Messages in this thread | | | Subject | Re: [PATCH v2] irqchip/gic-v4: fix occasional VLPI drop | From | Heyi Guo <> | Date | Tue, 29 Jan 2019 09:32:55 +0800 |
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Hi Marc,
Any comments?
Thanks,
Heyi
On 2019/1/24 21:37, Heyi Guo wrote: > 1. In current implementation, every VLPI will temporarily be mapped to > the first CPU in system (normally CPU0) and then moved to the real > scheduled CPU later. > > 2. So there is a time window and a VLPI may be sent to CPU0 instead of > the real scheduled vCPU, in a multi-CPU virtual machine. > > 3. However, CPU0 may have not been scheduled as a virtual CPU after > system boots up, so the value of its GICR_VPROPBASER is unknown at > that moment. > > 4. If the INTID of VLPI is larger than 2^(GICR_VPROPBASER.IDbits+1), > while IDbits is also in unknown state, GIC will behave as if the VLPI > is out of range and simply drop it, which results in interrupt missing > in Guest. > > As no code will clear GICR_VPROPBASER at runtime, we can safely > initialize the IDbits field at boot time for each CPU to get rid of > this issue. > > We also clear Valid bit of GICR_VPENDBASER in case any ancient > programming gets left in and causes memory corrupting. A new function > its_clear_vpend_valid() is added to reuse the code in > its_vpe_deschedule(). > > Signed-off-by: Heyi Guo <guoheyi@huawei.com> > Signed-off-by: Heyi Guo <heyi.guo@linaro.org> > --- > > Notes: > v2: > - Also wait GICR_VPENDBASER.Dirty bit to be 0 in initialization [Marc] > - Add a new function to reuse the code in its_vpe_deschedule() [Marc] > > drivers/irqchip/irq-gic-v3-its.c | 66 +++++++++++++++++++++++++++++----------- > 1 file changed, 49 insertions(+), 17 deletions(-) > > diff --git a/drivers/irqchip/irq-gic-v3-its.c b/drivers/irqchip/irq-gic-v3-its.c > index 3365d44..531e945 100644 > --- a/drivers/irqchip/irq-gic-v3-its.c > +++ b/drivers/irqchip/irq-gic-v3-its.c > @@ -2060,6 +2060,29 @@ static int __init allocate_lpi_tables(void) > return 0; > } > > +static u64 its_clear_vpend_valid(void __iomem *vlpi_base) > +{ > + u32 count = 1000000; /* 1s! */ > + bool clean; > + u64 val; > + > + val = gits_read_vpendbaser(vlpi_base + GICR_VPENDBASER); > + val &= ~GICR_VPENDBASER_Valid; > + gits_write_vpendbaser(val, vlpi_base + GICR_VPENDBASER); > + > + do { > + val = gits_read_vpendbaser(vlpi_base + GICR_VPENDBASER); > + clean = !(val & GICR_VPENDBASER_Dirty); > + if (!clean) { > + count--; > + cpu_relax(); > + udelay(1); > + } > + } while (!clean && count); > + > + return val; > +} > + > static void its_cpu_init_lpis(void) > { > void __iomem *rbase = gic_data_rdist_rd_base(); > @@ -2145,6 +2168,30 @@ static void its_cpu_init_lpis(void) > val |= GICR_CTLR_ENABLE_LPIS; > writel_relaxed(val, rbase + GICR_CTLR); > > + if (gic_rdists->has_vlpis) { > + void __iomem *vlpi_base = gic_data_rdist_vlpi_base(); > + > + /* > + * It's possible for CPU to receive VLPIs before it is > + * sheduled as a vPE, especially for the first CPU, and the > + * VLPI with INTID larger than 2^(IDbits+1) will be considered > + * as out of range and dropped by GIC. > + * So we initialize IDbits to known value to avoid VLPI drop. > + */ > + val = (LPI_NRBITS - 1) & GICR_VPROPBASER_IDBITS_MASK; > + pr_debug("GICv4: CPU%d: Init IDbits to 0x%llx for GICR_VPROPBASER\n", > + smp_processor_id(), val); > + gits_write_vpropbaser(val, vlpi_base + GICR_VPROPBASER); > + > + /* > + * Also clear Valid bit of GICR_VPENDBASER, in case some > + * ancient programming gets left in and has possibility of > + * corrupting memory. > + */ > + val = its_clear_vpend_valid(vlpi_base); > + WARN_ON(val & GICR_VPENDBASER_Dirty); > + } > + > /* Make sure the GIC has seen the above */ > dsb(sy); > out: > @@ -2757,26 +2804,11 @@ static void its_vpe_schedule(struct its_vpe *vpe) > static void its_vpe_deschedule(struct its_vpe *vpe) > { > void __iomem *vlpi_base = gic_data_rdist_vlpi_base(); > - u32 count = 1000000; /* 1s! */ > - bool clean; > u64 val; > > - /* We're being scheduled out */ > - val = gits_read_vpendbaser(vlpi_base + GICR_VPENDBASER); > - val &= ~GICR_VPENDBASER_Valid; > - gits_write_vpendbaser(val, vlpi_base + GICR_VPENDBASER); > - > - do { > - val = gits_read_vpendbaser(vlpi_base + GICR_VPENDBASER); > - clean = !(val & GICR_VPENDBASER_Dirty); > - if (!clean) { > - count--; > - cpu_relax(); > - udelay(1); > - } > - } while (!clean && count); > + val = its_clear_vpend_valid(vlpi_base); > > - if (unlikely(!clean && !count)) { > + if (unlikely(val & GICR_VPENDBASER_Dirty)) { > pr_err_ratelimited("ITS virtual pending table not cleaning\n"); > vpe->idai = false; > vpe->pending_last = true;
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