* [PATCH v2] arm64: Restrict undef hook for cpufeature registers @ 2021-05-17 18:02 Rob Herring 2021-06-08 15:20 ` Catalin Marinas 2021-06-23 14:00 ` Will Deacon 0 siblings, 2 replies; 5+ messages in thread From: Rob Herring @ 2021-05-17 18:02 UTC (permalink / raw) To: Will Deacon, Catalin Marinas; +Cc: linux-arm-kernel, Raphael Gault From: Raphael Gault <raphael.gault@arm.com> This commit modifies the mask of the mrs_hook declared in arch/arm64/kernel/cpufeatures.c which emulates only feature register access. This is necessary because this hook's mask was too large and thus masking any mrs instruction, even if not related to the emulated registers which made the pmu emulation inefficient. Signed-off-by: Raphael Gault <raphael.gault@arm.com> Signed-off-by: Rob Herring <robh@kernel.org> --- I don't *think* I'm going to need this for the perf userspace counter access, but this patch stands on its own as the PMU registers are not emulated. So please apply it. v2: - Fix warning for set but unused sys_reg --- arch/arm64/kernel/cpufeature.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c index efed2830d141..c773f7c3c007 100644 --- a/arch/arm64/kernel/cpufeature.c +++ b/arch/arm64/kernel/cpufeature.c @@ -2905,8 +2905,8 @@ static int emulate_mrs(struct pt_regs *regs, u32 insn) } static struct undef_hook mrs_hook = { - .instr_mask = 0xfff00000, - .instr_val = 0xd5300000, + .instr_mask = 0xffff0000, + .instr_val = 0xd5380000, .pstate_mask = PSR_AA32_MODE_MASK, .pstate_val = PSR_MODE_EL0t, .fn = emulate_mrs, -- 2.27.0 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel ^ permalink raw reply related [flat|nested] 5+ messages in thread
* Re: [PATCH v2] arm64: Restrict undef hook for cpufeature registers 2021-05-17 18:02 [PATCH v2] arm64: Restrict undef hook for cpufeature registers Rob Herring @ 2021-06-08 15:20 ` Catalin Marinas 2021-06-08 16:34 ` Will Deacon 2021-06-23 14:00 ` Will Deacon 1 sibling, 1 reply; 5+ messages in thread From: Catalin Marinas @ 2021-06-08 15:20 UTC (permalink / raw) To: Rob Herring; +Cc: Will Deacon, linux-arm-kernel, Raphael Gault On Mon, May 17, 2021 at 01:02:56PM -0500, Rob Herring wrote: > From: Raphael Gault <raphael.gault@arm.com> > > This commit modifies the mask of the mrs_hook declared in > arch/arm64/kernel/cpufeatures.c which emulates only feature register > access. This is necessary because this hook's mask was too large and > thus masking any mrs instruction, even if not related to the emulated > registers which made the pmu emulation inefficient. > > Signed-off-by: Raphael Gault <raphael.gault@arm.com> > Signed-off-by: Rob Herring <robh@kernel.org> > --- > I don't *think* I'm going to need this for the perf userspace counter > access, but this patch stands on its own as the PMU registers are not > emulated. So please apply it. > > v2: > - Fix warning for set but unused sys_reg > --- > arch/arm64/kernel/cpufeature.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c > index efed2830d141..c773f7c3c007 100644 > --- a/arch/arm64/kernel/cpufeature.c > +++ b/arch/arm64/kernel/cpufeature.c > @@ -2905,8 +2905,8 @@ static int emulate_mrs(struct pt_regs *regs, u32 insn) > } > > static struct undef_hook mrs_hook = { > - .instr_mask = 0xfff00000, > - .instr_val = 0xd5300000, > + .instr_mask = 0xffff0000, > + .instr_val = 0xd5380000, Acked-by: Catalin Marinas <catalin.marinas@arm.com> and changing Will's email address. -- Catalin _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel ^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH v2] arm64: Restrict undef hook for cpufeature registers 2021-06-08 15:20 ` Catalin Marinas @ 2021-06-08 16:34 ` Will Deacon 2021-06-11 16:04 ` Rob Herring 0 siblings, 1 reply; 5+ messages in thread From: Will Deacon @ 2021-06-08 16:34 UTC (permalink / raw) To: Catalin Marinas; +Cc: Rob Herring, linux-arm-kernel, Raphael Gault On Tue, Jun 08, 2021 at 04:20:43PM +0100, Catalin Marinas wrote: > On Mon, May 17, 2021 at 01:02:56PM -0500, Rob Herring wrote: > > From: Raphael Gault <raphael.gault@arm.com> > > > > This commit modifies the mask of the mrs_hook declared in > > arch/arm64/kernel/cpufeatures.c which emulates only feature register > > access. This is necessary because this hook's mask was too large and > > thus masking any mrs instruction, even if not related to the emulated > > registers which made the pmu emulation inefficient. > > > > Signed-off-by: Raphael Gault <raphael.gault@arm.com> > > Signed-off-by: Rob Herring <robh@kernel.org> > > --- > > I don't *think* I'm going to need this for the perf userspace counter > > access, but this patch stands on its own as the PMU registers are not > > emulated. So please apply it. > > > > v2: > > - Fix warning for set but unused sys_reg > > --- > > arch/arm64/kernel/cpufeature.c | 4 ++-- > > 1 file changed, 2 insertions(+), 2 deletions(-) > > > > diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c > > index efed2830d141..c773f7c3c007 100644 > > --- a/arch/arm64/kernel/cpufeature.c > > +++ b/arch/arm64/kernel/cpufeature.c > > @@ -2905,8 +2905,8 @@ static int emulate_mrs(struct pt_regs *regs, u32 insn) > > } > > > > static struct undef_hook mrs_hook = { > > - .instr_mask = 0xfff00000, > > - .instr_val = 0xd5300000, > > + .instr_mask = 0xffff0000, > > + .instr_val = 0xd5380000, > > Acked-by: Catalin Marinas <catalin.marinas@arm.com> > > and changing Will's email address. Should we update is_emulated() at the same time, or at least try to generate the instr_val value here using the same constants? Will _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel ^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH v2] arm64: Restrict undef hook for cpufeature registers 2021-06-08 16:34 ` Will Deacon @ 2021-06-11 16:04 ` Rob Herring 0 siblings, 0 replies; 5+ messages in thread From: Rob Herring @ 2021-06-11 16:04 UTC (permalink / raw) To: Will Deacon; +Cc: Catalin Marinas, linux-arm-kernel, Raphael Gault On Tue, Jun 8, 2021 at 10:35 AM Will Deacon <will@kernel.org> wrote: > > On Tue, Jun 08, 2021 at 04:20:43PM +0100, Catalin Marinas wrote: > > On Mon, May 17, 2021 at 01:02:56PM -0500, Rob Herring wrote: > > > From: Raphael Gault <raphael.gault@arm.com> > > > > > > This commit modifies the mask of the mrs_hook declared in > > > arch/arm64/kernel/cpufeatures.c which emulates only feature register > > > access. This is necessary because this hook's mask was too large and > > > thus masking any mrs instruction, even if not related to the emulated > > > registers which made the pmu emulation inefficient. > > > > > > Signed-off-by: Raphael Gault <raphael.gault@arm.com> > > > Signed-off-by: Rob Herring <robh@kernel.org> > > > --- > > > I don't *think* I'm going to need this for the perf userspace counter > > > access, but this patch stands on its own as the PMU registers are not > > > emulated. So please apply it. > > > > > > v2: > > > - Fix warning for set but unused sys_reg > > > --- > > > arch/arm64/kernel/cpufeature.c | 4 ++-- > > > 1 file changed, 2 insertions(+), 2 deletions(-) > > > > > > diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c > > > index efed2830d141..c773f7c3c007 100644 > > > --- a/arch/arm64/kernel/cpufeature.c > > > +++ b/arch/arm64/kernel/cpufeature.c > > > @@ -2905,8 +2905,8 @@ static int emulate_mrs(struct pt_regs *regs, u32 insn) > > > } > > > > > > static struct undef_hook mrs_hook = { > > > - .instr_mask = 0xfff00000, > > > - .instr_val = 0xd5300000, > > > + .instr_mask = 0xffff0000, > > > + .instr_val = 0xd5380000, > > > > Acked-by: Catalin Marinas <catalin.marinas@arm.com> > > > > and changing Will's email address. > > Should we update is_emulated() at the same time, or at least try to generate > the instr_val value here using the same constants? Something like the below patch? We can actually mask a bit more of the instruction (Crn and Crm:3) and then eliminate some of the is_emulated() checks. I'm not all that convinced it's an improvement in readability compared to a raw instr_val and mask nor having is_emulated depend on what was checked in the undef code. diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c index c773f7c3c007..6b3f50c11ab5 100644 --- a/arch/arm64/kernel/cpufeature.c +++ b/arch/arm64/kernel/cpufeature.c @@ -2825,11 +2825,7 @@ static void __maybe_unused cpu_enable_cnp(struct arm64_cpu_capabilities const *c */ static inline bool __attribute_const__ is_emulated(u32 id) { - return (sys_reg_Op0(id) == 0x3 && - sys_reg_CRn(id) == 0x0 && - sys_reg_Op1(id) == 0x0 && - (sys_reg_CRm(id) == 0 || - ((sys_reg_CRm(id) >= 4) && (sys_reg_CRm(id) <= 7)))); + return ((sys_reg_CRm(id) == 0) || (sys_reg_CRm(id) >= 4)); } /* @@ -2905,8 +2901,8 @@ static int emulate_mrs(struct pt_regs *regs, u32 insn) } static struct undef_hook mrs_hook = { - .instr_mask = 0xffff0000, - .instr_val = 0xd5380000, + .instr_mask = 0xffe00000 | sys_reg(Op0_mask, Op1_mask, CRn_mask, 8, 0), + .instr_val = 0xd5200000 | sys_reg(3, 0, 0, 0, 0), .pstate_mask = PSR_AA32_MODE_MASK, .pstate_val = PSR_MODE_EL0t, .fn = emulate_mrs, _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel ^ permalink raw reply related [flat|nested] 5+ messages in thread
* Re: [PATCH v2] arm64: Restrict undef hook for cpufeature registers 2021-05-17 18:02 [PATCH v2] arm64: Restrict undef hook for cpufeature registers Rob Herring 2021-06-08 15:20 ` Catalin Marinas @ 2021-06-23 14:00 ` Will Deacon 1 sibling, 0 replies; 5+ messages in thread From: Will Deacon @ 2021-06-23 14:00 UTC (permalink / raw) To: Rob Herring, Will Deacon, Catalin Marinas Cc: kernel-team, Will Deacon, Raphael Gault, linux-arm-kernel On Mon, 17 May 2021 13:02:56 -0500, Rob Herring wrote: > This commit modifies the mask of the mrs_hook declared in > arch/arm64/kernel/cpufeatures.c which emulates only feature register > access. This is necessary because this hook's mask was too large and > thus masking any mrs instruction, even if not related to the emulated > registers which made the pmu emulation inefficient. Applied to arm64 (for-next/cpufeature), thanks! [1/1] arm64: Restrict undef hook for cpufeature registers https://git.kernel.org/arm64/c/cf292e93f423 Cheers, -- Will https://fixes.arm64.dev https://next.arm64.dev https://will.arm64.dev _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel ^ permalink raw reply [flat|nested] 5+ messages in thread
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