linux-kernel - Re: [Xen-devel] [PATCH 4/8] xen/pvh: Bootstrap PVH guest

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Date:   Fri, 14 Oct 2016 14:55:30 -0400
From:   Boris Ostrovsky <boris.ostrovsky@...cle.com>
To:     Andrew Cooper <andrew.cooper3@...rix.com>, david.vrabel@...rix.com,
        JGross@...e.com
Cc:     Matt Fleming <matt@...eblueprint.co.uk>,
        xen-devel@...ts.xenproject.org, linux-kernel@...r.kernel.org,
        roger.pau@...rix.com
Subject: Re: [Xen-devel] [PATCH 4/8] xen/pvh: Bootstrap PVH guest

On 10/14/2016 02:38 PM, Andrew Cooper wrote:
>> +	jmp *%rax
>> +
>> +#else /* CONFIG_X86_64 */
>> +
>> +	call setup_pgtable_32
>> +
>> +	mov $_pa(initial_page_table), %eax
>> +	movl %eax, %cr3
>> +
>> +	movl %cr0, %eax
>> +	orl $(X86_CR0_PG | X86_CR0_PE), %eax
>> +	movl %eax, %cr0
>> +
>> +	ljmp $__BOOT_CS,$1f
>> +1:
>> +	call xen_prepare_pvh
> Why does xen_prepare_pvh need paging?  I can't spot anything which
> should need it, and it feels conceptually wrong.

xen_prepare_pvh() deals with virtual addresses. How can we run without paging?

(Also, startup_64, which is where we jump from here in 64-bit mode expects paging to be on).

-boris