| Message ID | 20231016115028.996656-4-michael.roth@amd.com |
|---|---|
| State | New |
| Headers | show |
| Series | KVM: gmem hooks/changes needed for x86 (other archs?) | expand |
Hi, On 16/10/2023 12:50, Michael Roth wrote: > guest_memfd pages are generally expected to be in some arch-defined > initial state prior to using them for guest memory. For SEV-SNP this > initial state is 'private', or 'guest-owned', and requires additional > operations to move these pages into a 'private' state by updating the > corresponding entries the RMP table. > > Allow for an arch-defined hook to handle updates of this sort, and go > ahead and implement one for x86 so KVM implementations like AMD SVM can > register a kvm_x86_ops callback to handle these updates for SEV-SNP > guests. > > The preparation callback is always called when allocating/grabbing > folios via gmem, and it is up to the architecture to keep track of > whether or not the pages are already in the expected state (e.g. the RMP > table in the case of SEV-SNP). > > In some cases, it is necessary to defer the preparation of the pages to > handle things like in-place encryption of initial guest memory payloads > before marking these pages as 'private'/'guest-owned', so also add a > helper that performs the same function as kvm_gmem_get_pfn(), but allows > for the preparation callback to be bypassed to allow for pages to be > accessed beforehand. This will be useful for Arm CCA, where the pages need to be moved into "Realm state". Some minor comments below. > > Link: https://lore.kernel.org/lkml/ZLqVdvsF11Ddo7Dq@google.com/ > Signed-off-by: Michael Roth <michael.roth@amd.com> > --- > arch/x86/include/asm/kvm-x86-ops.h | 1 + > arch/x86/include/asm/kvm_host.h | 2 ++ > arch/x86/kvm/x86.c | 6 ++++ > include/linux/kvm_host.h | 14 ++++++++ > virt/kvm/Kconfig | 4 +++ > virt/kvm/guest_memfd.c | 56 +++++++++++++++++++++++++++--- > 6 files changed, 78 insertions(+), 5 deletions(-) > > diff --git a/arch/x86/include/asm/kvm-x86-ops.h b/arch/x86/include/asm/kvm-x86-ops.h > index e3054e3e46d5..0c113f42d5c7 100644 > --- a/arch/x86/include/asm/kvm-x86-ops.h > +++ b/arch/x86/include/asm/kvm-x86-ops.h > @@ -134,6 +134,7 @@ KVM_X86_OP(msr_filter_changed) > KVM_X86_OP(complete_emulated_msr) > KVM_X86_OP(vcpu_deliver_sipi_vector) > KVM_X86_OP_OPTIONAL_RET0(vcpu_get_apicv_inhibit_reasons); > +KVM_X86_OP_OPTIONAL_RET0(gmem_prepare) > > #undef KVM_X86_OP > #undef KVM_X86_OP_OPTIONAL > diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h > index 95018cc653f5..66fc89d1858f 100644 > --- a/arch/x86/include/asm/kvm_host.h > +++ b/arch/x86/include/asm/kvm_host.h > @@ -1752,6 +1752,8 @@ struct kvm_x86_ops { > * Returns vCPU specific APICv inhibit reasons > */ > unsigned long (*vcpu_get_apicv_inhibit_reasons)(struct kvm_vcpu *vcpu); > + > + int (*gmem_prepare)(struct kvm *kvm, kvm_pfn_t pfn, gfn_t gfn, int max_order); > }; > > struct kvm_x86_nested_ops { > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > index 767236b4d771..33a4cc33d86d 