From: Robin Murphy <robin.murphy@arm.com>
To: James Morse <james.morse@arm.com>, Marc Zyngier <maz@kernel.org>
Cc: kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
kvmarm@lists.cs.columbia.edu
Subject: Re: [PATCH 1/5] KVM: arm64: Fix missing RES1 in emulation of DBGBIDR
Date: Tue, 18 Feb 2020 18:01:13 +0000 [thread overview]
Message-ID: <a02252f6-1e9a-2a35-9944-f23e161583ab@arm.com> (raw)
In-Reply-To: <c1bd5c57-666e-0d54-1e7c-e45d0535ffe3@arm.com>
On 18/02/2020 5:43 pm, James Morse wrote:
> Hi Marc,
>
> $subject typo: ~/DBGBIDR/DBGDIDR/
>
> On 16/02/2020 18:53, Marc Zyngier wrote:
>> The AArch32 CP14 DBGDIDR has bit 15 set to RES1, which our current
>> emulation doesn't set. Just add the missing bit.
>
> So it does.
>
> Reviewed-by: James Morse <james.morse@arm.com>
>
>
>> diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
>> index 3e909b117f0c..da82c4b03aab 100644
>> --- a/arch/arm64/kvm/sys_regs.c
>> +++ b/arch/arm64/kvm/sys_regs.c
>> @@ -1658,7 +1658,7 @@ static bool trap_dbgidr(struct kvm_vcpu *vcpu,
>> p->regval = ((((dfr >> ID_AA64DFR0_WRPS_SHIFT) & 0xf) << 28) |
>> (((dfr >> ID_AA64DFR0_BRPS_SHIFT) & 0xf) << 24) |
>> (((dfr >> ID_AA64DFR0_CTX_CMPS_SHIFT) & 0xf) << 20)
>> - | (6 << 16) | (el3 << 14) | (el3 << 12));
>> + | (6 << 16) | (1 << 15) | (el3 << 14) | (el3 << 12));
>
> Hmmm, where el3 is:
> | u32 el3 = !!cpuid_feature_extract_unsigned_field(pfr, ID_AA64PFR0_EL3_SHIFT);
>
> Aren't we depending on the compilers 'true' being 1 here?
Pretty much, but thankfully the only compilers we support are C compilers:
"The result of the logical negation operator ! is 0 if the value of its
operand compares unequal to 0, 1 if the value of its operand compares
equal to 0. The result has type int."
And now I have you to thank for flashbacks to bitwise logical operators
in Visual Basic... :P
Robin.
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next prev parent reply other threads:[~2020-02-18 18:01 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-16 18:53 [PATCH 0/5] Random debug/PMU fixes for 5.6 Marc Zyngier
2020-02-16 18:53 ` [PATCH 1/5] KVM: arm64: Fix missing RES1 in emulation of DBGBIDR Marc Zyngier
2020-02-18 17:43 ` James Morse
2020-02-18 18:01 ` Robin Murphy [this message]
2020-02-18 18:15 ` James Morse
2020-02-16 18:53 ` [PATCH 2/5] KVM: arm64: Refactor filtering of ID registers Marc Zyngier
2020-02-20 14:12 ` Andre Przywara
2020-02-16 18:53 ` [PATCH 3/5] kvm: arm64: Limit PMU version to ARMv8.1 Marc Zyngier
2020-02-18 17:43 ` James Morse
2020-02-19 9:46 ` Marc Zyngier
2020-02-19 10:18 ` James Morse
2020-02-19 11:14 ` Marc Zyngier
2020-02-16 18:53 ` [PATCH 4/5] KVM: arm64: Limit the debug architecture to ARMv8.0 Marc Zyngier
2020-02-18 17:45 ` James Morse
2020-02-16 18:53 ` [PATCH 5/5] KVM: arm64: Upgrade PMU support to ARMv8.4 Marc Zyngier
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