From: Dave Martin <Dave.Martin@arm.com>
To: Marc Zyngier <marc.zyngier@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>,
Christoffer Dall <cdall@kernel.org>,
kvmarm@lists.cs.columbia.edu,
linux-arm-kernel@lists.infradead.org,
Ard Biesheuvel <ard.biesheuvel@linaro.org>
Subject: Re: [PATCH v5 13/14] KVM: arm64: Fold redundant exit code checks out of fixup_guest_exit()
Date: Tue, 8 May 2018 13:30:31 +0100 [thread overview]
Message-ID: <20180508123031.GI7753@e103592.cambridge.arm.com> (raw)
In-Reply-To: <5b9460e5-207d-befd-446c-b9c7ec2bcc35@arm.com>
On Tue, May 08, 2018 at 12:59:39PM +0100, Marc Zyngier wrote:
> On 08/05/18 12:30, Dave Martin wrote:
> > On Tue, May 08, 2018 at 11:59:25AM +0100, Marc Zyngier wrote:
> >> On 04/05/18 17:05, Dave Martin wrote:
[...]
> >>> diff --git a/arch/arm64/kvm/hyp/switch.c b/arch/arm64/kvm/hyp/switch.c
> >>> index 39e9166..be09c52 100644
> >>> --- a/arch/arm64/kvm/hyp/switch.c
> >>> +++ b/arch/arm64/kvm/hyp/switch.c
> >>> @@ -385,11 +385,13 @@ static bool __hyp_text fixup_guest_exit(struct kvm_vcpu *vcpu, u64 *exit_code)
> >>> * same PC once the SError has been injected, and replay the
> >>> * trapping instruction.
> >>> */
> >>> - if (*exit_code == ARM_EXCEPTION_TRAP && !__populate_fault_info(vcpu))
> >>> + if (*exit_code != ARM_EXCEPTION_TRAP)
> >>> + goto exit;
> >>> +
> >>> + if (!__populate_fault_info(vcpu))
> >>> return true;
> >>>
> >>> - if (static_branch_unlikely(&vgic_v2_cpuif_trap) &&
> >>> - *exit_code == ARM_EXCEPTION_TRAP) {
> >>> + if (static_branch_unlikely(&vgic_v2_cpuif_trap)) {
> >>> bool valid;
> >>>
> >>> valid = kvm_vcpu_trap_get_class(vcpu) == ESR_ELx_EC_DABT_LOW &&
> >>> @@ -414,12 +416,12 @@ static bool __hyp_text fixup_guest_exit(struct kvm_vcpu *vcpu, u64 *exit_code)
> >>> if (!__skip_instr(vcpu))
> >>> *vcpu_cpsr(vcpu) &= ~DBG_SPSR_SS;
> >>> *exit_code = ARM_EXCEPTION_EL1_SERROR;
> >>> + goto exit;
> >>
> >> This goto...
> >>
> >>> }
> >>
> >> ... should be placed here. If this was a data abort, it cannot be a
> >> system register trap, and the below conditions cannot possibly apply.
> >
> > That sounds logically sensible, but to be clear, this would be a
> > semantic change to this function, right?
> >
> > (i.e., it forces skipping of the GICv3 handling code in a case where
> > it previously wasn't forced -- at least not within this function. The
> > arguments about whether vgic_v2_cpuif_trap and vgic_v3_cpuif_trap can
> > ever be true simultaneously still apply.)
>
> I agree that this is a slight semantic change, but one that makes sense,
> just like the one you've introduced in patch #12.
Agreed, just wanted to make sure I hadn't missed something in my
original refactoring.
