Date: Fri, 19 Jan 2024 19:40:32 +0100 From: Mateusz Guzik <mjguzik@gmail.com> To: Michael Zhilin <mizhka@gmail.com> Cc: Rozhuk Ivan <rozhuk.im@gmail.com>, FreeBSD Hackers <freebsd-hackers@freebsd.org>, FreeBSD Mailing List <freebsd-ports@freebsd.org> Subject: Re: kcmp implementation for mesa Message-ID: <CAGudoHEScHvfJBDqDULWJNFmxcm-G5WHGD8pvb0TzyaM5ajftQ@mail.gmail.com> In-Reply-To: <CAF19XBJ-5YMoayGoQv_zVxr%2BJKFRkXec9d5Az1oM6iCrpykbkQ@mail.gmail.com> References: <20240119131047.6975f574@rimwks.local> <CAF19XBJ-5YMoayGoQv_zVxr%2BJKFRkXec9d5Az1oM6iCrpykbkQ@mail.gmail.com>
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instead of messing with code like this it's probably time to implement
kcmp in the kernel
On 1/19/24, Michael Zhilin <mizhka@gmail.com> wrote:
> Hi Ivan,
>
> Looks good. Could you please put patch on reviews.freebsd.org?
>
> Thx,
> Michael
>
> On Fri, 19 Jan 2024, 14:11 Rozhuk Ivan, <rozhuk.im@gmail.com> wrote:
>
>> Hi!
>>
>>
>> graphics/mesa-* uses SYS_kcmp [1] to compare two fds:
>>
>> int
>> os_same_file_description(int fd1, int fd2)
>> {
>> pid_t pid = getpid();
>>
>> /* Same file descriptor trivially implies same file description */
>> if (fd1 == fd2)
>> return 0;
>>
>> return syscall(SYS_kcmp, pid, pid, KCMP_FILE, fd1, fd2);
>> }
>>
>> FreeBSD does not implemet this and we got in terminal:
>> "amdgpu: os_same_file_description couldn't determine if two DRM fds
>> reference the same file description."
>>
>>
>> Mesa say:
>> /* DRM file descriptors, file descriptions and buffer sharing.
>> *
>> * amdgpu_device_initialize first argument is a file descriptor (fd)
>> * representing a specific GPU.
>> * If a fd is duplicated using os_dupfd_cloexec,
>> * the file description will remain the same (os_same_file_description
>> will
>> * return 0).
>> * But if the same device is re-opened, the fd and the file description
>> will
>> * be different.
>> *
>> * amdgpu_screen_winsys's fd tracks the file description which was
>> * given to amdgpu_winsys_create. This is the fd used by the application
>> * using the driver and may be used in other ioctl (eg: drmModeAddFB)
>> *
>> * amdgpu_winsys's fd is the file description used to initialize the
>> * device handle in libdrm_amdgpu.
>> *
>> * The 2 fds can be different, even in systems with a single GPU, eg: if
>> * radv is initialized before radeonsi.
>> *
>> * This fd tracking is useful for buffer sharing because KMS/GEM handles
>> are
>> * specific to a DRM file description, i.e. the same handle value may
>> refer
>> * to different underlying BOs in different DRM file descriptions.
>> * As an example, if an app wants to use drmModeAddFB it'll need a KMS
>> handle
>> * valid for its fd (== amdgpu_screen_winsys::fd).
>> * If both fds are identical, there's nothing to do:
>> bo->u.real.kms_handle
>> * can be used directly (see amdgpu_bo_get_handle).
>> * If they're different, the BO has to be exported from the device fd as
>> * a dma-buf, then imported from the app fd as a KMS handle.
>> */
>>
>>
>>
>> I do few checks with dup() and os_dupfd_cloexec() and code show that fd
>> equal.
>>
>> Does this implementation will do that mesa expects?
>>
>>
>> #include <sys/user.h>
>> #include <fcntl.h>
>>
>> int
>> os_same_file_description(int fd1, int fd2) {
>> struct kinfo_file kif1, kif2;
>>
>> /* Same file descriptor trivially implies same file description
>> */
>> if (fd1 == fd2)
>> return (0);
>>
>> kif1.kf_structsize = sizeof(kif1);
>> kif2.kf_structsize = sizeof(kif2);
>> if (-1 == fcntl(fd1, F_KINFO, &kif1) ||
>> -1 == fcntl(fd2, F_KINFO, &kif2))
>> return (-1);
>>
>> if (kif1.kf_type != kif2.kf_type ||
>> 0 != memcmp(&kif1.kf_path, &kif2.kf_path,
>> sizeof(kif1.kf_path)))
>> return (3);
>>
>> switch (kif1.kf_type) {
>> case KF_TYPE_VNODE:
>> if (0 == memcmp(&kif1.kf_un.kf_file, &kif2.kf_un.kf_file,
>> sizeof(kif1.kf_un.kf_file)))
>> return (0);
>> return (3);
>> case KF_TYPE_SOCKET:
>> if (0 == memcmp(&kif1.kf_un.kf_sock, &kif2.kf_un.kf_sock,
>> sizeof(kif1.kf_un.kf_sock)))
>> return (0);
>> return (3);
>> case KF_TYPE_PIPE:
>> if (0 == memcmp(&kif1.kf_un.kf_pipe, &kif2.kf_un.kf_pipe,
>> sizeof(kif1.kf_un.kf_pipe)))
>> return (0);
>> return (3);
>> //case KF_TYPE_FIFO:
>> case KF_TYPE_KQUEUE:
>> if (0 == memcmp(&kif1.kf_un.kf_kqueue,
>> &kif2.kf_un.kf_kqueue,
>> sizeof(kif1.kf_un.kf_kqueue)))
>> return (0);
>> return (3);
>> //case KF_TYPE_MQUEUE:
>> //case KF_TYPE_SHM:
>> case KF_TYPE_SEM:
>> if (0 == memcmp(&kif1.kf_un.kf_sem, &kif2.kf_un.kf_sem,
>> sizeof(kif1.kf_un.kf_sem)))
>> return (0);
>> return (3);
>> case KF_TYPE_PTS:
>> if (0 == memcmp(&kif1.kf_un.kf_pts, &kif2.kf_un.kf_pts,
>> sizeof(kif1.kf_un.kf_pts)))
>> return (0);
>> return (3);
>> case KF_TYPE_PROCDESC:
>> if (0 == memcmp(&kif1.kf_un.kf_proc, &kif2.kf_un.kf_proc,
>> sizeof(kif1.kf_un.kf_proc)))
>> return (0);
>> return (3);
>> //case KF_TYPE_DEV:
>> case KF_TYPE_EVENTFD:
>> if (0 == memcmp(&kif1.kf_un.kf_eventfd,
>> &kif2.kf_un.kf_eventfd,
>> sizeof(kif1.kf_un.kf_eventfd)))
>> return (0);
>> return (3);
>> case KF_TYPE_TIMERFD:
>> if (0 == memcmp(&kif1.kf_un.kf_timerfd,
>> &kif2.kf_un.kf_timerfd,
>> sizeof(kif1.kf_un.kf_timerfd)))
>> return (0);
>> return (3);
>> }
>> /* Otherwise we can't tell */
>> return (-1);
>> }
>>
>>
>> Refs:
>> 1. https://man7.org/linux/man-pages/man2/kcmp.2.html
>>
>>
>>
>
--
Mateusz Guzik <mjguzik gmail.com>
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