On Wed, 25 May 2022 12:23:36 +0100
Alexandru Elisei <alexandru.elisei@xxxxxxx> wrote:
> host_ram_size() uses sysconf() to calculate the available ram, and
> sysconf() can fail. When that happens, host_ram_size() returns 0. kvmtool
> warns the user when the configured VM ram size exceeds the size of the
> host's memory, but doesn't take into account that host_ram_size() can
> return 0. If the function returns zero, skip the warning.
>
> Since this can only happen when the user sets the memory size (via the
> -m/--mem command line argument), skip the check entirely if the user hasn't
> set it. Move the check to kvm_run_validate_cfg(), as it checks for valid
> user configuration.
>
> Signed-off-by: Alexandru Elisei <alexandru.elisei@xxxxxxx>
> ---
> builtin-run.c | 20 +++++++++++++-------
> 1 file changed, 13 insertions(+), 7 deletions(-)
>
> diff --git a/builtin-run.c b/builtin-run.c
> index 4fc7cbed1d17..b1accbce7da3 100644
> --- a/builtin-run.c
> +++ b/builtin-run.c
> @@ -509,6 +509,8 @@ static void kvm_run_set_real_cmdline(struct kvm *kvm)
>
> static void kvm_run_validate_cfg(struct kvm *kvm)
> {
> + u64 available_ram;
Just a nit, you can pull this declaration inside the if statement below,
IIUC you will only need it there.
Otherwise looks fine:
Reviewed-by: Andre Przywara <andre.przywara@xxxxxxx>
> +
> if (kvm->cfg.kernel_filename && kvm->cfg.firmware_filename)
> die("Only one of --kernel or --firmware can be specified");
>
> @@ -518,6 +520,17 @@ static void kvm_run_validate_cfg(struct kvm *kvm)
>
> if (kvm->cfg.firmware_filename && kvm->cfg.initrd_filename)
> 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",
> + (unsigned long long)kvm->cfg.ram_size >> MB_SHIFT,
> + (unsigned long long)available_ram >> MB_SHIFT);
> + }
> + }
> }
>
> static struct kvm *kvm_cmd_run_init(int argc, const char **argv)
> @@ -596,13 +609,6 @@ 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
> - 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 >> MB_SHIFT,
> - (unsigned long long)host_ram_size() >> MB_SHIFT);
>
> if (!kvm->cfg.dev)
> kvm->cfg.dev = DEFAULT_KVM_DEV;
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