From: Suzuki K Poulose <suzuki.poulose@arm.com>
To: Auger Eric <eric.auger@redhat.com>, linux-arm-kernel@lists.infradead.org
Cc: kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org,
marc.zyngier@arm.com, cdall@kernel.org, pbonzini@redhat.com,
rkrcmar@redhat.com, will.deacon@arm.com, catalin.marinas@arm.com,
james.morse@arm.com, dave.martin@arm.com, julien.grall@arm.com,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v5 16/18] kvm: arm64: Set a limit on the IPA size
Date: Tue, 25 Sep 2018 12:10:20 +0100 [thread overview]
Message-ID: <57b0954d-9510-e0fd-45be-4191e9d58f00@arm.com> (raw)
In-Reply-To: <d915accb-966f-5c3d-f969-45512ebd8ca5@redhat.com>
On 09/25/2018 10:59 AM, Auger Eric wrote:
> Hi Suzuki,
>
> On 9/17/18 12:41 PM, Suzuki K Poulose wrote:
>> So far we have restricted the IPA size of the VM to the default
>> value (40bits). Now that we can manage the IPA size per VM and
>> support dynamic stage2 page tables, we can allow VMs to have
>> larger IPA. This patch introduces a the maximum IPA size
>> supported on the host.
> to be reworded
> This is decided by the following factors :
Sure
>> diff --git a/arch/arm64/kvm/reset.c b/arch/arm64/kvm/reset.c
>> index 51ecf0f7c912..76972b19bdd7 100644
>> --- a/arch/arm64/kvm/reset.c
>> +++ b/arch/arm64/kvm/reset.c
>> @@ -34,6 +34,9 @@
>> #include <asm/kvm_coproc.h>
>> #include <asm/kvm_mmu.h>
>>
>> +/* Maximum phys_shift supported for any VM on this host */
>> +static u32 kvm_ipa_limit;
>> +
>> /*
>> * ARMv8 Reset Values
>> */
>> @@ -135,6 +138,46 @@ int kvm_reset_vcpu(struct kvm_vcpu *vcpu)
>> return kvm_timer_vcpu_reset(vcpu);
>> }
>>
>> +void kvm_set_ipa_limit(void)
>> +{
>> + unsigned int ipa_max, va_max, parange;
>> +
>> + parange = read_sanitised_ftr_reg(SYS_ID_AA64MMFR0_EL1) & 0x7;
>> + ipa_max = id_aa64mmfr0_parange_to_phys_shift(parange);
>> +
>> + /* Raise the limit to the default size for backward compatibility */
>> + if (ipa_max < KVM_PHYS_SHIFT) {
>> + WARN_ONCE(1,
>> + "PARange is %d bits, unsupported configuration!",
>> + ipa_max);
>> + ipa_max = KVM_PHYS_SHIFT;
> I don't really get what does happen in this case. The CPU cannot handle
> PA up to ipa_max so can the VM run properly? In case it is a
> showstopper, kvm_set_ipa_limit should return an error, cascaded by
> init_common_resources. Otherwise the warning message may be reworded.
I think this was a warning added to warn against the older
Foundation model which had a 36bit PA size. So the VTCR was progammed
with a 36bit limit, while the KVM guest was allowed to create 40bit
IPA space, though it wouldn't fly well if someone tried to.
With this series, I think we may expose the real IPA_MAX (which could
be < 40bit) and warn the user if someone tried to create a VM with
40bit IPA (vm_type == 0) and let the call succeed (for the sake of ABI).
Marc, Christoffer, Eric
Thoughts ?
>> + }
>> +
>> + /* Clamp it to the PA size supported by the kernel */
>> + ipa_max = (ipa_max > PHYS_MASK_SHIFT) ? PHYS_MASK_SHIFT : ipa_max;
>> + /*
>> + * Since our stage2 table is dependent on the stage1 page table code,
>> + * we must always honor the following condition:
>> + *
>> + * Number of levels in Stage1 >= Number of levels in Stage2.
>> + *
>> + * So clamp the ipa limit further down to limit the number of levels.
