On 9/18/2020 4:01 PM, Andrew Jones wrote:
> On Thu, Sep 17, 2020 at 08:00:54PM +0800, Peng Liang wrote:
>> In AArch64, guest will read the same values of the ID regsiters with
>> host. Both of them read the values from arm64_ftr_regs. This patch
>> series add support to emulate and configure ID registers so that we can
>> control the value of ID registers that guest read.
>>
>> v1 -> v2:
>> - save the ID registers in sysreg file instead of a new struct
>> - apply a checker before setting the value to the register
>> - add doc for new KVM_CAP_ARM_CPU_FEATURE
>>
>> Peng Liang (7):
>> arm64: add a helper function to traverse arm64_ftr_regs
>> arm64: introduce check_features
>> kvm: arm64: save ID registers to sys_regs file
>> kvm: arm64: introduce check_user
>> kvm: arm64: implement check_user for ID registers
>> kvm: arm64: make ID registers configurable
>> kvm: arm64: add KVM_CAP_ARM_CPU_FEATURE extension
>>
>> Documentation/virt/kvm/api.rst | 8 +
>> arch/arm64/include/asm/cpufeature.h | 4 +
>> arch/arm64/include/asm/kvm_coproc.h | 2 +
>> arch/arm64/include/asm/kvm_host.h | 3 +
>> arch/arm64/kernel/cpufeature.c | 36 +++
>> arch/arm64/kvm/arm.c | 3 +
>> arch/arm64/kvm/sys_regs.c | 481 +++++++++++++++++++++++++++-
>> arch/arm64/kvm/sys_regs.h | 6 +
>> include/uapi/linux/kvm.h | 1 +
>> 9 files changed, 532 insertions(+), 12 deletions(-)
>>
>> --
>> 2.26.2
>>
>
> Hi Peng,
>
> I'd much rather see a series of patches where each patch converts a single
> ID register from using ID_SANITISED() to having its own table entry, where
> its own set_user() and reset() functions take into account its features
> using high level arm64_ftr* functions. Any ID registers that can still
> share code can certainly do so with some post-conversion refactoring.
>
> Thanks,
> drew
>
> .
>
Hi Andrew,
Thank you for your advise. I'll rework the code to use different set_user()
for different ID registers (maybe some general registers still use shareing
set_user()) and check the value defined by user space in its own set_user in
next version.
But do we need to implement reset() for ID registers? I think ID registers
are read-only in guest and guest won't and can't change their values. And
after 03fdfb2690099 ("KVM: arm64: Don't write junk to sysregs on reset"),
we won't write junk to sysregs on reset. So their values won't change on
reset?
Thanks,
Peng
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