Re: kern/57833: kernel panic on xorg exit

[Taylor R Campbell <riastradh%NetBSD.org@localhost>]

The following reply was made to PR kern/57833; it has been noted by GNATS.

From: Taylor R Campbell <riastradh%NetBSD.org@localhost>
To: Ramiro Aceves <ea1abz%gmail.com@localhost>
Cc: "David H. Gutteridge" <david%gutteridge.ca@localhost>,
	gnats-bugs%NetBSD.org@localhost, netbsd-bugs%NetBSD.org@localhost, RVP <rvp%SDF.ORG@localhost>
Subject: Re: kern/57833: kernel panic on xorg exit
Date: Thu, 18 Jan 2024 03:11:09 +0000

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 OK, that's getting pretty weird.  Can you please revert all your local
 changes, and apply just the attached patch?
 
 If it crashes, same request as before -- `print *obj', `info locals'
 in all frames, dmesg, plus `print segs[0]' in the bus_dmamem_kmap
 frame (which was frame 5 in your last reply).
 
 
 P.S. The pr57833-i915gempages-v5.patch file I gave you earlier is a
 git patch series.  You can apply it on top of a git repository wit the
 `git am' command, and bisect with `git bisect'.  If the smaller
 i915_gem_phys.patch attached to this message works, we can use that to
 try finding which other part of the changes might have broken things.
 
