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From: Julien Grall <Julien.Grall@arm.com>
To: Christoffer Dall <Christoffer.Dall@arm.com>,
	"kvmarm@lists.cs.columbia.edu" <kvmarm@lists.cs.columbia.edu>,
	"linux-arm-kernel@lists.infradead.org"
	<linux-arm-kernel@lists.infradead.org>
Cc: Marc Zyngier <Marc.Zyngier@arm.com>, nd <nd@arm.com>,
	"kvm@vger.kernel.org" <kvm@vger.kernel.org>
Subject: Re: [PATCH 06/14] KVM: arm/arm64: Factor out VMID into struct kvm_vmid
Date: Thu, 21 Feb 2019 11:02:56 +0000	[thread overview]
Message-ID: <1978ee57-c7bd-e55a-4e77-ad0b4b62d1d1@arm.com> (raw)
In-Reply-To: <20190124140032.8588-7-christoffer.dall@arm.com>

Hi Christoffer,

On 24/01/2019 14:00, Christoffer Dall wrote:
> Note that to avoid mapping the kvm_vmid_bits variable into hyp, we
> simply forego the masking of the vmid value in kvm_get_vttbr and rely on
> update_vmid to always assign a valid vmid value (within the supported
> range).

[...]

> -	kvm->arch.vmid = kvm_next_vmid;
> +	vmid->vmid = kvm_next_vmid;
>   	kvm_next_vmid++;
> -	kvm_next_vmid &= (1 << kvm_vmid_bits) - 1;
> -
> -	/* update vttbr to be used with the new vmid */
> -	pgd_phys = virt_to_phys(kvm->arch.pgd);
> -	BUG_ON(pgd_phys & ~kvm_vttbr_baddr_mask(kvm));
> -	vmid = ((u64)(kvm->arch.vmid) << VTTBR_VMID_SHIFT) & VTTBR_VMID_MASK(kvm_vmid_bits);
> -	kvm->arch.vttbr = kvm_phys_to_vttbr(pgd_phys) | vmid | cnp;
> +	kvm_next_vmid &= (1 << kvm_get_vmid_bits()) - 1;

The arm64 version of kvm_get_vmid_bits does not look cheap. Indeed it required 
to read the sanitized value of SYS_ID_AA64MMFR1_EL1 that is implemented using 
the function bsearch.

So wouldn't it be better to keep kvm_vmid_bits variable for use in update_vttbr()?

Cheers,

-- 
Julien Grall

WARNING: multiple messages have this Message-ID (diff)
From: Julien Grall <Julien.Grall@arm.com>
To: Christoffer Dall <Christoffer.Dall@arm.com>,
	"kvmarm@lists.cs.columbia.edu" <kvmarm@lists.cs.columbia.edu>,
	"linux-arm-kernel@lists.infradead.org"
	<linux-arm-kernel@lists.infradead.org>
Cc: Marc Zyngier <Marc.Zyngier@arm.com>, nd <nd@arm.com>,
	"kvm@vger.kernel.org" <kvm@vger.kernel.org>
Subject: Re: [PATCH 06/14] KVM: arm/arm64: Factor out VMID into struct kvm_vmid
Date: Thu, 21 Feb 2019 11:02:56 +0000	[thread overview]
Message-ID: <1978ee57-c7bd-e55a-4e77-ad0b4b62d1d1@arm.com> (raw)
In-Reply-To: <20190124140032.8588-7-christoffer.dall@arm.com>

Hi Christoffer,

On 24/01/2019 14:00, Christoffer Dall wrote:
> Note that to avoid mapping the kvm_vmid_bits variable into hyp, we
> simply forego the masking of the vmid value in kvm_get_vttbr and rely on
> update_vmid to always assign a valid vmid value (within the supported
> range).

[...]

> -	kvm->arch.vmid = kvm_next_vmid;
> +	vmid->vmid = kvm_next_vmid;
>   	kvm_next_vmid++;
> -	kvm_next_vmid &= (1 << kvm_vmid_bits) - 1;
> -
> -	/* update vttbr to be used with the new vmid */
> -	pgd_phys = virt_to_phys(kvm->arch.pgd);
> -	BUG_ON(pgd_phys & ~kvm_vttbr_baddr_mask(kvm));
> -	vmid = ((u64)(kvm->arch.vmid) << VTTBR_VMID_SHIFT) & VTTBR_VMID_MASK(kvm_vmid_bits);
> -	kvm->arch.vttbr = kvm_phys_to_vttbr(pgd_phys) | vmid | cnp;
> +	kvm_next_vmid &= (1 << kvm_get_vmid_bits()) - 1;

The arm64 version of kvm_get_vmid_bits does not look cheap. Indeed it required 
to read the sanitized value of SYS_ID_AA64MMFR1_EL1 that is implemented using 
the function bsearch.

So wouldn't it be better to keep kvm_vmid_bits variable for use in update_vttbr()?

