From: Sean Christopherson <seanjc@google.com>
To: "Chang S. Bae" <chang.seok.bae@intel.com>
Cc: Xiaoyao Li <xiaoyao.li@intel.com>,
Paolo Bonzini <pbonzini@redhat.com>,
Kiryl Shutsemau <kas@kernel.org>,
kvm@vger.kernel.org, x86@kernel.org, linux-coco@lists.linux.dev,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 1/6] KVM: x86: Add dedicated storage for guest RIP
Date: Tue, 14 Apr 2026 08:37:55 -0700 [thread overview]
Message-ID: <ad5fUya3W9BKO_iA@google.com> (raw)
In-Reply-To: <87e767b6-0324-44e6-92cb-f933002dec43@intel.com>
On Tue, Apr 14, 2026, Chang S. Bae wrote:
> On 4/14/2026 5:31 AM, Xiaoyao Li wrote:
> > Even leave RIP in regs[], what is the problem by just allocating the
> > index 16-31 to R16-R31 and making RIP the index 32?
>
> But why?
>
> Even though the array isn't explicitly labeled as GPRs, that's effectively
> how it's being used, and RIP isn't part of that set.
>
> I don't think there is any benefit of leaving it in regs[].
+1. Chang's earlier argument that RIP isn't a proper GPR swayed me over, e.g. RIP
doesn't have an architectural index.
Keeping RIP in regs[] saves one line of code in arch/x86/include/asm/kvm_host.h,
at the cost of making the code less readable (IMO) and incorrectly suggesting that
RIP can be accessed like other regs[].
next prev parent reply other threads:[~2026-04-14 15:38 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-04-09 22:42 [PATCH v2 0/6] KVM: x86: Reg cleanups / prep work for APX Sean Christopherson
2026-04-09 22:42 ` [PATCH v2 1/6] KVM: x86: Add dedicated storage for guest RIP Sean Christopherson
2026-04-10 18:43 ` Chang S. Bae
2026-04-14 12:31 ` Xiaoyao Li
2026-04-14 13:59 ` Chang S. Bae
2026-04-14 15:37 ` Sean Christopherson [this message]
2026-04-15 1:28 ` Xiaoyao Li
2026-04-09 22:42 ` [PATCH v2 2/6] KVM: x86: Drop the "EX" part of "EXREG" to avoid collision with APX Sean Christopherson
2026-04-13 11:23 ` Huang, Kai
2026-04-09 22:42 ` [PATCH v2 3/6] KVM: nVMX: Do a bitwise-AND of regs_avail when switching active VMCS Sean Christopherson
2026-04-09 22:42 ` [PATCH v2 4/6] KVM: x86: Add wrapper APIs to reset dirty/available register masks Sean Christopherson
2026-04-09 22:42 ` [PATCH v2 5/6] KVM: x86: Track available/dirty register masks as "unsigned long" values Sean Christopherson
2026-04-13 11:24 ` Huang, Kai
2026-04-13 11:28 ` Huang, Kai
2026-04-13 14:54 ` Sean Christopherson
2026-04-13 23:03 ` Huang, Kai
2026-04-14 2:12 ` Xiaoyao Li
2026-04-14 14:04 ` Sean Christopherson
2026-04-15 11:29 ` Xiaoyao Li
2026-04-15 12:20 ` Xiaoyao Li
2026-04-14 15:48 ` Sean Christopherson
2026-04-14 22:21 ` Huang, Kai
2026-04-09 22:42 ` [PATCH v2 6/6] KVM: x86: Use a proper bitmap for tracking available/dirty registers Sean Christopherson
2026-04-13 11:31 ` [PATCH v2 0/6] KVM: x86: Reg cleanups / prep work for APX Huang, Kai
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