From: Xianting TIan <xianting.tian@linux.alibaba.com> To: Arnd Bergmann <arnd@arndb.de> Cc: gregkh <gregkh@linuxfoundation.org>, Jiri Slaby <jirislaby@kernel.org>, Amit Shah <amit@kernel.org>, Omar Sandoval <osandov@fb.com>, linuxppc-dev <linuxppc-dev@lists.ozlabs.org>, "open list:DRM DRIVER FOR QEMU'S CIRRUS DEVICE" <virtualization@lists.linux-foundation.org>, Linux Kernel Mailing List <linux-kernel@vger.kernel.org>, Guo Ren <guoren@kernel.org> Subject: Re: [PATCH v4 1/2] tty: hvc: pass DMA capable memory to put_chars() Date: Thu, 12 Aug 2021 16:07:58 +0800 [thread overview] Message-ID: <f18d017b-d6f7-cf87-8859-8d6b50c7c289@linux.alibaba.com> (raw) In-Reply-To: <CAK8P3a2=BmVv0tvUKaca+LYxuAussAJtAJW9O3fRN2CbV2-9aw@mail.gmail.com> 在 2021/8/6 下午10:51, Arnd Bergmann 写道: > On Fri, Aug 6, 2021 at 5:01 AM Xianting Tian > <xianting.tian@linux.alibaba.com> wrote: >> @@ -163,6 +155,13 @@ static void hvc_console_print(struct console *co, const char *b, >> if (vtermnos[index] == -1) >> return; >> >> + list_for_each_entry(hp, &hvc_structs, next) >> + if (hp->vtermno == vtermnos[index]) >> + break; >> + >> + c = hp->c; >> + >> + spin_lock_irqsave(&hp->c_lock, flags); > The loop looks like it might race against changes to the list. It seems strange > that the print function has to actually search for the structure here. > > It may be better to have yet another array for the buffer pointers next to > the cons_ops[] and vtermnos[] arrays. > >> +/* >> + * 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)))) > I think you need a higher alignment for DMA buffers, instead of sizeof(long), > I would suggest ARCH_DMA_MINALIGN. As some ARCH(eg, x86, riscv) doesn't define ARCH_DMA_MINALIG, so i think it 's better remain the code unchanged, I will send v5 patch soon. > > Arnd
WARNING: multiple messages have this Message-ID (diff)
From: Xianting TIan <xianting.tian@linux.alibaba.com> To: Arnd Bergmann <arnd@arndb.de> Cc: Jiri Slaby <jirislaby@kernel.org>, Amit Shah <amit@kernel.org>, gregkh <gregkh@linuxfoundation.org>, Linux Kernel Mailing List <linux-kernel@vger.kernel.org>, "open list:DRM DRIVER FOR QEMU'S CIRRUS DEVICE" <virtualization@lists.linux-foundation.org>, Guo Ren <guoren@kernel.org>, linuxppc-dev <linuxppc-dev@lists.ozlabs.org>, Omar Sandoval <osandov@fb.com> Subject: Re: [PATCH v4 1/2] tty: hvc: pass DMA capable memory to put_chars() Date: Thu, 12 Aug 2021 16:07:58 +0800 [thread overview] Message-ID: <f18d017b-d6f7-cf87-8859-8d6b50c7c289@linux.alibaba.com> (raw) In-Reply-To: <CAK8P3a2=BmVv0tvUKaca+LYxuAussAJtAJW9O3fRN2CbV2-9aw@mail.gmail.com> 在 2021/8/6 下午10:51, Arnd Bergmann 写道: > On Fri, Aug 6, 2021 at 5:01 AM Xianting Tian > <xianting.tian@linux.alibaba.com> wrote: >> @@ -163,6 +155,13 @@ static void hvc_console_print(struct console *co, const char *b, >> if (vtermnos[index] == -1) >> return; >> >> + list_for_each_entry(hp, &hvc_structs, next) >> + if (hp->vtermno == vtermnos[index]) >> + break; >> + >> + c = hp->c; >> + >> + spin_lock_irqsave(&hp->c_lock, flags); > The loop looks like it might race against changes to the list. It seems strange > that the print function has to actually search for the structure here. > > It may be better to have yet another array for the buffer pointers next to > the cons_ops[] and vtermnos[] arrays. > >> +/* >> + * 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)))) > I think you need a higher alignment for DMA buffers, instead of sizeof(long), > I would suggest ARCH_DMA_MINALIGN. As some ARCH(eg, x86, riscv) doesn't define ARCH_DMA_MINALIG, so i think it 's better remain the code unchanged, I will send v5 patch soon. > > Arnd
next prev parent reply other threads:[~2021-08-12 8:08 UTC|newest] Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-08-06 3:01 [PATCH v4 0/2] make hvc pass dma capable memory to its backend Xianting Tian 2021-08-06 3:01 ` Xianting Tian 2021-08-06 3:01 ` [PATCH v4 1/2] tty: hvc: pass DMA capable memory to put_chars() Xianting Tian 2021-08-06 3:01 ` Xianting Tian 2021-08-06 14:51 ` Arnd Bergmann 2021-08-06 14:51 ` Arnd Bergmann 2021-08-06 14:51 ` Arnd Bergmann 2021-08-07 15:00 ` Xianting Tian 2021-08-07 15:00 ` Xianting Tian 2021-08-12 8:07 ` Xianting TIan [this message] 2021-08-12 8:07 ` Xianting TIan 2021-08-12 8:54 ` Arnd Bergmann 2021-08-12 8:54 ` Arnd Bergmann 2021-08-12 8:54 ` Arnd Bergmann 2021-08-12 9:14 ` Xianting TIan 2021-08-12 9:14 ` Xianting TIan 2021-08-06 3:01 ` [PATCH v4 2/2] virtio-console: remove unnecessary kmemdup() Xianting Tian 2021-08-06 3:01 ` Xianting Tian
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