[PATCH v3 kvmtool 09/13] builtin_run: Allow standard size specifiers for memory

[Andre Przywara]

On Wed, 25 May 2022 12:23:41 +0100
Alexandru Elisei <alexandru.elisei at arm.com> wrote:

Hi,

> From: Suzuki K Poulose <suzuki.poulose at arm.com>
> 
> Allow the user to use the standard B (bytes), K (kilobytes), M (megabytes),
> G (gigabytes), T (terabytes) and P (petabytes) suffixes for memory size.
> When none are specified, the default is megabytes.
> 
> Also raise an error if the guest specifies 0 as the memory size, instead
> of treating it as uninitialized, as kvmtool has done so far.
> 
> Signed-off-by: Suzuki K Poulose <suzuki.poulose at arm.com>
> Signed-off-by: Alexandru Elisei <alexandru.elisei at arm.com>
> ---
>  builtin-run.c | 65 +++++++++++++++++++++++++++++++++++++++++++++++----
>  1 file changed, 60 insertions(+), 5 deletions(-)
> 
> diff --git a/builtin-run.c b/builtin-run.c
> index 2ef159cdb2a3..a49698d5b2fe 100644
> --- a/builtin-run.c
> +++ b/builtin-run.c
> @@ -49,9 +49,11 @@
>  #include <ctype.h>
>  #include <stdio.h>
>  
> -#define MB_SHIFT		(20)
>  #define KB_SHIFT		(10)
> +#define MB_SHIFT		(20)
>  #define GB_SHIFT		(30)
> +#define TB_SHIFT		(40)
> +#define PB_SHIFT		(50)

Can we lose the parentheses?

>  
>  __thread struct kvm_cpu *current_kvm_cpu;
>  
> @@ -87,6 +89,60 @@ void kvm_run_set_wrapper_sandbox(void)
>  	kvm_run_wrapper = KVM_RUN_SANDBOX;
>  }
>  
> +static int parse_mem_unit(char **next)
> +{
> +	int shift = -1;
> +
> +	switch (**next) {
> +	case 'B': case 'b': shift = 0; break;
> +	case 'K': case 'k': shift = KB_SHIFT; break;
> +	case 'M': case 'm': shift = MB_SHIFT; break;
> +	case 'G': case 'g': shift = GB_SHIFT; break;
> +	case 'T': case 't': shift = TB_SHIFT; break;
> +	case 'P': case 'p': shift = PB_SHIFT; break;
> +	}
> +
> +	if (shift == -1) {
> +		/* The default is megabytes. */
> +		shift = MB_SHIFT;

Doesn't that look better inside the switch/case?
	default: return MB_SHIFT;

> +	} else {
> +		(*next)++;
> +	}
> +
> +	return shift;
> +}
> +
> +static u64 parse_mem_option(const char *nptr, char **next)
> +{
> +	u64 shift;
> +	u64 val;
> +
> +	val = strtoull(nptr, next, 10);
> +	if (errno == ERANGE)
> +		die("Memory too large: %s", nptr);

strtoull does not clear errno if it succeeds, so it retains the
previous error value. So we would need to set errno to 0 just before
calling strtoull.

> +	shift = parse_mem_unit(next);
> +
> +	if ((val << shift) < val)
> +		die("Memory too large: %s", nptr);
> +
> +	return val << shift;
> +}
> +
> +static int mem_parser(const struct option *opt, const char *arg, int unset)
> +{
> +	struct kvm *kvm = opt->ptr;
> +	char *next;
> +
> +	kvm->cfg.ram_size = parse_mem_option(arg, &next);
> +	if (kvm->cfg.ram_size == 0)
> +		die("Invalid RAM size: %s", arg);

Does 0 hold any significant value (anymore)? I think we die() if we
encounter invalid values in parse_mem_option()?

Cheers,
Andre

> +
> +	if (*next != '\0')
> +		die("Invalid memory specifier: %s", arg);
> +
> +	return 0;
> +}
> +
>  #ifndef OPT_ARCH_RUN
>  #define OPT_ARCH_RUN(...)
>  #endif
> @@ -97,8 +153,9 @@ void kvm_run_set_wrapper_sandbox(void)
>  	OPT_STRING('\0', "name", &(cfg)->guest_name, "guest name",	\
>  			"A name for the guest"),			\
>  	OPT_INTEGER('c', "cpus", &(cfg)->nrcpus, "Number of CPUs"),	\
> -	OPT_U64('m', "mem", &(cfg)->ram_size, "Virtual machine memory"	\
> -		" size in MB."),					\
> +	OPT_CALLBACK('m', "mem", NULL, "size[BKMGTP]",			\
> +		     "Virtual machine memory size, by default measured"	\
> +		     " in megabytes (M)", mem_parser, kvm),		\
>  	OPT_CALLBACK('d', "disk", kvm, "image or rootfs_dir", "Disk "	\
>  			" image or rootfs directory", img_name_parser,	\
>  			kvm),						\
> @@ -522,8 +579,6 @@ static void kvm_run_validate_cfg(struct kvm *kvm)
>  		pr_warning("Ignoring initrd file when loading a firmware image");
>  
>  	if (kvm->cfg.ram_size) {
> -		/* User specifies RAM size in megabytes. */
> -		kvm->cfg.ram_size <<= MB_SHIFT;
>  		available_ram = host_ram_size();
>  		if (available_ram && kvm->cfg.ram_size > available_ram) {
>  			pr_warning("Guest memory size %lluMB exceeds host physical RAM size %lluMB",