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

[Miguel Luis]

Hi Marc,

On 21/11/2023 18:02, Marc Zyngier wrote:
> On Tue, 21 Nov 2023 16:49:52 +0000,
> Miguel Luis <miguel.luis at oracle.com> wrote:
>> Hi Marc,
>>
>>> On 20 Nov 2023, at 12:09, Marc Zyngier <maz at kernel.org> 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@kernel.org
>>> [2] https://lore.kernel.org/r/20231120123721.851738-1-maz@kernel.org
>>> [3] https://git.kernel.org/pub/scm/linux/kernel/git/maz/arm-platforms.git/log/?h=kvm-arm64/nv-6.8-nv2-only
>>>
>> While I was testing this with kvmtool for 5.16 I noted the following on dmesg:
>>
>> [  803.014258] kvm [19040]: Unsupported guest sys_reg access at: 8129fa50 [600003c9]
>>                 { Op0( 3), Op1( 5), CRn( 1), CRm( 0), Op2( 2), func_read },
>>
>> This is CPACR_EL12.
> CPACR_EL12 is redirected to VNCR[0x100]. It really shouldn't trap...
>
>> Still need yet to debug.
> Can you disassemble the guest around the offending PC?

[ 1248.686350] kvm [7013]: Unsupported guest sys_reg access at: 812baa50 [600003c9]
                { Op0( 3), Op1( 5), CRn( 1), CRm( 0), Op2( 2), func_read },

 12baa00:    14000008     b    0x12baa20
 12baa04:    d000d501     adrp    x1, 0x2d5c000
 12baa08:    91154021     add    x1, x1, #0x550
 12baa0c:    f9400022     ldr    x2, [x1]
 12baa10:    f9400421     ldr    x1, [x1, #8]
 12baa14:    8a010042     and    x2, x2, x1
 12baa18:    d3441c42     ubfx    x2, x2, #4, #4
 12baa1c:    b4000082     cbz    x2, 0x12baa2c
 12baa20:    d2a175a0     mov    x0, #0xbad0000                 // #195887104
 12baa24:    f2994220     movk    x0, #0xca11
 12baa28:    d69f03e0     eret
 12baa2c:    d2c00080     mov    x0, #0x400000000               // #17179869184
 12baa30:    f2b10000     movk    x0, #0x8800, lsl #16
 12baa34:    f2800000     movk    x0, #0x0
 12baa38:    d51c1100     msr    hcr_el2, x0
 12baa3c:    d5033fdf     isb
 12baa40:    d53c4100     mrs    x0, sp_el1
 12baa44:    9100001f     mov    sp, x0
 12baa48:    d538d080     mrs    x0, tpidr_el1
 12baa4c:    d51cd040     msr    tpidr_el2, x0
 12baa50:    d53d1040     mrs    x0, cpacr_el12
 12baa54:    d5181040     msr    cpacr_el1, x0
 12baa58:    d53dc000     mrs    x0, vbar_el12
 12baa5c:    d518c000     msr    vbar_el1, x0
 12baa60:    d53c1120     mrs    x0, mdcr_el2
 12baa64:    9272f400     and    x0, x0, #0xffffffffffffcfff
 12baa68:    9266f400     and    x0, x0, #0xfffffffffcffffff
 12baa6c:    d51c1120     msr    mdcr_el2, x0
 12baa70:    d53d2040     mrs    x0, tcr_el12
 12baa74:    d5182040     msr    tcr_el1, x0
 12baa78:    d53d2000     mrs    x0, ttbr0_el12
 12baa7c:    d5182000     msr    ttbr0_el1, x0
 12baa80:    d53d2020     mrs    x0, ttbr1_el12
 12baa84:    d5182020     msr    ttbr1_el1, x0
 12baa88:    d53da200     mrs    x0, mair_el12
 12baa8c:    d518a200     msr    mair_el1, x0
 12baa90:    d5380761     mrs    x1, s3_0_c0_c7_3
 12baa94:    d3400c21     ubfx    x1, x1, #0, #4
 12baa98:    b4000141     cbz    x1, 0x12baac0
 12baa9c:    d53d2060     mrs    x0, s3_5_c2_c0_3


>> As for QEMU, it is having issues enabling _EL2 feature although EL2
>> is supported by checking KVM_CAP_ARM_EL2; need yet to debug this.
> The capability number changes at each release. Make sure you resync
> your includes.

Been there but it seems a different problem this time.

Thank you

Miguel

> 	M.
>