RISC-V: always select RISCV_ALTERNATIVE for non-xip kernels

When moving switch_to's has_fpu() over to using
riscv_has_extension_likely() rather than static branches, the FPU code
gained a dependency on the alternatives framework.
That dependency has now been removed, as riscv_has_extension_ikely() now
contains a fallback path, using __riscv_isa_extension_available(), but
if CONFIG_RISCV_ALTERNATIVE isn't selected when CONFIG_FPU is, has_fpu()
checks will not benefit from the "fast path" that the alternatives
framework provides.

We want to ensure that alternatives are available whenever
riscv_has_extension_[un]likely() is used, rather than silently falling
back to the slow path, but rather than rely on selecting
RISCV_ALTERNATIVE in the myriad of locations that may use
riscv_has_extension_[un]likely(), select it (almost) always instead by
adding it to the main RISCV config entry.
xip kernels cannot make use of the alternatives framework, so it is not
enabled for those configurations, although this is the status quo.

All current sites that select RISCV_ALTERNATIVE are converted to
dependencies on the option instead. The explicit dependencies on
!XIP_KERNEL can be dropped, as RISCV_ALTERNATIVE is not user selectable.

Fixes: 702e64550b12 ("riscv: fpu: switch has_fpu() to riscv_has_extension_likely()")
Link: https://lore.kernel.org/all/ZBruFRwt3rUVngPu@zx2c4.com/
Reported-by: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Reviewed-by: Jason A. Donenfeld <Jason@zx2c4.com>
Link: https://lore.kernel.org/r/20230324100538.3514663-3-conor.dooley@microchip.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index c5e42cc376048dbc9d960a6275b40c983acb7618..2f6976418d0a31265912bb1425a667f8c72c97ea 100644 (file)
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -126,6 +126,7 @@ config RISCV
        select OF_IRQ
        select PCI_DOMAINS_GENERIC if PCI
        select PCI_MSI if PCI
+       select RISCV_ALTERNATIVE if !XIP_KERNEL
        select RISCV_INTC
        select RISCV_TIMER if RISCV_SBI
        select SIFIVE_PLIC
@@ -401,9 +402,8 @@ config RISCV_ISA_C
 config RISCV_ISA_SVPBMT
        bool "SVPBMT extension support"
        depends on 64BIT && MMU
-       depends on !XIP_KERNEL
+       depends on RISCV_ALTERNATIVE
        default y
-       select RISCV_ALTERNATIVE
        help
           Adds support to dynamically detect the presence of the SVPBMT
           ISA-extension (Supervisor-mode: page-based memory types) and
@@ -428,8 +428,8 @@ config TOOLCHAIN_HAS_ZBB
 config RISCV_ISA_ZBB
        bool "Zbb extension support for bit manipulation instructions"
        depends on TOOLCHAIN_HAS_ZBB
-       depends on !XIP_KERNEL && MMU
-       select RISCV_ALTERNATIVE
+       depends on MMU
+       depends on RISCV_ALTERNATIVE
        default y
        help
           Adds support to dynamically detect the presence of the ZBB
@@ -443,9 +443,9 @@ config RISCV_ISA_ZBB
 
 config RISCV_ISA_ZICBOM
        bool "Zicbom extension support for non-coherent DMA operation"
-       depends on !XIP_KERNEL && MMU
+       depends on MMU
+       depends on RISCV_ALTERNATIVE
        default y
-       select RISCV_ALTERNATIVE
        select RISCV_DMA_NONCOHERENT
        help
           Adds support to dynamically detect the presence of the ZICBOM

diff --git a/arch/riscv/Kconfig.erratas b/arch/riscv/Kconfig.erratas
index 69621ae6d647aa369cee22c5751d3a55ec93e0b6..0c8f4652cd8289b62256f8c93756b84d327f4a88 100644 (file)
--- a/arch/riscv/Kconfig.erratas
+++ b/arch/riscv/Kconfig.erratas
@@ -2,8 +2,7 @@ menu "CPU errata selection"
 
 config ERRATA_SIFIVE
        bool "SiFive errata"
-       depends on !XIP_KERNEL
-       select RISCV_ALTERNATIVE
+       depends on RISCV_ALTERNATIVE
        help
          All SiFive errata Kconfig depend on this Kconfig. Disabling
          this Kconfig will disable all SiFive errata. Please say "Y"
@@ -35,8 +34,7 @@ config ERRATA_SIFIVE_CIP_1200
 
 config ERRATA_THEAD
        bool "T-HEAD errata"
-       depends on !XIP_KERNEL
-       select RISCV_ALTERNATIVE
+       depends on RISCV_ALTERNATIVE
        help
          All T-HEAD errata Kconfig depend on this Kconfig. Disabling
          this Kconfig will disable all T-HEAD errata. Please say "Y"