[tip: x86/urgent] x86/pkeys: Add quirk to disable PKU when XFEATURE_PKRU is missing

[tip-bot2 for Akihiro Suda]

The following commit has been merged into the x86/urgent branch of tip:

Commit-ID:     86049b4cf7a41cc5b33a556fc25772cc325f474f
Gitweb:        https://git.kernel.org/tip/86049b4cf7a41cc5b33a556fc25772cc325f474f
Author:        Akihiro Suda <akihiro.suda.cz@xxxxxxxxxxxxx>
AuthorDate:    Fri, 14 Mar 2025 17:48:18 +09:00
Committer:     Ingo Molnar <mingo@xxxxxxxxxx>
CommitterDate: Wed, 19 Mar 2025 22:37:32 +01:00

x86/pkeys: Add quirk to disable PKU when XFEATURE_PKRU is missing

Even when X86_FEATURE_PKU and X86_FEATURE_OSPKE are available,
XFEATURE_PKRU can be missing on some popular VM environments
such as Apple Virtualization.

In such a case, pkeys has to be disabled to avoid a boot time hang:

  WARNING: CPU: 0 PID: 1 at arch/x86/kernel/fpu/xstate.c:1003 get_xsave_addr_user+0x28/0x40
  (...)
  Call Trace:
   <TASK>
   ? get_xsave_addr_user+0x28/0x40
   ? __warn.cold+0x8e/0xea
   ? get_xsave_addr_user+0x28/0x40
   ? report_bug+0xff/0x140
   ? handle_bug+0x3b/0x70
   ? exc_invalid_op+0x17/0x70
   ? asm_exc_invalid_op+0x1a/0x20
   ? get_xsave_addr_user+0x28/0x40
   copy_fpstate_to_sigframe+0x1be/0x380
   ? __put_user_8+0x11/0x20
   get_sigframe+0xf1/0x280
   x64_setup_rt_frame+0x67/0x2c0
   arch_do_signal_or_restart+0x1b3/0x240
   syscall_exit_to_user_mode+0xb0/0x130
   do_syscall_64+0xab/0x1a0
   entry_SYSCALL_64_after_hwframe+0x77/0x7f

Tested with MacOS 13.5.2 running on MacBook Pro 2020 with
Intel(R) Core(TM) i7-1068NG7 CPU @ 2.30GHz.

[ mingo: Issue a boot time warning to give VMs a chance to fix this. ]

Fixes: 70044df250d0 ("x86/pkeys: Update PKRU to enable all pkeys before XSAVE")
Signed-off-by: Akihiro Suda <akihiro.suda.cz@xxxxxxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20250314084818.2826-1-akihiro.suda.cz@xxxxxxxxxxxxx
---
 arch/x86/kernel/cpu/common.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 7cce91b..4e6cf0b 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -519,6 +519,17 @@ static __always_inline void setup_pku(struct cpuinfo_x86 *c)
 	if (c == &boot_cpu_data) {
 		if (pku_disabled || !cpu_feature_enabled(X86_FEATURE_PKU))
 			return;
+		if (!cpu_has_xfeatures(XFEATURE_PKRU, NULL)) {
+			/*
+			 * Missing XFEATURE_PKRU is not really a valid
+			 * configuration at this point, but apparently
+			 * Apple Virtualization is affected by this,
+			 * so return with a FW warning instead of crashing
+			 * the bootup:
+			 */
+			WARN_ONCE(1, FW_BUG "Invalid XFEATURE_PKRU configuration.\n");
+			return;
+		}
 		/*
 		 * Setting CR4.PKE will cause the X86_FEATURE_OSPKE cpuid
 		 * bit to be set.  Enforce it.