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Fri, 05 Sep 2025 06:30:52 -0700 (PDT) Date: Fri, 5 Sep 2025 15:30:41 +0200 In-Reply-To: <20250905133035.275517-9-ardb+git@google.com> Mime-Version: 1.0 References: <20250905133035.275517-9-ardb+git@google.com> X-Developer-Key: i=ardb@kernel.org; a=openpgp; fpr=F43D03328115A198C90016883D200E9CA6329909 X-Developer-Signature: v=1; a=openpgp-sha256; l=1404; i=ardb@kernel.org; h=from:subject; bh=LG9z8ZfG/9lulzNu83d9OgD0HFnWetupMNmr542q5Ks=; b=owGbwMvMwCVmkMcZplerG8N4Wi2JIWPXM4Y7F0JYuPJPl/FPqAhOvOS/S0fsxmm5cIbmeQeWv /m6IntxRykLgxgXg6yYIovA7L/vdp6eKFXrPEsWZg4rE8gQBi5OAZjI+oeMDBuXdugdkF+/+e3a sumKH1zmv9ZLvBy+SMj9znyFJZlnEtUY/lnIbpn4UqD00YKSc7W+PmpfbbSXM27XOuGjy3zkxZ1 oSQ4A X-Mailer: git-send-email 2.51.0.355.g5224444f11-goog Message-ID: <20250905133035.275517-14-ardb+git@google.com> Subject: [PATCH v2 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 Content-Type: text/plain; charset="UTF-8" X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250905_063054_760315_B8DC33CB X-CRM114-Status: GOOD ( 14.28 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org 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 9b03f3d77a25..8b999c07c7d1 100644 --- a/arch/arm64/kernel/efi.c +++ b/arch/arm64/kernel/efi.c @@ -165,12 +165,19 @@ 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; } @@ -178,8 +185,8 @@ 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; -- 2.51.0.355.g5224444f11-goog