Re: [PATCH] KVM: PPC: Book3S HV: Handle virtual mode in XIVE VCPU push code

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On Mon, Apr 29, 2019 at 06:57:45PM +1000, Paul Mackerras wrote:
> From: Suraj Jitindar Singh <sjitindarsingh@xxxxxxxxx>
> 
> The code in book3s_hv_rmhandlers.S that pushes the XIVE virtual CPU
> context to the hardware currently assumes it is being called in real
> mode, which is usually true.  There is however a path by which it can
> be executed in virtual mode, in the case where indep_threads_mode = N.
> A virtual CPU executing on an offline secondary thread can take a
> hypervisor interrupt in virtual mode and return from the
> kvmppc_hv_entry() call after the kvm_secondary_got_guest label.
> It is possible for it to be given another vcpu to execute before it
> gets to execute the stop instruction.  In that case it will call
> kvmppc_hv_entry() for the second VCPU in virtual mode, and the XIVE
> vCPU push code will be executed in virtual mode.  The result in that
> case will be a host crash due to an unexpected data storage interrupt
> caused by executing the stdcix instruction in virtual mode.
> 
> This fixes it by adding a code path for virtual mode, which uses the
> virtual TIMA pointer and normal load/store instructions.
> 
> [paulus@xxxxxxxxxx - wrote patch description]
> 
> Signed-off-by: Paul Mackerras <paulus@xxxxxxxxxx>

Patch applied to my kvm-ppc-next tree.

Paul.



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