Re: [Xen-devel] [PATCH v02 1/7] arm: introduce remoteprocessor iommu module

[Andrii Tseglytskyi <andrii.tseglytskyi@xxxxxxxxxxxxxxx>]

Hi Stefano,

Thanks a lot for review.
Sorry for so late reply - I was in big rush last days.

On Fri, Jul 4, 2014 at 4:59 PM, Stefano Stabellini
<stefano.stabellini@xxxxxxxxxxxxx> wrote:
> On Thu, 26 Jun 2014, Andrii Tseglytskyi wrote:
>> This is a fisrst patch from patch series which was
>> developed to handle remote (external) processors
>> memory management units. Remote processors are
>> typically used for graphic rendering (GPUs) and
>> high quality video decoding (IPUs). They are typically
>> installed on such multimedia SoCs as OMAP4 / OMAP5.
>>
>> As soon as remoteprocessor MMU typically works with
>> pagetables filled by physical addresses, which are
>> allocated by domU kernel, it is almost impossible to
>> use them under Xen, intermediate physical addresses
>> allocated by kernel, need to be translated to machine
>> addresses.
>>
>> This patch introduces a simple framework to perform
>> pfn -> mfn translation for external MMUs.
>> It introduces basic data structures and algorithms
>> needed for translation.
>>
>> Typically, when MMU is configured, some it registers
>> are updated by new values. Introduced frameworks
>> uses traps as starting point of remoteproc MMUs
>> pagetables translation.
>>
>> Change-Id: Ia4d311a40289df46a003f5ae8706c150bee1885d
>> Signed-off-by: Andrii Tseglytskyi <andrii.tseglytskyi@xxxxxxxxxxxxxxx>
>
> There is one problem with this patch: you need to find a way to "pin"
> the p2m entries for the pfns and mfns found in the pagetables translated
> by remoteproc_iommu.c.  Otherwise Xen might decide to change the pfn to
> mfn mappings for the domain, breaking the pagetables already translated
> by remoteproc_iommu.c.  pfn to mfn mappings are not guaranteed to be
> stable. At the moment Xen on ARM wouldn't change pfn to mfn mappings
> under the guest feet, but features like memory sharing or swapping,
> supported on x86, could cause it to happen.
>
> In the past I tried to introduce a way to "pin the mappings, but never
> finished to upstream the patches, because it didn't need it anymore.
>

Thank you for this comment. I never thought that Xen may change
mappings, while domain is running. For sure it must be handled in my
code. Need to investigate this more deeply.

>
> Give a look at:
>
> http://marc.info/?l=xen-devel&m=138029864707973
>
> In particular you would need to introduce something like
> the pin function and call it from mmu_translate_pagetable.
>
>

OK. Thank you.

