[PATCH] PCI/MSI: Re-add checks for skip masking MSI-X on Xen PV

[Josef Johansson <josef@xxxxxxxxxxx>]

From: Josef Johansson <josef@xxxxxxxxxxx>


PCI/MSI: Re-add checks for skip masking MSI-X on Xen PV
    
'commit fcacdfbef5a1 ("PCI/MSI: Provide a new set of mask and unmask
functions")' introduced functions pci_msi_update_mask() and 
pci_msix_write_vector_ctrl() that were missing checks for
pci_msi_ignore_mask that existed in 'commit 446a98b19fd6 ("PCI/MSI: Use
new mask/unmask functions")'. This patch adds them back since it was
causing softlocks in amdgpu drivers under Xen.

As explained in 'commit 1a519dc7a73c ("PCI/MSI: Skip masking MSI-X
on Xen PV")', when running as Xen PV guest, masking MSI-X is a 
responsibility of the hypervisor.

Fixes: fcacdfbef5a1 ("PCI/MSI: Provide a new set of mask and unmask
functions")
Suggested-by: Jason Andryuk <jandryuk@xxxxxxxxx>
Signed-off-by: Josef Johansson <josef@xxxxxxxxxxx>
---

This patch solves a major issue with booting 5.15-rc1 under Xen
with amdgpu drivers. Specifically Lenovo P14s Gen 1, AMD 4750U.

The softlock below takes about ~2-3 minutes to release, and will
lock again if I switch between X and console, when staying in
X I can do things without it softlock.

I have to note that this is my first commit and PCI/MSI area is
not my area of expertise. I tried to mimic what was
obviously missing between the aforementioned commits. There may be
better ways to solve this problem, or other places to put the checks.
Should desc->msi_attrib.is_virtual be checked? It is not checked in
'commit 1a519dc7a73c ("PCI/MSI: Skip masking MSI-X on Xen PV")'

I should also note that my original problem with *flip done timeout*
inside drm during suspend/resume is not solved, but with this patch
at least the kernel boots properly.

The kernel is much more stable not running inside Xen, and much 
more stable running pci=nomsi (under Xen). Are we missing something
more regarding masking?

The error that occurs is:

