Re: [PATCH V2 17/23] kvm tools: Add ability to map guest RAM from hugetlbfs

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On 09/12/11 18:39, Sasha Levin wrote:
> On Fri, 2011-12-09 at 17:55 +1100, Matt Evans wrote:
>> Add a --hugetlbfs commandline option to give a path to hugetlbfs-map guest
>> memory (down in kvm__arch_init()).  For x86, guest memory is a normal
>> ANON mmap() if this option is not provided, otherwise a hugetlbfs mmap.
>>
>> Signed-off-by: Matt Evans <matt@xxxxxxxxxx>
>> ---
>>  tools/kvm/builtin-run.c      |    4 ++-
>>  tools/kvm/include/kvm/kvm.h  |    4 +-
>>  tools/kvm/include/kvm/util.h |    4 +++
>>  tools/kvm/kvm.c              |    4 +-
>>  tools/kvm/util.c             |   45 ++++++++++++++++++++++++++++++++++++++++++
>>  tools/kvm/x86/kvm.c          |   20 +++++++++++++++--
>>  6 files changed, 73 insertions(+), 8 deletions(-)
>>
>> diff --git a/tools/kvm/builtin-run.c b/tools/kvm/builtin-run.c
>> index 7969901..0acfe81 100644
>> --- a/tools/kvm/builtin-run.c
>> +++ b/tools/kvm/builtin-run.c
>> @@ -82,6 +82,7 @@ static const char *guest_mac;
>>  static const char *host_mac;
>>  static const char *script;
>>  static const char *guest_name;
>> +static const char *hugetlbfs_path;
>>  static struct virtio_net_params *net_params;
>>  static bool single_step;
>>  static bool readonly_image[MAX_DISK_IMAGES];
>> @@ -422,6 +423,7 @@ static const struct option options[] = {
>>  	OPT_CALLBACK('\0', "tty", NULL, "tty id",
>>  		     "Remap guest TTY into a pty on the host",
>>  		     tty_parser),
>> +	OPT_STRING('\0', "hugetlbfs", &hugetlbfs_path, "path", "Hugetlbfs path"),
>>  
>>  	OPT_GROUP("Kernel options:"),
>>  	OPT_STRING('k', "kernel", &kernel_filename, "kernel",
>> @@ -807,7 +809,7 @@ int kvm_cmd_run(int argc, const char **argv, const char *prefix)
>>  		guest_name = default_name;
>>  	}
>>  
>> -	kvm = kvm__init(dev, ram_size, guest_name);
>> +	kvm = kvm__init(dev, hugetlbfs_path, ram_size, guest_name);
>>  
>>  	kvm->single_step = single_step;
>>  
>> diff --git a/tools/kvm/include/kvm/kvm.h b/tools/kvm/include/kvm/kvm.h
>> index 5fe6e75..7159952 100644
>> --- a/tools/kvm/include/kvm/kvm.h
>> +++ b/tools/kvm/include/kvm/kvm.h
>> @@ -30,7 +30,7 @@ struct kvm_ext {
>>  void kvm__set_dir(const char *fmt, ...);
>>  const char *kvm__get_dir(void);
>>  
>> -struct kvm *kvm__init(const char *kvm_dev, u64 ram_size, const char *name);
>> +struct kvm *kvm__init(const char *kvm_dev, const char *hugetlbfs_path, u64 ram_size, const char *name);
>>  int kvm__recommended_cpus(struct kvm *kvm);
>>  int kvm__max_cpus(struct kvm *kvm);
>>  void kvm__init_ram(struct kvm *kvm);
>> @@ -54,7 +54,7 @@ int kvm__enumerate_instances(int (*callback)(const char *name, int pid));
>>  void kvm__remove_socket(const char *name);
>>  
>>  void kvm__arch_set_cmdline(char *cmdline, bool video);
>> -void kvm__arch_init(struct kvm *kvm, const char *kvm_dev, u64 ram_size, const char *name);
>> +void kvm__arch_init(struct kvm *kvm, const char *kvm_dev, const char *hugetlbfs_path, u64 ram_size, const char *name);
>>  void kvm__arch_setup_firmware(struct kvm *kvm);
>>  bool kvm__arch_cpu_supports_vm(void);
>>  void kvm__arch_periodic_poll(struct kvm *kvm);
>> diff --git a/tools/kvm/include/kvm/util.h b/tools/kvm/include/kvm/util.h