Cheers
---Dave
WARNING: multiple messages have this Message-ID (diff)
From: Dave.Martin@arm.com (Dave Martin)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH v5 13/14] KVM: arm64: Fold redundant exit code checks out of fixup_guest_exit()
Date: Tue, 8 May 2018 13:30:31 +0100 [thread overview]
Message-ID: <20180508123031.GI7753@e103592.cambridge.arm.com> (raw)
In-Reply-To: <5b9460e5-207d-befd-446c-b9c7ec2bcc35@arm.com>
On Tue, May 08, 2018 at 12:59:39PM +0100, Marc Zyngier wrote:
> On 08/05/18 12:30, Dave Martin wrote:
> > On Tue, May 08, 2018 at 11:59:25AM +0100, Marc Zyngier wrote:
> >> On 04/05/18 17:05, Dave Martin wrote:
[...]
> >>> diff --git a/arch/arm64/kvm/hyp/switch.c b/arch/arm64/kvm/hyp/switch.c
> >>> index 39e9166..be09c52 100644
> >>> --- a/arch/arm64/kvm/hyp/switch.c
> >>> +++ b/arch/arm64/kvm/hyp/switch.c
> >>> @@ -385,11 +385,13 @@ static bool __hyp_text fixup_guest_exit(struct kvm_vcpu *vcpu, u64 *exit_code)
> >>> * same PC once the SError has been injected, and replay the
> >>> * trapping instruction.
> >>> */
> >>> - if (*exit_code == ARM_EXCEPTION_TRAP && !__populate_fault_info(vcpu))
> >>> + if (*exit_code != ARM_EXCEPTION_TRAP)
> >>> + goto exit;
> >>> +
> >>> + if (!__populate_fault_info(vcpu))
> >>> return true;
> >>>
> >>> - if (static_branch_unlikely(&vgic_v2_cpuif_trap) &&
> >>> - *exit_code == ARM_EXCEPTION_TRAP) {
> >>> + if (static_branch_unlikely(&vgic_v2_cpuif_trap)) {
> >>> bool valid;
> >>>
> >>> valid = kvm_vcpu_trap_get_class(vcpu) == ESR_ELx_EC_DABT_LOW &&
> >>> @@ -414,12 +416,12 @@ static bool __hyp_text fixup_guest_exit(struct kvm_vcpu *vcpu, u64 *exit_code)
> >>> if (!__skip_instr(vcpu))
> >>> *vcpu_cpsr(vcpu) &= ~DBG_SPSR_SS;
> >>> *exit_code = ARM_EXCEPTION_EL1_SERROR;
> >>> + goto exit;
> >>
> >> This goto...
> >>
> >>> }
> >>
> >> ... should be placed here. If this was a data abort, it cannot be a
> >> system register trap, and the below conditions cannot possibly apply.
> >
> > That sounds logically sensible, but to be clear, this would be a
> > semantic change to this function, right?
> >
> > (i.e., it forces skipping of the GICv3 handling code in a case where
> > it previously wasn't forced -- at least not within this function. The
> > arguments about whether vgic_v2_cpuif_trap and vgic_v3_cpuif_trap can
> > ever be true simultaneously still apply.)
>
> I agree that this is a slight semantic change, but one that makes sense,
> just like the one you've introduced in patch #12.
Agreed, just wanted to make sure I hadn't missed something in my
original refactoring.