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 diff --git a/sys/external/bsd/drm2/dist/drm/i915/gem/i915_gem_phys.c b/sys/=
 external/bsd/drm2/dist/drm/i915/gem/i915_gem_phys.c
 index 3f68276eea5f..375246c43af6 100644
 --- a/sys/external/bsd/drm2/dist/drm/i915/gem/i915_gem_phys.c
 +++ b/sys/external/bsd/drm2/dist/drm/i915/gem/i915_gem_phys.c
 @@ -24,6 +24,98 @@ __KERNEL_RCSID(0, "$NetBSD: i915_gem_phys.c,v 1.8 2021/1=
 2/19 12:45:43 riastradh
  #include "i915_gem_region.h"
  #include "i915_scatterlist.h"
 =20
 +#ifdef __NetBSD__
 +
 +#include <uvm/uvm.h>
 +#include <uvm/uvm_extern.h>
 +
 +#include <machine/pmap_private.h> /* kvtopte, pmap_pte_clearbits */
 +
 +/*
 + * Version of bus_dmamem_map that uses pmap_kenter_pa, not pmap_enter,
 + * so that it isn't affected by pmap_page_protect on the physical
 + * address.  Adapted from sys/arch/x86/x86/bus_dma.c.
 + */
 +static int
 +bus_dmamem_kmap(bus_dma_tag_t t, bus_dma_segment_t *segs, int nsegs,
 +    size_t size, void **kvap, int flags)
 +{
 +	vaddr_t va;
 +	bus_addr_t addr;
 +	int curseg;
 +	const uvm_flag_t kmflags =3D
 +	    (flags & BUS_DMA_NOWAIT) !=3D 0 ? UVM_KMF_NOWAIT : 0;
 +	u_int pmapflags =3D PMAP_WIRED | VM_PROT_READ | VM_PROT_WRITE;
 +
 +	CTASSERT(PAGE_SIZE =3D=3D 4096);
 +	printf("%s: t=3D%p segs=3D%p nsegs=3D%d size=3D0x%zx kvap=3D%p flags=3D0x=
 %x\n",
 +	    __func__, t, segs, nsegs, size, kvap, flags);
 +
 +	size =3D round_page(size);
 +	if (flags & BUS_DMA_NOCACHE)
 +		pmapflags |=3D PMAP_NOCACHE;
 +
 +	va =3D uvm_km_alloc(kernel_map, size, 0, UVM_KMF_VAONLY | kmflags);
 +
 +	if (va =3D=3D 0)
 +		return ENOMEM;
 +
 +	printf("%s: va=3D%"PRIxVADDR"\n", __func__, va);
 +	*kvap =3D (void *)va;
 +
 +	for (curseg =3D 0; curseg < nsegs; curseg++) {
 +		printf("%s:%d size=3D0x%"PRIxBUSSIZE
 +		    " curseg=3D%d addr=3D0x%"PRIxBUSADDR" len=3D0x%"PRIxBUSSIZE
 +		    " end=3D0x%"PRIxBUSADDR"\n",
 +		    __func__, __LINE__, size,
 +		    curseg, segs[curseg].ds_addr, segs[curseg].ds_len,
 +		    segs[curseg].ds_addr + segs[curseg].ds_len);
 +		for (addr =3D segs[curseg].ds_addr;
 +		    addr < (segs[curseg].ds_addr + segs[curseg].ds_len);
 +		    addr +=3D PAGE_SIZE, va +=3D PAGE_SIZE, size -=3D PAGE_SIZE) {
 +			printf("%s:%d: size=3D0x%"PRIxBUSSIZE
 +			    " addr=3D0x%"PRIxBUSADDR,
 +			    __func__, __LINE__, size, addr);
 +			if (size =3D=3D 0)
 +				panic("_bus_dmamem_kmap: size botch");
 +			pmap_kenter_pa(va, addr,
 +			    VM_PROT_READ | VM_PROT_WRITE,
 +			    pmapflags);
 +		}
 +	}
 +	pmap_update(pmap_kernel());
 +
 +	return 0;
 +}
 +
 +static void
 +bus_dmamem_kunmap(bus_dma_tag_t t, void *kva, size_t size)
 +{
 +	pt_entry_t *pte, opte;
 +	vaddr_t va, sva, eva;
 +
 +	KASSERTMSG(((uintptr_t)kva & PGOFSET) =3D=3D 0, "kva=3D%p", kva);
 +
 +	size =3D round_page(size);
 +	sva =3D (vaddr_t)kva;
 +	eva =3D sva + size;
 +
 +	/*
 +	 * mark pages cacheable again.
 +	 */
 +	for (va =3D sva; va < eva; va +=3D PAGE_SIZE) {
 +		pte =3D kvtopte(va);
 +		opte =3D *pte;
 +		if ((opte & PTE_PCD) !=3D 0)
 +			pmap_pte_clearbits(pte, PTE_PCD);
 +	}
 +	pmap_kremove((vaddr_t)kva, size);
 +	pmap_update(pmap_kernel());
 +	uvm_km_free(kernel_map, (vaddr_t)kva, size, UVM_KMF_VAONLY);
 +}
 +
 +#endif
 +
  #include <linux/nbsd-namespace.h>
 =20
  static int i915_gem_object_get_pages_phys(struct drm_i915_gem_object *obj)
 @@ -65,7 +157,7 @@ static int i915_gem_object_get_pages_phys(struct drm_i91=
 5_gem_object *obj)
  	if (ret)
  		return -ENOMEM;
  	KASSERT(rsegs =3D=3D 1);
 -	ret =3D -bus_dmamem_map(dmat, &obj->mm.u.phys.seg, 1,
 +	ret =3D -bus_dmamem_kmap(dmat, &obj->mm.u.phys.seg, 1,
  	    roundup_pow_of_two(obj->base.size), &vaddr,
  	    BUS_DMA_WAITOK|BUS_DMA_COHERENT);
  	if (ret)
 @@ -83,7 +175,12 @@ static int i915_gem_object_get_pages_phys(struct drm_i9=
 15_gem_object *obj)
  	if (!st)
  		goto err_pci;
 =20
 +#ifdef __NetBSD__
 +	if (sg_alloc_table_from_bus_dmamem(st, dmat, &obj->mm.u.phys.seg, 1,
 +		GFP_KERNEL))
 +#else
  	if (sg_alloc_table(st, 1, GFP_KERNEL))
 +#endif
  		goto err_st;
 =20
  	sg =3D st->sgl;
 @@ -151,7 +248,7 @@ err_st:
  err_pci:
  #ifdef __NetBSD__
  	if (vaddr) {
 -		bus_dmamem_unmap(dmat, vaddr,
 +		bus_dmamem_kunmap(dmat, vaddr,
  		    roundup_pow_of_two(obj->base.size));
  	}
  	obj->mm.u.phys.kva =3D NULL;
 @@ -225,7 +322,7 @@ i915_gem_object_put_pages_phys(struct drm_i915_gem_obje=
 ct *obj,
  	kfree(pages);
 =20
  #ifdef __NetBSD__
 -	bus_dmamem_unmap(dmat, obj->mm.u.phys.kva,
 +	bus_dmamem_kunmap(dmat, obj->mm.u.phys.kva,
  	    roundup_pow_of_two(obj->base.size));
  	obj->mm.u.phys.kva =3D NULL;
  	bus_dmamem_free(dmat, &obj->mm.u.phys.seg, 1);
 
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