Re: [PATCH v11 00/43] KVM: arm64: Nested Virtualization support (FEAT_NV2 only)

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On 21-11-2023 03:11 pm, Marc Zyngier wrote:
On Tue, 21 Nov 2023 09:26:22 +0000,
Ganapatrao Kulkarni <gankulkarni@xxxxxxxxxxxxxxxxxxxxxx> wrote:



On 21-11-2023 02:38 pm, Marc Zyngier wrote:
On Tue, 21 Nov 2023 08:51:35 +0000,
Ganapatrao Kulkarni <gankulkarni@xxxxxxxxxxxxxxxxxxxxxx> wrote:


Hi Marc,

On 20-11-2023 06:39 pm, Marc Zyngier wrote:
This is the 5th drop of NV support on arm64 for this year, and most
probably the last one for this side of Christmas.

For the previous episodes, see [1].

What's changed:

- Drop support for the original FEAT_NV. No existing hardware supports
     it without FEAT_NV2, and the architecture is deprecating the former
     entirely. This results in fewer patches, and a slightly simpler
     model overall.

- Reorganise the series to make it a bit more logical now that FEAT_NV
     is gone.

- Apply the NV idreg restrictions on VM first run rather than on each
     access.

- Make the nested vgic shadow CPU interface a per-CPU structure rather
     than per-vcpu.

- Fix the EL0 timer fastpath

- Work around the architecture deficiencies when trapping WFI from a
     L2 guest.

- Fix sampling of nested vgic state (MISR, ELRSR, EISR)

- Drop the patches that have already been merged (NV trap forwarding,
     per-MMU VTCR)

- Rebased on top of 6.7-rc2 + the FEAT_E2H0 support [2].

The branch containing these patches (and more) is at [3]. As for the
previous rounds, my intention is to take a prefix of this series into
6.8, provided that it gets enough reviewing.

[1] https://lore.kernel.org/r/20230515173103.1017669-1-maz@xxxxxxxxxx
[2] https://lore.kernel.org/r/20231120123721.851738-1-maz@xxxxxxxxxx
[3] https://git.kernel.org/pub/scm/linux/kernel/git/maz/arm-platforms.git/log/?h=kvm-arm64/nv-6.8-nv2-only


V11 series is not booting on Ampere platform (I am yet to debug).
With lkvm, it is stuck at the very early stage itself and no early
boot prints/logs.

Are there any changes needed in kvmtool for V11?

Not really, I'm still using the version I had built for 6.5. Is the
problem with L1 or L2?

Stuck in the L1 itself.

I am using kvmtool from
https://git.kernel.org/pub/scm/linux/kernel/git/maz/kvmtool.git/log/?h=arm64/nv-5.16

Huh. That's positively ancient. Yet, you shouldn't get into a
situation where the L1 guest locks up.

I have pushed out my kvmtool branch[1]. Please give it a go.

No change, still L1 hangs. Captured ftrace and the L1 is keep looping/faulting around same address across kvm_entry and kvm_exits.

It is a weird behavior, L1 is faulting and looping around MDCR and AA64MMFR3_EL1 access in function __finalise_el2.

asm:
ffffffc080528a58:       d53dc000        mrs     x0, vbar_el12
ffffffc080528a5c:       d518c000        msr     vbar_el1, x0
ffffffc080528a60:       d53c1120        mrs     x0, mdcr_el2
ffffffc080528a64:       9272f400        and     x0, x0, #0xffffffffffffcfff
ffffffc080528a68:       9266f400        and     x0, x0, #0xfffffffffcffffff
ffffffc080528a6c:       d51c1120        msr     mdcr_el2, x0
ffffffc080528a70:       d53d2040        mrs     x0, tcr_el12
ffffffc080528a74:       d5182040        msr     tcr_el1, x0
ffffffc080528a78:       d53d2000        mrs     x0, ttbr0_el12
ffffffc080528a7c:       d5182000        msr     ttbr0_el1, x0
ffffffc080528a80:       d53d2020        mrs     x0, ttbr1_el12
ffffffc080528a84:       d5182020        msr     ttbr1_el1, x0
ffffffc080528a88:       d53da200        mrs     x0, mair_el12
ffffffc080528a8c:       d518a200        msr     mair_el1, x0
ffffffc080528a90:       d5380761        mrs     x1, s3_0_c0_c7_3
ffffffc080528a94:       d3400c21        ubfx    x1, x1, #0, #4
ffffffc080528a98: b4000141 cbz x1, ffffffc080528ac0 <__finalise_el2+0x270>
ffffffc080528a9c:       d53d2060        mrs     x0, s3_5_c2_c0_3