>
>>  xen/arch/arm/Makefile              |    1 +
>>  xen/arch/arm/remoteproc_iommu.c    |  412 
>> ++++++++++++++++++++++++++++++++++++
>>  xen/include/xen/remoteproc_iommu.h |   79 +++++++
>>  3 files changed, 492 insertions(+)
>>  create mode 100644 xen/arch/arm/remoteproc_iommu.c
>>  create mode 100644 xen/include/xen/remoteproc_iommu.h
>>
>> diff --git a/xen/arch/arm/Makefile b/xen/arch/arm/Makefile
>> index d70f6d5..0204d1c 100644
>> --- a/xen/arch/arm/Makefile
>> +++ b/xen/arch/arm/Makefile
>> @@ -15,6 +15,7 @@ obj-y += io.o
>>  obj-y += irq.o
>>  obj-y += kernel.o
>>  obj-y += mm.o
>> +obj-y += remoteproc_iommu.o
>>  obj-y += p2m.o
>>  obj-y += percpu.o
>>  obj-y += guestcopy.o
>> diff --git a/xen/arch/arm/remoteproc_iommu.c 
>> b/xen/arch/arm/remoteproc_iommu.c
>> new file mode 100644
>> index 0000000..b4d22d9
>> --- /dev/null
>> +++ b/xen/arch/arm/remoteproc_iommu.c
>> @@ -0,0 +1,412 @@
>> +/*
>> + * xen/arch/arm/remoteproc_iommu.c
>> + *
>> + * Andrii Tseglytskyi <andrii.tseglytskyi@xxxxxxxxxxxxxxx>
>> + * Copyright (c) 2014 GlobalLogic
>> + *
>> + * 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.
>> + */
>> +
>> +#include <xen/config.h>
>> +#include <xen/lib.h>
>> +#include <xen/errno.h>
>> +#include <xen/mm.h>
>> +#include <xen/vmap.h>
>> +#include <xen/init.h>
>> +#include <xen/sched.h>
>> +#include <xen/stdbool.h>
>> +#include <asm/system.h>
>> +#include <asm/current.h>
>> +#include <asm/io.h>
>> +#include <asm/p2m.h>
>> +
>> +#include <xen/remoteproc_iommu.h>
>> +
>> +#include "io.h"
>> +
>> +static struct mmu_info *mmu_list[] = {
>> +};
>> +
>> +#define mmu_for_each(pfunc, data)                       \
>> +({                                                      \
>> +    u32 __i;                                            \
>> +    int __res = 0;                                      \
>> +                                                        \
>> +    for ( __i = 0; __i < ARRAY_SIZE(mmu_list); __i++ )  \
>> +    {                                                   \
>> +        __res |= pfunc(mmu_list[__i], data);            \
>> +    }                                                   \
>> +    __res;                                              \
>> +})
>> +
>> +static int mmu_check_mem_range(struct mmu_info *mmu, paddr_t addr)
>> +{
>> +    if ( (addr >= mmu->mem_start) && (addr < (mmu->mem_start + 
>> mmu->mem_size)) )
>> +        return 1;
>> +
>> +    return 0;
>> +}
>> +
>> +static inline struct mmu_info *mmu_lookup(u32 addr)
>> +{
>> +    u32 i;
>> +
>> +    /* enumerate all registered MMU's and check is address in range */
>> +    for ( i = 0; i < ARRAY_SIZE(mmu_list); i++ )
>> +    {
>> +        if ( mmu_check_mem_range(mmu_list[i], addr) )
>> +            return mmu_list[i];
>> +    }
>> +
>> +    return NULL;
>> +}
>> +
>> +static int mmu_mmio_check(struct vcpu *v, paddr_t addr)
>> +{
>> +    return mmu_for_each(mmu_check_mem_range, addr);
>> +}
>> +
>> +static int mmu_copy_pagetable(struct mmu_info *mmu, struct mmu_pagetable 
>> *pgt)
>> +{
>> +    void __iomem *pagetable = NULL;
>> +    u32 maddr, i;
>> +
>> +    ASSERT(mmu);
>> +    ASSERT(pgt);
>> +
>> +    if ( !pgt->paddr )
>> +        return -EINVAL;
>> +
>> +    /* pagetable size can be more than one page */
>> +    for ( i = 0; i < MMU_PGD_TABLE_SIZE(mmu) / PAGE_SIZE; i++ )
>> +    {
>> +        /* lookup address where remoteproc pagetable is stored by kernel */
>> +        maddr = p2m_lookup(current->domain, pgt->paddr + i * PAGE_SIZE, 