Cheers,

-- 
Julien Grall
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

  parent reply	other threads:[~2019-02-21 11:02 UTC|newest]

Thread overview: 65+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-01-24 14:00 [PATCH 00/14] KVM: arm/arm64: Various rework in preparation of nested virt support Christoffer Dall
2019-01-24 14:00 ` Christoffer Dall
2019-01-24 14:00 ` [PATCH 01/14] arm/arm64: KVM: Introduce kvm_call_hyp_ret() Christoffer Dall
2019-01-24 14:00   ` Christoffer Dall
2019-01-24 14:00 ` [PATCH 02/14] arm64: KVM: Allow for direct call of HYP functions when using VHE Christoffer Dall
2019-01-24 14:00   ` Christoffer Dall
2019-01-24 14:00 ` [PATCH 03/14] arm64: KVM: Drop VHE-specific HYP call stub Christoffer Dall
2019-01-24 14:00   ` Christoffer Dall
2019-01-24 14:00 ` [PATCH 04/14] ARM: KVM: Teach some form of type-safety to kvm_call_hyp Christoffer Dall
2019-01-24 14:00   ` Christoffer Dall
2019-01-24 14:00 ` [PATCH 05/14] arm/arm64: KVM: Statically configure the host's view of MPIDR Christoffer Dall
2019-01-24 14:00   ` Christoffer Dall
2019-01-24 14:00 ` [PATCH 06/14] KVM: arm/arm64: Factor out VMID into struct kvm_vmid Christoffer Dall
2019-01-24 14:00   ` Christoffer Dall
2019-01-24 19:01   ` James Morse
2019-01-24 19:01     ` James Morse
2019-01-25 10:09     ` Marc Zyngier
2019-01-25 10:09       ` Marc Zyngier
2019-01-25 11:05   ` Julien Thierry
2019-01-25 11:05     ` Julien Thierry
2019-01-31 13:01     ` Marc Zyngier
2019-01-31 13:01       ` Marc Zyngier
2019-02-21 11:02   ` Julien Grall [this message]
2019-02-21 11:02     ` Julien Grall
2019-02-22  9:18     ` Marc Zyngier
2019-02-22  9:18       ` Marc Zyngier
2019-02-22 11:42       ` Julien Grall
2019-02-22 11:42         ` Julien Grall
2019-02-22 12:14         ` Marc Zyngier
2019-02-22 12:14           ` Marc Zyngier
2019-01-24 14:00 ` [PATCH 07/14] KVM: arm/arm64: Simplify bg_timer programming Christoffer Dall
2019-01-24 14:00   ` Christoffer Dall
2019-01-24 14:00 ` [PATCH 08/14] KVM: arm64: Fix ICH_ELRSR_EL2 sysreg naming Christoffer Dall
2019-01-24 14:00   ` Christoffer Dall
2019-01-24 14:00 ` [PATCH 09/14] KVM: arm64: Reuse sys_reg() macro when searching the trap table Christoffer Dall
2019-01-24 14:00   ` Christoffer Dall
2019-01-30  8:57   ` André Przywara
2019-01-30  8:57     ` André Przywara
2019-01-24 14:00 ` [PATCH 10/14] KVM: arm/arm64: consolidate arch timer trap handlers Christoffer Dall
2019-01-24 14:00   ` Christoffer Dall
2019-01-25 12:33   ` Julien Thierry
2019-01-25 12:33     ` Julien Thierry
2019-01-30 17:38     ` Marc Zyngier
2019-01-30 17:38       ` Marc Zyngier
2019-01-24 14:00 ` [PATCH 11/14] KVM: arm/arm64: timer: Rework data structures for multiple timers Christoffer Dall
2019-01-24 14:00   ` Christoffer Dall
2019-02-18 15:10   ` André Przywara
2019-02-18 15:10     ` André Przywara
2019-02-19 12:27     ` Christoffer Dall
2019-02-19 12:27       ` Christoffer Dall
2019-01-24 14:00 ` [PATCH 12/14] KVM: arm/arm64: arch_timer: Assign the phys timer on VHE systems Christoffer Dall
2019-01-24 14:00   ` Christoffer Dall
2019-02-18 15:10   ` André Przywara
2019-02-18 15:10     ` André Przywara
2019-02-19 12:43     ` Christoffer Dall
2019-02-19 12:43       ` Christoffer Dall
2019-02-20 17:58       ` Andre Przywara
2019-02-19 11:39   ` Alexandru Elisei
2019-02-19 11:39     ` Alexandru Elisei
2019-02-19 13:03     ` Christoffer Dall
2019-02-19 13:03       ` Christoffer Dall
2019-01-24 14:00 ` [PATCH 13/14] KVM: arm/arm64: Rework the timer code to use a timer_map Christoffer Dall
2019-01-24 14:00   ` Christoffer Dall
2019-01-24 14:00 ` [PATCH 14/14] KVM: arm/arm64: Move kvm_is_write_fault to header file Christoffer Dall
2019-01-24 14:00   ` Christoffer Dall

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