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X-CSE-ConnectionGUID: YliyFdmWT3enLofwYk+vbw== X-CSE-MsgGUID: dOuN/Ps1SO2BI3dRVCniEA== X-IronPort-AV: E=McAfee;i="6800,10657,11501"; a="55407397" X-IronPort-AV: E=Sophos;i="6.16,333,1744095600"; d="scan'208";a="55407397" Received: from orviesa001.jf.intel.com ([10.64.159.141]) by orvoesa111.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 23 Jul 2025 06:42:50 -0700 X-CSE-ConnectionGUID: yTIVkg39RNaz72vCTkFDrQ== X-CSE-MsgGUID: fJ/Nw4uCQcucq0aN5JJTDg== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.16,333,1744095600"; d="scan'208";a="196630738" Received: from xiaoyaol-hp-g830.ccr.corp.intel.com (HELO [10.124.247.1]) ([10.124.247.1]) by smtpauth.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 23 Jul 2025 06:42:29 -0700 Message-ID: Date: Wed, 23 Jul 2025 21:42:25 +0800 Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v16 09/22] KVM: x86: Enable KVM_GUEST_MEMFD for all 64-bit builds To: Fuad Tabba , kvm@vger.kernel.org, linux-arm-msm@vger.kernel.org, linux-mm@kvack.org, kvmarm@lists.linux.dev Cc: 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, 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, david@redhat.com, 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 References: <20250723104714.1674617-1-tabba@google.com> <20250723104714.1674617-10-tabba@google.com> Content-Language: en-US From: Xiaoyao Li In-Reply-To: <20250723104714.1674617-10-tabba@google.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 7/23/2025 6:47 PM, Fuad Tabba wrote: > Enable KVM_GUEST_MEMFD for all KVM x86 64-bit builds, i.e. for "default" > VM types when running on 64-bit KVM. This will allow using guest_memfd > to back non-private memory for all VM shapes, by supporting mmap() on > guest_memfd. > > Opportunistically clean up various conditionals that become tautologies > once x86 selects KVM_GUEST_MEMFD more broadly. Specifically, because > SW protected VMs, SEV, and TDX are all 64-bit only, private memory no > longer needs to take explicit dependencies on KVM_GUEST_MEMFD, because > it is effectively a prerequisite. > > Suggested-by: Sean Christopherson > Signed-off-by: Fuad Tabba Reviewed-by: Xiaoyao Li It matches with my thought on v14 that gmem can be allowed for all x86 VM types[*]. Get rid of .supports_gmem and achieve it through CONFIG_KVM_GUEST_MEMFD looks much cleaner! [*] https://lore.kernel.org/all/b5fe8f54-64df-4cfa-b86f-eed1cbddca7a@intel.com/ > --- > arch/x86/include/asm/kvm_host.h | 4 +--- > arch/x86/kvm/Kconfig | 12 ++++-------- > include/linux/kvm_host.h | 9 ++------- > virt/kvm/kvm_main.c | 4 ++-- > 4 files changed, 9 insertions(+), 20 deletions(-) > > diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h > index 7b0f2b3e492d..50366a1ca192 100644 > --- a/arch/x86/include/asm/kvm_host.h > +++ b/arch/x86/include/asm/kvm_host.h > @@ -2276,10 +2276,8 @@ void kvm_configure_mmu(bool enable_tdp, int tdp_forced_root_level, > int tdp_max_root_level, int tdp_huge_page_level); > > > -#ifdef CONFIG_KVM_GUEST_MEMFD > +#ifdef CONFIG_KVM_GENERIC_MEMORY_ATTRIBUTES > #define kvm_arch_has_private_mem(kvm) ((kvm)->arch.has_private_mem) > -#else > -#define