[PATCH v2 07/10] powerpc/perf: support BHRB disable bit and new filtering modes
Michael Ellerman
mpe at ellerman.id.au
Wed Jul 8 21:42:02 AEST 2020
Athira Rajeev <atrajeev at linux.vnet.ibm.com> writes:
> PowerISA v3.1 has few updates for the Branch History Rolling Buffer(BHRB).
^
a
> First is the addition of BHRB disable bit and second new filtering
^
is
> modes for BHRB.
>
> BHRB disable is controlled via Monitor Mode Control Register A (MMCRA)
> bit 26, namely "BHRB Recording Disable (BHRBRD)". This field controls
Most people call that bit 37.
> whether BHRB entries are written when BHRB recording is enabled by other
> bits. Patch implements support for this BHRB disable bit.
^
This
> Secondly PowerISA v3.1 introduce filtering support for
.. that should be in a separate patch please.
> PERF_SAMPLE_BRANCH_IND_CALL/COND. The patch adds BHRB filter support
^
This
> for "ind_call" and "cond" in power10_bhrb_filter_map().
>
> 'commit bb19af816025 ("powerpc/perf: Prevent kernel address leak to userspace via BHRB buffer")'
That doesn't need single quotes, and should be wrapped at 72 columns
like the rest of the text.
> added a check in bhrb_read() to filter the kernel address from BHRB buffer. Patch here modified
> it to avoid that check for PowerISA v3.1 based processors, since PowerISA v3.1 allows
> only MSR[PR]=1 address to be written to BHRB buffer.
And that should be a separate patch again please.
> Signed-off-by: Athira Rajeev <atrajeev at linux.vnet.ibm.com>
> ---
> arch/powerpc/perf/core-book3s.c | 27 +++++++++++++++++++++------
> arch/powerpc/perf/isa207-common.c | 13 +++++++++++++
> arch/powerpc/perf/power10-pmu.c | 13 +++++++++++--
> arch/powerpc/platforms/powernv/idle.c | 14 ++++++++++++++
> 4 files changed, 59 insertions(+), 8 deletions(-)
>
> diff --git a/arch/powerpc/perf/core-book3s.c b/arch/powerpc/perf/core-book3s.c
> index fad5159..9709606 100644
> --- a/arch/powerpc/perf/core-book3s.c
> +++ b/arch/powerpc/perf/core-book3s.c
> @@ -466,9 +466,13 @@ static void power_pmu_bhrb_read(struct perf_event *event, struct cpu_hw_events *
> * addresses at this point. Check the privileges before
> * exporting it to userspace (avoid exposure of regions
> * where we could have speculative execution)
> + * Incase of ISA 310, BHRB will capture only user-space
^
In case of ISA v3.1,
> + * address,hence include a check before filtering code
^ ^
addresses, hence .
> */
> - if (is_kernel_addr(addr) && perf_allow_kernel(&event->attr) != 0)
> - continue;
> + if (!(ppmu->flags & PPMU_ARCH_310S))
> + if (is_kernel_addr(addr) &&
> + perf_allow_kernel(&event->attr) != 0)
> + continue;
The indentation is weird. You should just check all three conditions
with &&.
>
> /* Branches are read most recent first (ie. mfbhrb 0 is
> * the most recent branch).
> @@ -1212,7 +1216,7 @@ static void write_mmcr0(struct cpu_hw_events *cpuhw, unsigned long mmcr0)
> static void power_pmu_disable(struct pmu *pmu)
> {
> struct cpu_hw_events *cpuhw;
> - unsigned long flags, mmcr0, val;
> + unsigned long flags, mmcr0, val, mmcra = 0;
You initialise it below.
> if (!ppmu)
> return;
> @@ -1245,12 +1249,23 @@ static void power_pmu_disable(struct pmu *pmu)
> mb();
> isync();
>
> + val = mmcra = cpuhw->mmcr[2];
> +
For mmcr0 (above), val is the variable we mutate and mmcr0 is the
original value. But here you've done the reverse, which is confusing.
> /*
> * Disable instruction sampling if it was enabled
> */
> - if (cpuhw->mmcr[2] & MMCRA_SAMPLE_ENABLE) {
> - mtspr(SPRN_MMCRA,
> - cpuhw->mmcr[2] & ~MMCRA_SAMPLE_ENABLE);
> + if (cpuhw->mmcr[2] & MMCRA_SAMPLE_ENABLE)
> + mmcra = cpuhw->mmcr[2] & ~MMCRA_SAMPLE_ENABLE;
You just loaded cpuhw->mmcr[2] into mmcra, use it rather than referring
back to cpuhw->mmcr[2] over and over.
> +
> + /* Disable BHRB via mmcra [:26] for p10 if needed */
> + if (!(cpuhw->mmcr[2] & MMCRA_BHRB_DISABLE))
You don't need to check that it's clear AFAICS. Just always set disable
and the check against val below will catch the nop case.
> + mmcra |= MMCRA_BHRB_DISABLE;
> +
> + /* Write SPRN_MMCRA if mmcra has either disabled
Comment format is wrong.
> + * instruction sampling or BHRB
Full stop please.
> + */
> + if (val != mmcra) {
> + mtspr(SPRN_MMCRA, mmcra);
> mb();
> isync();
> }
> diff --git a/arch/powerpc/perf/isa207-common.c b/arch/powerpc/perf/isa207-common.c
> index 7d4839e..463d925 100644
> --- a/arch/powerpc/perf/isa207-common.c
> +++ b/arch/powerpc/perf/isa207-common.c
> @@ -404,6 +404,12 @@ int isa207_compute_mmcr(u64 event[], int n_ev,
>
> mmcra = mmcr1 = mmcr2 = mmcr3 = 0;
>
> + /* Disable bhrb unless explicitly requested
> + * by setting MMCRA [:26] bit.
