Re: [PATCH v2 6/8] hw/intc: GICv3 redistributor ITS processing

[Peter Maydell]

On Thu, 1 Apr 2021 at 03:41, Shashi Mallela <shashi.mallela@linaro.org> wrote:
>
> Implemented lpi processing at redistributor to get lpi config info
> from lpi configuration table,determine priority,set pending state in
> lpi pending table and forward the lpi to cpuif.Added logic to invoke
> redistributor lpi processing with translated LPI which set/clear LPI
> from ITS device as part of ITS INT,CLEAR,DISCARD command and
> GITS_TRANSLATER processing.

Nit: commas should all have a space following.

>
> Signed-off-by: Shashi Mallela <shashi.mallela@linaro.org>
> ---
>  hw/intc/arm_gicv3.c        |   6 ++
>  hw/intc/arm_gicv3_cpuif.c  |  15 +++--
>  hw/intc/arm_gicv3_its.c    |   9 ++-
>  hw/intc/arm_gicv3_redist.c | 124 +++++++++++++++++++++++++++++++++++++
>  hw/intc/gicv3_internal.h   |   9 +++
>  5 files changed, 158 insertions(+), 5 deletions(-)
>
> diff --git a/hw/intc/arm_gicv3.c b/hw/intc/arm_gicv3.c
> index 66eaa97198..618fa1af95 100644
> --- a/hw/intc/arm_gicv3.c
> +++ b/hw/intc/arm_gicv3.c
> @@ -166,6 +166,12 @@ static void gicv3_redist_update_noirqset(GICv3CPUState 
> *cs)
>          cs->hppi.grp = gicv3_irq_group(cs->gic, cs, cs->hppi.irq);
>      }
>
> +    if (cs->gic->lpi_enable) {
> +        if (gicv3_redist_update_lpi(cs)) {
> +            seenbetter = true;
> +        }
> +    }

> +
>      /* If the best interrupt we just found would preempt whatever
>       * was the previous best interrupt before this update, then
>       * we know it's definitely the best one now.
> diff --git a/hw/intc/arm_gicv3_cpuif.c b/hw/intc/arm_gicv3_cpuif.c
> index 43ef1d7a84..c225b80f66 100644
> --- a/hw/intc/arm_gicv3_cpuif.c
> +++ b/hw/intc/arm_gicv3_cpuif.c
> @@ -899,9 +899,14 @@ static void icc_activate_irq(GICv3CPUState *cs, int irq)
>          cs->gicr_ipendr0 = deposit32(cs->gicr_ipendr0, irq, 1, 0);
>          gicv3_redist_update(cs);
>      } else {
> -        gicv3_gicd_active_set(cs->gic, irq);
> -        gicv3_gicd_pending_clear(cs->gic, irq);
> -        gicv3_update(cs->gic, irq, 1);
> +        if (irq >= GICV3_LPI_INTID_START) {
> +            gicv3_redist_lpi_pending(cs, irq, 0);
> +            gicv3_redist_update(cs);
> +        } else {
> +            gicv3_gicd_active_set(cs->gic, irq);
> +            gicv3_gicd_pending_clear(cs->gic, irq);
> +            gicv3_update(cs->gic, irq, 1);
> +        }
>      }
>  }
>
> @@ -1337,7 +1342,9 @@ static void icc_eoir_write(CPUARMState *env, const 
> ARMCPRegInfo *ri,
>           * valid interrupt value read from the Interrupt Acknowledge
>           * register" and so this is UNPREDICTABLE. We choose to ignore it.
>           */
> -        return;
> +        if (!(cs->gic->lpi_enable && (irq >= GICV3_LPI_INTID_START))) {
> +            return;
> +        }

This condition is in the wrong place. I think what you are trying to
do is modify "what is the set of numbers we consider to be valid IRQ
numbers", in which case you want to be changing the outer
"if (irq >= cs->gic->num_irq)" condition, not adding an extra one
inside it.

More importantly, the thing this condition is guarding is that
the code below it assumes that IRQ numbers are in range for the
GIC's own internal non-LPI interrupts. If you allow numbers
>= cs->gic->num_irq through, then you will get array overruns
when icc_deactivate_irq() tries to clear its Active bit.

>      }
>
>      if (icc_highest_active_group(cs) != grp) {
> diff --git a/hw/intc/arm_gicv3_its.c b/hw/intc/arm_gicv3_its.c
> index 0e3f176809..41e1e8b2a8 100644
> --- a/hw/intc/arm_gicv3_its.c
> +++ b/hw/intc/arm_gicv3_its.c
> @@ -226,6 +226,7 @@ static MemTxResult process_int(GICv3ITSState *s, uint64_t 
> value,
>      bool ite_valid = false;
>      uint64_t cte = 0;
>      bool cte_valid = false;
> +    uint64_t rdbase;
>      uint8_t buff[ITS_ITT_ENTRY_SIZE];
>      uint64_t itt_addr;
>
> @@ -278,12 +279,18 @@ static MemTxResult process_int(GICv3ITSState *s, 
> uint64_t value,
>               * since with a physical address the target address must be
>               * 64KB aligned
>               */
> -
> +            rdbase = (cte >> 1U) & RDBASE_MASK;

What's going on here? Shouldn't this be in a previous patch ?