kernel: ------------[ cut here ]------------
kernel: WARNING: CPU: 6 PID: 3754 at
drivers/gpu/drm/amd/amdgpu/../display/amdgp
u_dm/amdgpu_dm.c:8630 amdgpu_dm_commit_planes+0x9b4/0x9c0 [amdgpu]
kernel: Modules linked in: nf_tables nfnetlink vfat fat intel_rapl_msr wmi_bmof
intel_rapl_common pcspkr joydev uvcvideo k10temp sp5100_tco videobuf2_vmalloc vi
deobuf2_memops i2c_piix4 videobuf2_v4l2 videobuf2_common videodev mc iwlwifi thi
nkpad_acpi platform_profile ipmi_devintf ledtrig_audio ucsi_acpi cfg80211 ipmi_m
sghandler r8169 snd typec_ucsi soundcore typec rfkill wmi video amd_pmc i2c_scmi
 fuse xenfs ip_tables dm_thin_pool dm_persistent_data dm_bio_prison dm_crypt tru
sted asn1_encoder hid_multitouch amdgpu crct10dif_pclmul iommu_v2 crc32_pclmul c
rc32c_intel gpu_sched i2c_algo_bit drm_ttm_helper ttm drm_kms_helper ccp cec gha
sh_clmulni_intel sdhci_pci xhci_pci xhci_pci_renesas serio_raw cqhci drm sdhci x
hci_hcd mmc_core nvme ehci_pci ehci_hcd nvme_core xen_acpi_processor xen_privcmd
 xen_pciback xen_blkback xen_gntalloc xen_gntdev xen_evtchn uinput
kernel: CPU: 6 PID: 3754 Comm: Xorg Tainted: G   W 5.15.0-1.fc32.qubes.x86_64 #1
kernel: Hardware name: LENOVO 20Y1S02400/20Y1S02400, BIOS R1BET61W(1.30) 12/21/
2020
kernel: RIP: e030:amdgpu_dm_commit_planes+0x9b4/0x9c0 [amdgpu]
kernel: Code: 8b 45 b0 48 c7 c7 4b fc 90 c0 4c 89 55 88 8b b0 f0 03 00 00 e8 6d
cb ca ff 4c 8b 55 88 0f b6 55 ab 49 8b 72 08 e9 2b fa ff ff <0f> 0b e9 fa fe ff
ff e8 40 2f 6e c1 0f 1f 44 00 00 55 b9 27 00 00
kernel: RSP: e02b:ffffc90042d93638 EFLAGS: 00010002
kernel: RAX: ffff888110840210 RBX: 00000000000083c1 RCX: 0000000000000466
kernel: RDX: 0000000000000001 RSI: 0000000000000204 RDI: ffff888110840170
kernel: RBP: ffffc90042d936f8 R08: 0000000000000002 R09: 0000000000000001
kernel: R10: 0000000000000000 R11: ffff88810cb2e118 R12: ffff888110840210
kernel: R13: ffff88810cb2e000 R14: ffff888103d50400 R15: ffff888103bb2c00
kernel: FS:  0000718c6de4da40(0000) GS:ffff888140780000(0000)
knlGS:000000000000
0000
kernel: CS:  10000e030 DS: 0000 ES: 0000 CR0: 0000000080050033
kernel: CR2: 0000726ada294000 CR3: 0000000103f0e000 CR4: 0000000000050660
kernel: Call Trace:
kernel:  amdgpu_dm_atomic_commit_tail+0xc3e/0x1360 [amdgpu]
kernel:  commit_tail+0x94/0x130 [drm_kms_helper]
kernel:  drm_atomic_helper_commit+0x113/0x140 [drm_kms_helper]
kernel:  drm_client_modeset_commit_atomic+0x1fc/0x240 [drm]
kernel:  drm_client_modeset_commit_locked+0x53/0x80 [drm]
kernel:  drm_fb_helper_pan_display+0xdc/0x210 [drm_kms_helper]
kernel:  fb_pan_display+0x83/0x100
kernel:  fb_set_var+0x200/0x3b0
kernel:  fbcon_blank+0x186/0x280
kernel:  do_unblank_screen+0xaa/0x150
kernel:  complete_change_console+0x54/0x120
kernel:  vt_ioctl+0x31d/0x5f0
kernel:  tty_ioctl+0x312/0x780
kernel:  __x64_sys_ioctl+0x83/0xb0
kernel:  do_syscall_64+0x3b/0x90
kernel:  entry_SYSCALL_64_after_hwframe+0x44/0xae
kernel: RIP: 0033:0x718c6e33217b
kernel: Code: 0f 1e fa 48 8b 05 1d ad 0c 00 64 c7 00 26 00 00 00 48 c7 c0 ff ff
ff ff c3 66 0f 1f 44 00 00 f3 0f 1e fa b8 10 00 00 00 0f 05 <48> 3d 01 f0 ff ff
73 01 c3 48 8b 0d ed ac 0c 00 f7 d8 64 89 01 48
kernel: RSP: 002b:00007ffd5c6157c8 EFLAGS: 00000246 ORIG_RAX:
0000000000000010
kernel: RAX: ffffffffffffffda RBX: 0000000000000001 RCX: 0000718c6e33217b
kernel: RDX: 0000000000000001 RSI: 0000000000005605 RDI: 0000000000000014
kernel: RBP: 000057b9b2aa93f4 R08: 0000000000000000 R09: 0000000000000001
kernel: R10: fffffffffffff9ce R11: 0000000000000246 R12: 000057b9b2aa94b0
kernel: R13: 000057b9b2aa94a0 R14: 000057b9b2aa93f0 R15: 00007ffd5c615844
kernel: ---[ end trace 2c3e3998803422cb ]---
kernel: ------------[ cut here ]------------
kernel: WARNING: CPU: 6 PID: 3754 at
drivers/gpu/drm/amd/amdgpu/../display/amdgp
u_dm/amdgpu_dm.c:8217 prepare_flip_isr+0x64/0x70 [amdgpu]
kernel: Modules linked in: nf_tables nfnetlink vfat fat intel_rapl_msr wmi_bmof
intel_rapl_common pcspkr joydev uvcvideo k10temp sp5100_tco videobuf2_vmalloc vi
deobuf2_memops i2c_piix4 videobuf2_v4l2 videobuf2_common videodev mc iwlwifi thi
nkpad_acpi platform_profile ipmi_devintf ledtrig_audio ucsi_acpi cfg80211 ipmi_m
sghandler r8169 snd typec_ucsi soundcore typec rfkill wmi video amd_pmc i2c_scmi
 fuse xenfs ip_tables dm_thin_pool dm_persistent_data dm_bio_prison dm_crypt tru
sted asn1_encoder hid_multitouch amdgpu crct10dif_pclmul iommu_v2 crc32_pclmul c
rc32c_intel gpu_sched i2c_algo_bit drm_ttm_helper ttm drm_kms_helper ccp cec gha
sh_clmulni_intel sdhci_pci xhci_pci xhci_pci_renesas serio_raw cqhci drm sdhci x
hci_hcd mmc_core nvme ehci_pci ehci_hcd nvme_core xen_acpi_processor xen_privcmd
 xen_pciback xen_blkback xen_gntalloc xen_gntdev xen_evtchn uinput
kernel: CPU: 6 PID: 3754 Comm: Xorg Tainted: G W 5.15.0-1.fc32.qubes.x86_64 #1
kernel: Hardware name: LENOVO 20Y1S02400/20Y1S02400, BIOS R1BET61W(1.30) 12/21/
2020
kernel: RIP: e030:prepare_flip_isr+0x64/0x70 [amdgpu]
kernel: Code: 00 48 c7 80 38 01 00 00 00 00 00 00 66 90 c3 8b 97 f0 03 00 00 48
c7 c6 18 72 8d c0 48 c7 c7 90 5b a7 c0 e9 7e 6e 13 c1 0f 0b <0f> 0b eb b4 0f 1f
84 00 00 00 00 00 0f 1f 44 00 00 41 57 41 56 41
kernel: RSP: e02b:ffffc90042d93630 EFLAGS: 00010086
kernel: RAX: 0000000000000001 RBX: 00000000000083c1 RCX: 0000000000000466
kernel: RDX: 0000000000000001 RSI: 0000000000000204 RDI: ffff88810cb2e000
kernel: RBP: ffffc90042d936f8 R08: 0000000000000002 R09: 0000000000000001
kernel: R10: 0000000000000000 R11: ffff88810cb2e118 R12: ffff888110840210
kernel: R13: ffff88810cb2e000 R14: ffff888103d50400 R15: ffff888103bb2c00
kernel: FS:  0000718c6de4da40(0000) GS:ffff888140780000(0000) knlGS:000000000000
0000
kernel: CS:  10000e030 DS: 0000 ES: 0000 CR0: 0000000080050033
kernel: CR2: 0000726ada294000 CR3: 0000000103f0e000 CR4: 0000000000050660
kernel: Call Trace:
kernel:  amdgpu_dm_commit_planes+0x8bd/0x9c0 [amdgpu]
kernel:  amdgpu_dm_atomic_commit_tail+0xc3e/0x1360 [amdgpu]
kernel:  commit_tail+0x94/0x130 [drm_kms_helper]
kernel:  drm_atomic_helper_commit+0x113/0x140 [drm_kms_helper]
kernel:  drm_client_modeset_commit_atomic+0x1fc/0x240 [drm]
kernel:  drm_client_modeset_commit_locked+0x53/0x80 [drm]
kernel:  drm_fb_helper_pan_display+0xdc/0x210 [drm_kms_helper]
kernel:  fb_pan_display+0x83/0x100
kernel:  fb_set_var+0x200/0x3b0
kernel:  fbcon_blank+0x186/0x280
kernel:  do_unblank_screen+0xaa/0x150
kernel:  complete_change_console+0x54/0x120
kernel:  vt_ioctl+0x31d/0x5f0
kernel:  tty_ioctl+0x312/0x780
kernel:  __x64_sys_ioctl+0x83/0xb0
kernel:  do_syscall_64+0x3b/0x90
kernel:  entry_SYSCALL_64_after_hwframe+0x44/0xae
kernel: RIP: 0033:0x718c6e33217b
kernel: Code: 0f 1e fa 48 8b 05 1d ad 0c 00 64 c7 00 26 00 00 00 48 c7 c0 ff ff
ff ff c3 66 0f 1f 44 00 00 f3 0f 1e fa b8 10 00 00 00 0f 05 <48> 3d 01 f0 ff ff
73 01 c3 48 8b 0d ed ac 0c 00 f7 d8 64 89 01 48
kernel: RSP: 002b:00007ffd5c6157c8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
kernel: RAX: ffffffffffffffda RBX: 0000000000000001 RCX: 0000718c6e33217b
kernel: RDX: 0000000000000001 RSI: 0000000000005605 RDI: 0000000000000014
kernel: RBP: 000057b9b2aa93f4 R08: 0000000000000000 R09: 0000000000000001
kernel: R10: fffffffffffff9ce R11: 0000000000000246 R12: 000057b9b2aa94b0
kernel: R13: 000057b9b2aa94a0 R14: 000057b9b2aa93f0 R15: 00007ffd5c615844
kernel: ---[ end trace 2c3e3998803422cc ]---

