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Wed, 14 May 2025 10:44:05 -0700 (PDT) Date: Wed, 14 May 2025 19:43:45 +0200 In-Reply-To: <20250514174339.1834871-9-ardb+git@google.com> Precedence: bulk X-Mailing-List: linux-efi@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20250514174339.1834871-9-ardb+git@google.com> X-Developer-Key: i=ardb@kernel.org; a=openpgp; fpr=F43D03328115A198C90016883D200E9CA6329909 X-Developer-Signature: v=1; a=openpgp-sha256; l=1405; i=ardb@kernel.org; h=from:subject; bh=TxFz/hG01vyA1ZDzUGKKYj1NGAs9wXcTsurQl3x2mv4=; b=owGbwMvMwCFmkMcZplerG8N4Wi2JIUPlWqiwsrlNUoHqW/v7Ui9uq92Lzc5f1aDO/jh5Sb1fx 6+z3kc6SlkYxDgYZMUUWQRm/3238/REqVrnWbIwc1iZQIYwcHEKwEQCvjEyHOi68Gim9dW3Bd76 sn/tflxf2yIwn0XwqEn4l55ZF47WMDMy3GvUDTDOz7l4UdB6wdp1hx8qN+Q/kzllfp9vf+e51Ef fGAE= X-Mailer: git-send-email 2.49.0.1101.gccaa498523-goog Message-ID: <20250514174339.1834871-14-ardb+git@google.com> Subject: [RFC PATCH 5/7] arm64/efi: Use a semaphore to protect the EFI stack and FP/SIMD state From: Ard Biesheuvel To: linux-efi@vger.kernel.org Cc: linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Ard Biesheuvel , Will Deacon , Mark Rutland , Sebastian Andrzej Siewior , Peter Zijlstra From: Ard Biesheuvel Replace the spinlock in the arm64 glue code with a semaphore, so that the CPU can preempted while running the EFI runtime service. Signed-off-by: Ard Biesheuvel --- arch/arm64/kernel/efi.c | 13 ++++++++++--- 1 file changed, 10 insertions(+), 3 deletions(-) diff --git a/arch/arm64/kernel/efi.c b/arch/arm64/kernel/efi.c index 44ad5e759af4..d01ae156bb63 100644 --- a/arch/arm64/kernel/efi.c +++ b/arch/arm64/kernel/efi.c @@ -164,12 +164,19 @@ asmlinkage efi_status_t efi_handle_corrupted_x18(efi_status_t s, const char *f) return s; } -static DEFINE_RAW_SPINLOCK(efi_rt_lock); +static DEFINE_SEMAPHORE(efi_rt_lock, 1); bool arch_efi_call_virt_setup(void) { + /* + * This might be called from a non-sleepable context so try to take the + * lock but don't block on it. This should never occur in practice, as + * all EFI runtime calls are serialized under the efi_runtime_lock. + */ + if (WARN_ON(down_trylock(&efi_rt_lock))) + return false; + efi_virtmap_load(); - raw_spin_lock(&efi_rt_lock); __efi_fpsimd_begin(); return true; } @@ -177,8 +184,8 @@ bool arch_efi_call_virt_setup(void) void arch_efi_call_virt_teardown(void) { __efi_fpsimd_end(); - raw_spin_unlock(&efi_rt_lock); efi_virtmap_unload(); + up(&efi_rt_lock); } asmlinkage u64 *efi_rt_stack_top __ro_after_init;