[PATCH v5 28/38] arm64/sme: Save and restore streaming mode over EFI runtime calls

From: Mark Brown <broonie@kernel.org>
To: Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will@kernel.org>,
	Shuah Khan <skhan@linuxfoundation.org>,
	Shuah Khan <shuah@kernel.org>
Cc: Alan Hayward <alan.hayward@arm.com>,
	Luis Machado <luis.machado@arm.com>,
	Salil Akerkar <Salil.Akerkar@arm.com>,
	Basant Kumar Dwivedi <Basant.KumarDwivedi@arm.com>,
	Szabolcs Nagy <szabolcs.nagy@arm.com>,
	linux-arm-kernel@lists.infradead.org,
	linux-kselftest@vger.kernel.org, Mark Brown <broonie@kernel.org>
Subject: [PATCH v5 28/38] arm64/sme: Save and restore streaming mode over EFI runtime calls
Date: Wed, 27 Oct 2021 19:44:14 +0100	[thread overview]
Message-ID: <20211027184424.166237-29-broonie@kernel.org> (raw)
In-Reply-To: <20211027184424.166237-1-broonie@kernel.org>

When saving and restoring the floating point state over an EFI runtime
call ensure that we handle streaming mode, only handling FFR if we are not
in streaming mode and ensuring that we are in normal mode over the call
into runtime services.

We currently assume that ZA will not be modified by runtime services, the
specification is not yet finalised so this may need updating if that
changes.

Signed-off-by: Mark Brown <broonie@kernel.org>
---
 arch/arm64/kernel/fpsimd.c | 47 +++++++++++++++++++++++++++++++++-----
 1 file changed, 41 insertions(+), 6 deletions(-)

diff --git a/arch/arm64/kernel/fpsimd.c b/arch/arm64/kernel/fpsimd.c
index ebaf174bdf82..3551ed97e0f3 100644
--- a/arch/arm64/kernel/fpsimd.c
+++ b/arch/arm64/kernel/fpsimd.c
@@ -1046,21 +1046,25 @@ int vec_verify_vq_map(enum vec_type type)
 
 static void __init sve_efi_setup(void)
 {
-	struct vl_info *info = &vl_info[ARM64_VEC_SVE];
+	int max_vl = 0;
+	int i;
 
 	if (!IS_ENABLED(CONFIG_EFI))
 		return;
 
+	for (i = 0; i < ARRAY_SIZE(vl_info); i++)
+		max_vl = max(vl_info[i].max_vl, max_vl);
+
 	/*
 	 * alloc_percpu() warns and prints a backtrace if this goes wrong.
 	 * This is evidence of a crippled system and we are returning void,
 	 * so no attempt is made to handle this situation here.
 	 */
-	if (!sve_vl_valid(info->max_vl))
+	if (!sve_vl_valid(max_vl))
 		goto fail;
 
 	efi_sve_state = __alloc_percpu(
-		SVE_SIG_REGS_SIZE(sve_vq_from_vl(info->max_vl)), SVE_VQ_BYTES);
+		SVE_SIG_REGS_SIZE(sve_vq_from_vl(max_vl)), SVE_VQ_BYTES);
 	if (!efi_sve_state)
 		goto fail;
 
@@ -1841,6 +1845,7 @@ EXPORT_SYMBOL(kernel_neon_end);
 static DEFINE_PER_CPU(struct user_fpsimd_state, efi_fpsimd_state);
 static DEFINE_PER_CPU(bool, efi_fpsimd_state_used);
 static DEFINE_PER_CPU(bool, efi_sve_state_used);
+static DEFINE_PER_CPU(bool, efi_sm_state);
 
 /*
  * EFI runtime services support functions
@@ -1875,12 +1880,28 @@ void __efi_fpsimd_begin(void)
 		 */
 		if (system_supports_sve() && likely(efi_sve_state)) {
 			char *sve_state = this_cpu_ptr(efi_sve_state);
+			bool ffr = true;
+			u64 svcr;
 
 			__this_cpu_write(efi_sve_state_used, true);
 
+			/* If we are in streaming mode don't touch FFR */
+			if (system_supports_sme()) {
+				svcr = read_sysreg_s(SYS_SVCR_EL0);
+
+				ffr = svcr & SYS_SVCR_EL0_SM_MASK;
+
+				__this_cpu_write(efi_sm_state, ffr);
+			}
+
 			sve_save_state(sve_state + sve_ffr_offset(sve_max_vl()),
 				       &this_cpu_ptr(&efi_fpsimd_state)->fpsr,
-				       true);
+				       ffr);
+
+			if (system_supports_sme())
+				sysreg_clear_set_s(SYS_SVCR_EL0,
+						   SYS_SVCR_EL0_SM_MASK, 0);
+
 		} else {
 			fpsimd_save_state(this_cpu_ptr(&efi_fpsimd_state));
 		}
@@ -1903,11 +1924,25 @@ void __efi_fpsimd_end(void)
 		if (system_supports_sve() &&
 		    likely(__this_cpu_read(efi_sve_state_used))) {
 			char const *sve_state = this_cpu_ptr(efi_sve_state);
+			bool ffr = true;
+
+			/*
+			 * Restore streaming mode; EFI calls are
+			 * normal function calls so should not return in
+			 * streaming mode.
+			 */
+			if (system_supports_sme()) {
+				if (__this_cpu_read(efi_sm_state)) {
+					sysreg_clear_set_s(SYS_SVCR_EL0,
+							   0,
+							   SYS_SVCR_EL0_SM_MASK);
+					ffr = false;
+				}
+			}
 
-			sve_set_vq(sve_vq_from_vl(sve_get_vl()) - 1);
 			sve_load_state(sve_state + sve_ffr_offset(sve_max_vl()),
 				       &this_cpu_ptr(&efi_fpsimd_state)->fpsr,
-				       true);
+				       ffr);
 
 			__this_cpu_write(efi_sve_state_used, false);
 		} else {
-- 
2.30.2

