From: Marc Zyngier <maz@kernel.org>
To: Mark Rutland <mark.rutland@arm.com>
Cc: Will Deacon <will@kernel.org>,
kernel-team@android.com, kvmarm@lists.cs.columbia.edu,
linux-arm-kernel@lists.infradead.org, kvm@vger.kernel.org
Subject: Re: [PATCH 03/11] KVM: arm64: Make kvm_skip_instr() and co private to HYP
Date: Tue, 27 Oct 2020 16:17:31 +0000 [thread overview]
Message-ID: <bde9a2a8233f3d7e96751ad3640b11b7@kernel.org> (raw)
In-Reply-To: <20201026140435.GE12454@C02TD0UTHF1T.local>
On 2020-10-26 14:04, Mark Rutland wrote:
> On Mon, Oct 26, 2020 at 01:34:42PM +0000, Marc Zyngier wrote:
>> In an effort to remove the vcpu PC manipulations from EL1 on nVHE
>> systems, move kvm_skip_instr() to be HYP-specific. EL1's intent
>> to increment PC post emulation is now signalled via a flag in the
>> vcpu structure.
>>
>> Signed-off-by: Marc Zyngier <maz@kernel.org>
>
> [...]
>
>> +/*
>> + * Adjust the guest PC on entry, depending on flags provided by EL1
>> + * for the purpose of emulation (MMIO, sysreg).
>> + */
>> +static inline void __adjust_pc(struct kvm_vcpu *vcpu)
>> +{
>> + if (vcpu->arch.flags & KVM_ARM64_INCREMENT_PC) {
>> + kvm_skip_instr(vcpu);
>> + vcpu->arch.flags &= ~KVM_ARM64_INCREMENT_PC;
>> + }
>> +}
>
> What's your plan for restricting *when* EL1 can ask for the PC to be
> adjusted?
>
> I'm assuming that either:
>
> 1. You have EL2 sanity-check all responses from EL1 are permitted for
> the current state. e.g. if EL1 asks to increment the PC, EL2 must
> check that that was a sane response for the current state.
>
> 2. You raise the level of abstraction at the EL2/EL1 boundary, such
> that
> EL2 simply knows. e.g. if emulating a memory access, EL1 can either
> provide the response or signal an abort, but doesn't choose to
> manipulate the PC as EL2 will infer the right thing to do.
>
> I know that either are tricky in practice, so I'm curious what your
> view
> is. Generally option #2 is easier to fortify, but I guess we might have
> to do #1 since we also have to support unprotected VMs?
To be honest, I'm still in two minds about it, which is why I have
gone with this "middle of the road" option (moving the PC update
to EL2, but leave the control at EL1).
I guess the answer is "it depends". MMIO is easy to put in the #2 model,
while things like WFI/WFE really need #1. sysregs are yet another can of
worm.
M.
--
Jazz is not dead. It just smells funny...
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next prev parent reply other threads:[~2020-10-27 16:18 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 [this message]
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
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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