>> NULL);
>> +        if ( !maddr )
>> +        {
>> +            pr_mmu("failed to translate 0x%08lx to maddr", pgt->paddr + i * 
>> PAGE_SIZE);
>> +            return -EINVAL;
>> +        }
>> +
>> +        pagetable = ioremap_nocache(maddr, MMU_PGD_TABLE_SIZE(mmu));
>> +        if ( !pagetable )
>> +        {
>> +            pr_mmu("failed to map pagetable");
>> +            return -EINVAL;
>> +        }
>> +
>> +        /* copy pagetable to hypervisor memory */
>> +        clean_and_invalidate_xen_dcache_va_range(pagetable, PAGE_SIZE);
>> +        memcpy((u32*)((u32)pgt->kern_pagetable + i * PAGE_SIZE), pagetable, 
>> PAGE_SIZE);
>> +
>> +        iounmap(pagetable);
>> +    }
>> +
>> +    return 0;
>> +}
>> +
>> +struct mmu_pagetable *mmu_pagetable_lookup(struct mmu_info *mmu, u32 addr, 
>> bool is_maddr)
>> +{
>> +    struct mmu_pagetable *pgt;
>> +    u32 pgt_addr;
>> +
>> +    list_for_each_entry(pgt, &mmu->pagetables_list, link_node)
>> +    {
>> +        if ( is_maddr )
>> +            pgt_addr = pgt->maddr;
>> +        else
>> +            pgt_addr = pgt->paddr;
>> +
>> +        if ( pgt_addr == addr )
>> +            return pgt;
>> +    }
>> +
>> +    return NULL;
>> +}
>> +
>> +static struct mmu_pagetable *mmu_alloc_pagetable(struct mmu_info *mmu, u32 
>> paddr)
>> +{
>> +    struct mmu_pagetable *pgt;
>> +    u32 pgt_size = MMU_PGD_TABLE_SIZE(mmu);
>> +
>> +    pgt = xzalloc_bytes(sizeof(struct mmu_pagetable));
>> +    if ( !pgt )
>> +    {
>> +        pr_mmu("failed to alloc pagetable structure");
>> +        return NULL;
>> +    }
>> +
>> +    /* allocate pagetable managed by hypervisor */
>> +    pgt->hyp_pagetable = xzalloc_bytes(pgt_size);
>> +    if ( !pgt->hyp_pagetable )
>> +    {
>> +        pr_mmu("failed to alloc private hyp_pagetable");
>> +        return NULL;
>> +    }
>> +
>> +    /* alocate pagetable for ipa storing */
>> +    pgt->kern_pagetable = xzalloc_bytes(pgt_size);
>> +    if ( !pgt->kern_pagetable )
>> +    {
>> +        pr_mmu("failed to alloc private kern_pagetable");
>> +        return NULL;
>> +    }
>> +
>> +    pr_mmu("private pagetables for 0x%08x paddr %u bytes (main 0x%08x, temp 
>> 0x%08x)",
>> +           paddr, pgt_size, (u32)__pa(pgt->hyp_pagetable), 
>> (u32)__pa(pgt->kern_pagetable));
>> +
>> +    pgt->paddr = paddr;
>> +
>> +    list_add(&pgt->link_node, &mmu->pagetables_list);
>> +
>> +    return pgt;
>> +}
>> +
>> +static u32 mmu_translate_pagetable(struct mmu_info *mmu, u32 paddr)
>> +{
>> +    struct mmu_pagetable *pgt;
>> +    int res;
>> +
>> +    /* lookup using machine address first */
>> +    pgt = mmu_pagetable_lookup(mmu, paddr, true);
>> +    if ( !pgt )
>> +    {
>> +        /* lookup using kernel physical address */
>> +        pgt = mmu_pagetable_lookup(mmu, paddr, false);
>> +        if ( !pgt )
>> +        {
>> +            /* if pagetable doesn't exists in lookup list - allocate it */
>> +            pgt = mmu_alloc_pagetable(mmu, paddr);
>> +        }
>> +    }
>> +
>> +    pgt->maddr = MMU_INVALID_ADDRESS;
>> +
>> +    /* copy pagetable from domain to hypervisor */
>> +    res = mmu_copy_pagetable(mmu, pgt);
>> +     if ( res )
>> +        return res;
>> +
>> +    /* translate pagetable */
>> +    pgt->maddr = mmu->translate_pfunc(mmu, pgt);
>> +    return pgt->maddr;
>> +}
>> +
>> +static u32 mmu_trap_translate_pagetable(struct mmu_info *mmu, mmio_info_t 
>> *info)
>> +{
>> +    register_t *reg;
>> +    bool valid_trap = false;
>> +    u32 i, paddr;
>> +
