From: Suzuki K Poulose <suzuki.poulose@arm.com>
To: Peter Maydell <peter.maydell@linaro.org>
Cc: arm-mail-list <linux-arm-kernel@lists.infradead.org>,
kvmarm@lists.cs.columbia.edu, kvm-devel <kvm@vger.kernel.org>,
"Marc Zyngier" <marc.zyngier@arm.com>,
"Christoffer Dall" <cdall@kernel.org>,
"Eric Auger" <eric.auger@redhat.com>,
"Paolo Bonzini" <pbonzini@redhat.com>,
"Radim Krčmář" <rkrcmar@redhat.com>,
"Will Deacon" <will.deacon@arm.com>,
"Catalin Marinas" <catalin.marinas@arm.com>,
"James Morse" <james.morse@arm.com>,
"Dave P Martin" <dave.martin@arm.com>,
julien.grall@arm.com,
"lkml - Kernel Mailing List" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v5 18/18] kvm: arm64: Allow tuning the physical address size for VM
Date: Wed, 19 Sep 2018 11:03:11 +0100 [thread overview]
Message-ID: <e818aa74-a34e-91fa-ad5a-344816105840@arm.com> (raw)
In-Reply-To: <CAFEAcA_tphfZ_BKfAYuefStTipta0notyAR=NCnWFJ6nRfERpg@mail.gmail.com>
On 09/18/2018 06:15 PM, Peter Maydell wrote:
> On 18 September 2018 at 17:27, Suzuki K Poulose <Suzuki.Poulose@arm.com> wrote:
>> ---
>>
>> "On arm64, the physical address size for a VM (IPA Size limit) is limited
>> to 40bits by default. The limit can be configured if the host supports the
>> extension KVM_CAP_ARM_VM_IPA_SIZE. When supported, use
>> KVM_VM_TYPE_ARM_IPA_SIZE(IPA_Bits) to set the size in the machine type
>> identifier, where IPA_Bits is the maximum width of any physical
>> address used by the VM. The IPA_Bits is encoded in bits[7-0] of the
>> machine type identifier.
>>
>> e.g, to configure a guest to use 48bit physical address size :
>>
>> vm_fd = ioctl(dev_fd, KVM_CREATE_VM, KVM_VM_TYPE_ARM_IPA_SIZE(48));
>>
>> The requested size (IPA_Bits) must be :
>> 0 - Implies default 40bits (for backward compatibility)
>>
>> or
>>
>> N - Implies N bits, where N is a positive integer such that 32 <= N <=
>> Host_IPA_Limit
>>
>> Host_IPA_Limit is the maximum possible value for IPA_Bits on the host and
>> is dependent on the CPU capability and the kernel configuration. The limit
>> can
>> be retrieved using KVM_CAP_ARM_VM_IPA_SIZE of the KVM_CHECK_EXTENSION
>> ioctl() at run-time.
>>
>> Please note that configuring the IPA size does not affect the capability
>> exposed by the guest CPUs in ID_AA64MMFR0_EL1[PARange]. It only affects
>> the guest to host physical address (stage2) translations setup by the host.
>> "
>
> Thanks, this is much clearer. The only bit I'm not sure about is that
> last paragraph -- if I ask for a VM with a 48 bit address space why
> don't we tell the guest that that's what it has ?
The point is the IPA Size is not a limit on the CPU's PA size. e.g, if
this guest was a nested hypervisor with 48bit IPA, it could still
support a 52bit IPA nested guest within by simply looking up the CPU
PARange. The IPA size configuration here is simply a hint to the
hypervisor on where the memory banks would be kept. And this certainly
true on real platforms (e.g, my Juno has 42bit PARange on A57, while
A53 reports 40bit, with PA max at 40bits).
Suzuki
WARNING: multiple messages have this Message-ID (diff)
From: Suzuki K Poulose <suzuki.poulose@arm.com>
To: Peter Maydell <peter.maydell@linaro.org>
Cc: Christoffer Dall <cdall@kernel.org>,
kvm-devel <kvm@vger.kernel.org>,
Marc Zyngier <marc.zyngier@arm.com>,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will.deacon@arm.com>,
lkml - Kernel Mailing List <linux-kernel@vger.kernel.org>,
Dave P Martin <dave.martin@arm.com>,
Paolo Bonzini <pbonzini@redhat.com>,
kvmarm@lists.cs.columbia.edu,
arm-mail-list <linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH v5 18/18] kvm: arm64: Allow tuning the physical address size for VM
Date: Wed, 19 Sep 2018 11:03:11 +0100 [thread overview]
Message-ID: <e818aa74-a34e-91fa-ad5a-344816105840@arm.com> (raw)
In-Reply-To: <CAFEAcA_tphfZ_BKfAYuefStTipta0notyAR=NCnWFJ6nRfERpg@mail.gmail.com>
On 09/18/2018 06:15 PM, Peter Maydell wrote:
> On 18 September 2018 at 17:27, Suzuki K Poulose <Suzuki.Poulose@arm.com> wrote:
>> ---
>>
>> "On arm64, the physical address size for a VM (IPA Size limit) is limited
>> to 40bits by default. The limit can be configured if the host supports the
>> extension KVM_CAP_ARM_VM_IPA_SIZE. When supported, use
>> KVM_VM_TYPE_ARM_IPA_SIZE(IPA_Bits) to set the size in the machine type
>> identifier, where IPA_Bits is the maximum width of any physical
>> address used by the VM. The IPA_Bits is encoded in bits[7-0] of the
>> machine type identifier.
