Re: [Qemu-ppc] [PATCH qemu 1/2] exec, kvm, target-ppc: Move getrampagesize() to common code

[Alexey Kardashevskiy]

On 03/01/17 10:34, David Gibson wrote:
> On Thu, Dec 22, 2016 at 04:22:11PM +1100, Alexey Kardashevskiy wrote:
>> getrampagesize() returns the largest supported page size and mainly
>> used to know if huge pages are enabled.
>>
>> However is implemented in target-ppc/kvm.c and not available
>> in TCG or other architectures.
>>
>> This renames and moves gethugepagesize() to mmap-alloc.c where
>> fd-based analog of it is already implemented. This renames and moves
>> getrampagesize() to exec.c as it seems to be the common place for
>> helpers like this.
>>
>> This first user for it is going to be a spapr-pci-host-bridge which
>> needs to know the largest RAM page size so the guest could try
>> using bigger IOMMU pages to save memory.
>>
>> Signed-off-by: Alexey Kardashevskiy <address@hidden>
> 
> Reviewed-by: David Gibson <address@hidden>
> 
> Seems sensible to me, but I'm not comfortable merging this via my tree
> since it touches such core code.  Probably should go via Paolo.


Paolo, ping?



> 
>> ---
>>  include/exec/ram_addr.h   |   1 +
>>  include/qemu/mmap-alloc.h |   2 +
>>  exec.c                    |  82 ++++++++++++++++++++++++++++++++++++
>>  target-ppc/kvm.c          | 105 
>> ++--------------------------------------------
>>  util/mmap-alloc.c         |  25 +++++++++++
>>  5 files changed, 113 insertions(+), 102 deletions(-)
>>
>> diff --git a/include/exec/ram_addr.h b/include/exec/ram_addr.h
>> index 54d7108a9e..3935cbcfcd 100644
>> --- a/include/exec/ram_addr.h
>> +++ b/include/exec/ram_addr.h
>> @@ -91,6 +91,7 @@ typedef struct RAMList {
>>  } RAMList;
>>  extern RAMList ram_list;
>>  
>> +long qemu_getrampagesize(void);
>>  ram_addr_t last_ram_offset(void);
>>  void qemu_mutex_lock_ramlist(void);
>>  void qemu_mutex_unlock_ramlist(void);
>> diff --git a/include/qemu/mmap-alloc.h b/include/qemu/mmap-alloc.h
>> index 933c024ac5..50385e3f81 100644
>> --- a/include/qemu/mmap-alloc.h
>> +++ b/include/qemu/mmap-alloc.h
>> @@ -5,6 +5,8 @@
>>  
>>  size_t qemu_fd_getpagesize(int fd);
>>  
>> +size_t qemu_mempath_getpagesize(const char *mem_path);
>> +
>>  void *qemu_ram_mmap(int fd, size_t size, size_t align, bool shared);
>>  
>>  void qemu_ram_munmap(void *ptr, size_t size);
>> diff --git a/exec.c b/exec.c
>> index 08c558eecf..d73b477a70 100644
>> --- a/exec.c
>> +++ b/exec.c
>> @@ -32,6 +32,7 @@
>>  #endif
>>  #include "sysemu/kvm.h"
>>  #include "sysemu/sysemu.h"
>> +#include "sysemu/numa.h"
>>  #include "qemu/timer.h"
>>  #include "qemu/config-file.h"
>>  #include "qemu/error-report.h"
>> @@ -1218,6 +1219,87 @@ void qemu_mutex_unlock_ramlist(void)
>>  }
>>  
>>  #ifdef __linux__
>> +/*
>> + * FIXME TOCTTOU: this iterates over memory backends' mem-path, which
>> + * may or may not name the same files / on the same filesystem now as
>> + * when we actually open and map them.  Iterate over the file
>> + * descriptors instead, and use qemu_fd_getpagesize().
>> + */
>> +static int find_max_supported_pagesize(Object *obj, void *opaque)
>> +{
>> +    char *mem_path;
>> +    long *hpsize_min = opaque;
>> +
>> +    if (object_dynamic_cast(obj, TYPE_MEMORY_BACKEND)) {
>> +        mem_path = object_property_get_str(obj, "mem-path", NULL);
>> +        if (mem_path) {
>> +            long hpsize = qemu_mempath_getpagesize(mem_path);
>> +            if (hpsize < *hpsize_min) {
>> +                *hpsize_min = hpsize;
>> +            }
>> +        } else {
>> +            *hpsize_min = getpagesize();
>> +        }
>> +    }
>> +
>> +    return 0;
>> +}
>> +
>> +long qemu_getrampagesize(void)
>> +{
>> +    long hpsize = LONG_MAX;
>> +    long mainrampagesize;
>> +    Object *memdev_root;
>> +
>> +    if (mem_path) {
>> +        mainrampagesize = qemu_mempath_getpagesize(mem_path);