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -13301,6 +13301,12 @@ bool kvm_arch_no_poll(struct kvm_vcpu *vcpu) > } > EXPORT_SYMBOL_GPL(kvm_arch_no_poll); > > +#ifdef CONFIG_HAVE_KVM_GMEM_PREPARE > +int kvm_arch_gmem_prepare(struct kvm *kvm, gfn_t gfn, kvm_pfn_t pfn, int max_order) > +{ > + return static_call(kvm_x86_gmem_prepare)(kvm, pfn, gfn, max_order); > +} > +#endif > > int kvm_spec_ctrl_test_value(u64 value) > { > diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h > index 8c5c017ab4e9..c7f82c2f1bcf 100644 > --- a/include/linux/kvm_host.h > +++ b/include/linux/kvm_host.h > @@ -2403,9 +2403,19 @@ static inline bool kvm_mem_is_private(struct kvm *kvm, gfn_t gfn) > #endif /* CONFIG_KVM_GENERIC_MEMORY_ATTRIBUTES */ > > #ifdef CONFIG_KVM_PRIVATE_MEM > +int __kvm_gmem_get_pfn(struct kvm *kvm, struct kvm_memory_slot *slot, > + gfn_t gfn, kvm_pfn_t *pfn, int *max_order, bool prep); > int kvm_gmem_get_pfn(struct kvm *kvm, struct kvm_memory_slot *slot, > gfn_t gfn, kvm_pfn_t *pfn, int *max_order); > #else > +static inline int __kvm_gmem_get_pfn(struct kvm *kvm, > + struct kvm_memory_slot *slot, gfn_t gfn, > + kvm_pfn_t *pfn, int *max_order) Missing "bool prep" here ? minor nit: Do we need to export both __kvm_gmem_get_pfn and kvm_gmem_get_pfn ? I don't see anyone else using the former. We could have : #ifdef CONFIG_KVM_PRIVATE_MEM int __kvm_gmem_get_pfn(struct kvm *kvm, struct kvm_memory_slot *slot, gfn_t gfn, kvm_pfn_t *pfn, int *max_order, bool prep); #else static inline int __kvm_gmem_get_pfn(struct kvm *kvm, struct kvm_memory_slot *slot, gfn_t gfn, kvm_pfn_t *pfn, int *max_order, bool prep) { KVM_BUG_ON(1, kvm); return -EIO; } #endif static inline int kvm_gmem_get_pfn(struct kvm *kvm, struct kvm_memory_slot *slot, gfn_t gfn, kvm_pfn_t *pfn, int *max_order) { return __kvm_gmem_get_pfn(kvm, slot, gfn, pfn, max_order, true); } Suzuki > + KVM_BUG_ON(1, kvm); > + return -EIO; > +} > + > static inline int kvm_gmem_get_pfn(struct kvm *kvm, > struct kvm_memory_slot *slot, gfn_t gfn, > kvm_pfn_t *pfn, int *max_order) > @@ -2415,4 +2425,8 @@ static inline int kvm_gmem_get_pfn(struct kvm *kvm, > } > #endif /* CONFIG_KVM_PRIVATE_MEM */ > > +#ifdef CONFIG_HAVE_KVM_GMEM_PREPARE > +int kvm_arch_gmem_prepare(struct kvm *kvm, gfn_t gfn, kvm_pfn_t pfn, int max_order); > +#endif > + > #endif > diff --git a/virt/kvm/Kconfig b/virt/kvm/Kconfig > index 2c964586aa14..992cf6ed86ef 100644 > --- a/virt/kvm/Kconfig > +++ b/virt/kvm/Kconfig > @@ -109,3 +109,7 @@ config KVM_GENERIC_PRIVATE_MEM > select KVM_GENERIC_MEMORY_ATTRIBUTES > select KVM_PRIVATE_MEM > bool > + > +config HAVE_KVM_GMEM_PREPARE > + bool > + depends on KVM_PRIVATE_MEM > diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c > index f6f1b17a319c..72ff8b7b31d5 100644 > --- a/virt/kvm/guest_memfd.c > +++ b/virt/kvm/guest_memfd.c > @@ -44,7 +44,40 @@ static struct folio *kvm_gmem_get_huge_folio(struct inode *inode, pgoff_t index) > #endif > } > > -static struct folio *kvm_gmem_get_folio(struct inode *inode, pgoff_t index) > +static int kvm_gmem_prepare_folio(struct