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X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 15 Dec 2025 15:34:59.6499 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 67216313-5ca5-422a-5788-08de3bef81fb X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=3dd8961f-e488-4e60-8e11-a82d994e183d;Ip=[165.204.84.17];Helo=[satlexmb07.amd.com] X-MS-Exchange-CrossTenant-AuthSource: SN1PEPF0002529F.namprd05.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: DS7PR12MB6046 Content-Type: text/plain; charset="utf-8" kvm_gmem_populate(), and the associated post-populate callbacks, have some limited support for dealing with guests backed by hugepages by passing the order information along to each post-populate callback and iterating through the pages passed to kvm_gmem_populate() in hugepage-chunks. However, guest_memfd doesn't yet support hugepages, and in most cases additional changes in the kvm_gmem_populate() path would also be needed to actually allow for this functionality. This makes the existing code unecessarily complex, and makes changes difficult to work through upstream due to theoretical impacts on hugepage support that can't be considered properly without an actual hugepage implementation to reference. So for now, remove what's there so changes for things like in-place conversion can be implemented/reviewed more efficiently. Suggested-by: Vishal Annapurve Co-developed-by: Vishal Annapurve Signed-off-by: Vishal Annapurve Signed-off-by: Michael Roth Tested-By: Vishal Annapurve --- arch/x86/kvm/svm/sev.c | 94 ++++++++++++++++------------------------ arch/x86/kvm/vmx/tdx.c | 2 +- include/linux/kvm_host.h | 2 +- virt/kvm/guest_memfd.c | 30 +++++++------ 4 files changed, 56 insertions(+), 72 deletions(-) diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c index f59c65abe3cf..362c6135401a 100644 --- a/arch/x86/kvm/svm/sev.c +++ b/arch/x86/kvm/svm/sev.c @@ -2267,66 +2267,52 @@ struct sev_gmem_populate_args { int fw_error; }; =20 -static int sev_gmem_post_populate(struct kvm *kvm, gfn_t gfn_start, kvm_pf= n_t pfn, - void __user *src, int order, void *opaque) +static int sev_gmem_post_populate(struct kvm *kvm, gfn_t gfn, kvm_pfn_t pf= n, + void __user *src, void *opaque) { struct sev_gmem_populate_args *sev_populate_args =3D opaque; + struct sev_data_snp_launch_update fw_args =3D {0}; struct kvm_sev_info *sev =3D to_kvm_sev_info(kvm); - int n_private =3D 0, ret, i; - int npages =3D (1 << order); - gfn_t gfn; + bool assigned =3D false; + int level; + int ret; =20 if (WARN_ON_ONCE(sev_populate_args->type !=3D KVM_SEV_SNP_PAGE_TYPE_ZERO = && !src)) return -EINVAL; =20 - for (gfn =3D gfn_start, i =3D 0; gfn < gfn_start + npages; gfn++, i++) { - struct sev_data_snp_launch_update fw_args =3D {0}; - bool assigned =3D false; - int level; - - ret =3D snp_lookup_rmpentry((u64)pfn + i, &assigned, &level); - if (ret || assigned) { - pr_debug("%s: Failed to ensure GFN 0x%llx RMP entry is initial shared s= tate, ret: %d assigned: %d\n", - __func__, gfn, ret, assigned); - ret =3D ret ? -EINVAL : -EEXIST; - goto err; - } + ret =3D snp_lookup_rmpentry((u64)pfn, &assigned, &level); + if (ret || assigned) { + pr_debug("%s: Failed to ensure GFN 0x%llx RMP entry is initial shared st= ate, ret: %d assigned: %d\n", + __func__, gfn, ret, assigned); + ret =3D ret ? -EINVAL : -EEXIST; + goto out; + } =20 - if (src) { - void *vaddr =3D kmap_local_pfn(pfn + i); + if (src) { + void *vaddr =3D kmap_local_pfn(pfn); =20 - if (copy_from_user(vaddr, src + i * PAGE_SIZE, PAGE_SIZE)) { - ret =3D -EFAULT; - goto err; - } - kunmap_local(vaddr); + if (copy_from_user(vaddr, src, PAGE_SIZE)) { + ret =3D -EFAULT; + goto out; } - - ret =3D rmp_make_private(pfn + i, gfn << PAGE_SHIFT, PG_LEVEL_4K, - sev_get_asid(kvm), true); - if (ret) - goto err; - - n_private++; - - fw_args.gctx_paddr =3D __psp_pa(sev->snp_context); - fw_args.address =3D __sme_set(pfn_to_hpa(pfn + i)); - fw_args.page_size =3D PG_LEVEL_TO_RMP(PG_LEVEL_4K); - fw_args.page_type =3D sev_populate_args->type; - - ret =3D __sev_issue_cmd(sev_populate_args->sev_fd, SEV_CMD_SNP_LAUNCH_UP= DATE, - &fw_args, &sev_populate_args->fw_error); - if (ret) - goto fw_err; + kunmap_local(vaddr); } =20 - return 0; + ret =3D rmp_make_private(pfn, gfn << PAGE_SHIFT, PG_LEVEL_4K, + sev_get_asid(kvm), true); + if (ret) + goto out; + + fw_args.gctx_paddr =3D __psp_pa(sev->snp_context); + fw_args.address =3D __sme_set(pfn_to_hpa(pfn)); + fw_args.page_size =3D PG_LEVEL_TO_RMP(PG_LEVEL_4K); + fw_args.page_type =3D sev_populate_args->type; =20 -fw_err: + ret =3D __sev_issue_cmd(sev_populate_args->sev_fd, SEV_CMD_SNP_LAUNCH_UPD= ATE, + &fw_args, &sev_populate_args->fw_error); /* * If the firmware command failed handle the reclaim and cleanup of that - * PFN specially vs. prior pages which can be cleaned up below without - * needing to reclaim in advance. + * PFN before reporting an error. * * Additionally, when invalid CPUID function entries are detected, * firmware writes the expected values into the page and leaves it @@ -2336,26 +2322,20 @@ static int sev_gmem_post_populate(struct kvm *kvm, = gfn_t gfn_start, kvm_pfn_t pf * information to provide information on which CPUID leaves/fields * failed CPUID validation. */ - if (!snp_page_reclaim(kvm, pfn + i) && + if (ret && !snp_page_reclaim(kvm, pfn) && sev_populate_args->type =3D=3D KVM_SEV_SNP_PAGE_TYPE_CPUID && sev_populate_args->fw_error =3D=3D SEV_RET_INVALID_PARAM) { - void *vaddr =3D kmap_local_pfn(pfn + i); + void *vaddr =3D kmap_local_pfn(pfn); =20 - if (copy_to_user(src + i * PAGE_SIZE, vaddr, PAGE_SIZE)) + if (copy_to_user(src, vaddr, PAGE_SIZE)) pr_debug("Failed to write CPUID page back to userspace\n"); =20 kunmap_local(vaddr); } =20 - /* pfn + i is hypervisor-owned now, so skip below cleanup for it. */ - n_private--; - -err: - pr_debug("%s: exiting with error ret %d (fw_error %d), restoring %d gmem = PFNs to shared.\n", - __func__, ret, sev_populate_args->fw_error, n_private); - for (i =3D 0; i < n_private; i++) - kvm_rmp_make_shared(kvm, pfn + i, PG_LEVEL_4K); - +out: + pr_debug("%s: exiting with return code %d (fw_error %d)\n", + __func__, ret, sev_populate_args->fw_error); return ret; } =20 diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c index 2d7a4d52ccfb..4fb042ce8ed1 100644 --- a/arch/x86/kvm/vmx/tdx.c +++ b/arch/x86/kvm/vmx/tdx.c @@ -3118,7 +3118,7 @@ struct tdx_gmem_post_populate_arg { }; =20 static int tdx_gmem_post_populate(struct kvm *kvm, gfn_t gfn, kvm_pfn_t pf= n, - void __user *src, int order, void *_arg) + void __user *src, void *_arg) { struct tdx_gmem_post_populate_arg *arg =3D _arg; struct kvm_tdx *kvm_tdx =3D to_kvm_tdx(kvm); diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h index d93f75b05ae2..1d0cee72e560 100644 --- a/include/linux/kvm_host.h +++ b/include/linux/kvm_host.h @@ -2581,7 +2581,7 @@ int kvm_arch_gmem_prepare(struct kvm *kvm, gfn_t gfn,= kvm_pfn_t pfn, int max_ord * Returns the number of pages that were populated. */ typedef int (*kvm_gmem_populate_cb)(struct kvm *kvm, gfn_t gfn, kvm_pfn_t = pfn, - void __user *src, int order, void *opaque); + void __user *src, void *opaque); =20 long kvm_gmem_populate(struct kvm *kvm, gfn_t gfn, void __user *src, long = npages, kvm_gmem_populate_cb post_populate, void *opaque); diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c index fdaea3422c30..9dafa44838fe 100644 --- a/virt/kvm/guest_memfd.c +++ b/virt/kvm/guest_memfd.c @@ -151,6 +151,15 @@ static struct folio *kvm_gmem_get_folio(struct inode *= inode, pgoff_t