>> + * Since we can concatenate upto 16 tables at entry level, we could
>> + * go upto 4bits above the maximum VA addressible with the current
> addressable?
Sure
>> + * number of levels.
>> + */
>> + va_max = PGDIR_SHIFT + PAGE_SHIFT - 3;
>> + va_max += 4;
>> +
>> + if (va_max < ipa_max) {
>> + kvm_info("Limiting IPA limit to %dbytes due to host VA bits limitation\n",
>> + va_max);
>> + ipa_max = va_max;
> you have a trace for this limitation but none for the comparison against
> PHYS_MASK_SHIFT.
May be I could add a message which only mentions what is the limiting
factor kernel VA vs kernel PA support
>> + }
>> +
>> + kvm_ipa_limit = ipa_max;
>> +}
>> +
>> /*
>> * Configure the VTCR_EL2 for this VM. The VTCR value is common
>> * across all the physical CPUs on the system. We use system wide
>> diff --git a/virt/kvm/arm/arm.c b/virt/kvm/arm/arm.c
>> index 43e716bc3f08..631f9a3ad99a 100644
>> --- a/virt/kvm/arm/arm.c
>> +++ b/virt/kvm/arm/arm.c
>> @@ -1413,6 +1413,8 @@ static int init_common_resources(void)
>> kvm_vmid_bits = kvm_get_vmid_bits();
>> kvm_info("%d-bit VMID\n", kvm_vmid_bits);
>>
>> + kvm_set_ipa_limit();
> As we have a kvm_info for the supported vmid_bits, may be good to output
> the max IPA size supported by the host whatever the applied clamps?
Sure, will do that.
Thanks
Suzuki
next prev parent reply other threads:[~2018-09-25 11:09 UTC|newest]
Thread overview: 50+ 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 ` [PATCH v5 01/18] kvm: arm/arm64: Fix stage2_flush_memslot for 4 level page table 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 ` [PATCH v5 03/18] kvm: arm64: Add helper for loading the stage2 setting for a VM 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 ` [PATCH v5 05/18] kvm: arm64: Clean up VTCR_EL2 initialisation Suzuki K Poulose
2018-09-17 10:41 ` [PATCH v5 06/18] kvm: arm/arm64: Allow arch specific configurations for VM Suzuki K Poulose
2018-09-20 10:22 ` Auger Eric
2018-09-17 10:41 ` [PATCH v5 07/18] kvm: arm64: Configure VTCR_EL2 per VM Suzuki K Poulose
2018-09-20 10:21 ` Auger Eric
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
2018-09-20 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 ` [PATCH v5 10/18] kvm: arm64: Make stage2 page table layout dynamic Suzuki K Poulose
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
2018-09-20 14:07 ` Auger Eric
2018-09-20 15:22 ` Suzuki K Poulose
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
2018-09-20 14:25 ` Auger Eric
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 ` [PATCH v5 14/18] vgic: Add support for 52bit guest physical address Suzuki K Poulose
2018-09-21 14:57 ` Auger Eric
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
2018-09-25 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
2018-09-25 9:59 ` Auger Eric
2018-09-25 11:10 ` Suzuki K Poulose [this message]
2018-09-17 10:41 ` [PATCH v5 17/18] kvm: arm64: Limit the minimum number of page table levels Suzuki K Poulose
2018-09-25 10:00 ` Auger Eric
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 14:20 ` Peter Maydell
2018-09-17 14:43 ` Suzuki K Poulose
2018-09-18 1:55 ` Peter Maydell
2018-09-18 15:16 ` Suzuki K Poulose
2018-09-18 15:36 ` Peter Maydell
2018-09-18 16:27 ` Suzuki K Poulose
2018-09-18 17:15 ` Peter Maydell
2018-09-19 10:03 ` Suzuki K Poulose
2018-09-25 10:00 ` Auger Eric
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 ` [kvmtool PATCH v5 20/18] kvmtool: arm64: Add support for guest physical address size 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 ` [kvmtool PATCH v5 22/18] kvmtool: arm: Add support for creating VM with PA size Suzuki K Poulose
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