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Thu, 05 Jun 2025 11:30:30 -0700 (PDT) MIME-Version: 1.0 References: <20250605153800.557144-1-tabba@google.com> <20250605153800.557144-13-tabba@google.com> <4909d6dc-09f5-4960-b8be-5150b2a03e45@redhat.com> <8782284c-0ffc-489d-adfe-b25d5ccb77b3@redhat.com> <637ffae1-a61e-4d68-8332-9ec11a3a78d4@redhat.com> In-Reply-To: <637ffae1-a61e-4d68-8332-9ec11a3a78d4@redhat.com> From: Fuad Tabba Date: Thu, 5 Jun 2025 19:29:53 +0100 X-Gm-Features: AX0GCFsQbfhZC_FlYPxk85rO768zb9vVPjsu-8YXphOrtD0BhntZritMMuHZreE Message-ID: Subject: Re: [PATCH v11 12/18] KVM: x86: Enable guest_memfd shared memory for SW-protected VMs To: David Hildenbrand Cc: kvm@vger.kernel.org, linux-arm-msm@vger.kernel.org, linux-mm@kvack.org, kvmarm@lists.linux.dev, pbonzini@redhat.com, chenhuacai@kernel.org, mpe@ellerman.id.au, anup@brainfault.org, paul.walmsley@sifive.com, palmer@dabbelt.com, aou@eecs.berkeley.edu, seanjc@google.com, viro@zeniv.linux.org.uk, brauner@kernel.org, willy@infradead.org, akpm@linux-foundation.org, xiaoyao.li@intel.com, yilun.xu@intel.com, chao.p.peng@linux.intel.com, jarkko@kernel.org, amoorthy@google.com, dmatlack@google.com, isaku.yamahata@intel.com, mic@digikod.net, vbabka@suse.cz, vannapurve@google.com, ackerleytng@google.com, mail@maciej.szmigiero.name, michael.roth@amd.com, wei.w.wang@intel.com, liam.merwick@oracle.com, isaku.yamahata@gmail.com, kirill.shutemov@linux.intel.com, suzuki.poulose@arm.com, steven.price@arm.com, quic_eberman@quicinc.com, quic_mnalajal@quicinc.com, quic_tsoni@quicinc.com, quic_svaddagi@quicinc.com, quic_cvanscha@quicinc.com, quic_pderrin@quicinc.com, quic_pheragu@quicinc.com, catalin.marinas@arm.com, james.morse@arm.com, yuzenghui@huawei.com, oliver.upton@linux.dev, maz@kernel.org, will@kernel.org, qperret@google.com, keirf@google.com, roypat@amazon.co.uk, shuah@kernel.org, hch@infradead.org, jgg@nvidia.com, rientjes@google.com, jhubbard@nvidia.com, fvdl@google.com, hughd@google.com, jthoughton@google.com, peterx@redhat.com, pankaj.gupta@amd.com, ira.weiny@intel.com Content-Type: text/plain; charset="UTF-8" X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: DE73814000E X-Stat-Signature: gi48ypunew431pdg9cz55f18zobpdbb1 X-Rspam-User: X-HE-Tag: 1749148231-557636 X-HE-Meta: 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 pDRQ4rMl SOpnsq+wWdphdUSi0fPF1WMKbfd+w1pUFqtIk4fHcI1TCuETHIw6QzFA8+zCd4wUhg4afbGK6JEWbCi7tubcusCpS5Lv19gXFEQgqhG+ee2hrKIcEvA/HNElEn4xbUm8CGloKGaYrT4k7l+0WcDOcM2Hm+jPuZGmT0TaPtXEMH5sH4Iwr5LKoEi0YTGpTCo3hqpz6DsTDUWJZVKvDt61eVM33B2zlCAUljhCqKWRSMFIT0DLrT8ZdAu0NEdIB6lSkTcVO+/rB1TYwW/tgFkHDV1GvYfUQbkNkpepHVMq7EgkbK3SL65vZ7MNoNrZZAWiaKlaXahd5/OjEALXPfYfaBJtiJGsYn6nRyN6WsGu5TaPcScw= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, 5 Jun 2025 at 18:45, David Hildenbrand wrote: > > On 05.06.25 19:43, Fuad Tabba wrote: > > On Thu, 5 Jun 2025 at 18:35, David Hildenbrand wrote: > >> > >> On 05.06.25 18:11, Fuad Tabba wrote: > >>> On