index) mapping_gfp_mask(inode->i_mapping), policy); mpol_cond_put(policy); =20 + /* + * External interfaces like kvm_gmem_get_pfn() support dealing + * with hugepages to a degree, but internally, guest_memfd currently + * assumes that all folios are order-0 and handling would need + * to be updated for anything otherwise (e.g. page-clearing + * operations). + */ + WARN_ON_ONCE(folio_order(folio)); + return folio; } =20 @@ -829,7 +838,7 @@ long kvm_gmem_populate(struct kvm *kvm, gfn_t start_gfn= , void __user *src, long struct kvm_memory_slot *slot; void __user *p; =20 - int ret =3D 0, max_order; + int ret =3D 0; long i; =20 lockdep_assert_held(&kvm->slots_lock); @@ -848,7 +857,7 @@ long kvm_gmem_populate(struct kvm *kvm, gfn_t start_gfn= , void __user *src, long filemap_invalidate_lock(file->f_mapping); =20 npages =3D min_t(ulong, slot->npages - (start_gfn - slot->base_gfn), npag= es); - for (i =3D 0; i < npages; i +=3D (1 << max_order)) { + for (i =3D 0; i < npages; i++) { struct folio *folio; gfn_t gfn =3D start_gfn + i; pgoff_t index =3D kvm_gmem_get_index(slot, gfn); @@ -860,7 +869,7 @@ long kvm_gmem_populate(struct kvm *kvm, gfn_t start_gfn= , void __user *src, long break; } =20 - folio =3D __kvm_gmem_get_pfn(file, slot, index, &pfn, &is_prepared, &max= _order); + folio =3D __kvm_gmem_get_pfn(file, slot, index, &pfn, &is_prepared, NULL= ); if (IS_ERR(folio)) { ret =3D PTR_ERR(folio); 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X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 15 Dec 2025 15:35:20.2424 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: be8a2d57-494f-4f86-f800-08de3bef8e40 X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=3dd8961f-e488-4e60-8e11-a82d994e183d;Ip=[165.204.84.17];Helo=[satlexmb07.amd.com] X-MS-Exchange-CrossTenant-AuthSource: SN1PEPF000252A3.namprd05.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: MN2PR12MB4270 Content-Type: text/plain; charset="utf-8" guest_memfd currently uses the folio uptodate flag to track: 1) whether or not a page has been cleared before initial usage 2) whether or not the architecture hooks have been issued to put the page in a private state as defined by the architecture In practice, 2) is only actually being tracked for SEV-SNP VMs, and there do not seem to be any plans/reasons that would suggest this will change in the future, so this additional tracking/complexity is not really providing any general benefit to guest_memfd users. Future plans around in-place conversion and hugepage support, where the per-folio uptodate flag is planned to be used purely to track the initial clearing of folios, whereas conversion operations could trigger multiple transitions between 'prepared' and 'unprepared' and thus need separate tracking, will make the burden of tracking this information within guest_memfd even more complex, since preparation generally happens during fault time, on the "read-side" of any global locks that might protect state tracked by guest_memfd, and so may require more complex locking schemes to allow for concurrent handling of page faults for multiple vCPUs where the "preparedness" state tracked by guest_memfd might need to be updated as part of handling the fault. Instead of keeping this current/future complexity within guest_memfd for what is essentially just SEV-SNP, just drop the tracking for 2) and have the arch-specific preparation hooks get triggered unconditionally on every fault so the arch-specific hooks can check the preparation state directly and decide whether or not a folio still needs additional preparation. In the case of SEV-SNP, the preparation state is already checked again via the preparation hooks to avoid double-preparation, so nothing extra needs to be done to update the handling of things there. Signed-off-by: Michael Roth