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From: maobibo <maobibo@loongson.cn>
To: Paolo Bonzini <pbonzini@redhat.com>,
	Tianrui Zhao <zhaotianrui@loongson.cn>
Cc: Huacai Chen <chenhuacai@kernel.org>,
	WANG Xuerui <kernel@xen0n.name>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	loongarch@lists.linux.dev, linux-kernel@vger.kernel.org,
	kvm@vger.kernel.org, Jens Axboe <axboe@kernel.dk>,
	Mark Brown <broonie@kernel.org>,
	Alex Deucher <alexander.deucher@amd.com>,
	Oliver Upton <oliver.upton@linux.dev>
Subject: Re: [PATCH v2 02/29] LoongArch: KVM: Implement kvm module related interface
Date: Tue, 21 Feb 2023 18:18:40 +0800	[thread overview]
Message-ID: <2875aa3f-0dc4-4e48-17ad-42c703e12063@loongson.cn> (raw)
In-Reply-To: <3f16a8e1-21d9-808e-aa1a-4f1d6f6f291b@redhat.com>



在 2023/2/21 16:14, Paolo Bonzini 写道:
> 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?
The processor still in paged mode during world switch context. For example
when vm exits from guest mode to root mode, it executes world switch code
from kvm_vector_entry, PC register points to HVA address, however vmid from
LOONGARCH_CSR_GTLBC is not clear to root mode. If there is page fault
exception, hardware treats it exception from GPA-->HPA rather than that
from HVA --> HPA, since vmid info in CSR_GTLBC is not zero.

In page mode, there are two kinds of address: unmapped address and 
tlb mapped address. For unmapped address there is only cachable/uncachable
attribution, but not RWX attr; and there is no tlb handling for it.
For simplicity,  unmapped address can be treated as window filtered address.

It will be fully root mode only after this piece of code is executed
during world switch context; vmid is zero and PC points to HVA.
        ori     t0, zero, CSR_GSTAT_PVM
        csrxchg zero, t0, LOONGARCH_CSR_GSTAT
        /* Clear GTLBC.TGID field */
        csrrd   t0, LOONGARCH_CSR_GTLBC
        bstrins.w       t0, zero, CSR_GTLBC_TGID_SHIFT_END, CSR_GTLBC_TGID_SHIFT
        csrwr   t0, LOONGARCH_CSR_GTLBC

> 
> Can you please also add comments to kvm_vector_entry explaining the processor state after a VZ exception entry (interrupts, paging, ...)?
Yeap, we will add more comments about these critical exception entry.

Regards
Bibo, Mao
> 
> Paolo


  reply	other threads:[~2023-02-21 10:18 UTC|newest]

