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Re: [libvirt] [PATCH] add option to enforce minimal pagesize for hugetlbfs backed guests



On Thu, Feb 06, 2014 at 11:48:51AM -0500, Marcelo Tosatti wrote:
> 
> 
> Require a minimal pagesize for hugetlbfs backed guests. Fail guest initialization
> if hugetlbfs mount is configured with smaller page size.
> 
> Signed-off-by: Marcelo Tosatti <mtosatti redhat com>
> 

>  
> +#ifdef __linux__
> +
> +#include <sys/vfs.h>
> +
> +#define HUGETLBFS_MAGIC       0x958458f6
> +
> +static long gethugepagesize(const char *path)
> +{
> +    struct statfs fs;
> +    int ret;
> +
> +    do {
> +        ret = statfs(path, &fs);
> +    } while (ret != 0 && errno == EINTR);
> +
> +    if (ret != 0) {
> +        perror(path);
> +        return 0;
> +    }
> +
> +    if (fs.f_type != HUGETLBFS_MAGIC)
> +        return 0;
> +
> +    return fs.f_bsize;
> +}
> +#endif
> +
>  
>  int qemuProcessStart(virConnectPtr conn,
>                       virQEMUDriverPtr driver,
> @@ -3712,6 +3739,31 @@ int qemuProcessStart(virConnectPtr conn,
>                      "%s", _("Unable to set huge path in security driver"));
>              goto cleanup;
>          }
> +
> +        if (vm->def->mem.page_size) {
> +#ifdef __linux__
> +            unsigned long hpagesize = gethugepagesize(cfg->hugepagePath);
> +
> +            if (!hpagesize) {
> +                virReportError(VIR_ERR_INTERNAL_ERROR,
> +                               "%s", _("Unable to stat hugepage path"));
> +                goto cleanup;
> +            }
> +
> +            hpagesize /= 1024;
> +
> +            if (hpagesize < vm->def->mem.page_size) {
> +                    virReportError(VIR_ERR_INTERNAL_ERROR,
> +                    _("Error: hugetlbfs page size=%ld < pagesize=%lld"),
> +                    hpagesize, vm->def->mem.page_size);
> +                goto cleanup;
> +            }
> +#else
> +        virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
> +                       "%s", _("pagesize option unsupported"));
> +        goto cleanup;
> +#endif
> +        }
>      }

IMHO all of this code is something that belongs in QEMU, with libvirt
telling QEMU what min page size it wants via a CLI arg.

Regards,
Daniel
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