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

[Paolo Bonzini]

On 09/02/2017 06:43, Alexey Kardashevskiy wrote:
> 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?

It's just code movement, go ahead.

Paolo

> 
> 
>>
>>> ---
>>>  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)
>>>  {
>>>      /*
>>
> 
>

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