On Tue, Nov 03, 2020 at 05:03:15PM +0000, Alexandru Elisei wrote:
> Hi,
>
> On 11/3/20 10:02 AM, Andrew Jones wrote:
> > On Mon, Nov 02, 2020 at 11:34:44AM +0000, Nikos Nikoleris wrote:
> >> Now that we can change the translation granule at will, and since
> >> arm64 implementations can support a subset of the architecturally
> >> defined granules, we need to check and warn the user if the configured
> >> granule is not supported.
> > nit: it'd be better for this patch to come before the last patch.
> >
> >> Signed-off-by: Nikos Nikoleris <nikos.nikoleris@xxxxxxx>
> >> ---
> >> lib/arm64/asm/processor.h | 65 +++++++++++++++++++++++++++++++++++++++
> >> lib/arm/mmu.c | 3 ++
> >> 2 files changed, 68 insertions(+)
> >>
> >> diff --git a/lib/arm64/asm/processor.h b/lib/arm64/asm/processor.h
> >> index 02665b8..0eac928 100644
> >> --- a/lib/arm64/asm/processor.h
> >> +++ b/lib/arm64/asm/processor.h
> >> @@ -117,5 +117,70 @@ static inline u64 get_ctr(void)
> >>
> >> extern u32 dcache_line_size;
> >>
> >> +static inline unsigned long get_id_aa64mmfr0_el1(void)
> >> +{
> >> + unsigned long mmfr0;
> >> + asm volatile("mrs %0, id_aa64mmfr0_el1" : "=r" (mmfr0));
> >> + return mmfr0;
> >> +}
> >> +
> >> +/* From arch/arm64/include/asm/cpufeature.h */
> >> +static inline unsigned int
> >> +cpuid_feature_extract_unsigned_field_width(u64 features, int field, int width)
> >> +{
> >> + return (u64)(features << (64 - width - field)) >> (64 - width);
> >> +}
> >> +
> >> +#define ID_AA64MMFR0_TGRAN4_SHIFT 28
> >> +#define ID_AA64MMFR0_TGRAN64_SHIFT 24
> >> +#define ID_AA64MMFR0_TGRAN16_SHIFT 20
> >> +#define ID_AA64MMFR0_TGRAN4_SUPPORTED 0x0
> >> +#define ID_AA64MMFR0_TGRAN64_SUPPORTED 0x0
> >> +#define ID_AA64MMFR0_TGRAN16_SUPPORTED 0x1
> >> +
> >> +static inline bool system_supports_64kb_granule(void)
> >> +{
> >> + u64 mmfr0;
> >> + u32 val;
> >> +
> >> + mmfr0 = get_id_aa64mmfr0_el1();
> >> + val = cpuid_feature_extract_unsigned_field_width(
> >> + mmfr0, ID_AA64MMFR0_TGRAN4_SHIFT,4);
> >> +
> >> + return val == ID_AA64MMFR0_TGRAN64_SUPPORTED;
> >> +}
> >> +
> >> +static inline bool system_supports_16kb_granule(void)
> >> +{
> >> + u64 mmfr0;
> >> + u32 val;
> >> +
> >> + mmfr0 = get_id_aa64mmfr0_el1();
> >> + val = cpuid_feature_extract_unsigned_field_width(
> >> + mmfr0, ID_AA64MMFR0_TGRAN16_SHIFT, 4);
> >> +
> >> + return val == ID_AA64MMFR0_TGRAN16_SUPPORTED;
> >> +}
> >> +
> >> +static inline bool system_supports_4kb_granule(void)
> >> +{
> >> + u64 mmfr0;
> >> + u32 val;
> >> +
> >> + mmfr0 = get_id_aa64mmfr0_el1();
> >> + val = cpuid_feature_extract_unsigned_field_width(
> >> + mmfr0, ID_AA64MMFR0_TGRAN4_SHIFT, 4);
> >> +
> >> + return val == ID_AA64MMFR0_TGRAN4_SUPPORTED;
> >> +}
> >> +
> >> +#if PAGE_SIZE == 65536
> >> +#define system_supports_configured_granule system_supports_64kb_granule
> >> +#elif PAGE_SIZE == 16384
> >> +#define system_supports_configured_granule system_supports_16kb_granule
> >> +#elif PAGE_SIZE == 4096
> >> +#define system_supports_configured_granule system_supports_4kb_granule
> >> +#endif
> >> +
> >> #endif /* !__ASSEMBLY__ */
> >> #endif /* _ASMARM64_PROCESSOR_H_ */
> >> diff --git a/lib/arm/mmu.c b/lib/arm/mmu.c
> >> index 6d1c75b..51fa745 100644
> >> --- a/lib/arm/mmu.c
> >> +++ b/lib/arm/mmu.c
> >> @@ -163,6 +163,9 @@ void *setup_mmu(phys_addr_t phys_end)
> >>
> >> #ifdef __aarch64__
> >> init_alloc_vpage((void*)(4ul << 30));
> >> +
> >> + assert_msg(system_supports_configured_granule(),
> >> + "Unsupported translation granule %d\n", PAGE_SIZE);
> > ^
> > needs '%ld' to compile
> >> #endif
> >>
> >> mmu_idmap = alloc_page();
> >> --
> >> 2.17.1
> >>
> > I don't think we need the three separate functions. How about just
> > doing the following diff?
> >
> > Thanks,
> > drew
> >
> >
> > diff --git a/lib/arm/mmu.c b/lib/arm/mmu.c
> > index 540a1e842d5b..fef62f5a9866 100644
> > --- a/lib/arm/mmu.c
> > +++ b/lib/arm/mmu.c
> > @@ -160,6 +160,9 @@ void *setup_mmu(phys_addr_t phys_end)
> >
> > #ifdef __aarch64__
> > init_alloc_vpage((void*)(4ul << 30));
> > +
> > + assert_msg(system_supports_granule(PAGE_SIZE),
> > + "Unsupported translation granule: %ld\n", PAGE_SIZE);
> > #endif
> >
> > mmu_idmap = alloc_page();
> > diff --git a/lib/arm64/asm/processor.h b/lib/arm64/asm/processor.h
> > index 02665b84cc7e..dc493d1686bc 100644
> > --- a/lib/arm64/asm/processor.h
> > +++ b/lib/arm64/asm/processor.h
> > @@ -117,5 +117,21 @@ static inline u64 get_ctr(void)
> >
> > extern u32 dcache_line_size;
> >
> > +static inline unsigned long get_id_aa64mmfr0_el1(void)
> > +{
> > + unsigned long mmfr0;
> > + asm volatile("mrs %0, id_aa64mmfr0_el1" : "=r" (mmfr0));
> > + return mmfr0;
>
> I think we can safely use read_sysreg here, the other functions in this file do.
Agreed
>
> > +}
> > +
> > +static inline bool system_supports_granule(size_t granule)
> > +{
> > + u64 mmfr0 = get_id_aa64mmfr0_el1();
> > +
> > + return ((granule == SZ_4K && ((mmfr0 >> 28) & 0xf) == 0) ||
> > + (granule == SZ_64K && ((mmfr0 >> 24) & 0xf) == 0) ||
> > + (granule == SZ_16K && ((mmfr0 >> 20) & 0xf) == 1));
> > +}
>
> Or we can turn it into a switch statement and keep all the field defines. Either
> way looks good to me (funny how tgran16 stands out).
>
Keeping the defines is probably a good idea. Whether the function uses
a switch or an expression like above doesn't matter to me much. Keeping
LOC down in the lib/ code is a goal of kvm-unit-tests, but so is
readabilty. If the switch looks better, then let's go that way.
Thanks,
drew
