K pages.
>> +     */
>> +    rtas_st(rets, 2, sphb->dma64_window_size >> SPAPR_TCE_PAGE_SHIFT);
>> +    rtas_st(rets, 3, pgmask);
>> +    rtas_st(rets, 4, 0); /* DMA migration mask, not supported */
>> +
>> +    trace_spapr_iommu_ddw_query(buid, addr, avail, sphb->dma64_window_size,
>> +                                pgmask);
>> +    return;
>> +
>> +param_error_exit:
>> +    rtas_st(rets, 0, RTAS_OUT_PARAM_ERROR);
>> +}
>> +
>> +static void rtas_ibm_create_pe_dma_window(PowerPCCPU *cpu,
>> +                                          sPAPRMachineState *spapr,
>> +                                          uint32_t token, uint32_t nargs,
>> +                                          target_ulong args,
>> +                                          uint32_t nret, target_ulong rets)
>> +{
>> +    sPAPRPHBState *sphb;
>> +    sPAPRTCETable *tcet = NULL;
>> +    uint32_t addr, page_shift, window_shift, liobn;
>> +    uint64_t buid;
>> +    long ret;
>> +
>> +    if ((nargs != 5) || (nret != 4)) {
>
> Pascal bracket style again :-(


Am I breaking any code design guideline here?


>
>> +        goto param_error_exit;
>> +    }
>> +
>> +    buid = ((uint64_t)rtas_ld(args, 1) << 32) | rtas_ld(args, 2);


But here braces are ok? :-/


>> +    addr = rtas_ld(args, 0);
>> +    sphb = spapr_pci_find_phb(spapr, buid);
>> +    if (!sphb || !sphb->ddw_enabled) {
>> +        goto param_error_exit;
>> +    }
>> +
>> +    page_shift = rtas_ld(args, 3);
>> +    window_shift = rtas_ld(args, 4);
>> +    liobn = spapr_phb_get_free_liobn(sphb);
>> +
>> +    if (!liobn || !(sphb->page_size_mask & (1ULL << page_shift))) {
>> +        goto hw_error_exit;
>> +    }
>> +
>> +    ret = spapr_phb_dma_init_window(sphb, liobn, page_shift,
>> +                                    1ULL << window_shift);
>
> As already mentioned in a comment to another patch in this series, I
> think it maybe might be better to do some sanity checks on the
> window_shift value, too?


Well, as you suggested, I added a check to spapr_phb_dma_init_window() 
which makes this code return RTAS_OUT_HW_ERROR. Or I can add this here:

if (window_shift < page_shift) {
     goto param_error_exit;
}

and RTAS handler will return RTAS_OUT_PARAM_ERROR.
SPAPR does not say what is the correct reponse in this case...


>
>> +    tcet = spapr_tce_find_by_liobn(liobn);
>> +    trace_spapr_iommu_ddw_create(buid, addr, 1ULL << page_shift,
>> +                                 1ULL << window_shift,
>> +                                 tcet ? tcet->bus_offset : 0xbaadf00d,
>> +                                 liobn, ret);
>> +    if (ret || !tcet) {
>> +        goto hw_error_exit;
>> +    }
>> +
>> +    rtas_st(rets, 0, RTAS_OUT_SUCCESS);
>> +    rtas_st(rets, 1, liobn);
>> +    rtas_st(rets, 2, tcet->bus_offset >> 32);
>> +    rtas_st(rets, 3, tcet->bus_offset & ((uint32_t) -1));
>
> Why don't you simply use 0xffffffff instead of ((uint32_t) -1) ?
> That's shorter and much easier to understand at a first glance than
> calulating the type-cast in your brain ;-)


At a first glance I cannot tell if there are 7 or 8 or 9 "f"s in 
0xffffffff. I may accidentally add/remove one "f" and nobody will notice. 
Such typecast of (-1) is quite typical.


