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Message-ID: <aDCo_SczQOUaB2rS@google.com>
Date: Fri, 23 May 2025 09:57:33 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: Chao Gao <chao.gao@...el.com>
Cc: x86@...nel.org, linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
tglx@...utronix.de, dave.hansen@...el.com, pbonzini@...hat.com,
peterz@...radead.org, rick.p.edgecombe@...el.com, weijiang.yang@...el.com,
john.allen@....com, bp@...en8.de, chang.seok.bae@...el.com, xin3.li@...el.com,
Dave Hansen <dave.hansen@...ux.intel.com>, Eric Biggers <ebiggers@...gle.com>,
"H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>, Kees Cook <kees@...nel.org>,
Maxim Levitsky <mlevitsk@...hat.com>, Mitchell Levy <levymitchell0@...il.com>,
Nikolay Borisov <nik.borisov@...e.com>, Oleg Nesterov <oleg@...hat.com>,
Sohil Mehta <sohil.mehta@...el.com>, Stanislav Spassov <stanspas@...zon.de>,
Vignesh Balasubramanian <vigbalas@....com>
Subject: Re: [PATCH v8 0/6] Introduce CET supervisor state support
On Thu, May 22, 2025, Chao Gao wrote:
> Chao Gao (4):
> x86/fpu/xstate: Differentiate default features for host and guest FPUs
> x86/fpu: Initialize guest FPU permissions from guest defaults
> x86/fpu: Initialize guest fpstate and FPU pseudo container from guest
> defaults
> x86/fpu: Remove xfd argument from __fpstate_reset()
>
> Yang Weijiang (2):
> x86/fpu/xstate: Introduce "guest-only" supervisor xfeature set
> x86/fpu/xstate: Add CET supervisor xfeature support as a guest-only
> feature
Acked-by: Sean Christopherson <seanjc@...gle.com>
Side topic, and *probably* unrelated to this series, I tripped the following
WARN when running it through the KVM tests (though I don't think it has anything
to do with KVM?). The WARN is the version of xfd_validate_state() that's guarded
by CONFIG_X86_DEBUG_FPU=y.
WARNING: CPU: 232 PID: 15391 at arch/x86/kernel/fpu/xstate.c:1543 xfd_validate_state+0x65/0x70
Modules linked in: kvm_intel kvm irqbypass vfat fat dummy bridge stp llc intel_vsec cdc_acm cdc_ncm cdc_eem cdc_ether usbnet mii xhci_pci xhci_hcd ehci_pci ehci_hcd [last unloaded: kvm_intel]
CPU: 232 UID: 0 PID: 15391 Comm: DefaultEventMan Tainted: G S 6.15.0-smp--3542d5d75b5c-cet #678 NONE
Tainted: [S]=CPU_OUT_OF_SPEC
Hardware name: Google Izumi-EMR/izumi, BIOS 0.20240807.2-0 10/09/2024
RIP: 0010:xfd_validate_state+0x65/0x70
Code: 10 4c 3b 60 18 74 23 49 81 fe 80 c4 45 ab 74 15 4d 0b 7e 08 49 f7 d7 49 85 df 75 0e 5b 41 5c 41 5e 41 5f 5d c3 40 84 ed 75 f2 <0f> 0b eb ee 0f 1f 80 00 00 00 00 66 0f 1f 00 0f 1f 44 00 00 48 89
RSP: 0018:ff7ada85584a3e08 EFLAGS: 00010246
RAX: ff2c5d2908a53940 RBX: 00000000000e00ff RCX: ff2c5d2908a53940
RDX: 0000000000000001 RSI: 00000000000e00ff RDI: ff2c5d2908a521c0
RBP: 0000000000000001 R08: 0000000000000001 R09: 0000000000000000
R10: ffffffffaa56fa4d R11: 0000000000000000 R12: 0000000000040000
R13: ff2c5d2908a521c0 R14: ffffffffab45c480 R15: 0000000000000000
FS: 00007f21084d6700(0000) GS:ff2c5da752b41000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 00000001ca832006 CR4: 0000000000f73ef0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe07f0 DR7: 0000000000000400
PKRU: 00000000
Call Trace:
<TASK>
fpu__clear_user_states+0x9c/0x100
arch_do_signal_or_restart+0x142/0x210
exit_to_user_mode_loop+0x55/0x100
do_syscall_64+0x205/0x2c0
entry_SYSCALL_64_after_hwframe+0x4b/0x53
RIP: 0033:0x55ad185f2ee0
Code: 8c fc 48 8d 0d 6e d5 8e fc 4c 8d 05 64 cb 78 fc bf 03 00 00 00 ba 25 03 00 00 49 89 c1 31 c0 e8 e6 2e 08 00 cc cc cc cc cc cc <55> 48 89 e5 41 57 41 56 41 55 41 54 53 48 83 ec 28 49 89 d7 49 89
RSP: 002b:00007f21084d3e38 EFLAGS: 00000246 ORIG_RAX: 00000000000001b9
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 000055ad18136f73
RDX: 00007f21084d3e40 RSI: 00007f21084d3f70 RDI: 000000000000001b
RBP: 00007f21084d4f90 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000001
R13: 000011f03fbc2f00 R14: ffffffffffffffff R15: 0000000000000000
</TASK>
irq event stamp: 368
hardirqs last enabled at (367): [<ffffffffaaf5f1b8>] _raw_write_unlock_irq+0x28/0x40
hardirqs last disabled at (368): [<ffffffffaaf5487d>] __schedule+0x1bd/0xea0
softirqs last enabled at (0): [<ffffffffaa2aa1ca>] copy_process+0x38a/0x1350
softirqs last disabled at (0): [<0000000000000000>] 0x0
---[ end trace 0000000000000000 ]---
But I've hit the WARN once before, so whatever is going on is pre-existing. I
haven't done any experiments to see if the WARN fires more frequently with this
series. I mentioned it here purely out of convenience.
