Re: 回复: Re: [PATCH v1 1/2] drm/qxl: replace ioremap by ioremap_cache on arm64

["Christian König via Virtualization" <virtualization@lists.linux-foundation.org>]

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Hi Cong,

well than Dave must decide what to do here.

When QXL emulates a device it should also not use memory accesses which 
won't work on a physical device.

BTW: Your patch is really buggy, it misses the cases in ttm_module.c

Regards,
Christian.

Am 23.03.22 um 09:48 schrieb liucong2@kylinos.cn:
>
> Hi Christian,
>
>
> according to 'Arm Architecture Reference Manual Armv8,for Armv8-A
>
> architecture profile' pdf E2.6.5
>
>
> E2.6.5 Generation of Alignment faults by load/store multiple accesses to
>
>  Device memory
>
>
> When FEAT_LSMAOC is implemented and the value of the applicable nTLSMD
>
> field is 0, any memory access by an AArch32 Load Multiple or Store
>
> Multiple instruction to an address that the stage 1 translation
>
> assigns as Device-nGRE, Device-nGnRE, or Device-nGnRnE generates
>
> an Alignment fault.
>
>
> so it seems not just some ARM boards doesn't allow unaligned access to 
> MMIO
>
> space, all pci memory mapped as Device-nGnRE in arm64 cannot support
>
> unaligned access. and qxl is a device simulated by qemu, it should be 
> able to access
>
> to MMIO space in a more flexible way(PROT_NORMAL) than the real physical
>
> graphics card.
>
>
> ----
>
>
>
> Cong.
>
>
>
>
>
> *主　题：*Re: [PATCH v1 1/2] drm/qxl: replace ioremap by ioremap_cache on 
> arm64
> *日　期：*2022-03-23 15:15
> *发件人：*Christian König
> *收件人：*Cong 
> Liuairlied@redhat.comkraxel@redhat.comairlied@linux.iedaniel@ffwll.chray.huang@amd.comvirtualization@lists.linux-foundation.orgspice-devel@lists.freedesktop.orgdri-devel@lists.freedesktop.org 
>
>
>
> Am 22.03.22 um 10:34 schrieb Cong Liu:
> > qxl use ioremap to map ram_header and rom, in the arm64 implementation,
> > the device is mapped as DEVICE_nGnRE, it can not support unaligned
> > access.
>
> Well that some ARM boards doesn't allow unaligned access to MMIO space
> is a well known bug of those ARM boards.
>
> So as far as I know this is a hardware bug you are trying to workaround
> here and I'm not 100% sure that this is correct.
>
> Christian.
>
> >
> >    6.620515] pc : setup_hw_slot+0x24/0x60 [qxl]
> > [    6.620961] lr : setup_slot+0x34/0xf0 [qxl]
> > [    6.621376] sp : ffff800012b73760
> > [    6.621701] x29: ffff800012b73760 x28: 0000000000000001 x27: 
> 0000000010000000
> > [    6.622400] x26: 0000000000000001 x25: 0000000004000000 x24: 
> ffffcf376848c000
> > [    6.623099] x23: ffff0000c4087400 x22: ffffcf3718e17140 x21: 
> 0000000000000000
> > [    6.623823] x20: ffff0000c4086000 x19: ffff0000c40870b0 x18: 
> 0000000000000014
> > [    6.624519] x17: 000000004d3605ab x16: 00000000bb3b6129 x15: 
> 000000006e771809
> > [    6.625214] x14: 0000000000000001 x13: 007473696c5f7974 x12: 
> 696e696666615f65
> > [    6.625909] x11: 00000000d543656a x10: 0000000000000000 x9 : 
> ffffcf3718e085a4
