linux-kernel - Re: [RFC, PATCH 08/12] KVM: x86/tdp_mmu: Add phys_prepare() and phys_cleanup() to kvm_x86

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <t2im27kgcfsl2qltxbf3cear35szyoafczgvmmwootxthnbcdp@dasmg4bdfd6i>
Date: Thu, 8 May 2025 16:23:56 +0300
From: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To: Yan Zhao <yan.y.zhao@...el.com>
Cc: pbonzini@...hat.com, seanjc@...gle.com, rick.p.edgecombe@...el.com, 
	isaku.yamahata@...el.com, kai.huang@...el.com, tglx@...utronix.de, mingo@...hat.com, 
	bp@...en8.de, dave.hansen@...ux.intel.com, kvm@...r.kernel.org, x86@...nel.org, 
	linux-coco@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [RFC, PATCH 08/12] KVM: x86/tdp_mmu: Add phys_prepare() and
 phys_cleanup() to kvm_x86_ops

On Tue, May 06, 2025 at 07:55:17PM +0800, Yan Zhao wrote:
> On Fri, May 02, 2025 at 04:08:24PM +0300, Kirill A. Shutemov wrote:
> > The functions kvm_x86_ops::link_external_spt() and
> > kvm_x86_ops::set_external_spte() are used to assign new memory to a VM.
> > When using TDX with Dynamic PAMT enabled, the assigned memory must be
> > covered by PAMT.
> > 
> > The new function kvm_x86_ops::phys_prepare() is called before
> > link_external_spt() and set_external_spte() to ensure that the memory is
> > ready to be assigned to the virtual machine. In the case of TDX, it
> > makes sure that the memory is covered by PAMT.
> > 
> > kvm_x86_ops::phys_prepare() is called in a context where struct kvm_vcpu
> > is available, allowing the implementation to allocate memory from a
> > per-VCPU pool.
> > 
> Why not invoke phys_prepare() and phys_cleanup() in set_external_spte_present()?
> Or in tdx_sept_set_private_spte()/tdx_sept_link_private_spt()?

Because the memory pool we allocated from is per-vcpu and we lost access
to vcpu by then. And not all callers provide vcpu.


-- 
  Kiryl Shutsemau / Kirill A. Shutemov