It is discussed briefly at:
https://lore.kernel.org/linux-pci/CAKf6xpvGyCKVHsvauP54=0j10fxis4XiiqBNWH+1cpkbtt_QJw@xxxxxxxxxxxxxx/


diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c
index 0099a00af361..355b791e382f 100644
--- a/drivers/pci/msi.c
+++ b/drivers/pci/msi.c
@@ -148,6 +148,9 @@ static noinline void pci_msi_update_mask(struct msi_desc 
*desc, u32 clear, u32 s
        raw_spinlock_t *lock = &desc->dev->msi_lock;
        unsigned long flags;
 
+       if (pci_msi_ignore_mask || desc->msi_attrib.is_virtual)
+               return;
+
        raw_spin_lock_irqsave(lock, flags);
        desc->msi_mask &= ~clear;
        desc->msi_mask |= set;
@@ -181,6 +184,9 @@ static void pci_msix_write_vector_ctrl(struct msi_desc 
*desc, u32 ctrl)
 {
        void __iomem *desc_addr = pci_msix_desc_addr(desc);
 
+       if (pci_msi_ignore_mask || desc->msi_attrib.is_virtual)
+               return;
+
        writel(ctrl, desc_addr + PCI_MSIX_ENTRY_VECTOR_CTRL);
 }

--
2.31.1