>> +    } else {
>> +        mainrampagesize = getpagesize();
>> +    }
>> +
>> +    /* it's possible we have memory-backend objects with
>> +     * hugepage-backed RAM. these may get mapped into system
>> +     * address space via -numa parameters or memory hotplug
>> +     * hooks. we want to take these into account, but we
>> +     * also want to make sure these supported hugepage
>> +     * sizes are applicable across the entire range of memory
>> +     * we may boot from, so we take the min across all
>> +     * backends, and assume normal pages in cases where a
>> +     * backend isn't backed by hugepages.
>> +     */
>> +    memdev_root = object_resolve_path("/objects", NULL);
>> +    if (memdev_root) {
>> +        object_child_foreach(memdev_root, find_max_supported_pagesize, 
>> &hpsize);
>> +    }
>> +    if (hpsize == LONG_MAX) {
>> +        /* No additional memory regions found ==> Report main RAM page size 
>> */
>> +        return mainrampagesize;
>> +    }
>> +
>> +    /* If NUMA is disabled or the NUMA nodes are not backed with a
>> +     * memory-backend, then there is at least one node using "normal" RAM,
>> +     * so if its page size is smaller we have got to report that size 
>> instead.
>> +     */
>> +    if (hpsize > mainrampagesize &&
>> +        (nb_numa_nodes == 0 || numa_info[0].node_memdev == NULL)) {
>> +        static bool warned;
>> +        if (!warned) {
>> +            error_report("Huge page support disabled (n/a for main 
>> memory).");
>> +            warned = true;
>> +        }
>> +        return mainrampagesize;
>> +    }
>> +
>> +    return hpsize;
>> +}
>> +#else
>> +long qemu_getrampagesize(void)
>> +{
>> +    return getpagesize();
>> +}
>> +#endif
>> +
>> +#ifdef __linux__
>>  static int64_t get_file_size(int fd)
>>  {
>>      int64_t size = lseek(fd, 0, SEEK_END);
>> diff --git a/target-ppc/kvm.c b/target-ppc/kvm.c
>> index 6e91a4d8bb..e0abffa8ad 100644
>> --- a/target-ppc/kvm.c
>> +++ b/target-ppc/kvm.c
>> @@ -42,6 +42,7 @@
>>  #include "trace.h"
>>  #include "exec/gdbstub.h"
>>  #include "exec/memattrs.h"
>> +#include "exec/ram_addr.h"
>>  #include "sysemu/hostmem.h"
>>  #include "qemu/cutils.h"
>>  #if defined(TARGET_PPC64)
>> @@ -325,106 +326,6 @@ static void kvm_get_smmu_info(PowerPCCPU *cpu, struct 
>> kvm_ppc_smmu_info *info)
>>      kvm_get_fallback_smmu_info(cpu, info);
>>  }
>>  
>> -static long gethugepagesize(const char *mem_path)
>> -{
>> -    struct statfs fs;
>> -    int ret;
>> -
>> -    do {
>> -        ret = statfs(mem_path, &fs);
>> -    } while (ret != 0 && errno == EINTR);
>> -
>> -    if (ret != 0) {
>> -        fprintf(stderr, "Couldn't statfs() memory path: %s\n",
>> -                strerror(errno));
>> -        exit(1);
>> -    }
>> -
>> -#define HUGETLBFS_MAGIC       0x958458f6
>> -
>> -    if (fs.f_type != HUGETLBFS_MAGIC) {
>> -        /* Explicit mempath, but it's ordinary pages */
>> -        return getpagesize();
>> -    }
>> -
>> -    /* It's hugepage, return the huge page size */
>> -    return fs.f_bsize;
>> -}
>> -
>> -/*
>> - * FIXME TOCTTOU: this iterates over memory backends' mem-path, which
>> - * may or may not name the same files / on the same filesystem now as
>> - * when we actually open and map them.  Iterate over the file
>> - * descriptors instead, and use qemu_fd_getpagesize().
>> - */
>> -static int find_max_supported_pagesize(Object *obj, void *opaque)
>> -{
>> -    char *mem_path;
>> -    long *hpsize_min = opaque;
>> -
>> -    if (object_dynamic_cast(obj, TYPE_MEMORY_BACKEND)) {
>> -        mem_path = object_property_get_str(obj, "mem-path", NULL);
>> -        if (mem_path) {
>> -            long hpsize = gethugepagesize(mem_path);
>> -            if (hpsize < *hpsize_min) {
>> -                *hpsize_min = hpsize;
>> -            }
>> -        } else {
>> -            *hpsize_min = getpagesize();