> + */
Comment format again.
> + if (cpu_has_feature(CPU_FTR_ARCH_31))
> + mmcra |= MMCRA_BHRB_DISABLE;
Here we do a feature check before setting MMCRA_BHRB_DISABLE, but you
didn't above?
> +
> /* Second pass: assign PMCs, set all MMCR1 fields */
> for (i = 0; i < n_ev; ++i) {
> pmc = (event[i] >> EVENT_PMC_SHIFT) & EVENT_PMC_MASK;
> @@ -475,10 +481,17 @@ int isa207_compute_mmcr(u64 event[], int n_ev,
> }
>
> if (event[i] & EVENT_WANTS_BHRB) {
> + /* set MMCRA[:26] to 0 for Power10 to enable BHRB */
"set MMCRA[:26] to 0" == "clear MMCRA[:26]"
> + if (cpu_has_feature(CPU_FTR_ARCH_31))
> + mmcra &= ~MMCRA_BHRB_DISABLE;
Newline please.
> val = (event[i] >> EVENT_IFM_SHIFT) & EVENT_IFM_MASK;
> mmcra |= val << MMCRA_IFM_SHIFT;
> }
>
> + /* set MMCRA[:26] to 0 if there is user request for BHRB */
> + if (cpu_has_feature(CPU_FTR_ARCH_31) && has_branch_stack(pevents[i]))
> + mmcra &= ~MMCRA_BHRB_DISABLE;
> +
I think it would be cleaner if you did a single test, eg:
if (cpu_has_feature(CPU_FTR_ARCH_31) &&
(has_branch_stack(pevents[i]) || (event[i] & EVENT_WANTS_BHRB)))
mmcra &= ~MMCRA_BHRB_DISABLE;
> if (pevents[i]->attr.exclude_user)
> mmcr2 |= MMCR2_FCP(pmc);
>
> diff --git a/arch/powerpc/perf/power10-pmu.c b/arch/powerpc/perf/power10-pmu.c
> index d64d69d..07fb919 100644
> --- a/arch/powerpc/perf/power10-pmu.c
> +++ b/arch/powerpc/perf/power10-pmu.c
> @@ -82,6 +82,8 @@
>
> /* MMCRA IFM bits - POWER10 */
> #define POWER10_MMCRA_IFM1 0x0000000040000000UL
> +#define POWER10_MMCRA_IFM2 0x0000000080000000UL
> +#define POWER10_MMCRA_IFM3 0x00000000C0000000UL
> #define POWER10_MMCRA_BHRB_MASK 0x00000000C0000000UL
>
> /* Table of alternatives, sorted by column 0 */
> @@ -233,8 +235,15 @@ static u64 power10_bhrb_filter_map(u64 branch_sample_type)
> if (branch_sample_type & PERF_SAMPLE_BRANCH_ANY_RETURN)
> return -1;
>
> - if (branch_sample_type & PERF_SAMPLE_BRANCH_IND_CALL)
> - return -1;
> + if (branch_sample_type & PERF_SAMPLE_BRANCH_IND_CALL) {
> + pmu_bhrb_filter |= POWER10_MMCRA_IFM2;
> + return pmu_bhrb_filter;
> + }
> +
> + if (branch_sample_type & PERF_SAMPLE_BRANCH_COND) {
> + pmu_bhrb_filter |= POWER10_MMCRA_IFM3;
> + return pmu_bhrb_filter;
> + }
>
> if (branch_sample_type & PERF_SAMPLE_BRANCH_CALL)
> return -1;
> diff --git a/arch/powerpc/platforms/powernv/idle.c b/arch/powerpc/platforms/powernv/idle.c
> index 2dd4673..7db99c7 100644
> --- a/arch/powerpc/platforms/powernv/idle.c
> +++ b/arch/powerpc/platforms/powernv/idle.c
> @@ -611,6 +611,7 @@ static unsigned long power9_idle_stop(unsigned long psscr, bool mmu_on)
> unsigned long srr1;
> unsigned long pls;
> unsigned long mmcr0 = 0;
> + unsigned long mmcra_bhrb = 0;
> struct p9_sprs sprs = {}; /* avoid false used-uninitialised */
> bool sprs_saved = false;
>
> @@ -657,6 +658,15 @@ static unsigned long power9_idle_stop(unsigned long psscr, bool mmu_on)
> */
> mmcr0 = mfspr(SPRN_MMCR0);
> }
> +
> + if (cpu_has_feature(CPU_FTR_ARCH_31)) {
> + /* POWER10 uses MMCRA[:26] as BHRB disable bit
Comment format.
> + * to disable BHRB logic when not used. Hence Save and
> + * restore MMCRA after a state-loss idle.
> + */
> + mmcra_bhrb = mfspr(SPRN_MMCRA);
> + }
It's the whole mmcra it should be called mmcra?
> +
> if ((psscr & PSSCR_RL_MASK) >= pnv_first_spr_loss_level) {
> sprs.lpcr = mfspr(SPRN_LPCR);
> sprs.hfscr = mfspr(SPRN_HFSCR);
> @@ -721,6 +731,10 @@ static unsigned long power9_idle_stop(unsigned long psscr, bool mmu_on)
> mtspr(SPRN_MMCR0, mmcr0);
> }
>
> + /* Reload MMCRA to restore BHRB disable bit for POWER10 */
> + if (cpu_has_feature(CPU_FTR_ARCH_31))
> + mtspr(SPRN_MMCRA, mmcra_bhrb);
> +
> /*
> * DD2.2 and earlier need to set then clear bit 60 in MMCRA
> * to ensure the PMU starts running.
cheers
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