[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [PATCH] x86/vcpu: relax VCPUOP_initialise restriction for non-PV vCPUs
On Wed, Mar 20, 2024 at 02:06:27PM +0000, Andrew Cooper wrote: > On 20/03/2024 1:57 pm, Roger Pau Monne wrote: > > There's no reason to force HVM guests to have a valid vcpu_info area when > > initializing a vCPU, as the vCPU can also be brought online using the local > > APIC, and on that path there's no requirement for vcpu_info to be setup > > ahead > > of the bring up. Note an HVM vCPU can operate normally without making use > > of > > vcpu_info. > > > > Restrict the check against dummy_vcpu_info to only apply to PV guests. > > > > Fixes: 192df6f9122d ('x86: allow HVM guests to use hypercalls to bring up > > vCPUs') > > Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx> > > Thanks for looking into this. But, do we actually need to force this on > PV either? Possibly, having now taken a look at the users it does seem they could cope with unpopulated vcpu_info_area. Part of my understanding was that this was some kind of courtesy to PV guests in order to prevent starting them without a vcpu_info, which strictly speaking is not mandatory, but otherwise the guest vCPU won't be able to receive interrupts, not even IPIs. > The only interesting user of dummy_vcpu_info now is vcpu_info_populate() > which can cope with any arbitrary vCPU. > > I have a suspicion that we can (now) delete these two checks, delete the > dummy_vcpu_info object, and use a regular NULL pointer in > vcpu_info_{populate,reset}(), and in doing so, remove one of the bigger > pieces of PV-absurdity from Xen. I was expecting this to be something we can backport. OTOH removing the check completely (or even getting rid of dummy_vcpu_info) is not something that we would want to backport. I would rather do the removal of dummy_vcpu_info as followup work. > I can entirely believe that this is only safe to do with Jan's physical > registration changes in place. Quite possible. Thanks, Roger.
|
Lists.xenproject.org is hosted with RackSpace, monitoring our |