>> index dc2e0b9..1f6fbbd 100644
>> --- a/tools/kvm/include/kvm/util.h
>> +++ b/tools/kvm/include/kvm/util.h
>> @@ -20,6 +20,7 @@
>>  #include <limits.h>
>>  #include <sys/param.h>
>>  #include <sys/types.h>
>> +#include <linux/types.h>
>>  
>>  #ifdef __GNUC__
>>  #define NORETURN __attribute__((__noreturn__))
>> @@ -75,4 +76,7 @@ static inline void msleep(unsigned int msecs)
>>  {
>>  	usleep(MSECS_TO_USECS(msecs));
>>  }
>> +
>> +void *mmap_hugetlbfs(const char *htlbfs_path, u64 size);
>> +
>>  #endif /* KVM__UTIL_H */
>> diff --git a/tools/kvm/kvm.c b/tools/kvm/kvm.c
>> index c54f886..35ca2c5 100644
>> --- a/tools/kvm/kvm.c
>> +++ b/tools/kvm/kvm.c
>> @@ -306,7 +306,7 @@ int kvm__max_cpus(struct kvm *kvm)
>>  	return ret;
>>  }
>>  
>> -struct kvm *kvm__init(const char *kvm_dev, u64 ram_size, const char *name)
>> +struct kvm *kvm__init(const char *kvm_dev, const char *hugetlbfs_path, u64 ram_size, const char *name)
>>  {
>>  	struct kvm *kvm;
>>  	int ret;
>> @@ -339,7 +339,7 @@ struct kvm *kvm__init(const char *kvm_dev, u64 ram_size, const char *name)
>>  	if (kvm__check_extensions(kvm))
>>  		die("A required KVM extention is not supported by OS");
>>  
>> -	kvm__arch_init(kvm, kvm_dev, ram_size, name);
>> +	kvm__arch_init(kvm, kvm_dev, hugetlbfs_path, ram_size, name);
>>  
>>  	kvm->name = name;
>>  
>> diff --git a/tools/kvm/util.c b/tools/kvm/util.c
>> index 4efbce9..90b6a3b 100644
>> --- a/tools/kvm/util.c
>> +++ b/tools/kvm/util.c
>> @@ -4,6 +4,11 @@
>>  
>>  #include "kvm/util.h"
>>  
>> +#include <linux/magic.h>	/* For HUGETLBFS_MAGIC */
>> +#include <sys/mman.h>
>> +#include <sys/stat.h>
>> +#include <sys/statfs.h>
>> +
>>  static void report(const char *prefix, const char *err, va_list params)
>>  {
>>  	char msg[1024];
>> @@ -99,3 +104,43 @@ size_t strlcat(char *dest, const char *src, size_t count)
>>  
>>  	return res;
>>  }
>> +
>> +void *mmap_hugetlbfs(const char *htlbfs_path, u64 size)
>> +{
>> +	char mpath[PATH_MAX];
>> +	int fd;
>> +	int r;
>> +	struct statfs sfs;
>> +	void *addr;
>> +
>> +	do {
>> +		/*
>> +		 * QEMU seems to work around this returning EINTR...  Let's do
>> +		 * that too.
>> +		 */
>> +		r = statfs(htlbfs_path, &sfs);
>> +	} while (r && errno == EINTR);
>> +
>> +	if (r)
>> +		die("Can't stat %s\n", htlbfs_path);
>> +
>> +	if (sfs.f_type != HUGETLBFS_MAGIC) {
>> +		die("%s is not hugetlbfs!\n", htlbfs_path);
>> +	}
>> +
>> +	if (sfs.f_bsize == 0 || (unsigned long)sfs.f_bsize > size) {
>> +		die("Can't use hugetlbfs pagesize %ld for mem size %lld\n",
>> +		    sfs.f_bsize, size);
>> +	}
>> +
>> +	snprintf(mpath, PATH_MAX, "%s/kvmtoolXXXXXX", htlbfs_path);
>> +	fd = mkstemp(mpath);
>> +	if (fd < 0)
>> +		die("Can't open %s for hugetlbfs map\n", mpath);
>> +	unlink(mpath);
>> +	ftruncate(fd, size);
> 
> Getting this thing here:
> 
> cc1: warnings being treated as errors
> util.c: In function 'mmap_hugetlbfs':
> util.c:141:11: error: ignoring return value of 'ftruncate', declared with attribute warn_unused_result
> make: *** [util.o] Error 1
> 

Ooookay, I swear I'm not seeing that here, GCC 4.6.2 & no extra -W flags added.

I've added a check of ftruncate()'s return value, anyway.

Thanks,


Matt

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