From: Sean Christopherson <seanjc@google.com>
To: Rick P Edgecombe <rick.p.edgecombe@intel.com>
Cc: "x86@kernel.org" <x86@kernel.org>,
"zhangjiaji1@huawei.com" <zhangjiaji1@huawei.com>,
"kas@kernel.org" <kas@kernel.org>,
Xiaoyao Li <xiaoyao.li@intel.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"thomas.lendacky@amd.com" <thomas.lendacky@amd.com>,
"binbin.wu@linux.intel.com" <binbin.wu@linux.intel.com>,
"pbonzini@redhat.com" <pbonzini@redhat.com>,
"linux-coco@lists.linux.dev" <linux-coco@lists.linux.dev>,
"kvm@vger.kernel.org" <kvm@vger.kernel.org>,
"michael.roth@amd.com" <michael.roth@amd.com>
Subject: Re: [PATCH 14/14] KVM: x86: Add helpers to prepare kvm_run for userspace MMIO exit
Date: Tue, 3 Mar 2026 11:44:12 -0800 [thread overview]
Message-ID: <aac6DGISvMX4krhb@google.com> (raw)
In-Reply-To: <4574be9a29d75d565e553579ef6ce915ef33b19b.camel@intel.com>
On Tue, Mar 03, 2026, Rick P Edgecombe wrote:
> On Mon, 2026-03-02 at 18:24 -0800, Sean Christopherson wrote:
> > Ooh, better idea. Since TDX is the only direct user of
> > __kvm_prepare_emulated_mmio_exit() and it only supports lenths of 1, 2, 4, and 8,
> > kvm_prepare_emulated_mmio_exit() is the only path that actually needs to cap the
> > length. Then the inner helper can assert a valid length. Doesn't change anything
> > in practice, but I like the idea of making the caller be aware of the limitation
> > (even if that caller is itself a helper).
>
> Seems ok and an improvement over the patch. But looking at the other callers,
> there is quite a bit of min(8u, len) logic spread around. Might be worth a wider
> cleanup someday.
LOL, "might". :-)
Definitely a project for the future though, especially given how subtle and brittle
this all is.
next prev parent reply other threads:[~2026-03-03 19:44 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-02-25 1:20 [PATCH 00/14] KVM: x86: Emulator MMIO fix and cleanups Sean Christopherson
2026-02-25 1:20 ` [PATCH 01/14] KVM: x86: Use scratch field in MMIO fragment to hold small write values Sean Christopherson
2026-02-25 1:20 ` [PATCH 02/14] KVM: x86: Open code handling of completed MMIO reads in emulator_read_write() Sean Christopherson
2026-02-25 1:20 ` [PATCH 03/14] KVM: x86: Trace unsatisfied MMIO reads on a per-page basis Sean Christopherson
2026-02-25 1:20 ` [PATCH 04/14] KVM: x86: Use local MMIO fragment variable to clean up emulator_read_write() Sean Christopherson
2026-02-25 1:20 ` [PATCH 05/14] KVM: x86: Open code read vs. write userspace MMIO exits in emulator_read_write() Sean Christopherson
2026-02-25 1:20 ` [PATCH 06/14] KVM: x86: Move MMIO write tracing into vcpu_mmio_write() Sean Christopherson
2026-02-25 1:20 ` [PATCH 07/14] KVM: x86: Harden SEV-ES MMIO against on-stack use-after-free Sean Christopherson
2026-02-25 1:20 ` [PATCH 08/14] KVM: x86: Dedup kvm_sev_es_mmio_{read,write}() Sean Christopherson
2026-02-25 1:20 ` [PATCH 09/14] KVM: x86: Consolidate SEV-ES MMIO emulation into a single public API Sean Christopherson
2026-02-25 1:20 ` [PATCH 10/14] KVM: x86: Bury emulator read/write ops in emulator_{read,write}_emulated() Sean Christopherson
2026-02-25 1:20 ` [PATCH 11/14] KVM: x86: Fold emulator_write_phys() into write_emulate() Sean Christopherson
2026-02-25 1:20 ` [PATCH 12/14] KVM: x86: Rename .read_write_emulate() to .read_write_guest() Sean Christopherson
2026-02-25 1:20 ` [PATCH 13/14] KVM: x86: Don't panic the kernel if completing userspace I/O / MMIO goes sideways Sean Christopherson
2026-02-25 1:20 ` [PATCH 14/14] KVM: x86: Add helpers to prepare kvm_run for userspace MMIO exit Sean Christopherson
2026-02-25 17:32 ` Edgecombe, Rick P
2026-02-25 19:22 ` Sean Christopherson
2026-03-03 2:24 ` Sean Christopherson
2026-03-03 19:21 ` Edgecombe, Rick P
2026-03-03 19:44 ` Sean Christopherson [this message]
2026-03-03 19:51 ` Edgecombe, Rick P
2026-02-25 17:32 ` [PATCH 00/14] KVM: x86: Emulator MMIO fix and cleanups Edgecombe, Rick P
2026-02-25 20:19 ` Tom Lendacky
2026-02-27 20:19 ` Tom Lendacky
2026-03-05 17:07 ` Sean Christopherson
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