From: Greg KH <gregkh@linuxfoundation.org>
To: Xianting Tian <xianting.tian@linux.alibaba.com>
Cc: jirislaby@kernel.org, amit@kernel.org, arnd@arndb.de,
osandov@fb.com, shile.zhang@linux.alibaba.com,
linuxppc-dev@lists.ozlabs.org,
virtualization@lists.linux-foundation.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v10 2/3] tty: hvc: pass DMA capable memory to put_chars()
Date: Sat, 9 Oct 2021 13:58:43 +0200 [thread overview]
Message-ID: <YWGD8y9VfBIQBu2h@kroah.com> (raw)
In-Reply-To: <20211009114829.1071021-3-xianting.tian@linux.alibaba.com>
On Sat, Oct 09, 2021 at 07:48:28PM +0800, Xianting Tian wrote:
> --- a/drivers/tty/hvc/hvc_console.h
> +++ b/drivers/tty/hvc/hvc_console.h
> @@ -32,13 +32,21 @@
> */
> #define HVC_ALLOC_TTY_ADAPTERS 8
>
> +/*
> + * These sizes are most efficient for vio, because they are the
> + * native transfer size. We could make them selectable in the
> + * future to better deal with backends that want other buffer sizes.
> + */
> +#define N_OUTBUF 16
> +#define N_INBUF 16
> +
> +#define __ALIGNED__ __attribute__((__aligned__(sizeof(long))))
Does this conflict with what is in hvcs.c?
> +
> struct hvc_struct {
> struct tty_port port;
> spinlock_t lock;
> int index;
> int do_wakeup;
> - char *outbuf;
> - int outbuf_size;
> int n_outbuf;
> uint32_t vtermno;
> const struct hv_ops *ops;
> @@ -48,6 +56,18 @@ struct hvc_struct {
> struct work_struct tty_resize;
> struct list_head next;
> unsigned long flags;
> +
> + /* the buf is used in hvc console api for putting chars */
> + char cons_outbuf[N_OUTBUF] __ALIGNED__;
> + spinlock_t cons_outbuf_lock;
Did you look at the placement using pahole as to how this structure now
looks?
> +
> + /* the buf is for putting single char to tty */
> + char outchar;
> + spinlock_t outchar_lock;
So you have a lock for a character and a different one for a longer
string? Why can they not just use the same lock? Why are 2 needed at
all, can't you just use the first character of cons_outbuf[] instead?
Surely you do not have 2 sends happening at the same time, right?
> +
> + /* the buf is for putting chars to tty */
> + int outbuf_size;
> + char outbuf[0] __ALIGNED__;
I thought we were not allowing [0] anymore in kernel structures?
thanks,
greg k-h
WARNING: multiple messages have this Message-ID (diff)
From: Greg KH <gregkh@linuxfoundation.org>
To: Xianting Tian <xianting.tian@linux.alibaba.com>
Cc: arnd@arndb.de, amit@kernel.org, jirislaby@kernel.org,
shile.zhang@linux.alibaba.com, linux-kernel@vger.kernel.org,
virtualization@lists.linux-foundation.org,
linuxppc-dev@lists.ozlabs.org, osandov@fb.com
Subject: Re: [PATCH v10 2/3] tty: hvc: pass DMA capable memory to put_chars()
Date: Sat, 9 Oct 2021 13:58:43 +0200 [thread overview]
Message-ID: <YWGD8y9VfBIQBu2h@kroah.com> (raw)
In-Reply-To: <20211009114829.1071021-3-xianting.tian@linux.alibaba.com>
On Sat, Oct 09, 2021 at 07:48:28PM +0800, Xianting Tian wrote:
> --- a/drivers/tty/hvc/hvc_console.h
> +++ b/drivers/tty/hvc/hvc_console.h
> @@ -32,13 +32,21 @@
> */
> #define HVC_ALLOC_TTY_ADAPTERS 8
>
> +/*
> + * These sizes are most efficient for vio, because they are the
> + * native transfer size. We could make them selectable in the
> + * future to better deal with backends that want other buffer sizes.
> + */
> +#define N_OUTBUF 16
> +#define N_INBUF 16
> +
> +#define __ALIGNED__ __attribute__((__aligned__(sizeof(long))))
Does this conflict with what is in hvcs.c?
> +
> struct hvc_struct {
> struct tty_port port;
> spinlock_t lock;
> int index;
> int do_wakeup;
> - char *outbuf;
> - int outbuf_size;
> int n_outbuf;
> uint32_t vtermno;
> const struct hv_ops *ops;
> @@ -48,6 +56,18 @@ struct hvc_struct {
> struct work_struct tty_resize;
> struct list_head next;
> unsigned long flags;
> +
> + /* the buf is used in hvc console api for putting chars */
> + char cons_outbuf[N_OUTBUF] __ALIGNED__;
> + spinlock_t cons_outbuf_lock;
Did you look at the placement using pahole as to how this structure now
looks?
> +
> + /* the buf is for putting single char to tty */
> + char outchar;
> + spinlock_t outchar_lock;
So you have a lock for a character and a different one for a longer
string? Why can they not just use the same lock? Why are 2 needed at
all, can't you just use the first character of cons_outbuf[] instead?
Surely you do not have 2 sends happening at the same time, right?
