Re: [PATCH kvmtool 06/16] builtin-run.c: Always use ram_size in bytes

[Andre Przywara <andre.przywara@arm.com>]

On Mon, 23 Sep 2019 14:35:12 +0100
Alexandru Elisei <alexandru.elisei@arm.com> wrote:

Hi,

> The user can specify the virtual machine memory size, in MB, which is saved
> in cfg->ram_size. kvmtool validates it against the host memory size,
> converted from bytes to MB. ram_size is aftwerwards converted to bytes, and
> this is how it is used throughout the rest of the program.
> 
> Let's avoid any confusion about the unit of measurement and always use
> cfg->ram_size in bytes.

... which also means you can get rid of MIN_RAM_SIZE_MB in include/kvm/kvm-config.h.

Otherwise:
 
> Signed-off-by: Alexandru Elisei <alexandru.elisei@arm.com>

Reviewed-by: Andre Przywara <andre.przywara@arm.com>

Cheers,
Andre

> ---
>  builtin-run.c            | 19 ++++++++++---------
>  include/kvm/kvm-config.h |  2 +-
>  include/kvm/kvm.h        |  2 +-
>  3 files changed, 12 insertions(+), 11 deletions(-)
> 
> diff --git a/builtin-run.c b/builtin-run.c
> index cff44047bb1c..4e0c52b3e027 100644
> --- a/builtin-run.c
> +++ b/builtin-run.c
> @@ -262,7 +262,7 @@ static u64 host_ram_size(void)
>  		return 0;
>  	}
>  
> -	return (nr_pages * page_size) >> MB_SHIFT;
> +	return nr_pages * page_size;
>  }
>  
>  /*
> @@ -276,11 +276,11 @@ static u64 get_ram_size(int nr_cpus)
>  	u64 available;
>  	u64 ram_size;
>  
> -	ram_size	= 64 * (nr_cpus + 3);
> +	ram_size	= (64 * (nr_cpus + 3)) << MB_SHIFT;
>  
>  	available	= host_ram_size() * RAM_SIZE_RATIO;
>  	if (!available)
> -		available = MIN_RAM_SIZE_MB;
> +		available = MIN_RAM_SIZE_BYTE;
>  
>  	if (ram_size > available)
>  		ram_size	= available;
> @@ -531,13 +531,14 @@ static struct kvm *kvm_cmd_run_init(int argc, const char **argv)
>  
>  	if (!kvm->cfg.ram_size)
>  		kvm->cfg.ram_size = get_ram_size(kvm->cfg.nrcpus);
> +	else
> +		/* The user specifies the memory in MB. */
> +		kvm->cfg.ram_size <<= MB_SHIFT;
>  
>  	if (kvm->cfg.ram_size > host_ram_size())
>  		pr_warning("Guest memory size %lluMB exceeds host physical RAM size %lluMB",
> -			(unsigned long long)kvm->cfg.ram_size,
> -			(unsigned long long)host_ram_size());
> -
> -	kvm->cfg.ram_size <<= MB_SHIFT;
> +			(unsigned long long)kvm->cfg.ram_size >> MB_SHIFT,
> +			(unsigned long long)host_ram_size() >> MB_SHIFT);
>  
>  	if (!kvm->cfg.dev)
>  		kvm->cfg.dev = DEFAULT_KVM_DEV;
> @@ -647,12 +648,12 @@ static struct kvm *kvm_cmd_run_init(int argc, const char **argv)
>  	if (kvm->cfg.kernel_filename) {
>  		printf("  # %s run -k %s -m %Lu -c %d --name %s\n", KVM_BINARY_NAME,
>  		       kvm->cfg.kernel_filename,
> -		       (unsigned long long)kvm->cfg.ram_size / 1024 / 1024,
> +		       (unsigned long long)kvm->cfg.ram_size >> MB_SHIFT,
>  		       kvm->cfg.nrcpus, kvm->cfg.guest_name);
>  	} else if (kvm->cfg.firmware_filename) {
>  		printf("  # %s run --firmware %s -m %Lu -c %d --name %s\n", KVM_BINARY_NAME,
>  		       kvm->cfg.firmware_filename,
> -		       (unsigned long long)kvm->cfg.ram_size / 1024 / 1024,
> +		       (unsigned long long)kvm->cfg.ram_size >> MB_SHIFT,
>  		       kvm->cfg.nrcpus, kvm->cfg.guest_name);
>  	}
>  
> diff --git a/include/kvm/kvm-config.h b/include/kvm/kvm-config.h
> index a052b0bc7582..e0c9ee14e103 100644
> --- a/include/kvm/kvm-config.h
> +++ b/include/kvm/kvm-config.h
> @@ -22,7 +22,7 @@ struct kvm_config {
>  	struct kvm_config_arch arch;
>  	struct disk_image_params disk_image[MAX_DISK_IMAGES];
>  	struct vfio_device_params *vfio_devices;
> -	u64 ram_size;
> +	u64 ram_size;		/* Guest memory size, in bytes */
>  	u8  image_count;
>  	u8 num_net_devices;
>  	u8 num_vfio_devices;
> diff --git a/include/kvm/kvm.h b/include/kvm/kvm.h
> index 635ce0f40b1e..a866d5a825c4 100644
> --- a/include/kvm/kvm.h
> +++ b/include/kvm/kvm.h
> @@ -68,7 +68,7 @@ struct kvm {
>  	struct kvm_cpu		**cpus;
>  
>  	u32			mem_slots;	/* for KVM_SET_USER_MEMORY_REGION */
> -	u64			ram_size;
> +	u64			ram_size;	/* Guest memory size, in bytes */
>  	void			*ram_start;
>  	u64			ram_pagesize;
>  	struct list_head	mem_banks;