| Message ID | 1381147951-7609-2-git-send-email-ard.biesheuvel@linaro.org |
|---|---|
| State | New |
| Headers | show |
On Mon, 7 Oct 2013, Ard Biesheuvel wrote: > Stack/unstack the bottom 4 NEON registers on exception entry/exit > so we can use them in places where we are not allowed to sleep. If you want to use Neon in places where you're not allowed to sleep, this also means you are not going to be scheduled away unexpectedly. Why not simply save/restore those Neon regs locally instead? Same goes for interrupt context. Nicolas
On 8 October 2013 00:03, Nicolas Pitre <nicolas.pitre@linaro.org> wrote: > On Mon, 7 Oct 2013, Ard Biesheuvel wrote: > >> Stack/unstack the bottom 4 NEON registers on exception entry/exit >> so we can use them in places where we are not allowed to sleep. > > If you want to use Neon in places where you're not allowed to sleep, > this also means you are not going to be scheduled away unexpectedly. > Why not simply save/restore those Neon regs locally instead? Same goes > for interrupt context. > Hmm, I guess it is that simple: if you are certain you will not be interrupted between stacking and unstacking, you can basically do whatever you like at any time. That is quite good news, actually, if that means there is no penalty in general for allowing NEON in atomic context in some cases.
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index c044548..b97a458 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -98,6 +98,9 @@ config IOMMU_HELPER config KERNEL_MODE_NEON def_bool y +config STACK_NEON_REGS_ON_EXCEPTION + def_bool n + source "init/Kconfig" source "kernel/Kconfig.freezer" @@ -219,6 +222,17 @@ config FORCE_MAX_ZONEORDER default "14" if (ARM64_64K_PAGES && TRANSPARENT_HUGEPAGE) default "11" +config KERNEL_MODE_SYNC_CE_CRYPTO + bool "Support for synchronous crypto ciphers using Crypto Extensions" + depends on KERNEL_MODE_NEON + select STACK_NEON_REGS_ON_EXCEPTION + help + This enables support for using ARMv8 Crypto Extensions instructions + in places where sleeping is not allowed. The synchronous ciphers are + only allowed to use the bottom 4 NEON register q0 - q3, as stacking + the entire NEON register file at every exception is too costly. + + endmenu menu "Boot options" diff --git a/arch/arm64/include/asm/ptrace.h b/arch/arm64/include/asm/ptrace.h index 0dacbbf..17ea483 100644 --- a/arch/arm64/include/asm/ptrace.h +++ b/arch/arm64/include/asm/ptrace.h @@ -103,6 +103,9 @@ struct pt_regs { }; u64 orig_x0; u64 syscallno; +#ifdef CONFIG_STACK_NEON_REGS_ON_EXCEPTION + struct { u64 l, h; } qregs[4]; +#endif }; #define arch_has_single_step() (1) diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c index 666e231..73c944a 100644 --- a/arch/arm64/kernel/asm-offsets.c +++ b/arch/arm64/kernel/asm-offsets.c @@ -58,6 +58,9 @@ int main(void) DEFINE(S_PC, offsetof(struct pt_regs, pc)); DEFINE(S_ORIG_X0, offsetof(struct pt_regs, orig_x0)); DEFINE(S_SYSCALLNO, offsetof(struct pt_regs, syscallno)); +#ifdef CONFIG_STACK_NEON_REGS_ON_EXCEPTION + DEFINE(S_QREGS, offsetof(struct pt_regs, qregs)); +#endif DEFINE(S_FRAME_SIZE, sizeof(struct pt_regs)); BLANK(); DEFINE(MM_CONTEXT_ID, offsetof(struct mm_struct, context.id)); diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S index 3881fd1..c74dcca 100644 --- a/arch/arm64/kernel/entry.S +++ b/arch/arm64/kernel/entry.S @@ -58,6 +58,10 @@ push x4, x5 push x2, x3 push x0, x1 +#ifdef CONFIG_STACK_NEON_REGS_ON_EXCEPTION + add x21, sp, #S_QREGS + st1 {v0.16b-v3.16b}, [x21] +#endif .if \el == 0 mrs x21, sp_el0 .else @@ -86,6 +90,10 @@ .endm .macro kernel_exit, el, ret = 0 +#ifdef CONFIG_STACK_NEON_REGS_ON_EXCEPTION + add x21, sp, #S_QREGS + ld1 {v0.16b-v3.16b}, [x21] +#endif ldp x21, x22, [sp, #S_PC] // load ELR, SPSR .if \el == 0 ldr x23, [sp, #S_SP] // load return stack pointer
Stack/unstack the bottom 4 NEON registers on exception entry/exit so we can use them in places where we are not allowed to sleep. Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> --- arch/arm64/Kconfig | 14 ++++++++++++++ arch/arm64/include/asm/ptrace.h | 3 +++ arch/arm64/kernel/asm-offsets.c | 3 +++ arch/arm64/kernel/entry.S | 8 ++++++++ 4 files changed, 28 insertions(+)