>> +    reg = select_user_reg(guest_cpu_user_regs(), info->dabt.reg);
>> +
>> +    ASSERT(reg);
>> +
>> +    paddr = *reg;
>> +    if ( !paddr )
>> +        return MMU_INVALID_ADDRESS;
>> +
>> +    /* check is the register is a valid TTB register */
>> +    for ( i = 0; i < mmu->num_traps; i++ )
>> +    {
>> +        if ( mmu->trap_offsets[i] == (info->gpa - mmu->mem_start) )
>> +        {
>> +            valid_trap = true;
>> +            break;
>> +        }
>> +    }
>> +
>> +    if ( !valid_trap )
>> +        return MMU_INVALID_ADDRESS;
>> +
>> +    return mmu_translate_pagetable(mmu, paddr);
>> +}
>> +
>> +u32 mmu_translate_second_level(struct mmu_info *mmu, struct mmu_pagetable 
>> *pgt,
>> +                               u32 maddr, u32 hyp_addr)
>
> Is this actually used anywhere?
>
>
>> +{
>> +    u32 *pte_table = NULL, *hyp_pte_table = NULL, pte_table_size = 
>> PAGE_SIZE;
>> +    u32 i;
>> +
>> +    /* remap second level translation table */
>> +    pte_table = ioremap_nocache(maddr, MMU_PTE_TABLE_SIZE(mmu));
>> +    if ( !pte_table )
>> +    {
>> +        pr_mmu("failed to map pte_table");
>> +        return MMU_INVALID_ADDRESS;
>> +    }
>> +
>> +    /* allocate new second level pagetable once */
>> +    if ( 0 == hyp_addr )
>> +    {
>> +        if ( MMU_PTE_TABLE_SIZE(mmu) > PAGE_SIZE )
>> +            pte_table_size = MMU_PTE_TABLE_SIZE(mmu);
>> +
>> +        hyp_pte_table = xzalloc_bytes(pte_table_size);
>> +        if ( !hyp_pte_table )
>> +        {
>> +            pr_mmu("failed to alloc new iopt");
>> +            return MMU_INVALID_ADDRESS;
>> +        }
>> +    }
>> +    else
>> +    {
>> +        hyp_pte_table = __va(hyp_addr & 
>> MMU_SECTION_MASK(mmu->pg_data->pte_shift));
>> +    }
>> +
>> +    /* 2-nd level translation */
>> +    for ( i = 0; i < MMU_PTRS_PER_PTE(mmu); i++ )
>> +    {
>> +        paddr_t pt_maddr, pt_paddr, pt_flags;
>> +        u32 pt_mask = MMU_SECTION_MASK(mmu->pg_data->pte_shift);
>> +
>> +        if ( !pte_table[i] )
>> +        {
>> +            /* handle the case when page was removed */
>> +            if ( unlikely(hyp_pte_table[i]) )
>> +            {
>> +                hyp_pte_table[i] = 0;
>> +            }
>> +
>> +            continue;
>> +        }
>> +
>> +        pt_paddr = pte_table[i] & pt_mask;
>> +        pt_flags = pte_table[i] & ~pt_mask;
>> +        pt_maddr = p2m_lookup(current->domain, pt_paddr, NULL);
>> +        ASSERT(pt_maddr != INVALID_PADDR);
>> +
>> +        hyp_pte_table[i] = pt_maddr | pt_flags;
>> +        pgt->page_counter++;
>> +    }
>> +
>> +    iounmap(pte_table);
>> +
>> +    clean_and_invalidate_xen_dcache_va_range(hyp_pte_table, 
>> MMU_PTE_TABLE_SIZE(mmu));
>> +    return __pa(hyp_pte_table);
>> +}
>> +
>> +static int mmu_mmio_read(struct vcpu *v, mmio_info_t *info)
>> +{
>> +    struct mmu_info *mmu = NULL;
>> +    unsigned long flags;
>> +    register_t *r;
>> +
>> +    r = select_user_reg(guest_cpu_user_regs(), info->dabt.reg);
>> +
>> +    ASSERT(r);
>
> If you check on the domid in mmu_mmio_write, I would check here too
>
>
>> +    mmu = mmu_lookup(info->gpa);
>> +    if ( !mmu )
>> +    {
>> +        pr_mmu("can't get mmu for addr 0x%08x", (u32)info->gpa);
>> +        return -EINVAL;
>> +    }
>> +
>> +    spin_lock_irqsave(&mmu->lock, flags);
>> +    *r = readl(mmu->mem_map + ((u32)(info->gpa) - mmu->mem_start));
>> +    spin_unlock_irqrestore(&mmu->lock, flags);
>> +
>> +    return 1;
>
> It looks like you are returning the mfns here, is that correct?
>