>>
>> e.g, to configure a guest to use 48bit physical address size :
>>
>> vm_fd = ioctl(dev_fd, KVM_CREATE_VM, KVM_VM_TYPE_ARM_IPA_SIZE(48));
>>
>> The requested size (IPA_Bits) must be :
>> 0 - Implies default 40bits (for backward compatibility)
>>
>> or
>>
>> N - Implies N bits, where N is a positive integer such that 32 <= N <=
>> Host_IPA_Limit
>>
>> Host_IPA_Limit is the maximum possible value for IPA_Bits on the host and
>> is dependent on the CPU capability and the kernel configuration. The limit
>> can
>> be retrieved using KVM_CAP_ARM_VM_IPA_SIZE of the KVM_CHECK_EXTENSION
>> ioctl() at run-time.
>>
>> Please note that configuring the IPA size does not affect the capability
>> exposed by the guest CPUs in ID_AA64MMFR0_EL1[PARange]. It only affects
>> the guest to host physical address (stage2) translations setup by the host.
>> "
>
> Thanks, this is much clearer. The only bit I'm not sure about is that
> last paragraph -- if I ask for a VM with a 48 bit address space why
> don't we tell the guest that that's what it has ?
The point is the IPA Size is not a limit on the CPU's PA size. e.g, if
this guest was a nested hypervisor with 48bit IPA, it could still
support a 52bit IPA nested guest within by simply looking up the CPU
PARange. The IPA size configuration here is simply a hint to the
hypervisor on where the memory banks would be kept. And this certainly
true on real platforms (e.g, my Juno has 42bit PARange on A57, while
A53 reports 40bit, with PA max at 40bits).
Suzuki
WARNING: multiple messages have this Message-ID (diff)
From: suzuki.poulose@arm.com (Suzuki K Poulose)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH v5 18/18] kvm: arm64: Allow tuning the physical address size for VM
Date: Wed, 19 Sep 2018 11:03:11 +0100 [thread overview]
Message-ID: <e818aa74-a34e-91fa-ad5a-344816105840@arm.com> (raw)
In-Reply-To: <CAFEAcA_tphfZ_BKfAYuefStTipta0notyAR=NCnWFJ6nRfERpg@mail.gmail.com>
On 09/18/2018 06:15 PM, Peter Maydell wrote:
> On 18 September 2018 at 17:27, Suzuki K Poulose <Suzuki.Poulose@arm.com> wrote:
>> ---
>>
>> "On arm64, the physical address size for a VM (IPA Size limit) is limited
>> to 40bits by default. The limit can be configured if the host supports the
>> extension KVM_CAP_ARM_VM_IPA_SIZE. When supported, use
>> KVM_VM_TYPE_ARM_IPA_SIZE(IPA_Bits) to set the size in the machine type
>> identifier, where IPA_Bits is the maximum width of any physical
>> address used by the VM. The IPA_Bits is encoded in bits[7-0] of the
>> machine type identifier.
>>
>> e.g, to configure a guest to use 48bit physical address size :
>>
>> vm_fd = ioctl(dev_fd, KVM_CREATE_VM, KVM_VM_TYPE_ARM_IPA_SIZE(48));
>>
>> The requested size (IPA_Bits) must be :
>> 0 - Implies default 40bits (for backward compatibility)
>>
>> or
>>
>> N - Implies N bits, where N is a positive integer such that 32 <= N <=
>> Host_IPA_Limit
>>
>> Host_IPA_Limit is the maximum possible value for IPA_Bits on the host and
>> is dependent on the CPU capability and the kernel configuration. The limit
>> can
>> be retrieved using KVM_CAP_ARM_VM_IPA_SIZE of the KVM_CHECK_EXTENSION
>> ioctl() at run-time.
>>
>> Please note that configuring the IPA size does not affect the capability
>> exposed by the guest CPUs in ID_AA64MMFR0_EL1[PARange]. It only affects
>> the guest to host physical address (stage2) translations setup by the host.
>> "
>
> Thanks, this is much clearer. The only bit I'm not sure about is that
> last paragraph -- if I ask for a VM with a 48 bit address space why
> don't we tell the guest that that's what it has ?
