svn commit: r286787 - head/sys/x86/x86

[Jason Harmening]

On 08/16/15 04:50, Konstantin Belousov wrote:
> On Sun, Aug 16, 2015 at 12:03:58PM +0300, Konstantin Belousov wrote:
>> On Sun, Aug 16, 2015 at 10:16:53AM +0200, Roger Pau Monn?? wrote:
>>> pmap_map_io_transient contains some of this logic, but it uses
>>> vmem_alloc (with M_WAITOK) instead of a pcpu pageframe, which defeats
>>> part of the purpose of this change and cannot be used as-is.
>>
>> This logic can be repeated, but it is probably too much for the purpose.
>> It would be enough to have single frame (we cannot reuse CMAP1),
>> protected by a spin mutex.  I do not see much sense in providing
>> optimized per-cpu frames for this case.
> 
> Like this.  I only compiled the patch.
> 
> diff --git a/sys/amd64/amd64/pmap.c b/sys/amd64/amd64/pmap.c
> index 1e64fc8..9d2b2d9 100644
> --- a/sys/amd64/amd64/pmap.c
> +++ b/sys/amd64/amd64/pmap.c
> @@ -390,6 +390,8 @@ static struct md_page *pv_table;
>   */
>  pt_entry_t *CMAP1 = 0;
>  caddr_t CADDR1 = 0;
> +static vm_offset_t qframe = 0;
> +static struct mtx qframe_mtx;
>  
>  static int pmap_flags = PMAP_PDE_SUPERPAGE;	/* flags for x86 pmaps */
>  
> @@ -1031,7 +1033,7 @@ pmap_init(void)
>  	struct pmap_preinit_mapping *ppim;
>  	vm_page_t mpte;
>  	vm_size_t s;
> -	int i, pv_npg;
> +	int error, i, pv_npg;
>  
>  	/*
>  	 * Initialize the vm page array entries for the kernel pmap's
> @@ -1112,6 +1114,12 @@ pmap_init(void)
>  		printf("PPIM %u: PA=%#lx, VA=%#lx, size=%#lx, mode=%#x\n", i,
>  		    ppim->pa, ppim->va, ppim->sz, ppim->mode);
>  	}
> +
> +	mtx_init(&qframe_mtx, "qfrmlk", NULL, MTX_SPIN);
> +	error = vmem_alloc(kernel_arena, PAGE_SIZE, M_BESTFIT | M_WAITOK,
> +	    (vmem_addr_t *)&qframe);
> +	if (error != 0)
> +		panic("qframe allocation failed");
>  }
>  
>  static SYSCTL_NODE(_vm_pmap, OID_AUTO, pde, CTLFLAG_RD, 0,
> @@ -7019,13 +7027,28 @@ pmap_unmap_io_transient(vm_page_t page[], vm_offset_t vaddr[], int count,
>  vm_offset_t
>  pmap_quick_enter_page(vm_page_t m)
>  {
> +	vm_paddr_t paddr;
>  
> -	return (PHYS_TO_DMAP(VM_PAGE_TO_PHYS(m)));
> +	paddr = VM_PAGE_TO_PHYS(m);
> +	if (paddr < dmaplimit)
> +		return (PHYS_TO_DMAP(paddr));
> +	mtx_lock_spin(&qframe_mtx);
> +	KASSERT(*vtopte(qframe) == 0, ("qframe busy"));
> +	pte_store(vtopte(qframe), paddr | X86_PG_RW | X86_PG_V | X86_PG_A |
> +	    X86_PG_M | pmap_cache_bits(kernel_pmap, m->md.pat_mode, 0));
> +	invlpg(qframe);
> +	return (qframe);
>  }
>  
>  void
>  pmap_quick_remove_page(vm_offset_t addr)
>  {
> +
> +	if (addr != qframe)
> +		return;
> +	pte_store(vtopte(qframe), 0);
> +	invlpg(qframe);
> +	mtx_unlock_spin(&qframe_mtx);
>  }
>  
>  #include "opt_ddb.h"
> 

That looks fine to me.