No. This callback due to following reasons:
- to trap MMU registers I need to unmap memory, where they are mapped.
- I call table translation logic if only one specific register is
accessed for write
- I can't unmap not less than one page of memory
- if I unmap 1 page and more - I need to pass through all kernel read
/ write calls to this page, otherwise kernel code fails

>
>
>> +static int mmu_mmio_write(struct vcpu *v, mmio_info_t *info)
>> +{
>> +    struct mmu_info *mmu = NULL;
>> +    unsigned long flags;
>> +    register_t *r;
>> +    u32 new_addr, val;
>> +
>> +    r = select_user_reg(guest_cpu_user_regs(), info->dabt.reg);
>> +
>> +    ASSERT(r);
>> +
>> +    /* dom0 should not access remoteproc MMU */
>> +    if ( 0 == current->domain->domain_id )
>> +        return 1;
>
> This is too specific to one particular configuration.
> Would it be possible to generalize this somehow? At the very least you
> could introduce an XSM label to access the pagetables, so that you can
> dynamically configure the domains the can write to them.
>

I need to think about this. Sounds reasonable.

>
>> +    /* find corresponding MMU */
>> +    mmu = mmu_lookup(info->gpa);
>> +    if ( !mmu )
>> +    {
>> +        pr_mmu("can't get mmu for addr 0x%08x", (u32)info->gpa);
>> +        return -EINVAL;
>> +    }
>> +
>> +    ASSERT(v->domain == current->domain);
>
> You can remove this assert.
>

OK.