------------[ cut here ]------------
WARNING: CPU: 77 PID: 14821 at arch/x86/kernel/fpu/xstate.c:1466 xfd_validate_state+0x4a/0x50
Modules linked in: kvm_intel kvm irqbypass vfat fat dummy bridge stp llc intel_vsec cdc_acm cdc_ncm cdc_eem cdc_ether usbnet mii xhci_pci xhci_hcd ehci_pci ehci_hcd sr_mod cdrom loop [last unloaded: kvm]
CPU: 77 UID: 0 PID: 14821 Comm: futex-default-S Tainted: G S W 6.15.0-smp--a2104d5ba341-sink #605 NONE
Tainted: [S]=CPU_OUT_OF_SPEC, [W]=WARN
Hardware name: Google Izumi-EMR/izumi, BIOS 0.20240807.2-0 10/09/2024
RIP: 0010:xfd_validate_state+0x4a/0x50
Code: 50 0a a9 4d 8b 80 90 17 00 00 49 3b 48 18 74 1a 48 81 ff 80 a4 65 a7 74 0d 48 0b 47 08 48 f7 d0 48 85 f0 75 05 c3 84 d2 75 fb <0f> 0b c3 0f 1f 00 66 0f 1f 00 0f 1f 44 00 00 48 89 f8 48 8b 7f 10
RSP: 0018:ff1ba89ef124fe58 EFLAGS: 00010246
RAX: 0000000000000000 RBX: ffffffffa644871e RCX: 0000000000040000
RDX: 0000000000000001 RSI: 00000000000600ff RDI: ffffffffa765a480
RBP: 0000000000000000 R08: ff137abd4db65bc0 R09: 0000000000000000
R10: ffffffffa6775f8d R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: ff137abd4db65b80 R15: 0000000000000000
FS: 00007fea8bce7700(0000) GS:ff137afc151b3000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 00000001a87c0004 CR4: 0000000000f73ef0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe07f0 DR7: 0000000000000400
PKRU: 00000000
Call Trace:
<TASK>
fpu__clear_user_states+0x92/0xf0
arch_do_signal_or_restart+0x134/0x200
syscall_exit_to_user_mode+0x8a/0x110
do_syscall_64+0x8b/0x160
entry_SYSCALL_64_after_hwframe+0x4b/0x53
RIP: 0033:0x563afb5588c0
Code: f0 e9 df fc ff ff 48 8b 5d 88 4d 89 f0 e9 b5 fe ff ff cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc <55> 48 89 e5 41 57 41 56 41 55 41 54 53 50 49 89 d7 e8 0a 6f f2 01
RSP: 002b:00007fea8bce4e78 EFLAGS: 00000202 ORIG_RAX: 00000000000000e8
RAX: 0000000000000000 RBX: 000011fcd50a6dd0 RCX: 0000563af84d6b30
RDX: 00007fea8bce4e80 RSI: 00007fea8bce4fb0 RDI: 000000000000001e
RBP: 00007fea8bce5c30 R08: 0000000000000000 R09: 00007fea8bce6ca0
R10: 00000000000007d0 R11: 0000000000000202 R12: 0000000063239328
R13: 00000000680b9c83 R14: 00000000000007d0 R15: 000011fcd5c46150
</TASK>
irq event stamp: 496018
hardirqs last enabled at (496017): [<ffffffffa7158965>] _raw_spin_unlock_irqrestore+0x35/0x50
hardirqs last disabled at (496018): [<ffffffffa714e6fd>] __schedule+0x1bd/0xe90
softirqs last enabled at (495074): [<ffffffffa64c02ec>] __irq_exit_rcu+0x6c/0x130
softirqs last disabled at (495065): [<ffffffffa64c02ec>] __irq_exit_rcu+0x6c/0x130
---[ end trace 0000000000000000 ]---
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