Thu, 5 Jun 2025 at 16:49, David Hildenbrand wrote: > >>>> > >>>> On 05.06.25 17:37, Fuad Tabba wrote: > >>>>> Define the architecture-specific macro to enable shared memory support > >>>>> in guest_memfd for relevant software-only VM types, specifically > >>>>> KVM_X86_DEFAULT_VM and KVM_X86_SW_PROTECTED_VM. > >>>>> > >>>>> Enable the KVM_GMEM_SHARED_MEM Kconfig option if KVM_SW_PROTECTED_VM is > >>>>> enabled. > >>>>> > >>>>> Co-developed-by: Ackerley Tng > >>>>> Signed-off-by: Ackerley Tng > >>>>> Signed-off-by: Fuad Tabba > >>>>> --- > >>>>> arch/x86/include/asm/kvm_host.h | 10 ++++++++++ > >>>>> arch/x86/kvm/Kconfig | 1 + > >>>>> arch/x86/kvm/x86.c | 3 ++- > >>>>> 3 files changed, 13 insertions(+), 1 deletion(-) > >>>>> > >>>>> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h > >>>>> index 709cc2a7ba66..ce9ad4cd93c5 100644 > >>>>> --- a/arch/x86/include/asm/kvm_host.h > >>>>> +++ b/arch/x86/include/asm/kvm_host.h > >>>>> @@ -2255,8 +2255,18 @@ void kvm_configure_mmu(bool enable_tdp, int tdp_forced_root_level, > >>>>> > >>>>> #ifdef CONFIG_KVM_GMEM > >>>>> #define kvm_arch_supports_gmem(kvm) ((kvm)->arch.supports_gmem) > >>>>> + > >>>>> +/* > >>>>> + * CoCo VMs with hardware support that use guest_memfd only for backing private > >>>>> + * memory, e.g., TDX, cannot use guest_memfd with userspace mapping enabled. > >>>>> + */ > >>>>> +#define kvm_arch_supports_gmem_shared_mem(kvm) \ > >>>>> + (IS_ENABLED(CONFIG_KVM_GMEM_SHARED_MEM) && \ > >>>>> + ((kvm)->arch.vm_type == KVM_X86_SW_PROTECTED_VM || \ > >>>>> + (kvm)->arch.vm_type == KVM_X86_DEFAULT_VM)) > >>>>> #else > >>>>> #define kvm_arch_supports_gmem(kvm) false > >>>>> +#define kvm_arch_supports_gmem_shared_mem(kvm) false > >>>>> #endif > >>>>> > >>>>> #define kvm_arch_has_readonly_mem(kvm) (!(kvm)->arch.has_protected_state) > >>>>> diff --git a/arch/x86/kvm/Kconfig b/arch/x86/kvm/Kconfig > >>>>> index b37258253543..fdf24b50af9d 100644 > >>>>> --- a/arch/x86/kvm/Kconfig > >>>>> +++ b/arch/x86/kvm/Kconfig > >>>>> @@ -47,6 +47,7 @@ config KVM_X86 > >>>>> select KVM_GENERIC_HARDWARE_ENABLING > >>>>> select KVM_GENERIC_PRE_FAULT_MEMORY > >>>>> select KVM_GENERIC_GMEM_POPULATE if KVM_SW_PROTECTED_VM > >>>>> + select KVM_GMEM_SHARED_MEM if KVM_SW_PROTECTED_VM > >>>>> select KVM_WERROR if WERROR > >>>> > >>>> Is $subject and this still true, given that it's now also supported for > >>>> KVM_X86_DEFAULT_VM? > >>> > >>> True, just not the whole truth :) > >>> > >>> I guess a better one would be, for Software VMs (remove protected)? > >> > >> Now I am curious, what is a Hardware VM? :) > > > > The opposite of a software one! ;) i.e., hardware-supported CoCo, > > e.g., TDX, CCA... > > So, you mean a sofware VM is ... just an ordinary VM? :P > > "KVM: x86: Enable guest_memfd shared memory for ordinary (non-CoCo) VMs" ? > > But, whatever you prefer :) This sounds better. I was thrown off by the KVM_SW_PROTECTED_VM type :) /fuad > -- > Cheers, > > David / dhildenb >