>
>> +    spin_lock_irqsave(&mmu->lock, flags);
>> +
>> +    /* get new address of translated pagetable */
>> +    new_addr = mmu_trap_translate_pagetable(mmu, info);
>> +    if ( MMU_INVALID_ADDRESS != new_addr )
>> +        val = new_addr;
>> +    else
>> +        val = *r;
>> +
>> +    writel(val, mmu->mem_map + ((u32)(info->gpa) - mmu->mem_start));
>> +    spin_unlock_irqrestore(&mmu->lock, flags);
>> +
>> +    return 1;
>> +}
>> +
>> +static int mmu_init(struct mmu_info *mmu, u32 data)
>> +{
>> +    ASSERT(mmu);
>> +    ASSERT(!mmu->mem_map);
>> +
>> +    INIT_LIST_HEAD(&mmu->pagetables_list);
>> +
>> +    /* map MMU memory */
>> +    mmu->mem_map = ioremap_nocache(mmu->mem_start, mmu->mem_size);
>> +     if ( !mmu->mem_map )
>> +    {
>> +        pr_mmu("failed to map memory");
>> +        return -EINVAL;
>> +    }
>> +
>> +    pr_mmu("memory map = 0x%pS", _p(mmu->mem_map));
>> +
>> +    spin_lock_init(&mmu->lock);
>> +
>> +    return 0;
>> +}
>> +
>> +static int mmu_init_all(void)
>> +{
>> +    int res;
>> +
>> +    res = mmu_for_each(mmu_init, 0);
>> +    if ( res )
>> +    {
>> +        printk("%s error during init %d\n", __func__, res);
>> +        return res;
>> +    }
>> +
>> +    return 0;
>> +}
>> +
>> +const struct mmio_handler remoteproc_mmio_handler = {
>> +    .check_handler = mmu_mmio_check,
>> +    .read_handler  = mmu_mmio_read,
>> +    .write_handler = mmu_mmio_write,
>> +};
>> +
>> +__initcall(mmu_init_all);
>> +
>> +/*
>> + * Local variables:
>> + * mode: C
>> + * c-file-style: "BSD"
>> + * c-basic-offset: 4
>> + * indent-tabs-mode: nil
>> + * End:
>> + */
>> diff --git a/xen/include/xen/remoteproc_iommu.h 
>> b/xen/include/xen/remoteproc_iommu.h
>> new file mode 100644
>> index 0000000..22e2951
>> --- /dev/null
>> +++ b/xen/include/xen/remoteproc_iommu.h
>> @@ -0,0 +1,79 @@
>> +/*
>> + * xen/include/xen/remoteproc_iommu.h
>> + *
>> + * Andrii Tseglytskyi <andrii.tseglytskyi@xxxxxxxxxxxxxxx>
>> + * Copyright (c) 2014 GlobalLogic
>> + *
>> + * 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.
>> + */
>> +
>> +#ifndef _REMOTEPROC_IOMMU_H_
>> +#define _REMOTEPROC_IOMMU_H_
>> +
>> +#include <asm/types.h>
>> +
>> +#define MMU_SECTION_SIZE(shift)     (1UL << (shift))
>> +#define MMU_SECTION_MASK(shift)     (~(MMU_SECTION_SIZE(shift) - 1))
>> +
>> +/* 4096 first level descriptors for "supersection" and "section" */
>> +#define MMU_PTRS_PER_PGD(mmu)       (1UL << (32 - 
>> (mmu->pg_data->pgd_shift)))
>> +#define MMU_PGD_TABLE_SIZE(mmu)     (MMU_PTRS_PER_PGD(mmu) * sizeof(u32))
>> +
>> +/* 256 second level descriptors for "small" and "large" pages */
>> +#define MMU_PTRS_PER_PTE(mmu)       (1UL << ((mmu->pg_data->pgd_shift) - 
>> (mmu->pg_data->pte_shift)))
>> +#define MMU_PTE_TABLE_SIZE(mmu)     (MMU_PTRS_PER_PTE(mmu) * sizeof(u32))
>> +
>> +/* 16 sections in supersection */
>> +#define MMU_SECTION_PER_SUPER(mmu)  (1UL << ((mmu->pg_data->super_shift) - 
>> (mmu->pg_data->section_shift)))
>> +
>> +#define MMU_INVALID_ADDRESS ((u32)(-1))
>> +
>> +#define pr_mmu(fmt, ...) \
>> +     printk("%s: %s: "fmt"\n", __func__, ((mmu) ? (mmu)->name : ""), 
>> ##__VA_ARGS__)
>> +
>> +struct pagetable_data {
>> +     /* 1st level translation */
>> +     u32 pgd_shift;
>> +     u32 pte_shift;
>> +     u32 super_shift;
>> +     u32 section_shift;
>> +     /* 2nd level translation */
>> +     u32 pte_large_shift;
>> +};
>> +
>> +struct mmu_pagetable {
>> +     u32                                     *hyp_pagetable;
>> +     u32                                     *kern_pagetable;
>> +     u32                                     paddr;
>> +     u32                                     maddr;
>> +     struct list_head        link_node;
>> +     u32                                     page_counter;
>> +};
>> +
>> +struct mmu_info {
>> +     const char                              *name;
>> +     const struct pagetable_data *pg_data;
>> +     /* register where phys pointer to pagetable is stored */
>> +     u32                                     *trap_offsets;
>> +     paddr_t                         mem_start;
>> +     u32                                     mem_size;
>> +     spinlock_t                      lock;
>> +     struct list_head        pagetables_list;
>> +     u32                                     num_traps;
>> +     void __iomem            *mem_map;
>> +     u32     (*translate_pfunc)(struct mmu_info *, struct mmu_pagetable *);
>> +     void (*print_pagetable_pfunc)(struct mmu_info *);
>> +};
>> +
>> +u32 mmu_translate_second_level(struct mmu_info *mmu, struct mmu_pagetable 
>> *pgt,
>> +                               u32 maddr, u32 hyp_addr);
>> +
>> +#endif /* _REMOTEPROC_IOMMU_H_ */
>> --
>> 1.7.9.5
>>
>>
>> _______________________________________________
>> Xen-devel mailing list
>> Xen-devel@xxxxxxxxxxxxx
>> http://lists.xen.org/xen-devel
>>



-- 

Andrii Tseglytskyi | Embedded Dev
GlobalLogic
www.globallogic.com

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