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From: Marc Zyngier <maz@kernel.org>
To: James Morse <james.morse@arm.com>
Cc: linux-arm-kernel@lists.infradead.org,
	kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org,
	Julien Thierry <julien.thierry.kdev@gmail.com>,
	Suzuki K Poulose <suzuki.poulose@arm.com>,
	Andrew Scull <ascull@google.com>, Will Deacon <will@kernel.org>,
	Quentin Perret <qperret@google.com>,
	David Brazdil <dbrazdil@google.com>,
	kernel-team@android.com
Subject: Re: [PATCH 08/11] KVM: arm64: Inject AArch32 exceptions from HYP
Date: Wed, 28 Oct 2020 20:24:37 +0000	[thread overview]
Message-ID: <9c130c8e438f59ecd0072feea9addbcc@kernel.org> (raw)
In-Reply-To: <3691596f-fb42-a6e0-8aca-5a1605219c23@arm.com>

On 2020-10-28 19:20, James Morse wrote:
> Hi Marc,
> 
> On 27/10/2020 19:21, Marc Zyngier wrote:
>>>> +static inline u32 __vcpu_read_cp15(const struct kvm_vcpu *vcpu, int 
>>>> reg)
>>>> +{
>>>> +    return __vcpu_read_sys_reg(vcpu, reg / 2);
>>>> +}
> 
>>> Doesn't this re-implement the issue 3204be4109ad biased?
> 
>> I don't think it does. The issue existed when accessing the 32bit 
>> shadow,
>> and we had to pick which side of the 64bit register had our 32bit 
>> value.
>> Here, we directly access the 64bit file, which is safe.
> 
> Because its not accessing the copro union, and the two users are both
> straight forward aliases.
> 
> ...
> 
> What do I get if I call:
> | __vcpu_read_cp15(vcpu, c6_IFAR);
> 
> Won't this return the value of c6_DFAR instead as they live in the
> same 64 bit register.

Yes, that would break. Not in this bit of code though.

> 
> 
>> But thinking of it, we may as well change the call sites to directly
>> use the 64bit enum, rather than playing games
> 
> Great!

Yeah, and there is a bunch of ... crap around this aliasing.
Unfortunately, I just noticed that 32bit guests are borked in -rc1.
Debug time.

         M.
-- 
Jazz is not dead. It just smells funny...

  reply	other threads:[~2020-10-28 21:48 UTC|newest]

Thread overview: 34+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-26 13:34 [PATCH 00/11] KVM: arm64: Move PC/ELR/SPSR/PSTATE updatess to EL2 Marc Zyngier
2020-10-26 13:34 ` [PATCH 01/11] KVM: arm64: Don't adjust PC on SError during SMC trap Marc Zyngier
2020-10-26 13:53   ` Mark Rutland
2020-10-26 14:08     ` Marc Zyngier
2020-10-26 14:22       ` Mark Rutland
2020-10-26 13:34 ` [PATCH 02/11] KVM: arm64: Move kvm_vcpu_trap_il_is32bit into kvm_skip_instr32() Marc Zyngier
2020-10-26 13:55   ` Mark Rutland
2020-10-26 13:34 ` [PATCH 03/11] KVM: arm64: Make kvm_skip_instr() and co private to HYP Marc Zyngier
2020-10-26 14:04   ` Mark Rutland
2020-10-27 16:17     ` Marc Zyngier
2020-10-27 10:55   ` Suzuki K Poulose
2020-10-27 11:08     ` Marc Zyngier
2020-10-26 13:34 ` [PATCH 04/11] KVM: arm64: Move PC rollback on SError " Marc Zyngier
2020-10-26 14:06   ` Mark Rutland
2020-10-27 14:56   ` James Morse
2020-10-27 14:59     ` Marc Zyngier
2020-10-26 13:34 ` [PATCH 05/11] KVM: arm64: Move VHE direct sysreg accessors into kvm_host.h Marc Zyngier
2020-10-26 14:07   ` Mark Rutland
2020-10-26 13:34 ` [PATCH 06/11] KVM: arm64: Add basic hooks for injecting exceptions from EL2 Marc Zyngier
2020-10-26 13:34 ` [PATCH 07/11] KVM: arm64: Inject AArch64 exceptions from HYP Marc Zyngier
2020-10-26 14:22   ` Mark Rutland
2020-10-27 16:21     ` Marc Zyngier
2020-10-27 17:41   ` James Morse
2020-10-27 18:49     ` Marc Zyngier
2020-10-26 13:34 ` [PATCH 08/11] KVM: arm64: Inject AArch32 " Marc Zyngier
2020-10-26 14:26   ` Mark Rutland
2020-10-27 17:41   ` James Morse
2020-10-27 19:21     ` Marc Zyngier
2020-10-28 19:20       ` James Morse
2020-10-28 20:24         ` Marc Zyngier [this message]
2020-10-26 13:34 ` [PATCH 09/11] KVM: arm64: Remove SPSR manipulation primitives Marc Zyngier
2020-10-26 14:30   ` Mark Rutland
2020-10-26 13:34 ` [PATCH 10/11] KVM: arm64: Consolidate exception injection Marc Zyngier
2020-10-26 13:34 ` [PATCH 11/11] KVM: arm64: Get rid of the AArch32 register mapping code Marc Zyngier

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