Reviewed-By: Vishal Annapurve Reviewed-by: Pankaj Gupta Tested-By: Vishal Annapurve --- virt/kvm/guest_memfd.c | 44 ++++++++++++------------------------------ 1 file changed, 12 insertions(+), 32 deletions(-) diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c index 9dafa44838fe..8b1248f42aae 100644 --- a/virt/kvm/guest_memfd.c +++ b/virt/kvm/guest_memfd.c @@ -76,11 +76,6 @@ static int __kvm_gmem_prepare_folio(struct kvm *kvm, str= uct kvm_memory_slot *slo return 0; } =20 -static inline void kvm_gmem_mark_prepared(struct folio *folio) -{ - folio_mark_uptodate(folio); -} - /* * Process @folio, which contains @gfn, so that the guest can use it. * The folio must be locked and the gfn must be contained in @slot. @@ -90,13 +85,7 @@ static inline void kvm_gmem_mark_prepared(struct folio *= folio) static int kvm_gmem_prepare_folio(struct kvm *kvm, struct kvm_memory_slot = *slot, gfn_t gfn, struct folio *folio) { - unsigned long nr_pages, i; pgoff_t index; - int r; - - nr_pages =3D folio_nr_pages(folio); - for (i =3D 0; i < nr_pages; i++) - clear_highpage(folio_page(folio, i)); =20 /* * Preparing huge folios should always be safe, since it should @@ -114,11 +103,8 @@ static int kvm_gmem_prepare_folio(struct kvm *kvm, str= uct kvm_memory_slot *slot, WARN_ON(!IS_ALIGNED(slot->gmem.pgoff, folio_nr_pages(folio))); index =3D kvm_gmem_get_index(slot, gfn); index =3D ALIGN_DOWN(index, folio_nr_pages(folio)); - r =3D __kvm_gmem_prepare_folio(kvm, slot, index, folio); - if (!r) - kvm_gmem_mark_prepared(folio); =20 - return r; + return __kvm_gmem_prepare_folio(kvm, slot, index, folio); } =20 /* @@ -429,7 +415,7 @@ static vm_fault_t kvm_gmem_fault_user_mapping(struct vm= _fault *vmf) =20 if (!folio_test_uptodate(folio)) { clear_highpage(folio_page(folio, 0)); - kvm_gmem_mark_prepared(folio); + folio_mark_uptodate(folio); } =20 vmf->page =3D folio_file_page(folio, vmf->pgoff); @@ -766,7 +752,7 @@ void kvm_gmem_unbind(struct kvm_memory_slot *slot) static struct folio *__kvm_gmem_get_pfn(struct file *file, struct kvm_memory_slot *slot, pgoff_t index, kvm_pfn_t *pfn, - bool *is_prepared, int *max_order) + int *max_order) { struct file *slot_file =3D READ_ONCE(slot->gmem.file); struct gmem_file *f =3D file->private_data; @@ -796,7 +782,6 @@ static struct folio *__kvm_gmem_get_pfn(struct file *fi= le, if (max_order) *max_order =3D 0; =20 - *is_prepared =3D folio_test_uptodate(folio); return folio; } =20 @@ -806,19 +791,22 @@ int kvm_gmem_get_pfn(struct kvm *kvm, struct kvm_memo= ry_slot *slot, { pgoff_t index =3D kvm_gmem_get_index(slot, gfn); struct folio *folio; - bool is_prepared =3D false; int r =3D 0; =20 CLASS(gmem_get_file, file)(slot); if (!file) return -EFAULT; =20 - folio =3D __kvm_gmem_get_pfn(file, slot, index, pfn, &is_prepared, max_or= der); + folio =3D __kvm_gmem_get_pfn(file, slot, index, pfn, max_order); if (IS_ERR(folio)) return PTR_ERR(folio); =20 - if (!is_prepared) - r =3D kvm_gmem_prepare_folio(kvm, slot, gfn, folio); + if (!folio_test_uptodate(folio)) { + clear_highpage(folio_page(folio, 0)); + folio_mark_uptodate(folio); + } + + r =3D kvm_gmem_prepare_folio(kvm, slot, gfn, folio); =20 folio_unlock(folio); =20 @@ -861,7 +849,6 @@ long kvm_gmem_populate(struct kvm *kvm, gfn_t start_gfn= , void __user *src, long struct folio *folio; 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X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 15 Dec 2025 15:35:40.8519 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 2447d2f2-fedd-4966-d7e6-08de3bef9a89 X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=3dd8961f-e488-4e60-8e11-a82d994e183d;Ip=[165.204.84.17];Helo=[satlexmb07.amd.com] X-MS-Exchange-CrossTenant-AuthSource: SN1PEPF000252A3.namprd05.