powerpc/64: Reclaim CPU_FTR_SUBCORE

We are running low on CPU feature bits, so we only want to use them when
it's really necessary.

CPU_FTR_SUBCORE is only used in one place, and only in C, so we don't
need it in order to make asm patching work. It can only be set on
"Power8" CPUs, which in practice means POWER8, POWER8E and POWER8NVL.
There are no plans to implement it on future CPUs, but if there ever
were we could retrofit it then.

Although KVM uses subcores, it never looks at the CPU feature, it either
looks at the ISA level or the threads_per_subcore value.

So drop the CPU feature and do a PVR check instead. Drop the device tree
"subcore" feature as we no longer support doing anything with it, and we
will drop it from skiboot too.

Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

diff --git a/arch/powerpc/include/asm/cputable.h b/arch/powerpc/include/asm/cputable.h
index c2d509584a98070accd6be62519fa992e5bc1f3f..d02ad93bf70892f8d342b9d8890a4e1b8065eed6 100644 (file)
--- a/arch/powerpc/include/asm/cputable.h
+++ b/arch/powerpc/include/asm/cputable.h
@@ -214,7 +214,6 @@ enum {
 #define CPU_FTR_DAWR                   LONG_ASM_CONST(0x0400000000000000)
 #define CPU_FTR_DABRX                  LONG_ASM_CONST(0x0800000000000000)
 #define CPU_FTR_PMAO_BUG               LONG_ASM_CONST(0x1000000000000000)
-#define CPU_FTR_SUBCORE                        LONG_ASM_CONST(0x2000000000000000)
 #define CPU_FTR_POWER9_DD1             LONG_ASM_CONST(0x4000000000000000)
 
 #ifndef __ASSEMBLY__
@@ -463,7 +462,7 @@ enum {
            CPU_FTR_STCX_CHECKS_ADDRESS | CPU_FTR_POPCNTB | CPU_FTR_POPCNTD | \
            CPU_FTR_ICSWX | CPU_FTR_CFAR | CPU_FTR_HVMODE | CPU_FTR_VMX_COPY | \
            CPU_FTR_DBELL | CPU_FTR_HAS_PPR | CPU_FTR_DAWR | \
-           CPU_FTR_ARCH_207S | CPU_FTR_TM_COMP | CPU_FTR_SUBCORE)
+           CPU_FTR_ARCH_207S | CPU_FTR_TM_COMP)
 #define CPU_FTRS_POWER8E (CPU_FTRS_POWER8 | CPU_FTR_PMAO_BUG)
 #define CPU_FTRS_POWER8_DD1 (CPU_FTRS_POWER8 & ~CPU_FTR_DBELL)
 #define CPU_FTRS_POWER9 (CPU_FTR_USE_TB | CPU_FTR_LWSYNC | \

diff --git a/arch/powerpc/kernel/dt_cpu_ftrs.c b/arch/powerpc/kernel/dt_cpu_ftrs.c
index 76eebba13a1df2a1c41af4c9d6dd69b26929e7ae..4c7656dc4e04f09bed8b9bbc8d8f979876237202 100644 (file)
--- a/arch/powerpc/kernel/dt_cpu_ftrs.c
+++ b/arch/powerpc/kernel/dt_cpu_ftrs.c
@@ -643,7 +643,6 @@ static struct dt_cpu_feature_match __initdata
        {"processor-control-facility", feat_enable_dbell, CPU_FTR_DBELL},
        {"processor-control-facility-v3", feat_enable_dbell, CPU_FTR_DBELL},
        {"processor-utilization-of-resources-register", feat_enable_purr, 0},
-       {"subcore", feat_enable, CPU_FTR_SUBCORE},
        {"no-execute", feat_enable, 0},
        {"strong-access-ordering", feat_enable, CPU_FTR_SAO},
        {"cache-inhibited-large-page", feat_enable_large_ci, 0},

diff --git a/arch/powerpc/platforms/powernv/subcore.c b/arch/powerpc/platforms/powernv/subcore.c
index 0babef11136fc8daba7f2666fed3f3b649cc2bd8..8c6119280c1306afd399d2c86ce88381882ab5df 100644 (file)
--- a/arch/powerpc/platforms/powernv/subcore.c
+++ b/arch/powerpc/platforms/powernv/subcore.c
@@ -407,7 +407,13 @@ static DEVICE_ATTR(subcores_per_core, 0644,
 
 static int subcore_init(void)
 {
-       if (!cpu_has_feature(CPU_FTR_SUBCORE))
+       unsigned pvr_ver;
+
+       pvr_ver = PVR_VER(mfspr(SPRN_PVR));
+
+       if (pvr_ver != PVR_POWER8 &&
+           pvr_ver != PVR_POWER8E &&
+           pvr_ver != PVR_POWER8NVL)
                return 0;
 
        /*