Re: 32bit PAE PV guest on 64bit hypervisor

From: Jeremy Fitzhardinge <jeremy@goop.org>
To: mukesh.rathor@oracle.com
Cc: xen-devel <xen-devel@lists.xensource.com>
Subject: Re: 32bit PAE PV guest on 64bit hypervisor
Date: Tue, 14 Apr 2009 08:59:47 -0700	[thread overview]
Message-ID: <49E4B2F3.1050307@goop.org> (raw)
In-Reply-To: <49E40563.4010505@oracle.com>

Mukesh Rathor wrote:
> Hi,
>
> Been chasing down this message from guest boot:
>
> (XEN) mm.c:1841:d1 Error pfn 7f36a: rd=ffff8300cea28080,
> od=0000000000000000, caf=00000000, taf=0000000000000000
> (XEN) mm.c:730:d1 Error getting mfn 7f36a (pfn 5555555555555555) from L1
> entry 000000007f36a025 for dom1
> (XEN) mm.c:3700:d1 ptwr_emulate: fixing up invalid PAE PTE
> 000000007f36a025
>
> Firstly, on a >64GB system, looks like a 32bit guest can get mfn above 
> 64G.
>
> The above msg comes when the PV guest tries to do WP check. To that end,
> it does set_pte for mapping a (some swapper) temp page in test_wp_bit():
>
>       __set_fixmap(FIX_WP_TEST, __pa_symbol(&swapper_pg_dir), 
> PAGE_READONLY);
>       boot_cpu_data.wp_works_ok = do_test_wp_bit();
>       clear_fixmap(FIX_WP_TEST);
>
> ...
> /* use writable pagetables */
> static inline void set_pte(pte_t *ptep, pte_t pte)
> {
>         ptep->pte_high = pte.pte_high;
>     smp_wmb();
>     ptep->pte_low = pte.pte_low;
> }

What kernel version is this?

    J