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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 09:30:16AM +0000, Wei Liu wrote:
> 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?
>

To keep the total ring buffer size unchanged (still 40k) when
PAGE_SIZE=4k. Because in VMBUS_RING_SIZE() (which I plan to rename as
HV_RING_SIZE()), the hv_ring_buffer size is already added.

Regards,
Boqun

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

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