linux-kernel - Re: [PATCH v2 02/29] LoongArch: KVM: Implement kvm module related interface

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Message-ID: <3f16a8e1-21d9-808e-aa1a-4f1d6f6f291b@redhat.com>
Date:   Tue, 21 Feb 2023 09:14:06 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     maobibo <maobibo@...ngson.cn>,
        Tianrui Zhao <zhaotianrui@...ngson.cn>
Cc:     Huacai Chen <chenhuacai@...nel.org>,
        WANG Xuerui <kernel@...0n.name>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        loongarch@...ts.linux.dev, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org, Jens Axboe <axboe@...nel.dk>,
        Mark Brown <broonie@...nel.org>,
        Alex Deucher <alexander.deucher@....com>,
        Oliver Upton <oliver.upton@...ux.dev>
Subject: Re: [PATCH v2 02/29] LoongArch: KVM: Implement kvm module related
 interface

On 2/21/23 07:59, maobibo wrote:
>> Also, why does the world switch code need a copy?
> There will be problem in world switch code if there is page fault reenter,
> since pgd register is shared between root kernel and kvm hypervisor.
> World switch entry need be unmapped area, cannot be tlb mapped area.

So if I understand correctly the processor is in direct address 
translation mode until the "csrwr t0, LOONGARCH_CSR_CRMD" instruction. 
Where does it leave paged mode?

Can you please also add comments to kvm_vector_entry explaining the 
processor state after a VZ exception entry (interrupts, paging, ...)?

Paolo