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: MN0PR12MB5836 Content-Type: text/plain; charset="utf-8" In the past, KVM_SEV_SNP_LAUNCH_UPDATE accepted a non-page-aligned 'uaddr' parameter to copy data from, but continuing to support this with new functionality like in-place conversion and hugepages in the pipeline has proven to be more trouble than it is worth, since there are no known users that have been identified who use a non-page-aligned 'uaddr' parameter. Rather than locking guest_memfd into continuing to support this, go ahead and document page-alignment as a requirement and begin enforcing this in the handling function. Signed-off-by: Michael Roth Reviewed-By: Vishal Annapurve --- Documentation/virt/kvm/x86/amd-memory-encryption.rst | 2 +- arch/x86/kvm/svm/sev.c | 6 +++++- 2 files changed, 6 insertions(+), 2 deletions(-) diff --git a/Documentation/virt/kvm/x86/amd-memory-encryption.rst b/Documen= tation/virt/kvm/x86/amd-memory-encryption.rst index 1ddb6a86ce7f..5a88d0197cb3 100644 --- a/Documentation/virt/kvm/x86/amd-memory-encryption.rst +++ b/Documentation/virt/kvm/x86/amd-memory-encryption.rst @@ -523,7 +523,7 @@ Returns: 0 on success, < 0 on error, -EAGAIN if caller = should retry =20 struct kvm_sev_snp_launch_update { __u64 gfn_start; /* Guest page number to load/encry= pt data into. */ - __u64 uaddr; /* Userspace address of data to be= loaded/encrypted. */ + __u64 uaddr; /* 4k-aligned address of data to b= e loaded/encrypted. */ __u64 len; /* 4k-aligned length in bytes to c= opy into guest memory.*/ __u8 type; /* The type of the guest pages bei= ng initialized. */ __u8 pad0; diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c index 362c6135401a..90c512ca24a9 100644 --- a/arch/x86/kvm/svm/sev.c +++ b/arch/x86/kvm/svm/sev.c @@ -2366,6 +2366,11 @@ static int snp_launch_update(struct kvm *kvm, struct= kvm_sev_cmd *argp) params.type !=3D KVM_SEV_SNP_PAGE_TYPE_CPUID)) return -EINVAL; =20 + src =3D params.type =3D=3D KVM_SEV_SNP_PAGE_TYPE_ZERO ? 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X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 15 Dec 2025 15:36:08.5477 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: acc023cb-672d-4819-5cbb-08de3befab0c X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=3dd8961f-e488-4e60-8e11-a82d994e183d;Ip=[165.204.84.17];Helo=[satlexmb07.amd.com] X-MS-Exchange-CrossTenant-AuthSource: SN1PEPF0002529D.namprd05.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: LV8PR12MB9692 Content-Type: text/plain; charset="utf-8" Since it was never possible to use a non-PAGE_SIZE-aligned @source_addr, go ahead and document this as a requirement. This is in preparation for enforcing page-aligned @source_addr for all architectures in guest_memfd. Signed-off-by: Michael Roth Reviewed-By: Vishal Annapurve --- Documentation/virt/kvm/x86/intel-tdx.rst | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/Documentation/virt/kvm/x86/intel-tdx.rst b/Documentation/virt/= kvm/x86/intel-tdx.rst index 5efac62c92c7..6a222e9d0954 100644 --- a/Documentation/virt/kvm/x86/intel-tdx.rst +++ b/Documentation/virt/kvm/x86/intel-tdx.rst @@ -156,7 +156,7 @@ KVM_TDX_INIT_MEM_REGION :Returns: 0 on success, <0 on error =20 Initialize @nr_pages TDX guest private memory starting from @gpa with user= space -provided data from @source_addr. +provided data from @source_addr. @source_addr must be PAGE_SIZE-aligned. =20 Note, before calling this sub command, memory attribute of the range [gpa, gpa + nr_pages] needs to be private. 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X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 15 Dec 2025 15:36:22.1407 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: bfb4c022-dcb2-48fe-39bb-08de3befb326 X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=3dd8961f-e488-4e60-8e11-a82d994e183d;Ip=[165.204.84.17];Helo=[satlexmb07.amd.com] X-MS-Exchange-CrossTenant-AuthSource: SN1PEPF000252A0.namprd05.