From: Binbin Wu <binbin.wu@linux.intel.com>
To: Dave Hansen <dave.hansen@intel.com>,
Dmytro Maluka <dmaluka@chromium.org>,
kvm@vger.kernel.org, Sean Christopherson <seanjc@google.com>,
Paolo Bonzini <pbonzini@redhat.com>,
Isaku Yamahata <isaku.yamahata@intel.com>
Cc: Thomas Gleixner <tglx@kernel.org>, Ingo Molnar <mingo@redhat.com>,
Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
"maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)"
<x86@kernel.org>, "H. Peter Anvin" <hpa@zytor.com>,
Kiryl Shutsemau <kas@kernel.org>,
Rick Edgecombe <rick.p.edgecombe@intel.com>,
"open list:X86 ARCHITECTURE (32-BIT AND 64-BIT)"
<linux-kernel@vger.kernel.org>,
"open list:X86 TRUST DOMAIN EXTENSIONS (TDX)"
<linux-coco@lists.linux.dev>
Subject: Re: [PATCH] KVM: TDX: Fix APIC MSR ranges in tdx_has_emulated_msr()
Date: Thu, 19 Mar 2026 09:14:46 +0800 [thread overview]
Message-ID: <cb99e44c-8bc9-4bab-b485-9f63a4d0b262@linux.intel.com> (raw)
In-Reply-To: <94b06319-2be8-4f01-87d1-8989ae1ca85d@intel.com>
On 3/19/2026 3:42 AM, Dave Hansen wrote:
> On 3/18/26 12:01, Dmytro Maluka wrote:
>> + case X2APIC_MSR(APIC_ISR) ... X2APIC_MSR(APIC_ISR) + APIC_ISR_NR - 1:
>> + case X2APIC_MSR(APIC_TMR) ... X2APIC_MSR(APIC_TMR) + APIC_ISR_NR - 1:
>> + case X2APIC_MSR(APIC_IRR) ... X2APIC_MSR(APIC_IRR) + APIC_ISR_NR - 1:
>
> Thanks for the patch, Dmytro.
>
> <sigh>
>
> So this code never worked (at least for a big chunk of the ranges.
> Isaku, could you please go try to figure out if there are tests for this
> somewhere, and why this never bit us?
The bug doesn't cause problems for TDs because:
- These x2apic MSRs (TASKPRI, PROCPRI, EOI, ISRx, TMRx, IRRx) are virtualized by CPU,
when a TD accesses these MSRs, it doesn't cause #VE, thus no TDVMCALL from the TD to
request the emulation of these MSRs.
- The bug make the "false" range of APIC MSRs smaller, so it doesn't impact the result
for the rest of the APIC MSRs.
The bug could be triggered if a TD issues a TDVMCALL directly to request the
read/write operations for these x2apic MSRs, but a sane TD will not do it.
Currently, we don't have dedicated KVM selftests code to call TDVMCALL directly to request
the emulation for these x2apic MSRs.
>
> It might also be handy to have a:
>
> #define X2APIC_LAST_MSR(r) (X2APIC_MSR(x)+APIC_ISR_NR-1)
>
> so that the resulting code is a bit more readable:
>
> case X2APIC_MSR(APIC_IRR) ... X2APIC_LAST_MSR(APIC_IRR):
>
> Dmytro, if you feel a burning need to respin this, don't let me stop
> you. I can probably just fix this up when it gets applied, or Isaku can
> make those changes and resend it too.
>
next prev parent reply other threads:[~2026-03-19 1:14 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-03-18 19:01 [PATCH] KVM: TDX: Fix APIC MSR ranges in tdx_has_emulated_msr() Dmytro Maluka
2026-03-18 19:42 ` Dave Hansen
2026-03-18 20:30 ` Dmytro Maluka
2026-03-19 1:14 ` Binbin Wu [this message]
2026-03-19 1:48 ` Dave Hansen
2026-03-19 7:40 ` Binbin Wu
2026-03-19 19:33 ` Edgecombe, Rick P
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