Thread overview: 70+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-02-20  6:57 [PATCH v2 00/29] Add KVM LoongArch support Tianrui Zhao
2023-02-20  6:57 ` [PATCH v2 01/29] LoongArch: KVM: Add kvm related header files Tianrui Zhao
2023-02-20 18:22   ` Paolo Bonzini
2023-02-21  2:56     ` Tianrui Zhao
2023-02-21  6:49       ` Paolo Bonzini
2023-02-20 18:54   ` WANG Xuerui
2023-02-21  4:36   ` Xi Ruoyao
2023-02-24  1:27     ` Tianrui Zhao
2023-02-20  6:57 ` [PATCH v2 02/29] LoongArch: KVM: Implement kvm module related interface Tianrui Zhao
2023-02-20 17:46   ` Paolo Bonzini
2023-02-21  3:02     ` Tianrui Zhao
2023-02-21  6:59     ` maobibo
2023-02-21  8:14       ` Paolo Bonzini
2023-02-21 10:18         ` maobibo [this message]
2023-02-21 10:37           ` WANG Xuerui
2023-02-21 11:39             ` maobibo
2023-02-21 12:38               ` WANG Xuerui
2023-02-20  6:57 ` [PATCH v2 03/29] LoongArch: KVM: Implement kvm hardware enable, disable interface Tianrui Zhao
2023-02-20  6:57 ` [PATCH v2 04/29] LoongArch: KVM: Implement VM related functions Tianrui Zhao
2023-02-20  6:57 ` [PATCH v2 05/29] LoongArch: KVM: Add vcpu related header files Tianrui Zhao
2023-02-20 18:57   ` WANG Xuerui
2023-02-27  1:39     ` Tianrui Zhao
2023-02-21  4:44   ` Xi Ruoyao
2023-02-21  6:46     ` maobibo
2023-02-21  6:48       ` Paolo Bonzini
2023-02-21  7:12       ` Xi Ruoyao
2023-02-21  7:35         ` Paolo Bonzini
2023-02-20  6:57 ` [PATCH v2 06/29] LoongArch: KVM: Implement vcpu create and destroy interface Tianrui Zhao
2023-02-20 17:53   ` Paolo Bonzini
2023-02-22  1:52     ` Tianrui Zhao
2023-02-22 12:17       ` Paolo Bonzini
2023-02-23  1:23         ` Tianrui Zhao
2023-02-20  6:57 ` [PATCH v2 07/29] LoongArch: KVM: Implement vcpu run interface Tianrui Zhao
2023-02-20 18:44   ` Paolo Bonzini
2023-02-22  2:08     ` Tianrui Zhao
2023-02-20  6:57 ` [PATCH v2 08/29] LoongArch: KVM: Implement vcpu handle exit interface Tianrui Zhao
2023-02-20 17:46   ` Paolo Bonzini
2023-02-20 18:45   ` Paolo Bonzini
2023-02-21  3:17     ` Tianrui Zhao
2023-02-20  6:57 ` [PATCH v2 09/29] LoongArch: KVM: Implement vcpu get, vcpu set registers Tianrui Zhao
2023-02-20  6:57 ` [PATCH v2 10/29] LoongArch: KVM: Implement vcpu ENABLE_CAP, CHECK_EXTENSION ioctl interface Tianrui Zhao
2023-02-20  6:57 ` [PATCH v2 11/29] LoongArch: KVM: Implement fpu related operations for vcpu Tianrui Zhao
2023-02-20  6:57 ` [PATCH v2 12/29] LoongArch: KVM: Implement vcpu interrupt operations Tianrui Zhao
2023-02-20  6:57 ` [PATCH v2 13/29] LoongArch: KVM: Implement misc vcpu related interfaces Tianrui Zhao
2023-02-20 18:50   ` Paolo Bonzini
2023-02-21  3:19     ` Tianrui Zhao
2023-02-20  6:57 ` [PATCH v2 14/29] LoongArch: KVM: Implement vcpu load and vcpu put operations Tianrui Zhao
2023-02-20  6:57 ` [PATCH v2 15/29] LoongArch: KVM: Implement vcpu status description Tianrui Zhao
2023-02-20  6:57 ` [PATCH v2 16/29] LoongArch: KVM: Implement update VM id function Tianrui Zhao
2023-02-20  6:57 ` [PATCH v2 17/29] LoongArch: KVM: Implement virtual machine tlb operations Tianrui Zhao
2023-02-20  6:57 ` [PATCH v2 18/29] LoongArch: KVM: Implement vcpu timer operations Tianrui Zhao
2023-02-20  6:57 ` [PATCH v2 19/29] LoongArch: KVM: Implement kvm mmu operations Tianrui Zhao
2023-02-20  6:57 ` [PATCH v2 20/29] LoongArch: KVM: Implement handle csr excption Tianrui Zhao
2023-02-20  6:57 ` [PATCH v2 21/29] LoongArch: KVM: Implement handle iocsr exception Tianrui Zhao
2023-02-20  6:57 ` [PATCH v2 22/29] LoongArch: KVM: Implement handle idle exception Tianrui Zhao
2023-02-20 18:40   ` Paolo Bonzini
2023-02-21  9:48     ` Tianrui Zhao
2023-02-20  6:57 ` [PATCH v2 23/29] LoongArch: KVM: Implement handle gspr exception Tianrui Zhao
2023-02-20  6:57 ` [PATCH v2 24/29] LoongArch: KVM: Implement handle mmio exception Tianrui Zhao
2023-02-20  6:57 ` [PATCH v2 25/29] LoongArch: KVM: Implement handle fpu exception Tianrui Zhao
2023-02-20  6:57 ` [PATCH v2 26/29] LoongArch: KVM: Implement kvm exception vector Tianrui Zhao
2023-02-20  6:57 ` [PATCH v2 27/29] LoongArch: KVM: Implement vcpu world switch Tianrui Zhao
2023-02-21  7:45   ` Paolo Bonzini
2023-02-21 13:00     ` Tianrui Zhao
2023-02-21  8:18   ` Paolo Bonzini
2023-02-21 12:58     ` Tianrui Zhao
2023-02-20  6:57 ` [PATCH v2 28/29] LoongArch: KVM: Implement probe virtualization when loongarch cpu init Tianrui Zhao
2023-02-20  6:57 ` [PATCH v2 29/29] LoongArch: KVM: Enable kvm config and add the makefile Tianrui Zhao
2023-02-20  9:47   ` kernel test robot
2023-02-20 11:09   ` kernel test robot

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