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Re: [PATCH v2 fixed 08/16] util/mmap-alloc: Factor out calculation of pa
From: |
David Hildenbrand |
Subject: |
Re: [PATCH v2 fixed 08/16] util/mmap-alloc: Factor out calculation of pagesize to mmap_pagesize() |
Date: |
Mon, 24 Feb 2020 11:50:37 +0100 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.5.0 |
On 19.02.20 23:46, Peter Xu wrote:
> On Wed, Feb 12, 2020 at 02:42:46PM +0100, David Hildenbrand wrote:
>> Factor it out and add a comment.
>>
>> Reviewed-by: Igor Kotrasinski <address@hidden>
>> Acked-by: Murilo Opsfelder Araujo <address@hidden>
>> Reviewed-by: Richard Henderson <address@hidden>
>> Cc: "Michael S. Tsirkin" <address@hidden>
>> Cc: Murilo Opsfelder Araujo <address@hidden>
>> Cc: Greg Kurz <address@hidden>
>> Cc: Eduardo Habkost <address@hidden>
>> Cc: "Dr. David Alan Gilbert" <address@hidden>
>> Cc: Igor Mammedov <address@hidden>
>> Signed-off-by: David Hildenbrand <address@hidden>
>> ---
>> util/mmap-alloc.c | 21 ++++++++++++---------
>> 1 file changed, 12 insertions(+), 9 deletions(-)
>>
>> diff --git a/util/mmap-alloc.c b/util/mmap-alloc.c
>> index 27dcccd8ec..82f02a2cec 100644
>> --- a/util/mmap-alloc.c
>> +++ b/util/mmap-alloc.c
>> @@ -82,17 +82,27 @@ size_t qemu_mempath_getpagesize(const char *mem_path)
>> return qemu_real_host_page_size;
>> }
>>
>> +static inline size_t mmap_pagesize(int fd)
>> +{
>> +#if defined(__powerpc64__) && defined(__linux__)
>> + /* Mappings in the same segment must share the same page size */
>> + return qemu_fd_getpagesize(fd);
>> +#else
>> + return qemu_real_host_page_size;
>> +#endif
>> +}
>
> Pure question: This will return 4K even for huge pages on x86, is this
> what we want?
(was asking myself the same question) I *think* it's intended. It's
mainly only used to allocate one additional guard page. The callers of
qemu_ram_mmap() make sure that the size is properly aligned (e.g., to
huge pages).
Of course, a 4k guard page is sufficient - unless we can't use that
(special case for ppc64 here).
Thanks!
--
Thanks,
David / dhildenb
- [PATCH v2 fixed 04/16] util: vfio-helpers: Factor out removal from qemu_vfio_undo_mapping(), (continued)
- [PATCH v2 fixed 04/16] util: vfio-helpers: Factor out removal from qemu_vfio_undo_mapping(), David Hildenbrand, 2020/02/12
- [PATCH v2 fixed 06/16] exec: Reuse qemu_ram_apply_settings() in qemu_ram_remap(), David Hildenbrand, 2020/02/12
- [PATCH v2 fixed 05/16] exec: Factor out setting ram settings (madvise ...) into qemu_ram_apply_settings(), David Hildenbrand, 2020/02/12
- [PATCH v2 fixed 07/16] exec: Drop "shared" parameter from ram_block_add(), David Hildenbrand, 2020/02/12
- [PATCH v2 fixed 08/16] util/mmap-alloc: Factor out calculation of pagesize to mmap_pagesize(), David Hildenbrand, 2020/02/12
- Re: [PATCH v2 fixed 08/16] util/mmap-alloc: Factor out calculation of pagesize to mmap_pagesize(), Peter Xu, 2020/02/24
- Re: [PATCH v2 fixed 08/16] util/mmap-alloc: Factor out calculation of pagesize to mmap_pagesize(), David Hildenbrand, 2020/02/24
[PATCH v2 fixed 09/16] util/mmap-alloc: Factor out reserving of a memory region to mmap_reserve(), David Hildenbrand, 2020/02/12
[PATCH v2 fixed 10/16] util/mmap-alloc: Factor out populating of memory to mmap_populate(), David Hildenbrand, 2020/02/12