Re: [Xen-devel] [PATCH v02 6/7] arm: introduce do_translate_pagetable hypercall

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Thu, 26 Jun 2014, Andrii Tseglytskyi wrote:
> The reason of the patch is the following - some remoteprocs
> are quite complicated, and their MMUs can handle several
> pagetables. Good example is a OMAP5 GPU, which allocates
> several pagetables during it work. Additional requirement
> is that not all pagetable physical addresses are stored
> in MMU registers. Some pagetables may be allocated and
> then their physical addresses are sent to GPU using private
> message loop between GPU kernel driver and GPU remoteproc.
> 
> Patch is developed to handle this. At any moment of time
> kernel can perform translation of such pagetables, before
> sending their addresses to GPU remoteproc.
> 
> Change-Id: Ie84012163205c3a2f920dc4cf07327a244647c93
> Signed-off-by: Andrii Tseglytskyi <andrii.tseglytskyi@xxxxxxxxxxxxxxx>
> ---
>  xen/arch/arm/remoteproc_iommu.c |   22 ++++++++++++++++++++++
>  xen/arch/arm/traps.c            |    1 +
>  xen/include/public/xen.h        |    1 +
>  xen/include/xen/hypercall.h     |   12 ++++++++++++
>  4 files changed, 36 insertions(+)
> 
> diff --git a/xen/arch/arm/remoteproc_iommu.c b/xen/arch/arm/remoteproc_iommu.c
> index 3b3da3b..316ceb4 100644
> --- a/xen/arch/arm/remoteproc_iommu.c
> +++ b/xen/arch/arm/remoteproc_iommu.c
> @@ -23,6 +23,8 @@
>  #include <xen/init.h>
>  #include <xen/sched.h>
>  #include <xen/stdbool.h>
> +#include <xen/hypercall.h>
> +#include <xen/guest_access.h>
>  #include <asm/system.h>
>  #include <asm/current.h>
>  #include <asm/io.h>
> @@ -382,6 +384,26 @@ static int mmu_init(struct mmu_info *mmu, u32 data)
>      return 0;
>  }
>  
> +long do_translate_pagetable(int cmd, 
> XEN_GUEST_HANDLE_PARAM(xen_pagetable_addr_t) pgt_addr)
> +{
> +    struct xen_pagetable_addr pgt;
> +    struct mmu_info *mmu = NULL;
> +
> +    if ( copy_from_guest(&pgt, pgt_addr, 1) )
> +        return -EFAULT;
> +
> +    mmu = mmu_lookup(pgt.reg);
> +    if ( !mmu )
> +    {
> +        pr_mmu("can't get mmu for addr 0x%08x", pgt.reg);
> +        return -EINVAL;
> +    }
> +
> +    pgt.maddr = mmu_translate_pagetable(mmu, pgt.paddr);
> +
> +    return copy_to_guest(pgt_addr, &pgt, 1);
> +}
> +
>  static int mmu_init_all(void)
>  {
>      int res;
> diff --git a/xen/arch/arm/traps.c b/xen/arch/arm/traps.c
> index 21c7b26..05b5184 100644
> --- a/xen/arch/arm/traps.c
> +++ b/xen/arch/arm/traps.c
> @@ -1012,6 +1012,7 @@ static arm_hypercall_t arm_hypercall_table[] = {
>      HYPERCALL(hvm_op, 2),
>      HYPERCALL(grant_table_op, 3),
>      HYPERCALL_ARM(vcpu_op, 3),
> +    HYPERCALL(translate_pagetable, 2),
>  };
>  
>  typedef int (*arm_psci_fn_t)(uint32_t, register_t);
> diff --git a/xen/include/public/xen.h b/xen/include/public/xen.h
> index 8c5697e..91ca6a1 100644
> --- a/xen/include/public/xen.h
> +++ b/xen/include/public/xen.h
> @@ -101,6 +101,7 @@ DEFINE_XEN_GUEST_HANDLE(xen_ulong_t);
>  #define __HYPERVISOR_kexec_op             37
>  #define __HYPERVISOR_tmem_op              38
>  #define __HYPERVISOR_xc_reserved_op       39 /* reserved for XenClient */
> +#define __HYPERVISOR_translate_pagetable  40

It might be best to introduce this hypercall as an arch memory op
(xen/arch/arm/mm.c:arch_memory_op), rather than a full blown new
hypercall. Otherwise you'll need to provide an empty stub implementation
for x86.


>  /* Architecture-specific hypercall definitions. */
>  #define __HYPERVISOR_arch_0               48
> diff --git a/xen/include/xen/hypercall.h b/xen/include/xen/hypercall.h
> index a9e5229..a025435 100644
> --- a/xen/include/xen/hypercall.h
> +++ b/xen/include/xen/hypercall.h
> @@ -136,6 +136,18 @@ extern long
>  do_tmem_op(
>      XEN_GUEST_HANDLE_PARAM(tmem_op_t) uops);
>  
> +struct xen_pagetable_addr {
> +     u32 reg;
> +     u32 paddr;
> +     u32 maddr;

Could you please comment what these fields are for exactly?


> +};
> +typedef struct xen_pagetable_addr xen_pagetable_addr_t;
> +DEFINE_XEN_GUEST_HANDLE(xen_pagetable_addr_t);
> +
> +extern long
> +do_translate_pagetable(
> +     int cmd, XEN_GUEST_HANDLE_PARAM(xen_pagetable_addr_t) pgt_addr);
> +
>  extern long
>  do_xenoprof_op(int op, XEN_GUEST_HANDLE_PARAM(void) arg);

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