inode *inode, pgoff_t index, struct folio *folio) > +{ > +#ifdef CONFIG_HAVE_KVM_GMEM_PREPARE > + struct list_head *gmem_list = &inode->i_mapping->private_list; > + struct kvm_gmem *gmem; > + > + list_for_each_entry(gmem, gmem_list, entry) { > + struct kvm_memory_slot *slot; > + struct kvm *kvm = gmem->kvm; > + struct page *page; > + kvm_pfn_t pfn; > + gfn_t gfn; > + int rc; > + > + slot = xa_load(&gmem->bindings, index); > + if (!slot) > + continue; > + > + page = folio_file_page(folio, index); > + pfn = page_to_pfn(page); > + gfn = slot->base_gfn + index - slot->gmem.pgoff; > + rc = kvm_arch_gmem_prepare(kvm, gfn, pfn, compound_order(compound_head(page))); > + if (rc) { > + pr_warn_ratelimited("gmem: Failed to prepare folio for index %lx, error %d.\n", > + index, rc); > + return rc; > + } > + } > + > +#endif > + return 0; > +} > + > +static struct folio *kvm_gmem_get_folio(struct inode *inode, pgoff_t index, bool prep) > { > struct folio *folio; > > @@ -74,6 +107,12 @@ static struct folio *kvm_gmem_get_folio(struct inode *inode, pgoff_t index) > folio_mark_uptodate(folio); > } > > + if (prep && kvm_gmem_prepare_folio(inode, index, folio)) { > + folio_unlock(folio); > + folio_put(folio); > + return NULL; > + } > + > /* > * Ignore accessed, referenced, and dirty flags. The memory is > * unevictable and there is no storage to write back to. > @@ -178,7 +217,7 @@ static long kvm_gmem_allocate(struct inode *inode, loff_t offset, loff_t len) > break; > } > > - folio = kvm_gmem_get_folio(inode, index); > + folio = kvm_gmem_get_folio(inode, index, true); > if (!folio) { > r = -ENOMEM; > break; > @@ -537,8 +576,8 @@ void kvm_gmem_unbind(struct kvm_memory_slot *slot) > fput(file); > } > > -int kvm_gmem_get_pfn(struct kvm *kvm, struct kvm_memory_slot *slot, > - gfn_t gfn, kvm_pfn_t *pfn, int *max_order) > +int __kvm_gmem_get_pfn(struct kvm *kvm, struct kvm_memory_slot *slot, > + gfn_t gfn, kvm_pfn_t *pfn, int *max_order, bool prep) > { > pgoff_t index, huge_index; > struct kvm_gmem *gmem; > @@ -559,7 +598,7 @@ int kvm_gmem_get_pfn(struct kvm *kvm, struct kvm_memory_slot *slot, > goto out_fput; > } > > - folio = kvm_gmem_get_folio(file_inode(file), index); > + folio = kvm_gmem_get_folio(file_inode(file), index, prep); > if (!folio) { > r = -ENOMEM; > goto out_fput; > @@ -600,4 +639,11 @@ int kvm_gmem_get_pfn(struct kvm *kvm, struct kvm_memory_slot *slot, > > return r; > } > +EXPORT_SYMBOL_GPL(__kvm_gmem_get_pfn); > + > +int kvm_gmem_get_pfn(struct kvm *kvm, struct kvm_memory_slot *slot, > + gfn_t gfn, kvm_pfn_t *pfn, int *max_order) > +{ > + return __kvm_gmem_get_pfn(kvm, slot, gfn, pfn, max_order, true); > +} > EXPORT_SYMBOL_GPL(kvm_gmem_get_pfn);
