Re: 回复: Re: 回复: Re: 回复: Re: [PATCH v1 1/2] drm/qxl: replace ioremap by ioremap_cache on arm64
Christian König
christian.koenig at amd.com
Thu Mar 24 09:20:40 UTC 2022
Hi Cong,
when I understand Robin correctly all mapping (host, guest, kernel,
userspace etc..) must have the same caching attributes unless you use
the S2FWB feature introduced with Armv8.4.
If you don't follow those rules you usually run into coherency issues or
even worse system hangs. So you not only need to adjust the kernel
mappings, but also the function for userspace mappings to follow those
rules.
Additional to that I think I read Robin correctly that mapping the
resource write combined should be sufficient to solve your problem. So I
suggest to use that instead.
On the other hand if you manage to fix this completely for arm64 by
updating all the places to use cached mappings I'm fine with it as well.
It's then up to Dave to decide if that's something we want because QXL
is intentionally emulating a hardware device as far as I know.
Regards,
Christian.
Am 24.03.22 um 08:04 schrieb liucong2 at kylinos.cn:
>
> Hi Christian,
>
>
> Can you help explain more detail under what circumstances userspace
> mapping
>
> will be problematic, you mean cached mappings also need adjustment in
>
> function ttm_prot_from_caching?
>
>
> Regards,
>
> Cong.
>
>
>
>
> *主 题：*Re: 回复: Re: 回复: Re: [PATCH v1 1/2] drm/qxl: replace ioremap
> by ioremap_cache on arm64
> *日 期：*2022-03-23 18:17
> *发件人：*Christian König
> *收件人：*liucong2 at kylinos.cnairlied@redhat.comkraxel at redhat.comairlied@linux.iedaniel at ffwll.chray.huang@amd.comvirtualization at lists.linux-foundation.orgspice-devel@lists.freedesktop.orgdri-devel at lists.freedesktop.org
>
>
> Hi Cong,
>
> yes I've seen that, but that is still not sufficient.
>
> You need to update the check in ttm_module.c as well or otherwise
> your userspace mapping might not work correctly either.
>
> Regards,
> Christian.
>
> Am 23.03.22 um 11:00 schrieb liucong2 at kylinos.cn:
>>
>> Hi Christian,
>>
>>
>> another commit fix the case in ttm. I send two patches at the
>> same time, but seems I miss
>>
>> '--cover-letter' when run format-patch or some other bad
>> operation.
>>
>> ----
>>
>>
>> Regards,
>>
>> Cong.
>>
>>
>>
>>
>> *主 题：*Re: 回复: Re: [PATCH v1 1/2] drm/qxl: replace
>> ioremap by ioremap_cache on arm64
>> *日 期：*2022-03-23 17:34
>> *发件人：*Christian König
>> *收件人：*liucong2 at kylinos.cnairlied@redhat.comkraxel at redhat.comairlied@linux.iedaniel at ffwll.chray.huang@amd.comvirtualization at lists.linux-foundation.orgspice-devel@lists.freedesktop.orgdri-devel at lists.freedesktop.org
>>
>>
>> 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 at 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：*CongLiuairlied at redhat.comkraxel@redhat.comairlied at linux.iedaniel@ffwll.chray.huang at amd.comvirtualization@lists.linux-foundation.orgspice-devel at 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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