linux-kernel - Re: [Xen-devel] [PATCH] xen/hvc-console: Make it work with HVM guests.

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Message-ID: <20131023161518.GA28413@phenom.dumpdata.com>
Date:	Wed, 23 Oct 2013 12:15:18 -0400
From:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
To:	Julien Grall <julien.grall@...aro.org>
Cc:	ian.campbell@...rix.com, linux-kernel@...r.kernel.org,
	xen-devel@...ts.xenproject.org
Subject: Re: [Xen-devel] [PATCH] xen/hvc-console: Make it work with HVM
 guests.

On Sun, Oct 06, 2013 at 09:52:40PM +0100, Julien Grall wrote:
> On 09/30/2013 03:45 PM, Konrad Rzeszutek Wilk wrote:
> >On Fri, Sep 27, 2013 at 10:49:37PM +0100, Julien Grall wrote:
> >>On 09/27/2013 10:25 PM, Konrad Rzeszutek Wilk wrote:
> >>
> >>>@@ -641,7 +641,20 @@ struct console xenboot_console = {
> >>>
> >>>  void xen_raw_console_write(const char *str)
> >>>  {
> >>>-	dom0_write_console(0, str, strlen(str));
> >>>+	ssize_t len = strlen(str);
> >>>+	int rc = 0;
> >>>+
> >>>+	if (xen_domain()) {
> >>>+		dom0_write_console(0, str, len);
> >>>+		if (rc == -ENOSYS && xen_hvm_domain())
> >>>+			goto outb_print;
> >>>+
> >>>+	} else if (xen_cpuid_base()) {
> >>>+		int i;
> >>>+outb_print:
> >>>+		for (i = 0; i < len; i++)
> >>>+			outb(str[i], 0xe9);
> >>>+	}
> >>>  }
> >>
> >>xen_cpuid_base and outb(0xe9) is x86 specific and won't compile on ARM.
> >
> >Odd, I see outb defined in arch/arm and arch/arm64 ?(arch/arm[|64]/include/asm.io.h)
> 
> On ARM32 the IO access is memory mapped (the exact address depends
> on Linux configuration).
> The main problem is not the outb macro but the ioport 0xe9.On ARM,
> this ioport is not trapped by Xen.
> 
> >You are of course right about xen_cpuid_base.
> >
> >How about this:
> 
> For the ARM side, the code looks good.

Can I that as 'Acked-by' ? thanks
> 
> > From 04b772d2b819f0dda2163e3193fa7cd447a6245c Mon Sep 17 00:00:00 2001
> >From: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
> >Date: Fri, 27 Sep 2013 17:18:13 -0400
> >Subject: [PATCH] xen/hvc: If we use xen_raw_printk let it also work on HVM
> >  guests.
> >
> >The xen_raw_printk works great for debugging purposes. We use
> >for PV guests and we can also use it for HVM guests.
> >
> >However, for HVM guests we have a fallback of using the 0xe9
> >port in case the hypervisor does not support an HVM guest of
> >using the console_io hypercall. As such lets use 0xe9 during
> >early bootup, and once the hyper-page is setup and if the
> >console_io hypercall is supported - use that. Otherwise we
> >will fallback to using the 0xe9 after early bootup.
> >
> >We also alter the return value for dom0_write_console to return
> >an error value instead of zero. The HVC API has been supporting
> >returning error values for quite some time.
> >
> >P.S.
> >To use (and to see the output in the Xen ring buffer) one has to build
> >the hypervisor with 'debug=y'.
> >
> >Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
> >[v1: ifdef xen_cpuid_base as it is X86 specific]
> >---
> >  drivers/tty/hvc/hvc_xen.c | 19 +++++++++++++++++--
> >  1 file changed, 17 insertions(+), 2 deletions(-)
> >
> >diff --git a/drivers/tty/hvc/hvc_xen.c b/drivers/tty/hvc/hvc_xen.c
> >index e61c36c..6458c9f 100644
> >--- a/drivers/tty/hvc/hvc_xen.c
> >+++ b/drivers/tty/hvc/hvc_xen.c
> >@@ -183,7 +183,7 @@ static int dom0_write_console(uint32_t vtermno, const char *str, int len)
> >  {
> >  	int rc = HYPERVISOR_console_io(CONSOLEIO_write, len, (char *)str);
> >  	if (rc < 0)
> >-		return 0;
> >+		return rc;
> >
> >  	return len;
> >  }
> >@@ -641,7 +641,22 @@ struct console xenboot_console = {
> >
> >  void xen_raw_console_write(const char *str)
> >  {
> >-	dom0_write_console(0, str, strlen(str));
> >+	ssize_t len = strlen(str);
> >+	int rc = 0;
> >+
> >+	if (xen_domain()) {
> >+		rc = dom0_write_console(0, str, len);
> >+#ifdef CONFIG_X86
> >+		if (rc == -ENOSYS && xen_hvm_domain())
> >+			goto outb_print;
> >+
> >+	} else if (xen_cpuid_base()) {
> >+		int i;
> >+outb_print:
> >+		for (i = 0; i < len; i++)
> >+			outb(str[i], 0xe9);
> >+#endif
> >+	}
> >  }
> >
> >  void xen_raw_printk(const char *fmt, ...)
> >
> 
> 
> -- 
> Julien Grall
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