On Thu, Feb 08, 2024, Suzuki K Poulose wrote: > > diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h > > index 8c5c017ab4e9..c7f82c2f1bcf 100644 > > --- a/include/linux/kvm_host.h > > +++ b/include/linux/kvm_host.h > > @@ -2403,9 +2403,19 @@ static inline bool kvm_mem_is_private(struct kvm *kvm, gfn_t gfn) > > #endif /* CONFIG_KVM_GENERIC_MEMORY_ATTRIBUTES */ > > #ifdef CONFIG_KVM_PRIVATE_MEM > > +int __kvm_gmem_get_pfn(struct kvm *kvm, struct kvm_memory_slot *slot, > > + gfn_t gfn, kvm_pfn_t *pfn, int *max_order, bool prep); > > int kvm_gmem_get_pfn(struct kvm *kvm, struct kvm_memory_slot *slot, > > gfn_t gfn, kvm_pfn_t *pfn, int *max_order); > > #else > > +static inline int __kvm_gmem_get_pfn(struct kvm *kvm, > > + struct kvm_memory_slot *slot, gfn_t gfn, > > + kvm_pfn_t *pfn, int *max_order) > > Missing "bool prep" here ? > > minor nit: Do we need to export both __kvm_gmem_get_pfn and kvm_gmem_get_pfn Minor nit on the nit: s/export/expose. My initial reaction was "we should *never* export any of these" :-) > ? I don't see anyone else using the former. > > We could have : > > #ifdef CONFIG_KVM_PRIVATE_MEM > int __kvm_gmem_get_pfn(struct kvm *kvm, struct kvm_memory_slot *slot, > gfn_t gfn, kvm_pfn_t *pfn, int *max_order, bool prep); > #else > static inline int __kvm_gmem_get_pfn(struct kvm *kvm, > struct kvm_memory_slot *slot, gfn_t gfn, > kvm_pfn_t *pfn, int *max_order, > bool prep) > { > KVM_BUG_ON(1, kvm); > return -EIO; > } > #endif > > static inline int kvm_gmem_get_pfn(struct kvm *kvm, > struct kvm_memory_slot *slot, gfn_t gfn, > kvm_pfn_t *pfn, int *max_order) > { > return __kvm_gmem_get_pfn(kvm, slot, gfn, pfn, max_order, true); > } I suspect all of this will be moot. As discussed on the PUCK call[1] and in the SNP enabling series[2], the plan is to have guest_memfd do (or at least initiate) the actual copying into the backing pages, e.g. to guarantee that the pages are in the correct state, that the appropriate locks are held, etc. [1] https://drive.google.com/drive/folders/116YTH1h9yBZmjqeJc03cV4_AhSe-VBkc?resourcekey=0-sOGeFEUi60-znJJmZBsTHQ&usp=drive_link [2] https://lore.kernel.org/all/ZcLuGxZ-w4fPmFxd@google.com
diff --git a/arch/x86/include/asm/kvm-x86-ops.h b/arch/x86/include/asm/kvm-x86-ops.h index e3054e3e46d5..0c113f42d5c7 100644 --- a/arch/x86/include/asm/kvm-x86-ops.h +++ b/arch/x86/include/asm/kvm-x86-ops.h @@ -134,6 +134,7 @@ KVM_X86_OP(msr_filter_changed) KVM_X86_OP(complete_emulated_msr) KVM_X86_OP(vcpu_deliver_sipi_vector) KVM_X86_OP_OPTIONAL_RET0(vcpu_get_apicv_inhibit_reasons); +KVM_X86_OP_OPTIONAL_RET0(gmem_prepare) #undef KVM_X86_OP #undef KVM_X86_OP_OPTIONAL diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h index 95018cc653f5..66fc89d1858f 100644 --- a/arch/x86/include/asm/kvm_host.h +++ b/arch/x86/include/asm/kvm_host.h @@ -1752,6 +1752,8 @@ struct kvm_x86_ops { * Returns vCPU specific APICv inhibit reasons */ unsigned long (*vcpu_get_apicv_inhibit_reasons)(struct kvm_vcpu *vcpu); + + int (*gmem_prepare)(struct kvm *kvm, kvm_pfn_t pfn, gfn_t gfn, int max_order); }; struct kvm_x86_nested_ops { diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 767236b4d771..33a4cc33d86d 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -13301,6 +13301,12 @@ bool kvm_arch_no_poll(struct kvm_vcpu *vcpu) } EXPORT_SYMBOL_GPL(kvm_arch_no_poll); +#ifdef CONFIG_HAVE_KVM_GMEM_PREPARE +int