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[86.9.131.95]) by smtp.gmail.com with ESMTPSA id t16-20020a7bc3d0000000b003f1692ebd0asm10262398wmj.3.2023.04.18.09.58.31 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 18 Apr 2023 09:58:31 -0700 (PDT) From: Stafford Horne To: LKML Cc: Linux OpenRISC , Stafford Horne , Oleg Nesterov , Jonas Bonn , Stefan Kristiansson Subject: [PATCH 2/4] openrisc: Support storing and restoring fpu state Date: Tue, 18 Apr 2023 17:58:11 +0100 Message-Id: <20230418165813.1900991-3-shorne@gmail.com> X-Mailer: git-send-email 2.39.1 In-Reply-To: <20230418165813.1900991-1-shorne@gmail.com> References: <20230418165813.1900991-1-shorne@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-openrisc@vger.kernel.org OpenRISC floating point state is not so expensive to save as OpenRISC uses general purpose registers for floating point instructions. We need to save only the floating point status and control register, FPCSR. Add support to maintain the FPCSR unconditionally upon exceptions and switches. On machines that do not support FPU this will always just store 0x0 and restore is a no-op. On FPU systems this adds an additional special purpose register read/write and read/write to memory (already cached). Signed-off-by: Stafford Horne --- arch/openrisc/include/asm/ptrace.h | 4 ++-- arch/openrisc/kernel/entry.S | 14 ++++++++++++++ arch/openrisc/kernel/traps.c | 5 +++-- 3 files changed, 19 insertions(+), 4 deletions(-) diff --git a/arch/openrisc/include/asm/ptrace.h b/arch/openrisc/include/asm/ptrace.h index 01f81d4e97dc..375147ff71fc 100644 --- a/arch/openrisc/include/asm/ptrace.h +++ b/arch/openrisc/include/asm/ptrace.h @@ -59,7 +59,7 @@ struct pt_regs { * -1 for all other exceptions. */ long orig_gpr11; /* For restarting system calls */ - long dummy; /* Cheap alignment fix */ + long fpcsr; /* Floating point control status register. */ long dummy2; /* Cheap alignment fix */ }; @@ -115,6 +115,6 @@ static inline long regs_return_value(struct pt_regs *regs) #define PT_GPR31 124 #define PT_PC 128 #define PT_ORIG_GPR11 132 -#define PT_SYSCALLNO 136 +#define PT_FPCSR 136 #endif /* __ASM_OPENRISC_PTRACE_H */ diff --git a/arch/openrisc/kernel/entry.S b/arch/openrisc/kernel/entry.S index a130c4dac48d..c7b47e571220 100644 --- a/arch/openrisc/kernel/entry.S +++ b/arch/openrisc/kernel/entry.S @@ -106,6 +106,8 @@ l.mtspr r0,r3,SPR_EPCR_BASE ;\ l.lwz r3,PT_SR(r1) ;\ l.mtspr r0,r3,SPR_ESR_BASE ;\ + l.lwz r3,PT_FPCSR(r1) ;\ + l.mtspr r0,r3,SPR_FPCSR ;\ l.lwz r2,PT_GPR2(r1) ;\ l.lwz r3,PT_GPR3(r1) ;\ l.lwz r4,PT_GPR4(r1) ;\ @@ -175,6 +177,8 @@ handler: ;\ /* r30 already save */ ;\ l.sw PT_GPR31(r1),r31 ;\ TRACE_IRQS_OFF_ENTRY ;\ + l.mfspr r30,r0,SPR_FPCSR ;\ + l.sw PT_FPCSR(r1),r30 ;\ /* Store -1 in orig_gpr11 for non-syscall exceptions */ ;\ l.addi r30,r0,-1 ;\ l.sw PT_ORIG_GPR11(r1),r30 @@ -215,6 +219,8 @@ handler: ;\ /* Store -1 in orig_gpr11 for non-syscall exceptions */ ;\ l.addi r30,r0,-1 ;\ l.sw PT_ORIG_GPR11(r1),r30 ;\ + l.mfspr r30,r0,SPR_FPCSR ;\ + l.sw PT_FPCSR(r1),r30 ;\ l.addi r3,r1,0 ;\ /* r4 is exception EA */ ;\ l.addi r5,r0,vector ;\ @@ -1087,6 +1093,10 @@ ENTRY(_switch) l.sw PT_GPR28(r1),r28 l.sw PT_GPR30(r1),r30 + /* Store the old FPU state to new pt_regs */ + l.mfspr r29,r0,SPR_FPCSR + l.sw PT_FPCSR(r1),r29 + l.addi r11,r10,0 /* Save old 'current' to 'last' return value*/ /* We use thread_info->ksp for storing the address of the above @@ -1109,6 +1119,10 @@ ENTRY(_switch) l.lwz r29,PT_SP(r1) l.sw TI_KSP(r10),r29 + /* Restore the old value of FPCSR */ + l.lwz r29,PT_FPCSR(r1) + l.mtspr r0,r29,SPR_FPCSR + /* ...and restore the registers, except r11 because the return value * has already been set above. */ diff --git a/arch/openrisc/kernel/traps.c b/arch/openrisc/kernel/traps.c index fd9a0f2b66c4..f5bbe6b55849 100644 --- a/arch/openrisc/kernel/traps.c +++ b/arch/openrisc/kernel/traps.c @@ -75,8 +75,9 @@ void show_registers(struct pt_regs *regs) in_kernel = 0; printk("CPU #: %d\n" - " PC: %08lx SR: %08lx SP: %08lx\n", - smp_processor_id(), regs->pc, regs->sr, regs->sp); + " PC: %08lx SR: %08lx SP: %08lx FPCSR: %08lx\n", + smp_processor_id(), regs->pc, regs->sr, regs->sp, + regs->fpcsr); printk("GPR00: %08lx GPR01: %08lx GPR02: %08lx GPR03: %08lx\n", 0L, regs->gpr[1], regs->gpr[2], regs->gpr[3]); printk("GPR04: %08lx GPR05: %08lx GPR06: %08lx GPR07: %08lx\n", -- 2.39.1