Hi,
Thank you for having a look! Replies below.
On Wed, Jun 01, 2022 at 02:39:55PM +0100, Andre Przywara wrote:
> On Wed, 25 May 2022 12:23:41 +0100
> Alexandru Elisei <alexandru.elisei@xxxxxxx> wrote:
>
> Hi,
>
> > From: Suzuki K Poulose <suzuki.poulose@xxxxxxx>
> >
> > 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@xxxxxxx>
> > Signed-off-by: Alexandru Elisei <alexandru.elisei@xxxxxxx>
> > ---
> > 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?
Yes.
>
> >
> > __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;
I think that change alone breaks the logic.
The code needs to advance next if and only if it matches on one of the
characters. I'll have a go at advancing next in each of the switch arms
above (with the exception of the default one, which I'll add) to see how it
ends up looking.
>
> > + } 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.
This was intentional on my part, because I was under the impression that
kvmtool treats all instances where errno != 0 as a fatal error. I think I
was wrong about that, I see at least one instance when that isn't the case,
in kvm_setup_guest_init -> extract_file. So it isn't a rule that a non-zero
errno is a fatal error.
I'll change the code to zero errno 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()?
strtoull does not consider an error to convert the string "0" to an
unsigned long long.
Thanks,
Alex
>
> 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",
>
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