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Re: [PATCH] Revert "tools/firmware/ovmf: Use OvmfXen platform file is exist"
- To: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Tue, 22 Jun 2021 18:10:39 +0200
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- Cc: Anthony PERARD <anthony.perard@xxxxxxxxxx>, George Dunlap <George.Dunlap@xxxxxxxxxxxxx>, Ian Jackson <iwj@xxxxxxxxxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>, Julien Grall <julien@xxxxxxx>, Xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- Delivery-date: Tue, 22 Jun 2021 16:10:49 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 22.06.2021 17:39, Andrew Cooper wrote:
> This reverts commit aad7b5c11d51d57659978e04702ac970906894e8.
>
> The change from OvmfX64 to OvmfXen causes a change in behaviour, whereby
> OvmfXen maps its shared info page at the top of address space. When trying to
> migrate such a domain, XENMEM_maximum_gpfn returns a very large value. This
> has uncovered multiple issues:
>
> 1) The userspace hypercall wrappers truncate all return values to int on
> Linux and Solaris. This needs fixing in Xen.
> 2) 32bit toolstacks can't migrate any domain with RAM above the 2^40 mark,
> because of virtual address constraints. This needs fixing in OVMF.
And I suspect even that presently enforce boundary of 2^40 is actually
too high, and things still wouldn't work when getting close. At the
very least the tool stack then depends on a fairly big chunk of memory
(2^30 bytes) to be available in one single, virtually contiguous piece.
Iirc 32-bit Linux can be configured to not even leave this much space
for user mode.
Jan
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