ftrace:
kvm-vcpu-0-88776 [001] ...1. 6076.581774: kvm_exit: TRAP: HSR_EC: 0x0018 (SYS64), PC: 0x0000000080528a6c kvm-vcpu-0-88776 [001] d..1. 6076.581774: kvm_entry: PC: 0x0000000080528a6c kvm-vcpu-0-88776 [001] ...1. 6076.581775: kvm_exit: TRAP: HSR_EC: 0x0018 (SYS64), PC: 0x0000000080528a90 kvm-vcpu-0-88776 [001] d..1. 6076.581776: kvm_entry: PC: 0x0000000080528a90 kvm-vcpu-0-88776 [001] ...1. 6076.581778: kvm_exit: TRAP: HSR_EC: 0x0018 (SYS64), PC: 0x0000000080528a60 kvm-vcpu-0-88776 [001] d..1. 6076.581778: kvm_entry: PC: 0x0000000080528a60 kvm-vcpu-0-88776 [001] ...1. 6076.581779: kvm_exit: TRAP: HSR_EC: 0x0018 (SYS64), PC: 0x0000000080528a6c kvm-vcpu-0-88776 [001] d..1. 6076.581779: kvm_entry: PC: 0x0000000080528a6c kvm-vcpu-0-88776 [001] ...1. 6076.581780: kvm_exit: TRAP: HSR_EC: 0x0018 (SYS64), PC: 0x0000000080528a90 kvm-vcpu-0-88776 [001] d..1. 6076.581781: kvm_entry: PC: 0x0000000080528a90 kvm-vcpu-0-88776 [001] ...1. 6076.581783: kvm_exit: TRAP: HSR_EC: 0x0018 (SYS64), PC: 0x0000000080528a60 kvm-vcpu-0-88776 [001] d..1. 6076.581783: kvm_entry: PC: 0x0000000080528a60 kvm-vcpu-0-88776 [001] ...1. 6076.581784: kvm_exit: TRAP: HSR_EC: 0x0018 (SYS64), PC: 0x0000000080528a6c kvm-vcpu-0-88776 [001] d..1. 6076.581784: kvm_entry: PC: 0x0000000080528a6c kvm-vcpu-0-88776 [001] ...1. 6076.581785: kvm_exit: TRAP: HSR_EC: 0x0018 (SYS64), PC: 0x0000000080528a90 kvm-vcpu-0-88776 [001] d..1. 6076.581786: kvm_entry: PC: 0x0000000080528a90 kvm-vcpu-0-88776 [001] ...1. 6076.581788: kvm_exit: TRAP: HSR_EC: 0x0018 (SYS64), PC: 0x0000000080528a60 kvm-vcpu-0-88776 [001] d..1. 6076.581788: kvm_entry: PC: 0x0000000080528a60 kvm-vcpu-0-88776 [001] ...1. 6076.581789: kvm_exit: TRAP: HSR_EC: 0x0018 (SYS64), PC: 0x0000000080528a6c kvm-vcpu-0-88776 [001] d..1. 6076.581789: kvm_entry: PC: 0x0000000080528a6c kvm-vcpu-0-88776 [001] ...1. 6076.581790: kvm_exit: TRAP: HSR_EC: 0x0018 (SYS64), PC: 0x0000000080528a90



Thanks,
Ganapat





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