linux-kernel - Re: [PATCH 15/25] KVM: TDX: Make pmu

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Message-ID: <d566cce2-2c78-4547-a2c0-75087e06f790@redhat.com>
Date: Tue, 10 Sep 2024 19:23:10 +0200
From: Paolo Bonzini <pbonzini@...hat.com>
To: Rick Edgecombe <rick.p.edgecombe@...el.com>, seanjc@...gle.com,
 kvm@...r.kernel.org
Cc: kai.huang@...el.com, isaku.yamahata@...il.com,
 tony.lindgren@...ux.intel.com, xiaoyao.li@...el.com,
 linux-kernel@...r.kernel.org, Isaku Yamahata <isaku.yamahata@...el.com>
Subject: Re: [PATCH 15/25] KVM: TDX: Make pmu_intel.c ignore guest TD case

On 8/13/24 00:48, Rick Edgecombe wrote:
> From: Isaku Yamahata<isaku.yamahata@...el.com>
> 
> Because TDX KVM doesn't support PMU yet (it's future work of TDX KVM
> support as another patch series) and pmu_intel.c touches vmx specific
> structure in vcpu initialization, as workaround add dummy structure to
> struct vcpu_tdx and pmu_intel.c can ignore TDX case.
> 
> Signed-off-by: Isaku Yamahata<isaku.yamahata@...el.com>
> Signed-off-by: Rick Edgecombe<rick.p.edgecombe@...el.com>

Would be nicer not to have this dummy member at all if possible.

Could vcpu_to_lbr_desc() return NULL, and then lbr_desc can be checked 
in intel_pmu_init() and intel_pmu_refresh()?  Then the checks for 
is_td_vcpu(vcpu), both inside WARN_ON_ONCE() and outside, can also be 
changed to check NULL-ness of vcpu_to_lbr_desc().

Also please add a WARN_ON_ONCE(is_td_vcpu(vcpu)), or 
WARN_ON_ONCE(!lbr_desc) given the above suggestion, to return early from 
vmx_passthrough_lbr_msrs().

Thanks,

Paolo