> > [    6.626616] x8 : 00000000006c7871 x7 : 000000000000000a x6 : 
> 0000000000000017
> > [    6.627343] x5 : 0000000000001400 x4 : ffff800011f63400 x3 : 
> 0000000014000000
> > [    6.628047] x2 : 0000000000000000 x1 : ffff0000c40870b0 x0 : 
> ffff0000c4086000
> > [    6.628751] Call trace:
> > [    6.628994]  setup_hw_slot+0x24/0x60 [qxl]
> > [    6.629404]  setup_slot+0x34/0xf0 [qxl]
> > [    6.629790]  qxl_device_init+0x6f0/0x7f0 [qxl]
> > [    6.630235]  qxl_pci_probe+0xdc/0x1d0 [qxl]
> > [    6.630654]  local_pci_probe+0x48/0xb8
> > [    6.631027]  pci_device_probe+0x194/0x208
> > [    6.631464]  really_probe+0xd0/0x458
> > [    6.631818]  __driver_probe_device+0x124/0x1c0
> > [    6.632256]  driver_probe_device+0x48/0x130
> > [    6.632669]  __driver_attach+0xc4/0x1a8
> > [    6.633049]  bus_for_each_dev+0x78/0xd0
> > [    6.633437]  driver_attach+0x2c/0x38
> > [    6.633789]  bus_add_driver+0x154/0x248
> > [    6.634168]  driver_register+0x6c/0x128
> > [    6.635205]  __pci_register_driver+0x4c/0x58
> > [    6.635628]  qxl_init+0x48/0x1000 [qxl]
> > [    6.636013]  do_one_initcall+0x50/0x240
> > [    6.636390]  do_init_module+0x60/0x238
> > [    6.636768]  load_module+0x2458/0x2900
> > [    6.637136]  __do_sys_finit_module+0xbc/0x128
> > [    6.637561]  __arm64_sys_finit_module+0x28/0x38
> > [    6.638004]  invoke_syscall+0x74/0xf0
> > [    6.638366]  el0_svc_common.constprop.0+0x58/0x1a8
> > [    6.638836]  do_el0_svc+0x2c/0x90
> > [    6.639216]  el0_svc+0x40/0x190
> > [    6.639526]  el0t_64_sync_handler+0xb0/0xb8
> > [    6.639934]  el0t_64_sync+0x1a4/0x1a8
> > [    6.640294] Code: 910003fd f9484804 f9400c23 8b050084 (f809c083)
> > [    6.640889] ---[ end trace 95615d89b7c87f95 ]---
> >
> > Signed-off-by: Cong Liu
> > ---
> >   drivers/gpu/drm/qxl/qxl_kms.c | 10 ++++++++++
> >   1 file changed, 10 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/qxl/qxl_kms.c 
> b/drivers/gpu/drm/qxl/qxl_kms.c
> > index 4dc5ad13f12c..0e61ac04d8ad 100644
> > --- a/drivers/gpu/drm/qxl/qxl_kms.c
> > +++ b/drivers/gpu/drm/qxl/qxl_kms.c
> > @@ -165,7 +165,11 @@ int qxl_device_init(struct qxl_device *qdev,
> >   (int)qdev->surfaceram_size / 1024,
> >   (sb == 4) ? "64bit" : "32bit");
> >
> > +#ifdef CONFIG_ARM64
> > + qdev->rom = ioremap_cache(qdev->rom_base, qdev->rom_size);
> > +#else
> >   qdev->rom = ioremap(qdev->rom_base, qdev->rom_size);
> > +#endif
> >   if (!qdev->rom) {
> >   pr_err("Unable to ioremap ROM\n");
> >   r = -ENOMEM;
> > @@ -183,9 +187,15 @@ int qxl_device_init(struct qxl_device *qdev,
> >   goto rom_unmap;
> >   }
> >
> > +#ifdef CONFIG_ARM64
> > + qdev->ram_header = ioremap_cache(qdev->vram_base +
> > +   qdev->rom->ram_header_offset,
> > +   sizeof(*qdev->ram_header));
> > +#else
> >   qdev->ram_header = ioremap(qdev->vram_base +
> >     qdev->rom->ram_header_offset,
> >     sizeof(*qdev->ram_header));
> > +#endif
> >   if (!qdev->ram_header) {
> >   DRM_ERROR("Unable to ioremap RAM header\n");
> >   r = -ENOMEM;
>

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