The point is the IPA Size is not a limit on the CPU's PA size. e.g, if
this guest was a nested hypervisor with 48bit IPA, it could still
support a 52bit IPA nested guest within by simply looking up the CPU
PARange. The IPA size configuration here is simply a hint to the
hypervisor on where the memory banks would be kept. And this certainly
true on real platforms (e.g, my Juno has 42bit PARange on A57, while
A53 reports 40bit, with PA max at 40bits).
Suzuki
next prev parent reply other threads:[~2018-09-19 10:02 UTC|newest]
Thread overview: 120+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-17 10:41 [PATCH v5 00/18] kvm: arm64: Dynamic IPA and 52bit IPA Suzuki K Poulose
2018-09-17 10:41 ` Suzuki K Poulose
2018-09-17 10:41 ` [PATCH v5 01/18] kvm: arm/arm64: Fix stage2_flush_memslot for 4 level page table Suzuki K Poulose
2018-09-17 10:41 ` Suzuki K Poulose
2018-09-17 10:41 ` [PATCH v5 02/18] kvm: arm/arm64: Remove spurious WARN_ON Suzuki K Poulose
2018-09-17 10:41 ` Suzuki K Poulose
2018-09-17 10:41 ` Suzuki K Poulose
2018-09-17 10:41 ` [PATCH v5 03/18] kvm: arm64: Add helper for loading the stage2 setting for a VM Suzuki K Poulose
2018-09-17 10:41 ` Suzuki K Poulose
2018-09-17 10:41 ` Suzuki K Poulose
2018-09-17 10:41 ` [PATCH v5 04/18] arm64: Add a helper for PARange to physical shift conversion Suzuki K Poulose
2018-09-17 10:41 ` Suzuki K Poulose
2018-09-17 10:41 ` [PATCH v5 05/18] kvm: arm64: Clean up VTCR_EL2 initialisation Suzuki K Poulose
2018-09-17 10:41 ` Suzuki K Poulose
2018-09-17 10:41 ` [PATCH v5 06/18] kvm: arm/arm64: Allow arch specific configurations for VM Suzuki K Poulose
2018-09-17 10:41 ` Suzuki K Poulose
2018-09-20 10:22 ` Auger Eric
2018-09-20 10:22 ` Auger Eric
2018-09-20 10:22 ` Auger Eric
2018-09-17 10:41 ` [PATCH v5 07/18] kvm: arm64: Configure VTCR_EL2 per VM Suzuki K Poulose
2018-09-17 10:41 ` Suzuki K Poulose
2018-09-17 10:41 ` Suzuki K Poulose
2018-09-20 10:21 ` Auger Eric
2018-09-20 10:21 ` Auger Eric
2018-09-20 10:38 ` Suzuki K Poulose
2018-09-20 10:38 ` Suzuki K Poulose
2018-09-20 10:38 ` Suzuki K Poulose
2018-09-17 10:41 ` [PATCH v5 08/18] kvm: arm/arm64: Prepare for VM specific stage2 translations Suzuki K Poulose
2018-09-17 10:41 ` Suzuki K Poulose
2018-09-20 14:07 ` Auger Eric
2018-09-20 14:07 ` Auger Eric
2018-09-20 14:07 ` Auger Eric
2018-09-17 10:41 ` [PATCH v5 09/18] kvm: arm64: Prepare for dynamic stage2 page table layout Suzuki K Poulose
2018-09-17 10:41 ` Suzuki K Poulose
2018-09-17 10:41 ` Suzuki K Poulose
2018-09-17 10:41 ` [PATCH v5 10/18] kvm: arm64: Make stage2 page table layout dynamic Suzuki K Poulose
2018-09-17 10:41 ` Suzuki K Poulose
2018-09-20 14:07 ` Auger Eric
2018-09-20 14:07 ` Auger Eric
2018-09-17 10:41 ` [PATCH v5 11/18] kvm: arm64: Dynamic configuration of VTTBR mask Suzuki K Poulose
2018-09-17 10:41 ` Suzuki K Poulose
2018-09-20 14:07 ` Auger Eric
2018-09-20 14:07 ` Auger Eric
2018-09-20 15:22 ` Suzuki K Poulose
2018-09-20 15:22 ` Suzuki K Poulose
2018-09-20 15:22 ` Suzuki K Poulose
2018-09-25 11:56 ` Auger Eric
2018-09-25 11:56 ` Auger Eric
2018-09-17 10:41 ` [PATCH v5 12/18] kvm: arm64: Configure VTCR_EL2.SL0 per VM Suzuki K Poulose
2018-09-17 10:41 ` Suzuki K Poulose