kvm_arch_gmem_prepare(struct kvm *kvm, gfn_t gfn, kvm_pfn_t pfn, int max_order) +{ + return static_call(kvm_x86_gmem_prepare)(kvm, pfn, gfn, max_order); +} +#endif int kvm_spec_ctrl_test_value(u64 value) { diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h index 8c5c017ab4e9..c7f82c2f1bcf 100644 --- a/include/linux/kvm_host.h +++ b/include/linux/kvm_host.h @@ -2403,9 +2403,19 @@ static inline bool kvm_mem_is_private(struct kvm *kvm, gfn_t gfn) #endif /* CONFIG_KVM_GENERIC_MEMORY_ATTRIBUTES */ #ifdef CONFIG_KVM_PRIVATE_MEM +int __kvm_gmem_get_pfn(struct kvm *kvm, struct kvm_memory_slot *slot, + gfn_t gfn, kvm_pfn_t *pfn, int *max_order, bool prep); int kvm_gmem_get_pfn(struct kvm *kvm, struct kvm_memory_slot *slot, gfn_t gfn, kvm_pfn_t *pfn, int *max_order); #else +static inline int __kvm_gmem_get_pfn(struct kvm *kvm, + struct kvm_memory_slot *slot, gfn_t gfn, + kvm_pfn_t *pfn, int *max_order) +{ + KVM_BUG_ON(1, kvm); + return -EIO; +} + static inline int kvm_gmem_get_pfn(struct kvm *kvm, struct kvm_memory_slot *slot, gfn_t gfn, kvm_pfn_t *pfn, int *max_order) @@ -2415,4 +2425,8 @@ static inline int kvm_gmem_get_pfn(struct kvm *kvm, } #endif /* CONFIG_KVM_PRIVATE_MEM */ +#ifdef CONFIG_HAVE_KVM_GMEM_PREPARE +int kvm_arch_gmem_prepare(struct kvm *kvm, gfn_t gfn, kvm_pfn_t pfn, int max_order); +#endif + #endif diff --git a/virt/kvm/Kconfig b/virt/kvm/Kconfig index 2c964586aa14..992cf6ed86ef 100644 --- a/virt/kvm/Kconfig +++ b/virt/kvm/Kconfig @@ -109,3 +109,7 @@ config KVM_GENERIC_PRIVATE_MEM select KVM_GENERIC_MEMORY_ATTRIBUTES select KVM_PRIVATE_MEM bool + +config HAVE_KVM_GMEM_PREPARE + bool + depends on KVM_PRIVATE_MEM diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c index f6f1b17a319c..72ff8b7b31d5 100644 --- a/virt/kvm/guest_memfd.c +++ b/virt/kvm/guest_memfd.c @@ -44,7 +44,40 @@ static struct folio *kvm_gmem_get_huge_folio(struct inode *inode, pgoff_t index) #endif } -static struct folio *kvm_gmem_get_folio(struct inode *inode, pgoff_t index) +static int kvm_gmem_prepare_folio(struct inode *inode, pgoff_t index, struct folio *folio) +{ +#ifdef CONFIG_HAVE_KVM_GMEM_PREPARE + struct list_head *gmem_list = &inode->i_mapping->private_list; + struct kvm_gmem *gmem; + + list_for_each_entry(gmem, gmem_list, entry) { + struct kvm_memory_slot *slot; + struct kvm *kvm = gmem->kvm; + struct page *page; + kvm_pfn_t pfn; + gfn_t gfn; + int rc; + + slot = xa_load(&gmem->bindings, index); + if (!slot) + continue; + + page = folio_file_page(folio, index); + pfn = page_to_pfn(page); + gfn = slot->base_gfn + index - slot->gmem.pgoff; + rc = kvm_arch_gmem_prepare(kvm, gfn, pfn, compound_order(compound_head(page))); + if (rc) { + pr_warn_ratelimited("gmem: Failed to prepare folio for index %lx, error %d.