Cheers
---Dave
next prev parent reply other threads:[~2018-05-08 12:30 UTC|newest]
Thread overview: 60+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-05-04 16:05 [PATCH v5 00/14] KVM: arm64: Optimise FPSIMD context switching Dave Martin
2018-05-04 16:05 ` Dave Martin
2018-05-04 16:05 ` [PATCH v5 01/14] thread_info: Add update_thread_flag() helpers Dave Martin
2018-05-04 16:05 ` Dave Martin
2018-05-04 16:05 ` [PATCH v5 02/14] arm64: Use update{,_tsk}_thread_flag() Dave Martin
2018-05-04 16:05 ` Dave Martin
2018-05-04 16:05 ` [PATCH v5 03/14] KVM: arm/arm64: Introduce kvm_arch_vcpu_run_pid_change Dave Martin
2018-05-04 16:05 ` Dave Martin
2018-05-08 8:56 ` Marc Zyngier
2018-05-08 8:56 ` Marc Zyngier
2018-05-04 16:05 ` [PATCH v5 04/14] KVM: arm64: Convert lazy FPSIMD context switch trap to C Dave Martin
2018-05-04 16:05 ` Dave Martin
2018-05-08 9:10 ` Marc Zyngier
2018-05-08 9:10 ` Marc Zyngier
2018-05-04 16:05 ` [PATCH v5 05/14] arm64: fpsimd: Generalise context saving for non-task contexts Dave Martin
2018-05-04 16:05 ` Dave Martin
2018-05-08 9:20 ` Marc Zyngier
2018-05-08 9:20 ` Marc Zyngier
2018-05-04 16:05 ` [PATCH v5 06/14] KVM: arm64: Optimise FPSIMD handling to reduce guest/host thrashing Dave Martin
2018-05-04 16:05 ` Dave Martin
2018-05-08 9:58 ` Marc Zyngier
2018-05-08 9:58 ` Marc Zyngier
2018-05-08 10:14 ` Dave Martin
2018-05-08 10:14 ` Dave Martin
2018-05-04 16:05 ` [PATCH v5 07/14] arm64/sve: Move read_zcr_features() out of cpufeature.h Dave Martin
2018-05-04 16:05 ` Dave Martin
2018-05-04 16:05 ` [PATCH v5 08/14] arm64/sve: Switch sve_pffr() argument from task to thread Dave Martin
2018-05-04 16:05 ` Dave Martin
2018-05-04 16:05 ` [PATCH v5 09/14] arm64/sve: Move sve_pffr() to fpsimd.h and make inline Dave Martin
2018-05-04 16:05 ` Dave Martin
2018-05-04 16:05 ` [PATCH v5 10/14] KVM: arm64: Save host SVE context as appropriate Dave Martin
2018-05-04 16:05 ` Dave Martin
2018-05-08 10:38 ` Marc Zyngier
2018-05-08 10:38 ` Marc Zyngier
2018-05-08 11:25 ` Dave Martin
2018-05-08 11:25 ` Dave Martin
2018-05-08 11:57 ` Marc Zyngier
2018-05-08 11:57 ` Marc Zyngier
2018-05-08 12:40 ` Dave Martin
2018-05-08 12:40 ` Dave Martin
2018-05-04 16:05 ` [PATCH v5 11/14] KVM: arm64: Remove eager host SVE state saving Dave Martin
2018-05-04 16:05 ` Dave Martin
2018-05-04 16:05 ` [PATCH v5 12/14] KVM: arm64: Remove redundant *exit_code changes in fpsimd_guest_exit() Dave Martin
2018-05-04 16:05 ` Dave Martin
2018-05-08 10:51 ` Marc Zyngier
2018-05-08 10:51 ` Marc Zyngier
2018-05-04 16:05 ` [PATCH v5 13/14] KVM: arm64: Fold redundant exit code checks out of fixup_guest_exit() Dave Martin
2018-05-04 16:05 ` Dave Martin
2018-05-08 10:59 ` Marc Zyngier
2018-05-08 10:59 ` Marc Zyngier
2018-05-08 11:30 ` Dave Martin
2018-05-08 11:30 ` Dave Martin
2018-05-08 11:59 ` Marc Zyngier
2018-05-08 11:59 ` Marc Zyngier
2018-05-08 12:30 ` Dave Martin [this message]
2018-05-08 12:30 ` Dave Martin
2018-05-04 16:05 ` [PATCH v5 14/14] KVM: arm64: Invoke FPSIMD context switch trap from C Dave Martin
2018-05-04 16:05 ` Dave Martin
2018-05-08 11:03 ` Marc Zyngier
2018-05-08 11:03 ` Marc Zyngier
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