>              /*
>               * Current implementation only supports rdbase == procnum
>               * Hence rdbase physical address is ignored
>               */
>          } else {
> +            rdbase = (cte >> 1U) & RDBASE_PROCNUM_MASK;
> +            if ((cmd == CLEAR) || (cmd == DISCARD)) {
> +                gicv3_redist_process_lpi(&s->gicv3->cpu[rdbase], pIntid, 0);
> +            } else {
> +                gicv3_redist_process_lpi(&s->gicv3->cpu[rdbase], pIntid, 1);
> +            }
>
>              if (cmd == DISCARD) {
>                  /* remove mapping from interrupt translation table */
> diff --git a/hw/intc/arm_gicv3_redist.c b/hw/intc/arm_gicv3_redist.c
> index 325b974e70..71c648a616 100644
> --- a/hw/intc/arm_gicv3_redist.c
> +++ b/hw/intc/arm_gicv3_redist.c
> @@ -254,6 +254,8 @@ static MemTxResult gicr_writel(GICv3CPUState *cs, hwaddr 
> offset,
>          if (cs->gicr_typer & GICR_TYPER_PLPIS) {
>              if (value & GICR_CTLR_ENABLE_LPIS) {
>                  cs->gicr_ctlr |= GICR_CTLR_ENABLE_LPIS;
> +                /* Check for any pending interr in pending table */
> +                gicv3_redist_update(cs);
>              } else {
>                  cs->gicr_ctlr &= ~GICR_CTLR_ENABLE_LPIS;
>              }
> @@ -548,6 +550,128 @@ MemTxResult gicv3_redist_write(void *opaque, hwaddr 
> offset, uint64_t data,
>      return r;
>  }
>
> +bool gicv3_redist_update_lpi(GICv3CPUState *cs)

Could we have a comment explaining what this function does, please ?

> +{
> +    AddressSpace *as = &cs->gic->sysmem_as;
> +    uint64_t lpict_baddr, lpipt_baddr;
> +    uint32_t pendt_size = 0;
> +    uint8_t lpite;
> +    uint8_t prio, pend;
> +    int i;
> +    bool seenbetter = false;
> +
> +    if ((!cs->gicr_ctlr & GICR_CTLR_ENABLE_LPIS) || !cs->gicr_propbaser ||
> +        !cs->gicr_pendbaser || cs->lpi_outofrange) {
> +        return seenbetter;
> +    }
> +
> +    lpict_baddr = FIELD_EX64(cs->gicr_propbaser, GICR_PROPBASER, PHYADDR);
> +    lpict_baddr <<= R_GICR_PROPBASER_PHYADDR_SHIFT;
> +
> +    lpipt_baddr =  FIELD_EX64(cs->gicr_pendbaser, GICR_PENDBASER, PHYADDR);
> +    lpipt_baddr <<= R_GICR_PENDBASER_PHYADDR_SHIFT;
> +
> +    /* Determine the highest priority pending interrupt among LPIs */
> +    pendt_size = (1UL << (FIELD_EX64(cs->gicr_propbaser, GICR_PROPBASER,
> +                          IDBITS) - 1));

This is where you should be handling "actually the table is empty"
or "table size is capped at the implementation's maximum size".

> +
> +    for (i = 0; i < pendt_size; i++) {
> +        address_space_read(as, lpipt_baddr +
> +                (((GICV3_LPI_INTID_START + i) / 8) * sizeof(pend)),
> +                MEMTXATTRS_UNSPECIFIED, &pend, sizeof(pend));
> +
> +        if ((1 << ((GICV3_LPI_INTID_START + i) % 8)) & pend) {
> +            address_space_read(as, lpict_baddr + (i * sizeof(lpite)),
> +                      MEMTXATTRS_UNSPECIFIED, &lpite, sizeof(lpite));
> +
> +            prio = ((lpite >> LPI_CTE_PRIORITY_OFFSET) &
> +                     LPI_CTE_PRIORITY_MASK);
> +            prio &= LPI_PRIORITY_MASK;
> +
> +            if (prio < cs->hppi.prio) {
> +                cs->hppi.irq = GICV3_LPI_INTID_START + i;
> +                cs->hppi.prio = prio;
> +                /* LPIs are always non-secure Grp1 interrupts */
> +                cs->hppi.grp = GICV3_G1NS;
> +                seenbetter = true;
> +            }
> +        }
> +    }

Oof. How big is an LPI configuration table, typically? I'm not sure we want
to be scanning the entire LPI configuration table in guest memory for every
time gicv3_redist_update() is called if we can avoid it.

A bit of benchmarking of how much this slows down emulation might
be interesting.

