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Re: [PATCH] vVMX: Cleanup partial vCPU initialization

To: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx

From: Ross Lagerwall <ross.lagerwall@xxxxxxxxxx>

Date: Mon, 27 Oct 2025 09:53:15 +0000

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Cc: Jan Beulich <jbeulich@xxxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>

Delivery-date: Mon, 27 Oct 2025 09:53:42 +0000

List-id: Xen developer discussion <xen-devel.lists.xenproject.org>

On 10/24/25 7:08 PM, Andrew Cooper wrote:

On 24/10/2025 5:20 pm, Ross Lagerwall wrote:

If nested vCPU initialization fails, cleanup the allocated memory since
it is no longer handled by the caller.

Fixes: c47984aabead ("nvmx: implement support for MSR bitmaps")
Fixes: f5bdb4aaa165 ("x86/hvm: Obsolete the use of HVM_PARAM_NESTEDHVM")
Signed-off-by: Ross Lagerwall <ross.lagerwall@xxxxxxxxxx>


AFAICT, this is because of hvm_vcpu_initialise() not calling
nestedhvm_vcpu_destroy() if nestedhvm_vcpu_initialise() fails?

I think this is an improvement in the short term, but we really need to
fix our object lifecycle.  Relatedly, I should dust off the fault-ttl
series because it would be able to find this failure automatically.

~Andrew

Having hvm_vcpu_initialise() call nestedhvm_vcpu_destroy() would be one

way of fixing it (albeit it is complicated because some cleanup is also

done in vcpu_relinquish_resources()). But IMO generally a partial

failure of an initialization function should be handled up internally

rather than expecting the caller to deal with it.

Ross

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