6.6-stable patches

added patches:
	kvm-arm64-fix-kernel-bug-due-to-bad-backport-of-fpsimd-sve-sme-fix.patch

diff --git a/queue-6.6/kvm-arm64-fix-kernel-bug-due-to-bad-backport-of-fpsimd-sve-sme-fix.patch b/queue-6.6/kvm-arm64-fix-kernel-bug-due-to-bad-backport-of-fpsimd-sve-sme-fix.patch
new file mode 100644 (file)
index 0000000..f70151b
--- /dev/null
+++ b/queue-6.6/kvm-arm64-fix-kernel-bug-due-to-bad-backport-of-fpsimd-sve-sme-fix.patch
@@ -0,0 +1,86 @@
+From will@kernel.org  Fri Aug 22 16:24:21 2025
+From: Will Deacon <will@kernel.org>
+Date: Fri, 22 Aug 2025 15:04:02 +0100
+Subject: KVM: arm64: Fix kernel BUG() due to bad backport of FPSIMD/SVE/SME fix
+To: stable@vger.kernel.org
+Cc: linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, Will Deacon <will@kernel.org>, Ard Biesheuvel <ardb@kernel.org>, Lee Jones <lee@kernel.org>, Sasha Levin <sashal@kernel.org>, Greg Kroah-Hartman <gregkh@linuxfoundation.org>, Mark Rutland <mark.rutland@arm.com>, Fuad Tabba <tabba@google.com>, Marc Zyngier <maz@kernel.org>
+Message-ID: <20250822140402.2688-1-will@kernel.org>
+
+From: Will Deacon <will@kernel.org>
+
+Upstream commit fbc7e61195e2 ("KVM: arm64: Unconditionally save+flush
+host FPSIMD/SVE/SME state") relies on interrupts being disabled during
+fpsimd_save_and_flush_cpu_state() so that a softirq cannot be taken
+while the host floating point context is being saved and potentially try
+to use kernel-mode NEON.
+
+Unfortunately, stable kernels without 9b19700e623f ("arm64: fpsimd: Drop
+unneeded 'busy' flag") leave interrupts enabled in
+fpsimd_save_and_flush_cpu_state() and so the BUG_ON(!may_use_simd()) in
+kernel_neon_begin() has been observed to trigger in real-world usage:
+
+ |  kernel BUG at arch/arm64/kernel/fpsimd.c:1904!
+ |  Internal error: Oops - BUG: 00000000f2000800 [#1] PREEMPT SMP
+ |
+ |  Call trace:
+ |   kernel_neon_begin+0xdc/0x12c
+ |   ...
+ |   crypto_aead_decrypt+0x5c/0x6c
+ |   seqiv_aead_decrypt+0x88/0x9c
+ |   crypto_aead_decrypt+0x5c/0x6c
+ |   esp_input+0x280/0x364
+ |   xfrm_input+0x6ac/0x16f8
+ |   ...
+ |   net_rx_action+0x13c/0x31c
+ |   handle_softirqs+0x124/0x3d0
+ |   __do_softirq+0x14/0x20
+ |   ____do_softirq+0x10/0x20
+ |   call_on_irq_stack+0x3c/0x74
+ |   do_softirq_own_stack+0x1c/0x2c
+ |   __irq_exit_rcu+0x54/0xb4
+ |   irq_exit_rcu+0x10/0x1c
+ |   el1_interrupt+0x38/0x58
+ |   el1h_64_irq_handler+0x18/0x24
+ |   el1h_64_irq+0x68/0x6c
+ |   fpsimd_save+0xe4/0x130
+ |   kvm_arch_vcpu_load_fp+0x2c/0x58
+ |   kvm_arch_vcpu_load+0x88/0x26c
+ |   kvm_sched_in+0x2c/0x3c
+
+Given that 9b19700e623f ("arm64: fpsimd: Drop unneeded 'busy' flag") is
+not a fix in its own right, has non-trivial dependencies and is a
+reasonably invasive change to the in-kernel use of fpsimd, opt instead
+for a simple fix to use the softirq-safe {get,put}_cpu_fpsimd_context()
+helpers in fpsimd_save_and_flush_cpu_state().
+
+Cc: Ard Biesheuvel <ardb@kernel.org>
+Cc: Lee Jones <lee@kernel.org>
+Cc: Sasha Levin <sashal@kernel.org>
+Cc: Mark Rutland <mark.rutland@arm.com>
+Cc: Fuad Tabba <tabba@google.com>
+Cc: Marc Zyngier <maz@kernel.org>
+Cc: <stable@vger.kernel.org> # 5.15.y, 6.1.y and 6.6.y
+Fixes: 806d5c1e1d2e ("KVM: arm64: Unconditionally save+flush host FPSIMD/SVE/SME state") # 6.6.y
+Fixes: 04c50cc23a49 ("KVM: arm64: Unconditionally save+flush host FPSIMD/SVE/SME state") # 6.1.y
+Fixes: 5289ac43b69c ("KVM: arm64: Unconditionally save+flush host FPSIMD/SVE/SME state") # 5.15.y
+Signed-off-by: Will Deacon <will@kernel.org>
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+---
+ arch/arm64/kernel/fpsimd.c |    4 ++--
+ 1 file changed, 2 insertions(+), 2 deletions(-)
+
+--- a/arch/arm64/kernel/fpsimd.c
++++ b/arch/arm64/kernel/fpsimd.c
+@@ -1876,10 +1876,10 @@ void fpsimd_save_and_flush_cpu_state(voi
+       if (!system_supports_fpsimd())
+               return;
+       WARN_ON(preemptible());
+-      __get_cpu_fpsimd_context();
++      get_cpu_fpsimd_context();
+       fpsimd_save();
+       fpsimd_flush_cpu_state();
+-      __put_cpu_fpsimd_context();
++      put_cpu_fpsimd_context();
+ }
+ 
+ #ifdef CONFIG_KERNEL_MODE_NEON

diff --git a/queue-6.6/series b/queue-6.6/series
index 0b982c5690eb6cfb234c1d0a7e60486bbe7a0dfe..0b9a5f1a2c0c30f05eb7e7bd882b35241915bb99 100644 (file)
--- a/queue-6.6/series
+++ b/queue-6.6/series
@@ -476,3 +476,4 @@ cpufreq-cppc-set-the-frequency-used-for-computing-the-capacity.patch
 arm64-amu-use-capacity_ref_freq-to-set-amu-ratio.patch
 topology-set-capacity_freq_ref-in-all-cases.patch
 sched-fair-fix-frequency-selection-for-non-invariant-case.patch
+kvm-arm64-fix-kernel-bug-due-to-bad-backport-of-fpsimd-sve-sme-fix.patch