Excerpts from Shawn Anastasio's message of August 21, 2020 11:08 am:
> Since migration of guests using SAO to ISA 3.1 hosts may cause issues,
> disable PROT_SAO in LPARs by default and introduce a new Kconfig option
> PPC_PROT_SAO_LPAR to allow users to enable it if desired.
I think this should be okay. Could you also update the selftest to skip
if we have PPC_FEATURE2_ARCH_3_1 set?
Thanks,
Nick
Acked-by: Nicholas Piggin <npig...@gmail.com>
>
> Signed-off-by: Shawn Anastasio <sh...@anastas.io>
> ---
> arch/powerpc/Kconfig | 12 ++++++++++++
> arch/powerpc/include/asm/mman.h | 9 +++++++--
> 2 files changed, 19 insertions(+), 2 deletions(-)
>
> diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
> index 1f48bbfb3ce9..65bed1fdeaad 100644
> --- a/arch/powerpc/Kconfig
> +++ b/arch/powerpc/Kconfig
> @@ -860,6 +860,18 @@ config PPC_SUBPAGE_PROT
>
> If unsure, say N here.
>
> +config PPC_PROT_SAO_LPAR
> + bool "Support PROT_SAO mappings in LPARs"
> + depends on PPC_BOOK3S_64
> + help
> + This option adds support for PROT_SAO mappings from userspace
> + inside LPARs on supported CPUs.
> +
> + This may cause issues when performing guest migration from
> + a CPU that supports SAO to one that does not.
> +
> + If unsure, say N here.
> +
> config PPC_COPRO_BASE
> bool
>
> diff --git a/arch/powerpc/include/asm/mman.h b/arch/powerpc/include/asm/mman.h
> index 4ba303ea27f5..7cb6d18f5cd6 100644
> --- a/arch/powerpc/include/asm/mman.h
> +++ b/arch/powerpc/include/asm/mman.h
> @@ -40,8 +40,13 @@ static inline bool arch_validate_prot(unsigned long prot,
> unsigned long addr)
> {
> if (prot & ~(PROT_READ | PROT_WRITE | PROT_EXEC | PROT_SEM | PROT_SAO))
> return false;
> - if ((prot & PROT_SAO) && !cpu_has_feature(CPU_FTR_SAO))
> - return false;
> + if (prot & PROT_SAO) {
> + if (!cpu_has_feature(CPU_FTR_SAO))
> + return false;
> + if (firmware_has_feature(FW_FEATURE_LPAR) &&
> + !IS_ENABLED(CONFIG_PPC_PROT_SAO_LPAR))
> + return false;
> + }
> return true;
> }
> #define arch_validate_prot arch_validate_prot
> --
> 2.28.0
>
>