2018-09-20 14:25 ` Auger Eric
2018-09-20 14:25 ` Auger Eric
2018-09-20 15:25 ` Suzuki K Poulose
2018-09-20 15:25 ` Suzuki K Poulose
2018-09-20 15:25 ` Suzuki K Poulose
2018-09-17 10:41 ` [PATCH v5 13/18] kvm: arm64: Switch to per VM IPA limit Suzuki K Poulose
2018-09-17 10:41 ` Suzuki K Poulose
2018-09-17 10:41 ` [PATCH v5 14/18] vgic: Add support for 52bit guest physical address Suzuki K Poulose
2018-09-17 10:41 ` Suzuki K Poulose
2018-09-21 14:57 ` Auger Eric
2018-09-21 14:57 ` Auger Eric
2018-09-25 10:49 ` Suzuki K Poulose
2018-09-25 10:49 ` Suzuki K Poulose
2018-09-17 10:41 ` [PATCH v5 15/18] kvm: arm64: Add 52bit support for PAR to HPFAR conversoin Suzuki K Poulose
2018-09-17 10:41 ` Suzuki K Poulose
2018-09-17 10:41 ` Suzuki K Poulose
2018-09-25 9:59 ` Auger Eric
2018-09-25 9:59 ` Auger Eric
2018-09-17 10:41 ` [PATCH v5 16/18] kvm: arm64: Set a limit on the IPA size Suzuki K Poulose
2018-09-17 10:41 ` Suzuki K Poulose
2018-09-25 9:59 ` Auger Eric
2018-09-25 9:59 ` Auger Eric
2018-09-25 9:59 ` Auger Eric
2018-09-25 11:10 ` Suzuki K Poulose
2018-09-25 11:10 ` Suzuki K Poulose
2018-09-25 11:10 ` Suzuki K Poulose
2018-09-17 10:41 ` [PATCH v5 17/18] kvm: arm64: Limit the minimum number of page table levels Suzuki K Poulose
2018-09-17 10:41 ` Suzuki K Poulose
2018-09-25 10:00 ` Auger Eric
2018-09-25 10:00 ` Auger Eric
2018-09-25 10:25 ` Suzuki K Poulose
2018-09-25 10:25 ` Suzuki K Poulose
2018-09-17 10:41 ` [PATCH v5 18/18] kvm: arm64: Allow tuning the physical address size for VM Suzuki K Poulose
2018-09-17 10:41 ` Suzuki K Poulose
2018-09-17 14:20 ` Peter Maydell
2018-09-17 14:20 ` Peter Maydell
2018-09-17 14:43 ` Suzuki K Poulose
2018-09-17 14:43 ` Suzuki K Poulose
2018-09-18 1:55 ` Peter Maydell
2018-09-18 1:55 ` Peter Maydell
2018-09-18 1:55 ` Peter Maydell
2018-09-18 15:16 ` Suzuki K Poulose
2018-09-18 15:16 ` Suzuki K Poulose
2018-09-18 15:36 ` Peter Maydell
2018-09-18 15:36 ` Peter Maydell
2018-09-18 16:27 ` Suzuki K Poulose
2018-09-18 16:27 ` Suzuki K Poulose
2018-09-18 16:27 ` Suzuki K Poulose
2018-09-18 17:15 ` Peter Maydell
2018-09-18 17:15 ` Peter Maydell
2018-09-19 10:03 ` Suzuki K Poulose [this message]
2018-09-19 10:03 ` Suzuki K Poulose
2018-09-19 10:03 ` Suzuki K Poulose
2018-09-25 10:00 ` Auger Eric
2018-09-25 10:00 ` Auger Eric
2018-09-25 10:24 ` Suzuki K Poulose
2018-09-25 10:24 ` Suzuki K Poulose
2018-09-25 10:24 ` Suzuki K Poulose
2018-09-17 10:41 ` [kvmtool PATCH v5 19/18] kvmtool: Allow backends to run checks on the KVM device fd Suzuki K Poulose
2018-09-17 10:41 ` Suzuki K Poulose
2018-09-17 10:41 ` Suzuki K Poulose
2018-09-17 10:41 ` [kvmtool PATCH v5 20/18] kvmtool: arm64: Add support for guest physical address size Suzuki K Poulose
2018-09-17 10:41 ` Suzuki K Poulose
2018-09-17 10:41 ` Suzuki K Poulose
2018-09-17 10:41 ` [kvmtool PATCH v5 21/18] kvmtool: arm64: Switch memory layout Suzuki K Poulose
2018-09-17 10:41 ` Suzuki K Poulose
2018-09-17 10:41 ` Suzuki K Poulose
2018-09-17 10:41 ` [kvmtool PATCH v5 22/18] kvmtool: arm: Add support for creating VM with PA size Suzuki K Poulose
2018-09-17 10:41 ` Suzuki K Poulose
2018-09-17 10:41 ` Suzuki K Poulose
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