\n", + index, rc); + return rc; + } + } + +#endif + return 0; +} + +static struct folio *kvm_gmem_get_folio(struct inode *inode, pgoff_t index, bool prep) { struct folio *folio; @@ -74,6 +107,12 @@ static struct folio *kvm_gmem_get_folio(struct inode *inode, pgoff_t index) folio_mark_uptodate(folio); } + if (prep && kvm_gmem_prepare_folio(inode, index, folio)) { + folio_unlock(folio); + folio_put(folio); + return NULL; + } + /* * Ignore accessed, referenced, and dirty flags. The memory is * unevictable and there is no storage to write back to. @@ -178,7 +217,7 @@ static long kvm_gmem_allocate(struct inode *inode, loff_t offset, loff_t len) break; } - folio = kvm_gmem_get_folio(inode, index); + folio = kvm_gmem_get_folio(inode, index, true); if (!folio) { r = -ENOMEM; break; @@ -537,8 +576,8 @@ void kvm_gmem_unbind(struct kvm_memory_slot *slot) fput(file); } -int kvm_gmem_get_pfn(struct kvm *kvm, struct kvm_memory_slot *slot, - gfn_t gfn, kvm_pfn_t *pfn, int *max_order) +int __kvm_gmem_get_pfn(struct kvm *kvm, struct kvm_memory_slot *slot, + gfn_t gfn, kvm_pfn_t *pfn, int *max_order, bool prep) { pgoff_t index, huge_index; struct kvm_gmem *gmem; @@ -559,7 +598,7 @@ int kvm_gmem_get_pfn(struct kvm *kvm, struct kvm_memory_slot *slot, goto out_fput; } - folio = kvm_gmem_get_folio(file_inode(file), index); + folio = kvm_gmem_get_folio(file_inode(file), index, prep); if (!folio) { r = -ENOMEM; goto out_fput; @@ -600,4 +639,11 @@ int kvm_gmem_get_pfn(struct kvm *kvm, struct kvm_memory_slot *slot, return r; } +EXPORT_SYMBOL_GPL(__kvm_gmem_get_pfn); + +int kvm_gmem_get_pfn(struct kvm *kvm, struct kvm_memory_slot *slot, + gfn_t gfn, kvm_pfn_t *pfn, int *max_order) +{ + return __kvm_gmem_get_pfn(kvm, slot, gfn, pfn, max_order, true); +} EXPORT_SYMBOL_GPL(kvm_gmem_get_pfn);
guest_memfd pages are generally expected to be in some arch-defined initial state prior to using them for guest memory. For SEV-SNP this initial state is 'private', or 'guest-owned', and requires additional operations to move these pages into a 'private' state by updating the corresponding entries the RMP table. Allow for an arch-defined hook to handle updates of this sort, and go ahead and implement one for x86 so KVM implementations like AMD SVM can register a kvm_x86_ops callback to handle these updates for SEV-SNP guests. The preparation callback is always called when allocating/grabbing folios via gmem, and it is up to the architecture to keep track of whether or not the pages are already in the expected state (e.g. the RMP table in the case of SEV-SNP). In some cases, it is necessary to defer the preparation of the pages to handle things like in-place encryption of initial guest memory payloads before marking these pages as 'private'/'guest-owned', so also add a helper that performs the same function as kvm_gmem_get_pfn(), but allows for the preparation callback to be bypassed to allow for pages to be accessed beforehand. Link: https://lore.kernel.org/lkml/ZLqVdvsF11Ddo7Dq@google.com/ Signed-off-by: Michael Roth <michael.roth@amd.com> --- arch/x86/include/asm/kvm-x86-ops.h | 1 + arch/x86/include/asm/kvm_host.h | 2 ++ arch/x86/kvm/x86.c | 6 ++++ include/linux/kvm_host.h | 14 ++++++++ virt/kvm/Kconfig | 4 +++ virt/kvm/guest_memfd.c | 56 +++++++++++++++++++++++++++--- 6 files changed, 78 insertions(+), 5 deletions(-)