>
>> +
>> +    return;
>> +
>> +hw_error_exit:
>> +    rtas_st(rets, 0, RTAS_OUT_HW_ERROR);
>> +    return;
>> +
>> +param_error_exit:
>> +    rtas_st(rets, 0, RTAS_OUT_PARAM_ERROR);
>> +}
>> +
>> +static void rtas_ibm_remove_pe_dma_window(PowerPCCPU *cpu,
>> +                                          sPAPRMachineState *spapr,
>> +                                          uint32_t token, uint32_t nargs,
>> +                                          target_ulong args,
>> +                                          uint32_t nret, target_ulong rets)
>> +{
>> +    sPAPRPHBState *sphb;
>> +    sPAPRTCETable *tcet;
>> +    uint32_t liobn;
>> +    long ret;
>> +
>> +    if ((nargs != 1) || (nret != 1)) {
>
>   (╯°□°)╯︵ ┻━┻
>
>> +        goto param_error_exit;
>> +    }
>> +
>> +    liobn = rtas_ld(args, 0);
>> +    tcet = spapr_tce_find_by_liobn(liobn);
>> +    if (!tcet) {
>> +        goto param_error_exit;
>> +    }
>> +
>> +    sphb = SPAPR_PCI_HOST_BRIDGE(OBJECT(tcet)->parent);
>> +    if (!sphb || !sphb->ddw_enabled) {
>> +        goto param_error_exit;
>> +    }
>> +
>> +    ret = spapr_phb_dma_remove_window(sphb, tcet);
>> +    trace_spapr_iommu_ddw_remove(liobn, ret);
>> +    if (ret) {
>> +        goto hw_error_exit;
>> +    }
>> +
>> +    rtas_st(rets, 0, RTAS_OUT_SUCCESS);
>> +    return;
>> +
>> +hw_error_exit:
>> +    rtas_st(rets, 0, RTAS_OUT_HW_ERROR);
>> +    return;
>> +
>> +param_error_exit:
>> +    rtas_st(rets, 0, RTAS_OUT_PARAM_ERROR);
>> +}
>> +
>> +static void rtas_ibm_reset_pe_dma_window(PowerPCCPU *cpu,
>> +                                         sPAPRMachineState *spapr,
>> +                                         uint32_t token, uint32_t nargs,
>> +                                         target_ulong args,
>> +                                         uint32_t nret, target_ulong rets)
>> +{
>> +    sPAPRPHBState *sphb;
>> +    uint64_t buid;
>> +    uint32_t addr;
>> +    long ret;
>> +
>> +    if ((nargs != 3) || (nret != 1)) {
>
>   ┬─┬ ︵ /(.□. \）
>
>> +        goto param_error_exit;
>> +    }
>> +
>> +    buid = ((uint64_t)rtas_ld(args, 1) << 32) | rtas_ld(args, 2);
>> +    addr = rtas_ld(args, 0);
>> +    sphb = spapr_pci_find_phb(spapr, buid);
>> +    if (!sphb || !sphb->ddw_enabled) {
>> +        goto param_error_exit;
>> +    }
>> +
>> +    ret = spapr_phb_dma_reset(sphb);
>> +    trace_spapr_iommu_ddw_reset(buid, addr, ret);
>> +    if (ret) {
>> +        goto hw_error_exit;
>> +    }
>> +
>> +    rtas_st(rets, 0, RTAS_OUT_SUCCESS);
>> +
>> +    return;
>> +
>> +hw_error_exit:
>> +    rtas_st(rets, 0, RTAS_OUT_HW_ERROR);
>> +    return;
>> +
>> +param_error_exit:
>> +    rtas_st(rets, 0, RTAS_OUT_PARAM_ERROR);
>> +}
>> +
>> +static void spapr_rtas_ddw_init(void)
>> +{
>> +    spapr_rtas_register(RTAS_IBM_QUERY_PE_DMA_WINDOW,
>> +                        "ibm,query-pe-dma-window",
>> +                        rtas_ibm_query_pe_dma_window);
>> +    spapr_rtas_register(RTAS_IBM_CREATE_PE_DMA_WINDOW,
>> +                        "ibm,create-pe-dma-window",
>> +                        rtas_ibm_create_pe_dma_window);
>> +    spapr_rtas_register(RTAS_IBM_REMOVE_PE_DMA_WINDOW,
>> +                        "ibm,remove-pe-dma-window",
>> +                        rtas_ibm_remove_pe_dma_window);
>> +    spapr_rtas_register(RTAS_IBM_RESET_PE_DMA_WINDOW,
>> +                        "ibm,reset-pe-dma-window",
>> +                        rtas_ibm_reset_pe_dma_window);
>> +}
>> +
>> +type_init(spapr_rtas_ddw_init)
>
>   Thomas
>


-- 
Alexey