> +    return seenbetter;
> +}
> +
> +void gicv3_redist_lpi_pending(GICv3CPUState *cs, int irq, int level)
> +{
> +    AddressSpace *as = &cs->gic->sysmem_as;
> +    uint64_t lpipt_baddr;
> +    bool ispend = false;
> +    uint8_t pend;
> +
> +    /*
> +     * get the bit value corresponding to this irq in the
> +     * lpi pending table
> +     */
> +    lpipt_baddr = FIELD_EX64(cs->gicr_pendbaser, GICR_PENDBASER, PHYADDR);
> +    lpipt_baddr <<= R_GICR_PENDBASER_PHYADDR_SHIFT;
> +
> +    address_space_read(as, lpipt_baddr + ((irq / 8) * sizeof(pend)),
> +                         MEMTXATTRS_UNSPECIFIED, &pend, sizeof(pend));
> +    ispend = ((pend >> (irq % 8)) & 0x1);
> +
> +    if (ispend) {
> +        if (!level) {
> +            /*
> +             * clear the pending bit and update the lpi pending table
> +             */
> +            pend &= ~(1 << (irq % 8));
> +
> +            address_space_write(as, lpipt_baddr + ((irq / 8) * sizeof(pend)),
> +                                 MEMTXATTRS_UNSPECIFIED, &pend, 
> sizeof(pend));
> +        }
> +    } else {
> +        if (level) {
> +            /*
> +             * if pending bit is not already set for this irq,turn-on the
> +             * pending bit and update the lpi pending table
> +             */
> +            pend |= (1 << (irq % 8));
> +
> +            address_space_write(as, lpipt_baddr + ((irq / 8) * sizeof(pend)),
> +                                 MEMTXATTRS_UNSPECIFIED, &pend, 
> sizeof(pend));
> +        }
> +    }
> +}
>
> +void gicv3_redist_process_lpi(GICv3CPUState *cs, int irq, int level)
> +{
> +    AddressSpace *as = &cs->gic->sysmem_as;
> +    uint64_t lpict_baddr;
> +    uint8_t lpite;
> +
> +    if ((!cs->gicr_ctlr & GICR_CTLR_ENABLE_LPIS) || !cs->gicr_propbaser ||
> +         !cs->gicr_pendbaser || cs->lpi_outofrange) {
> +        return;
> +    }
> +
> +    lpict_baddr = FIELD_EX64(cs->gicr_propbaser, GICR_PROPBASER, PHYADDR);
> +    lpict_baddr <<= R_GICR_PROPBASER_PHYADDR_SHIFT;
> +
> +    /* get the lpi config table entry corresponding to this irq */
> +    address_space_read(as, lpict_baddr + ((irq - GICV3_LPI_INTID_START) *
> +                        sizeof(lpite)), MEMTXATTRS_UNSPECIFIED,
> +                        &lpite, sizeof(lpite));
> +
> +    /* check if this irq is enabled before proceeding further */
> +    if (!(lpite & LPI_CTE_ENABLED)) {
> +        return;
> +    }
> +
> +    /* set/clear the pending bit for this irq */
> +    gicv3_redist_lpi_pending(cs, irq, level);
> +
> +    gicv3_redist_update(cs);
> +}
> +
>  void gicv3_redist_set_irq(GICv3CPUState *cs, int irq, int level)
>  {
>      /* Update redistributor state for a change in an external PPI input line 
> */
> diff --git a/hw/intc/gicv3_internal.h b/hw/intc/gicv3_internal.h
> index a2718704d4..4c97c22850 100644
> --- a/hw/intc/gicv3_internal.h
> +++ b/hw/intc/gicv3_internal.h
> @@ -306,6 +306,12 @@ FIELD(GITS_TYPER, CIL, 36, 1)
>
>  #define L1TABLE_ENTRY_SIZE         8
>
> +#define LPI_CTE_ENABLE_OFFSET      0
> +#define LPI_CTE_ENABLED          VALID_MASK
> +#define LPI_CTE_PRIORITY_OFFSET    2
> +#define LPI_CTE_PRIORITY_MASK     ((1U << 6) - 1)
> +#define LPI_PRIORITY_MASK         0xfc
> +
>  #define GITS_CMDQ_ENTRY_SIZE               32
>  #define NUM_BYTES_IN_DW                     8
>
> @@ -444,6 +450,9 @@ MemTxResult gicv3_redist_write(void *opaque, hwaddr 
> offset, uint64_t data,
>                                 unsigned size, MemTxAttrs attrs);
>  void gicv3_dist_set_irq(GICv3State *s, int irq, int level);
>  void gicv3_redist_set_irq(GICv3CPUState *cs, int irq, int level);
> +void gicv3_redist_process_lpi(GICv3CPUState *cs, int irq, int level);
> +void gicv3_redist_lpi_pending(GICv3CPUState *cs, int irq, int level);
> +bool gicv3_redist_update_lpi(GICv3CPUState *cs);
>  void gicv3_redist_send_sgi(GICv3CPUState *cs, int grp, int irq, bool ns);
>  void gicv3_init_cpuif(GICv3State *s);

thanks
-- PMM