| Message ID | 20210118094533.2874082-11-maz@kernel.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | arm64: Early CPU feature override, and applications to VHE, BTI and PAuth | expand |
On Mon, Jan 18, 2021 at 09:45:22AM +0000, Marc Zyngier wrote: > __read_sysreg_by_encoding() is used by a bunch of cpufeature helpers, > which should take the feature override into account. Let's do that. > > For a good measure (and because we are likely to need to further > down the line), make this helper available to the rest of the > non-modular kernel. > > Code that needs to know the *real* features of a CPU can still > use read_sysreg_s(), and find the bare, ugly truth. > > Signed-off-by: Marc Zyngier <maz@kernel.org> > --- > arch/arm64/include/asm/cpufeature.h | 1 + > arch/arm64/kernel/cpufeature.c | 15 +++++++++++++-- > 2 files changed, 14 insertions(+), 2 deletions(-) > > diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h > index 465d2cb63bfc..fe0130d6c0ff 100644 > --- a/arch/arm64/include/asm/cpufeature.h > +++ b/arch/arm64/include/asm/cpufeature.h > @@ -602,6 +602,7 @@ void __init setup_cpu_features(void); > void check_local_cpu_capabilities(void); > > u64 read_sanitised_ftr_reg(u32 id); > +u64 __read_sysreg_by_encoding(u32 sys_id); > > static inline bool cpu_supports_mixed_endian_el0(void) > { > diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c > index aaa075c6f029..48a011935d8c 100644 > --- a/arch/arm64/kernel/cpufeature.c > +++ b/arch/arm64/kernel/cpufeature.c > @@ -1149,14 +1149,17 @@ u64 read_sanitised_ftr_reg(u32 id) > EXPORT_SYMBOL_GPL(read_sanitised_ftr_reg); > > #define read_sysreg_case(r) \ > - case r: return read_sysreg_s(r) > + case r: val = read_sysreg_s(r); break; > > /* > * __read_sysreg_by_encoding() - Used by a STARTING cpu before cpuinfo is populated. > * Read the system register on the current CPU > */ > -static u64 __read_sysreg_by_encoding(u32 sys_id) > +u64 __read_sysreg_by_encoding(u32 sys_id) > { > + struct arm64_ftr_reg *regp; > + u64 val; > + > switch (sys_id) { > read_sysreg_case(SYS_ID_PFR0_EL1); > read_sysreg_case(SYS_ID_PFR1_EL1); > @@ -1199,6 +1202,14 @@ static u64 __read_sysreg_by_encoding(u32 sys_id) > BUG(); > return 0; > } > + > + regp = get_arm64_ftr_reg(sys_id); > + if (regp && regp->override_mask && regp->override_val) { > + val &= ~*regp->override_mask; > + val |= (*regp->override_val & *regp->override_mask); > + } > + > + return val; Ah, now the previous patch makes more sense. I don't particularly like this but I can't tell how to work around it. I was hoping that the overriding feature behaves more like a secondary CPU that limits all the overridden features. However, this approach would fail for FTR_EXACT cases (like PAC, though I wonder whether it fails already with your previous patch since the boot CPU value won't match the override, hence dropping to the safe one).
