linux-kernel - Re: [PATCH V10 14/14] xen/pvh: vcpu info placement, load CS selector, and remove debug printk.

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Message-ID: <52AAF0DE.9030607@citrix.com>
Date:	Fri, 13 Dec 2013 11:34:54 +0000
From:	David Vrabel <david.vrabel@...rix.com>
To:	Konrad Rzeszutek Wilk <konrad@...nel.org>
CC:	<xen-devel@...ts.xenproject.org>, <linux-kernel@...r.kernel.org>,
	<george.dunlap@...citrix.com>, <ian.jackson@...citrix.com>,
	<mukesh.rathor@...cle.com>, <tim@....org>, <jbeulich@...e.com>,
	<boris.ostrovsky@...cle.com>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
Subject: Re: [PATCH V10 14/14] xen/pvh: vcpu info placement, load CS selector,
 and remove debug printk.

On 13/12/13 02:10, Konrad Rzeszutek Wilk wrote:
> From: Mukesh Rathor <mukesh.rathor@...cle.com>
> 
> This patch addresses 3 things:
>    - Resolve vcpu info placement fixme.
>    - Load CS selector for PVH after switching to new gdt.
>    - Remove printk in case of failure to map pnfs in p2m. This because qemu
>      has lot of expected failures when mapping HVM pages.
[...]
> @@ -1423,7 +1425,20 @@ static void __init xen_setup_stackprotector(void)
>  {
>  	/* PVH TBD/FIXME: investigate setup_stack_canary_segment */
>  	if (xen_feature(XENFEAT_auto_translated_physmap)) {
> +		unsigned long dummy;
> +
>  		switch_to_new_gdt(0);
> +#ifdef CONFIG_X86_64
> +		asm volatile ("pushq %0\n"
> +			      "leaq 1f(%%rip),%0\n"
> +			      "pushq %0\n"
> +			      "lretq\n"
> +			      "1:\n"
> +			      : "=&r" (dummy) : "0" (__KERNEL_CS));

Why does CS need to be reloaded here?

David
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