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Re: [PATCH v2 4/9] xen/pvh: Bootstrap PVH guest

From Boris Ostrovsky <boris.ostrovsky@oracle.com>
Newsgroups linux.kernel
Subject Re: [PATCH v2 4/9] xen/pvh: Bootstrap PVH guest
Date 2017-02-03 17:20 +0100
Message-ID <t6OKB-40r-3@gated-at.bofh.it> (permalink)
References <t3Ydu-2X9-77@gated-at.bofh.it> <t3Z9w-3wx-7@gated-at.bofh.it> <t6GtI-6ST-5@gated-at.bofh.it>
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>> +
>> +	__HEAD
>> +
>> +/* Entry point for PVH guests. */
> Could you add some comments about register conetnts at entry?

Reference to Xen's docs/misc/hvmlite.markdown would be sifficient?




>> +gdt:
>> +	.word	gdt_end - gdt
>> +	.long	_pa(gdt)
> This is a rather strange construct: the NULL descriptor of the
> GDT being used as space for lgdt operand.
>
>> +	.word	0
>> +	.quad	0x0000000000000000 /* NULL descriptor */
> And this comment is wrong: the NULL descriptor is at "gdt:".

I'll change it to:

gdt:
        .word   gdt_end - gdt_start
        .long   _pa(gdt_start)
        .word   0
gdt_start:
        .quad   0x0000000000000000 /* NULL descriptor */
        .quad   0x0000000000000000 /* reserved */
#ifdef CONFIG_X86_64
        .quad   0x00af9a000000ffff /* __KERNEL_CS */
#else
        .quad   0x00cf9a000000ffff /* __KERNEL_CS */
#endif
        .quad   0x00cf92000000ffff /* __KERNEL_DS */
gdt_end:


>
>> +#ifdef CONFIG_X86_64
>> +	.quad	0x00af9a000000ffff /* __KERNEL_CS */
> Mind adding comments about the semantics of those constants?
> Or use GDT_ENTRY() macro?
>
>> +#else
>> +	.quad	0x00cf9a000000ffff /* __KERNEL_CS */
>> +#endif
>> +	.quad	0x00cf92000000ffff /* __KERNEL_DS */
>> +gdt_end:
>> +
>> +	.bss
>> +	.balign 4
>> +early_stack:
>> +	.fill 16, 1, 0
> Is the stack size large enough? With a hypercall being executed in
> xen_prepare_pvh() I doubt this will be okay.

What do you think it should be then?

-boris

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Thread

Re: [PATCH v2 4/9] xen/pvh: Bootstrap PVH guest Juergen Gross <jgross@suse.com> - 2017-02-03 08:30 +0100
  Re: [PATCH v2 4/9] xen/pvh: Bootstrap PVH guest Boris Ostrovsky <boris.ostrovsky@oracle.com> - 2017-02-03 17:20 +0100
    Re: [PATCH v2 4/9] xen/pvh: Bootstrap PVH guest Juergen Gross <jgross@suse.com> - 2017-02-03 17:50 +0100
      Re: [Xen-devel] [PATCH v2 4/9] xen/pvh: Bootstrap PVH guest Andrew Cooper <andrew.cooper3@citrix.com> - 2017-02-03 19:10 +0100

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