>> -        }
>> -    }
>> -
>> -    return 0;
>> -}
>> -
>> -static long getrampagesize(void)
>> -{
>> -    long hpsize = LONG_MAX;
>> -    long mainrampagesize;
>> -    Object *memdev_root;
>> -
>> -    if (mem_path) {
>> -        mainrampagesize = gethugepagesize(mem_path);
>> -    } else {
>> -        mainrampagesize = getpagesize();
>> -    }
>> -
>> -    /* it's possible we have memory-backend objects with
>> -     * hugepage-backed RAM. these may get mapped into system
>> -     * address space via -numa parameters or memory hotplug
>> -     * hooks. we want to take these into account, but we
>> -     * also want to make sure these supported hugepage
>> -     * sizes are applicable across the entire range of memory
>> -     * we may boot from, so we take the min across all
>> -     * backends, and assume normal pages in cases where a
>> -     * backend isn't backed by hugepages.
>> -     */
>> -    memdev_root = object_resolve_path("/objects", NULL);
>> -    if (memdev_root) {
>> -        object_child_foreach(memdev_root, find_max_supported_pagesize, 
>> &hpsize);
>> -    }
>> -    if (hpsize == LONG_MAX) {
>> -        /* No additional memory regions found ==> Report main RAM page size 
>> */
>> -        return mainrampagesize;
>> -    }
>> -
>> -    /* If NUMA is disabled or the NUMA nodes are not backed with a
>> -     * memory-backend, then there is at least one node using "normal" RAM,
>> -     * so if its page size is smaller we have got to report that size 
>> instead.
>> -     */
>> -    if (hpsize > mainrampagesize &&
>> -        (nb_numa_nodes == 0 || numa_info[0].node_memdev == NULL)) {
>> -        static bool warned;
>> -        if (!warned) {
>> -            error_report("Huge page support disabled (n/a for main 
>> memory).");
>> -            warned = true;
>> -        }
>> -        return mainrampagesize;
>> -    }
>> -
>> -    return hpsize;
>> -}
>> -
>>  static bool kvm_valid_page_size(uint32_t flags, long rampgsize, uint32_t 
>> shift)
>>  {
>>      if (!(flags & KVM_PPC_PAGE_SIZES_REAL)) {
>> @@ -454,7 +355,7 @@ static void kvm_fixup_page_sizes(PowerPCCPU *cpu)
>>          has_smmu_info = true;
>>      }
>>  
>> -    rampagesize = getrampagesize();
>> +    rampagesize = qemu_getrampagesize();
>>  
>>      /* Convert to QEMU form */
>>      memset(&env->sps, 0, sizeof(env->sps));
>> @@ -2177,7 +2078,7 @@ uint64_t kvmppc_rma_size(uint64_t current_size, 
>> unsigned int hash_shift)
>>      /* Find the largest hardware supported page size that's less than
>>       * or equal to the (logical) backing page size of guest RAM */
>>      kvm_get_smmu_info(POWERPC_CPU(first_cpu), &info);
>> -    rampagesize = getrampagesize();
>> +    rampagesize = qemu_getrampagesize();
>>      best_page_shift = 0;
>>  
>>      for (i = 0; i < KVM_PPC_PAGE_SIZES_MAX_SZ; i++) {
>> diff --git a/util/mmap-alloc.c b/util/mmap-alloc.c
>> index 5a85aa3c89..564c79109c 100644
>> --- a/util/mmap-alloc.c
>> +++ b/util/mmap-alloc.c
>> @@ -39,6 +39,31 @@ size_t qemu_fd_getpagesize(int fd)
>>      return getpagesize();
>>  }
>>  
>> +size_t qemu_mempath_getpagesize(const char *mem_path)
>> +{
>> +#ifdef CONFIG_LINUX
>> +    struct statfs fs;
>> +    int ret;
>> +
>> +    do {
>> +        ret = statfs(mem_path, &fs);
>> +    } while (ret != 0 && errno == EINTR);
>> +
>> +    if (ret != 0) {
>> +        fprintf(stderr, "Couldn't statfs() memory path: %s\n",
>> +                strerror(errno));
>> +        exit(1);
>> +    }
>> +
>> +    if (fs.f_type == HUGETLBFS_MAGIC) {
>> +        /* It's hugepage, return the huge page size */
>> +        return fs.f_bsize;
>> +    }
>> +#endif
>> +
>> +    return getpagesize();
>> +}
>> +
>>  void *qemu_ram_mmap(int fd, size_t size, size_t align, bool shared)
>>  {
>>      /*
> 


-- 
Alexey

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