On 1/22/21 6:53 PM, Catalin Marinas wrote: > On Mon, Jan 18, 2021 at 09:45:22AM +0000, Marc Zyngier wrote: >> __read_sysreg_by_encoding() is used by a bunch of cpufeature helpers, >> which should take the feature override into account. Let's do that. >> >> For a good measure (and because we are likely to need to further >> down the line), make this helper available to the rest of the >> non-modular kernel. >> >> Code that needs to know the *real* features of a CPU can still >> use read_sysreg_s(), and find the bare, ugly truth. >> >> Signed-off-by: Marc Zyngier <maz@kernel.org> >> diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c >> index aaa075c6f029..48a011935d8c 100644 >> --- a/arch/arm64/kernel/cpufeature.c >> +++ b/arch/arm64/kernel/cpufeature.c >> @@ -1149,14 +1149,17 @@ u64 read_sanitised_ftr_reg(u32 id) >> EXPORT_SYMBOL_GPL(read_sanitised_ftr_reg); >> >> #define read_sysreg_case(r) \ >> - case r: return read_sysreg_s(r) >> + case r: val = read_sysreg_s(r); break; >> >> /* >> * __read_sysreg_by_encoding() - Used by a STARTING cpu before cpuinfo is populated. >> * Read the system register on the current CPU >> */ >> -static u64 __read_sysreg_by_encoding(u32 sys_id) >> +u64 __read_sysreg_by_encoding(u32 sys_id) >> { >> + struct arm64_ftr_reg *regp; >> + u64 val; >> + >> switch (sys_id) { >> read_sysreg_case(SYS_ID_PFR0_EL1); >> read_sysreg_case(SYS_ID_PFR1_EL1); >> @@ -1199,6 +1202,14 @@ static u64 __read_sysreg_by_encoding(u32 sys_id) >> BUG(); >> return 0; >> } >> + >> + regp = get_arm64_ftr_reg(sys_id); >> + if (regp && regp->override_mask && regp->override_val) { >> + val &= ~*regp->override_mask; >> + val |= (*regp->override_val & *regp->override_mask); >> + } >> + >> + return val; > > Ah, now the previous patch makes more sense. I don't particularly like > this but I can't tell how to work around it. I was hoping that the > overriding feature behaves more like a secondary CPU that limits all the > overridden features. However, this approach would fail for FTR_EXACT > cases (like PAC, though I wonder whether it fails already with your > previous patch since the boot CPU value won't match the override, hence > dropping to the safe one). > Correct !For FTR_EXACT, we dont want to override a value that is not safe, e.g PAC. This is handled correctly in the previous patch and thus we are covered. Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h index 465d2cb63bfc..fe0130d6c0ff 100644 --- a/arch/arm64/include/asm/cpufeature.h +++ b/arch/arm64/include/asm/cpufeature.h @@ -602,6 +602,7 @@ void __init setup_cpu_features(void); void check_local_cpu_capabilities(void); u64 read_sanitised_ftr_reg(u32 id); +u64 __read_sysreg_by_encoding(u32 sys_id); static inline bool cpu_supports_mixed_endian_el0(void) { diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c index aaa075c6f029..48a011935d8c 100644 --- a/arch/arm64/kernel/cpufeature.c +++ b/arch/arm64/kernel/cpufeature.c @@ -1149,14 +1149,17 @@ u64 read_sanitised_ftr_reg(u32 id) EXPORT_SYMBOL_GPL(read_sanitised_ftr_reg); #define read_sysreg_case(r) \ - case r: return read_sysreg_s(r) + case r: val = read_sysreg_s(r); break; /* * __read_sysreg_by_encoding() - Used by a STARTING cpu before cpuinfo is populated. * Read the system register on the current CPU */ -static u64 __read_sysreg_by_encoding(u32 sys_id) +u64 __read_sysreg_by_encoding(u32 sys_id) { + struct arm64_ftr_reg *regp; + u64 val; + switch (sys_id) { read_sysreg_case(SYS_ID_PFR0_EL1); read_sysreg_case(SYS_ID_PFR1_EL1); @@ -1199,6 +1202,14 @@ static u64 __read_sysreg_by_encoding(u32 sys_id) BUG(); return 0; } + + regp = get_arm64_ftr_reg(sys_id); + if (regp && regp->override_mask && regp->override_val) { + val &= ~*regp->override_mask; + val |= (*regp->override_val & *regp->override_mask); + } + + return val; } #include <linux/irqchip/arm-gic-v3.h>
__read_sysreg_by_encoding() is used by a bunch of cpufeature helpers, which should take the feature override into account. Let's do that. For a good measure (and because we are likely to need to further down the line), make this helper available to the rest of the non-modular kernel. Code that needs to know the *real* features of a CPU can still use read_sysreg_s(), and find the bare, ugly truth. Signed-off-by: Marc Zyngier <maz@kernel.org> --- arch/arm64/include/asm/cpufeature.h | 1 + arch/arm64/kernel/cpufeature.c | 15 +++++++++++++-- 2 files changed, 14 insertions(+), 2 deletions(-)