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Re: SEV guest debugging support for Qemu
From: |
Ashish Kalra |
Subject: |
Re: SEV guest debugging support for Qemu |
Date: |
Mon, 28 Sep 2020 13:26:39 +0000 |
User-agent: |
Mutt/1.9.4 (2018-02-28) |
Hello Paolo,
On Sat, Sep 26, 2020 at 02:02:20AM +0200, Paolo Bonzini wrote:
> On 26/09/20 01:48, Ashish Kalra wrote:
> > Thanks for your input, i have one additional query with reference to this
> > support :
> >
> > For all explicitly unecrypted guest memory regions such as S/W IOTLB bounce
> > buffers,
> > dma_decrypted() allocated regions and for guest regions marked as
> > "__bss_decrypted",
> > we need to ensure that DBG_DECRYPT API calls are bypassed for such
> > regions and those regions are dumped as un-encrypted.
>
> Yes those would be a bit different as they would be physical memory
> accesses. Those currently go through address_space_read in memory_dump
> (monitor/misc.c), and would have to use the MemoryDebugOps instead.
> That is the place to hook into in order to read the KVM page encryption
> bitmap (which is not per-CPU, so another MemoryDebugOps entry
> get_phys_addr_attrs?); the MemTxAttrs can then be passed to the read
> function in the MemoryDebugOps.
>
Actually, currently we do this in sev_dbg_crypt() in KVM itself by
checking the page encryption bitmap and if it is an un-encrypted guest
memory region then returning the un-encrypted buffer read from user
back to it as it is.
> > This guest memory regions encryption status is found using KVM's page
> > encryption bitmap
> > support which is part of the page encryption bitmap hypercall interface of
> > the
> > KVM/QEMU SEV live migration patches.
> >
> > As this additional debug support is dependent on the KVM's page encryption
> > bitmap
> > support, are there any updates on KVM SEV live migration patches ?
>
> Sorry about that, I've been busy with QEMU. I'll review them as soon as
> possible.H
Looking forward to your updates and reviews regarding the same.
Thanks,
Ashish
- Re: SEV guest debugging support for Qemu, (continued)
Re: SEV guest debugging support for Qemu, Paolo Bonzini, 2020/09/25
SEV guest debugging support for Qemu, Kalra, Ashish, 2020/09/22