Re: [Qemu-devel] [kvm-unit-tests PATCH 3/4] arm/arm64: GICv2: add GICD_ITARGETSR testing

[Auger Eric <eric.auger@redhat.com>]

Hi Andre,
On 23/11/2016 15:13, Andre Przywara wrote:
> Hi Eric,
> 
> thanks for having such a close look (as always!).
> 
> On 23/11/16 13:51, Auger Eric wrote:
>> Hi Andre,
>>
>> On 23/11/2016 14:24, Auger Eric wrote:
>>> Hi,
>>>
>>> On 18/11/2016 15:20, Andrew Jones wrote:
>>>> On Thu, Nov 17, 2016 at 05:57:51PM +0000, Andre Przywara wrote:
>>>>> Some tests for the ITARGETS registers.
>>>>> Bits corresponding to non-existent CPUs must be RAZ/WI.
>>>>> These registers must be byte-accessible, also check that accesses beyond
>>>>> the implemented IRQ limit are actually read-as-zero/write-ignore.
>>>>>
>>>>> Signed-off-by: Andre Przywara <andre.przywara@arm.com>
>>>>> ---
>>>>>  arm/gic.c         | 54 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
>>>>>  lib/arm/asm/gic.h |  1 +
>>>>>  2 files changed, 55 insertions(+)
>>>>>
>>>>> diff --git a/arm/gic.c b/arm/gic.c
>>>>> index a27da2c..02b1be1 100644
>>>>> --- a/arm/gic.c
>>>>> +++ b/arm/gic.c
>>>>> @@ -397,6 +397,57 @@ static bool test_priorities(int nr_irqs, void *priptr)
>>>>>  	return true;
>>>>>  }
>>>>>  
>>>>> +static bool test_targets(int nr_irqs)
>>>>> +{
>>>>> +	void *targetsptr = gicv2_dist_base() + GICD_ITARGETSR;
>>>>> +	u32 orig_targets;
>>>>> +	u32 cpu_mask;
>>>>> +	u32 pattern, reg;
>>>>> +
>>>>> +	orig_targets = readl(targetsptr + 32);
>>>>> +	report_prefix_push("ITARGETSR");
>>>>> +
>>>>> +	cpu_mask = (1 << nr_cpus) - 1;
>>>>
>>>> Shouldn't this be 1 << (nr_cpus - 1) ?
>>> original looks correct to me.
>>>>
>>>> Is this test always going to be gicv2-only? We should probably comment it,
>>>> if so. We don't want to risk this being run when nr_cpus can be larger
>>>> than 8.
>>>>
>>>>> +	cpu_mask |= cpu_mask << 8;
> 
> So this instruction is supposed to copy bits[7:0] into bits[15:8] (not
> caring about the other bits, which are zero anyway).
> 
>>>>> +	cpu_mask |= cpu_mask << 16;
> 
> And this one copies bits[15:0] into bits[31:16].
> 
>>> Don't we miss the 4th byte mask?
> 
> I don't think so, the idea is just to copy the lowest byte into all the
> other three bytes of that word and thus to propagate the byte mask for
> one IRQ into a word covering four interrupts. Does that make sense?

Hum yes that's fully correct. Sorry for the noise.
> I take it this deserves a comment then ...
> 
>>>>> +
>>>>> +	/* Check that bits for non implemented CPUs are RAZ/WI. */
>>>>> +	if (nr_cpus < 8) {
>>>>> +		writel(0xffffffff, targetsptr + 32);
>>>>> +		report("bits for %d non-existent CPUs masked",
>>>>> +		       !(readl(targetsptr + 32) & ~cpu_mask), 8 - nr_cpus);
>>
>> yep on AMD overdrive with smp=4 I get:
>>
>> FAIL: gicv2: mmio: ITARGETSR: bits for 4 non-existent CPUs masked
> 
> I guess because you don't have
> http://lists.infradead.org/pipermail/linux-arm-kernel/2016-November/468296.html
> in your host kernel?
> This was one of the two genuine bugs I spotted with this.

Ah ok cool!

Cheers

Eric
> 
> Cheers,
> Andre.
> 
>>>>> +	} else {
>>>>> +		report_skip("CPU masking (all CPUs implemented)");
>>>>> +	}
>>>>> +
>>>>> +	report("accesses beyond limit RAZ/WI",
>>>>> +	       test_readonly_32(targetsptr + nr_irqs, true));
>>>>> +
>>>>> +	pattern = 0x0103020f;
>>>>> +	writel(pattern, targetsptr + 32);
>>>>> +	reg = readl(targetsptr + 32);
>>>>> +	report("register content preserved (%08x => %08x)",
>>>>> +	       reg == (pattern & cpu_mask), pattern & cpu_mask, reg);
>>>>> +
>>>>> +	/*
>>>>> +	 * The TARGETS registers are byte accessible, do a byte-wide
>>>>> +	 * read and write of known content to check for this.
>>>>> +	 */
>>>>> +	reg = readb(targetsptr + 33);
>>>>> +	report("byte reads successful (0x%08x => 0x%02x)",
>>>>> +	       reg == (BYTE(pattern, 1) & cpu_mask),
>>>>> +	       pattern & cpu_mask, reg);
>>>>> +
>>>>> +	pattern = REPLACE_BYTE(pattern, 2, 0x04);
>>>>> +	writeb(BYTE(pattern, 2), targetsptr + 34);
>>>>> +	reg = readl(targetsptr + 32);
>>>>> +	report("byte writes successful (0x%02x => 0x%08x)",
>>>>> +	       reg == (pattern & cpu_mask), BYTE(pattern, 2), reg);
>>>>
>>>> Last patch also had a byte addressability test. Maybe we should make
>>>> a helper function?
>>>>
>>>>> +
>>>>> +	writel(orig_targets, targetsptr + 32);
>>>>> +	return true;
>>>>
>>>> Function can/should be void.
>>>>
>>>>> +}
>>>>> +
>>>>>  static int gic_test_mmio(int gic_version)
>>>>>  {
>>>>>  	u32 reg;
>>>>> @@ -436,6 +487,9 @@ static int gic_test_mmio(int gic_version)
>>>>>  
>>>>>  	test_priorities(nr_irqs, gic_dist_base + GICD_IPRIORITYR);
>>>>>  
>>>>> +	if (gic_version == 2)
>>>>> +		test_targets(nr_irqs);
>>>>> +
>>>>>  	return 0;
>>>>>  }
>>>>>  
>>>>> diff --git a/lib/arm/asm/gic.h b/lib/arm/asm/gic.h
>>>>> index cef748d..6f170cb 100644
>>>>> --- a/lib/arm/asm/gic.h
>>>>> +++ b/lib/arm/asm/gic.h
>>>>> @@ -14,6 +14,7 @@
>>>>>  #define GICD_IGROUPR			0x0080
>>>>>  #define GICD_ISENABLER			0x0100
>>>>>  #define GICD_IPRIORITYR			0x0400
>>>>> +#define GICD_ITARGETSR			0x0800
>>>>>  #define GICD_SGIR			0x0f00
>>>>>  #define GICD_ICPIDR2			0x0fe8
>>>>>  
>>>>> -- 
>>>>> 2.9.0
>>>>>
>>>>>
>>>>
>>>> Thanks,
>>>> drew
>>>>
>