> +
> + /* the buf is for putting chars to tty */
> + int outbuf_size;
> + char outbuf[0] __ALIGNED__;
I thought we were not allowing [0] anymore in kernel structures?
thanks,
greg k-h
WARNING: multiple messages have this Message-ID (diff)
From: Greg KH <gregkh@linuxfoundation.org>
To: Xianting Tian <xianting.tian@linux.alibaba.com>
Cc: arnd@arndb.de, amit@kernel.org, jirislaby@kernel.org,
shile.zhang@linux.alibaba.com, linux-kernel@vger.kernel.org,
virtualization@lists.linux-foundation.org,
linuxppc-dev@lists.ozlabs.org, osandov@fb.com
Subject: Re: [PATCH v10 2/3] tty: hvc: pass DMA capable memory to put_chars()
Date: Sat, 9 Oct 2021 13:58:43 +0200 [thread overview]
Message-ID: <YWGD8y9VfBIQBu2h@kroah.com> (raw)
In-Reply-To: <20211009114829.1071021-3-xianting.tian@linux.alibaba.com>
On Sat, Oct 09, 2021 at 07:48:28PM +0800, Xianting Tian wrote:
> --- a/drivers/tty/hvc/hvc_console.h
> +++ b/drivers/tty/hvc/hvc_console.h
> @@ -32,13 +32,21 @@
> */
> #define HVC_ALLOC_TTY_ADAPTERS 8
>
> +/*
> + * These sizes are most efficient for vio, because they are the
> + * native transfer size. We could make them selectable in the
> + * future to better deal with backends that want other buffer sizes.
> + */
> +#define N_OUTBUF 16
> +#define N_INBUF 16
> +
> +#define __ALIGNED__ __attribute__((__aligned__(sizeof(long))))
Does this conflict with what is in hvcs.c?
> +
> struct hvc_struct {
> struct tty_port port;
> spinlock_t lock;
> int index;
> int do_wakeup;
> - char *outbuf;
> - int outbuf_size;
> int n_outbuf;
> uint32_t vtermno;
> const struct hv_ops *ops;
> @@ -48,6 +56,18 @@ struct hvc_struct {
> struct work_struct tty_resize;
> struct list_head next;
> unsigned long flags;
> +
> + /* the buf is used in hvc console api for putting chars */
> + char cons_outbuf[N_OUTBUF] __ALIGNED__;
> + spinlock_t cons_outbuf_lock;
Did you look at the placement using pahole as to how this structure now
looks?
> +
> + /* the buf is for putting single char to tty */
> + char outchar;
> + spinlock_t outchar_lock;
So you have a lock for a character and a different one for a longer
string? Why can they not just use the same lock? Why are 2 needed at
all, can't you just use the first character of cons_outbuf[] instead?
Surely you do not have 2 sends happening at the same time, right?
> +
> + /* the buf is for putting chars to tty */
> + int outbuf_size;
> + char outbuf[0] __ALIGNED__;
I thought we were not allowing [0] anymore in kernel structures?
thanks,
greg k-h
_______________________________________________
Virtualization mailing list
Virtualization@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/virtualization
next prev parent reply other threads:[~2021-10-09 11:58 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-09 11:48 [PATCH v10 0/3] make hvc pass dma capable memory to its backend Xianting Tian
2021-10-09 11:48 ` Xianting Tian
2021-10-09 11:48 ` [PATCH v10 1/3] tty: hvc: use correct dma alignment size Xianting Tian
2021-10-09 11:48 ` Xianting Tian
2021-10-09 11:48 ` [PATCH v10 2/3] tty: hvc: pass DMA capable memory to put_chars() Xianting Tian
2021-10-09 11:48 ` Xianting Tian
2021-10-09 11:55 ` Greg KH
2021-10-09 11:55 ` Greg KH
2021-10-09 11:55 ` Greg KH
2021-10-09 11:58 ` Greg KH [this message]
2021-10-09 11:58 ` Greg KH
2021-10-09 11:58 ` Greg KH
2021-10-09 15:45 ` Xianting Tian
2021-10-09 15:45 ` Xianting Tian
2021-10-10 5:33 ` Greg KH
2021-10-10 5:33 ` Greg KH
2021-10-10 5:33 ` Greg KH
2021-10-14 8:34 ` Xianting Tian
2021-10-14 8:34 ` Xianting Tian
2021-10-14 8:41 ` Greg KH
2021-10-14 8:41 ` Greg KH
2021-10-14 8:41 ` Greg KH
2021-10-14 8:56 ` Xianting Tian
2021-10-14 8:56 ` Xianting Tian
2021-10-09 11:48 ` [PATCH v10 3/3] virtio-console: remove unnecessary kmemdup() Xianting Tian
2021-10-09 11:48 ` Xianting Tian
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=YWGD8y9VfBIQBu2h@kroah.com \
--to=gregkh@linuxfoundation.org \
--cc=amit@kernel.org \
--cc=arnd@arndb.de \
--cc=jirislaby@kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linuxppc-dev@lists.ozlabs.org \
--cc=osandov@fb.com \
--cc=shile.zhang@linux.alibaba.com \
--cc=virtualization@lists.linux-foundation.org \
--cc=xianting.tian@linux.alibaba.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.