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    SubjectRe: [PATCH v3 08/11] Input: hyperv-keyboard: Make ringbuffer at least take two pages
    On Mon, Sep 14, 2020 at 04:46:00PM +0800, Boqun Feng wrote:
    > On Thu, Sep 10, 2020 at 10:34:52PM +0800, Boqun Feng wrote:
    > > When PAGE_SIZE > HV_HYP_PAGE_SIZE, we need the ringbuffer size to be at
    > > least 2 * PAGE_SIZE: one page for the header and at least one page of
    > > the data part (because of the alignment requirement for double mapping).
    > >
    > > So make sure the ringbuffer sizes to be at least 2 * PAGE_SIZE when
    > > using vmbus_open() to establish the vmbus connection.
    > >
    > > Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
    > > ---
    > > drivers/input/serio/hyperv-keyboard.c | 4 ++--
    > > 1 file changed, 2 insertions(+), 2 deletions(-)
    > >
    > > diff --git a/drivers/input/serio/hyperv-keyboard.c b/drivers/input/serio/hyperv-keyboard.c
    > > index df4e9f6f4529..6ebc61e2db3f 100644
    > > --- a/drivers/input/serio/hyperv-keyboard.c
    > > +++ b/drivers/input/serio/hyperv-keyboard.c
    > > @@ -75,8 +75,8 @@ struct synth_kbd_keystroke {
    > >
    > > #define HK_MAXIMUM_MESSAGE_SIZE 256
    > >
    > > -#define KBD_VSC_SEND_RING_BUFFER_SIZE (40 * 1024)
    > > -#define KBD_VSC_RECV_RING_BUFFER_SIZE (40 * 1024)
    > > +#define KBD_VSC_SEND_RING_BUFFER_SIZE max(40 * 1024, (int)(2 * PAGE_SIZE))
    > > +#define KBD_VSC_RECV_RING_BUFFER_SIZE max(40 * 1024, (int)(2 * PAGE_SIZE))
    > >
    >
    > Hmm.. just realized there is a problem here, if PAGE_SIZE = 16k, then
    > 40 * 1024 > 2 * PAGE_SIZE, however in the ring buffer size should also
    > be page aligned, otherwise vmbus_open() will fail.
    >
    > I plan to modify this as
    >
    > in linux/hyperv.h:
    >
    > #define VMBUS_RING_SIZE(payload_sz) PAGE_ALIGN(sizeof(struct hv_ring_buffer) + (playload_sz))
    >
    > and here:
    >
    > #define KBD_VSC_SEND_RING_BUFFER_SIZE VMBUS_RING_SIZE(36 * 1024)
    > #define KBD_VSC_RECV_RING_BUFFER_SIZE VMBUS_RING_SIZE(36 * 1024)
    >
    > and the similar change for patch #9.

    OOI why do you reduce the size by 4k here?

    Wei.

    >
    > Thoughts?
    >
    > Regards,
    > Boqun
    >
    > > #define XTKBD_EMUL0 0xe0
    > > #define XTKBD_EMUL1 0xe1
    > > --
    > > 2.28.0
    > >

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