[PATCH] KVM: Add Kconfig option to signal cross-endian guests
Paolo Bonzini
pbonzini at redhat.com
Thu Jul 9 05:57:33 PDT 2015
On 09/07/2015 11:48, Laurent Vivier wrote:
>
>
> On 09/07/2015 09:49, Thomas Huth wrote:
>> The option for supporting cross-endianness legacy guests in
>> the vhost and tun code should only be available on systems
>> that support cross-endian guests.
>
> I'm sure I misunderstand something, but what happens if we use QEMU with
> TCG instead of KVM, i.e. a big endian powerpc kernel guest on x86_64
> little endian host ?
TCG does not yet support irqfd/ioeventfd, so it cannot be used with vhost.
Paolo
> Do you forbid the use of vhost in this case ?
>
>> Signed-off-by: Thomas Huth <thuth at redhat.com>
>> ---
>> arch/arm/kvm/Kconfig | 1 +
>> arch/arm64/kvm/Kconfig | 1 +
>> arch/powerpc/kvm/Kconfig | 1 +
>> drivers/net/Kconfig | 1 +
>> drivers/vhost/Kconfig | 1 +
>> virt/kvm/Kconfig | 3 +++
>> 6 files changed, 8 insertions(+)
>>
>> diff --git a/arch/arm/kvm/Kconfig b/arch/arm/kvm/Kconfig
>> index bfb915d..9d8f363 100644
>> --- a/arch/arm/kvm/Kconfig
>> +++ b/arch/arm/kvm/Kconfig
>> @@ -31,6 +31,7 @@ config KVM
>> select KVM_VFIO
>> select HAVE_KVM_EVENTFD
>> select HAVE_KVM_IRQFD
>> + select KVM_CROSS_ENDIAN_GUESTS
>> depends on ARM_VIRT_EXT && ARM_LPAE && ARM_ARCH_TIMER
>> ---help---
>> Support hosting virtualized guest machines.
>> diff --git a/arch/arm64/kvm/Kconfig b/arch/arm64/kvm/Kconfig
>> index bfffe8f..9af39fe 100644
>> --- a/arch/arm64/kvm/Kconfig
>> +++ b/arch/arm64/kvm/Kconfig
>> @@ -31,6 +31,7 @@ config KVM
>> select KVM_VFIO
>> select HAVE_KVM_EVENTFD
>> select HAVE_KVM_IRQFD
>> + select KVM_CROSS_ENDIAN_GUESTS
>> ---help---
>> Support hosting virtualized guest machines.
>>
>> diff --git a/arch/powerpc/kvm/Kconfig b/arch/powerpc/kvm/Kconfig
>> index 3caec2c..e028710 100644
>> --- a/arch/powerpc/kvm/Kconfig
>> +++ b/arch/powerpc/kvm/Kconfig
>> @@ -79,6 +79,7 @@ config KVM_BOOK3S_64_HV
>> select KVM_BOOK3S_HV_POSSIBLE
>> select MMU_NOTIFIER
>> select CMA
>> + select KVM_CROSS_ENDIAN_GUESTS
>> ---help---
>> Support running unmodified book3s_64 guest kernels in
>> virtual machines on POWER7 and PPC970 processors that have
>> diff --git a/drivers/net/Kconfig b/drivers/net/Kconfig
>> index c18f9e6..0c4ce47 100644
>> --- a/drivers/net/Kconfig
>> +++ b/drivers/net/Kconfig
>> @@ -261,6 +261,7 @@ config TUN
>> config TUN_VNET_CROSS_LE
>> bool "Support for cross-endian vnet headers on little-endian kernels"
>> default n
>> + depends on KVM_CROSS_ENDIAN_GUESTS
>> ---help---
>> This option allows TUN/TAP and MACVTAP device drivers in a
>> little-endian kernel to parse vnet headers that come from a
>> diff --git a/drivers/vhost/Kconfig b/drivers/vhost/Kconfig
>> index 533eaf0..4d8ae6b 100644
>> --- a/drivers/vhost/Kconfig
>> +++ b/drivers/vhost/Kconfig
>> @@ -35,6 +35,7 @@ config VHOST
>>
>> config VHOST_CROSS_ENDIAN_LEGACY
>> bool "Cross-endian support for vhost"
>> + depends on KVM_CROSS_ENDIAN_GUESTS
>> default n
>> ---help---
>> This option allows vhost to support guests with a different byte
>> diff --git a/virt/kvm/Kconfig b/virt/kvm/Kconfig
>> index e2c876d..cc7b28a 100644
>> --- a/virt/kvm/Kconfig
>> +++ b/virt/kvm/Kconfig
>> @@ -47,3 +47,6 @@ config KVM_GENERIC_DIRTYLOG_READ_PROTECT
>> config KVM_COMPAT
>> def_bool y
>> depends on COMPAT && !S390
>> +
>> +config KVM_CROSS_ENDIAN_GUESTS
>> + bool
>>
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