kvm_arch_has_private_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 c763446d9b9f..4e43923656d0 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_WERROR if WERROR > + select KVM_GUEST_MEMFD if X86_64 > > config KVM > tristate "Kernel-based Virtual Machine (KVM) support" > @@ -79,16 +80,11 @@ config KVM_WERROR > > If in doubt, say "N". > > -config KVM_X86_PRIVATE_MEM > - select KVM_GENERIC_MEMORY_ATTRIBUTES > - select KVM_GUEST_MEMFD > - bool > - > config KVM_SW_PROTECTED_VM > bool "Enable support for KVM software-protected VMs" > depends on EXPERT > depends on KVM_X86 && X86_64 > - select KVM_X86_PRIVATE_MEM > + select KVM_GENERIC_MEMORY_ATTRIBUTES > help > Enable support for KVM software-protected VMs. Currently, software- > protected VMs are purely a development and testing vehicle for > @@ -138,7 +134,7 @@ config KVM_INTEL_TDX > bool "Intel Trust Domain Extensions (TDX) support" > default y > depends on INTEL_TDX_HOST > - select KVM_X86_PRIVATE_MEM > + select KVM_GENERIC_MEMORY_ATTRIBUTES > select HAVE_KVM_ARCH_GMEM_POPULATE > help > Provides support for launching Intel Trust Domain Extensions (TDX) > @@ -162,7 +158,7 @@ config KVM_AMD_SEV > depends on KVM_AMD && X86_64 > depends on CRYPTO_DEV_SP_PSP && !(KVM_AMD=y && CRYPTO_DEV_CCP_DD=m) > select ARCH_HAS_CC_PLATFORM > - select KVM_X86_PRIVATE_MEM > + select KVM_GENERIC_MEMORY_ATTRIBUTES > select HAVE_KVM_ARCH_GMEM_PREPARE > select HAVE_KVM_ARCH_GMEM_INVALIDATE > select HAVE_KVM_ARCH_GMEM_POPULATE > diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h > index 56ea8c862cfd..4d1c44622056 100644 > --- a/include/linux/kvm_host.h > +++ b/include/linux/kvm_host.h > @@ -719,11 +719,7 @@ static inline int kvm_arch_vcpu_memslots_id(struct kvm_vcpu *vcpu) > } > #endif > > -/* > - * Arch code must define kvm_arch_has_private_mem if support for guest_memfd is > - * enabled. > - */ > -#if !defined(kvm_arch_has_private_mem) && !IS_ENABLED(CONFIG_KVM_GUEST_MEMFD) > +#ifndef CONFIG_KVM_GENERIC_MEMORY_ATTRIBUTES > static inline bool kvm_arch_has_private_mem(struct kvm *kvm) > { > return false; > @@ -2505,8 +2501,7 @@ bool kvm_arch_post_set_memory_attributes(struct kvm *kvm, > > static inline bool kvm_mem_is_private(struct kvm *kvm, gfn_t gfn) > { > - return IS_ENABLED(CONFIG_KVM_GUEST_MEMFD) && > - kvm_get_memory_attributes(kvm, gfn) & KVM_MEMORY_ATTRIBUTE_PRIVATE; > + return kvm_get_memory_attributes(kvm, gfn) & KVM_MEMORY_ATTRIBUTE_PRIVATE; > } > #else > static inline bool kvm_mem_is_private(struct kvm *kvm, gfn_t gfn) > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c > index aa86dfd757db..4f57cb92e109 100644 > --- a/virt/kvm/kvm_main.c > +++ b/virt/kvm/kvm_main.c > @@ -1588,7 +1588,7 @@ static int check_memory_region_flags(struct kvm *kvm, > { > u32 valid_flags = KVM_MEM_LOG_DIRTY_PAGES; > > - if (kvm_arch_has_private_mem(kvm)) > + if (IS_ENABLED(CONFIG_KVM_GUEST_MEMFD)) > valid_flags |= KVM_MEM_GUEST_MEMFD; > > /* Dirty logging private memory is not currently supported. */ > @@ -4917,7 +4917,7 @@ static int kvm_vm_ioctl_check_extension_generic(struct kvm *kvm, long arg) > #endif > #ifdef CONFIG_KVM_GUEST_MEMFD > case KVM_CAP_GUEST_MEMFD: > - return !kvm || kvm_arch_has_private_mem(kvm); > + return 1; > #endif > default: > break;