Re: [PATCH] KVM: arm64: Increase number of memslots to 512

[Auger Eric <eric.auger@redhat.com>]

Hi Linu,

On 11/01/2017 17:52, linucherian@gmail.com wrote:
> From: Linu Cherian <linu.cherian@cavium.com>
> 
> Having only 32 memslots is a real constraint for the maximum number of
> PCI devices that can be assigned to a single guest. Assuming each PCI
> device/virtual function having two memory BAR regions, we could assign
> only 15 devices/virtual functions to a guest.
> 
> So increase KVM_MEM_SLOTS_NUM to 512 as done in other archs like x86 and
> powerpc. For this, KVM_USER_MEM_SLOTS has been changed to 508.
> 
> Signed-off-by: Linu Cherian <linu.cherian@cavium.com>

> ---
>  arch/arm/kvm/arm.c                | 3 +++
>  arch/arm64/include/asm/kvm_host.h | 2 +-
>  2 files changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
> index 8f92efa..a19389b 100644
> --- a/arch/arm/kvm/arm.c
> +++ b/arch/arm/kvm/arm.c
> @@ -221,6 +221,9 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
>  	case KVM_CAP_MAX_VCPUS:
>  		r = KVM_MAX_VCPUS;
>  		break;
> +	case KVM_CAP_NR_MEMSLOTS:
> +		r = KVM_USER_MEM_SLOTS;
> +		break;
This change is not documented in the commit message and I think it
should since we now allow KVM/ARM to report the number of available user
mem slots. I would personally suggest to put it in a sepate patch as it
was done on s390 for instance
(http://marc.info/?l=linux-s390&m=136422861316920&w=2)

Thanks

Eric

>  	case KVM_CAP_MSI_DEVID:
>  		if (!kvm)
>  			r = -EINVAL;
> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
> index e505038..88f017d 100644
> --- a/arch/arm64/include/asm/kvm_host.h
> +++ b/arch/arm64/include/asm/kvm_host.h
> @@ -30,7 +30,7 @@
>  
>  #define __KVM_HAVE_ARCH_INTC_INITIALIZED
>  
> -#define KVM_USER_MEM_SLOTS 32
> +#define KVM_USER_MEM_SLOTS 508
>  #define KVM_PRIVATE_MEM_SLOTS 4
>  #define KVM_COALESCED_MMIO_PAGE_OFFSET 1
>  #define KVM_HALT_POLL_NS_DEFAULT 500000
>