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: CY5PR12MB6552 Content-Type: text/plain; charset="utf-8" Currently the post-populate callbacks handle copying source pages into private GPA ranges backed by guest_memfd, where kvm_gmem_populate() acquires the filemap invalidate lock, then calls a post-populate callback which may issue a get_user_pages() on the source pages prior to copying them into the private GPA (e.g. TDX). This will not be compatible with in-place conversion, where the userspace page fault path will attempt to acquire filemap invalidate lock while holding the mm->mmap_lock, leading to a potential ABBA deadlock[1]. Address this by hoisting the GUP above the filemap invalidate lock so that these page faults path can be taken early, prior to acquiring the filemap invalidate lock. It's not currently clear whether this issue is reachable with the current implementation of guest_memfd, which doesn't support in-place conversion, however it does provide a consistent mechanism to provide stable source/target PFNs to callbacks rather than punting to vendor-specific code, which allows for more commonality across architectures, which may be worthwhile even without in-place conversion. As part of this change, also begin enforcing that the 'src' argument to kvm_gmem_populate() must be page-aligned, as this greatly reduces the complexity around how the post-populate callbacks are implemented, and since no current in-tree users support using a non-page-aligned 'src' argument. Suggested-by: Sean Christopherson Co-developed-by: Sean Christopherson Signed-off-by: Sean Christopherson Co-developed-by: Vishal Annapurve Signed-off-by: Vishal Annapurve Signed-off-by: Michael Roth Tested-By: Vishal Annapurve --- arch/x86/kvm/svm/sev.c | 32 ++++++++------- arch/x86/kvm/vmx/tdx.c | 15 +------ include/linux/kvm_host.h | 4 +- virt/kvm/guest_memfd.c | 84 +++++++++++++++++++++++++++------------- 4 files changed, 77 insertions(+), 58 deletions(-) diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c index 90c512ca24a9..11ae008aec8a 100644 --- a/arch/x86/kvm/svm/sev.c +++ b/arch/x86/kvm/svm/sev.c @@ -2268,7 +2268,7 @@ struct sev_gmem_populate_args { }; =20 static int sev_gmem_post_populate(struct kvm *kvm, gfn_t gfn, kvm_pfn_t pf= n, - void __user *src, void *opaque) + struct page *src_page, void *opaque) { struct sev_gmem_populate_args *sev_populate_args =3D opaque; struct sev_data_snp_launch_update fw_args =3D {0}; @@ -2277,7 +2277,7 @@ static int sev_gmem_post_populate(struct kvm *kvm, gf= n_t gfn, kvm_pfn_t pfn, int level; int ret; =20 - if (WARN_ON_ONCE(sev_populate_args->type !=3D KVM_SEV_SNP_PAGE_TYPE_ZERO = && !src)) + if (WARN_ON_ONCE(sev_populate_args->type !=3D KVM_SEV_SNP_PAGE_TYPE_ZERO = && !src_page)) return -EINVAL; =20 ret =3D snp_lookup_rmpentry((u64)pfn, &assigned, &level); @@ -2288,14 +2288,14 @@ static int sev_gmem_post_populate(struct kvm *kvm, = gfn_t gfn, kvm_pfn_t pfn, goto out; } =20 - if (src) { - void *vaddr =3D kmap_local_pfn(pfn); + if (src_page) { + void *src_vaddr =3D kmap_local_pfn(page_to_pfn(src_page)); + void *dst_vaddr =3D kmap_local_pfn(pfn); =20 - if (copy_from_user(vaddr, src, PAGE_SIZE)) { - ret =3D -EFAULT; - goto out; - } - kunmap_local(vaddr); + memcpy(dst_vaddr, src_vaddr, PAGE_SIZE); + + kunmap_local(src_vaddr); + kunmap_local(dst_vaddr); } =20 ret =3D rmp_make_private(pfn, gfn << PAGE_SHIFT, PG_LEVEL_4K, @@ -2325,17 +2325,19 @@ static int sev_gmem_post_populate(struct kvm *kvm, = gfn_t gfn, kvm_pfn_t pfn, if (ret && !snp_page_reclaim(kvm, pfn) && sev_populate_args->type =3D=3D KVM_SEV_SNP_PAGE_TYPE_CPUID && sev_populate_args->fw_error =3D=3D SEV_RET_INVALID_PARAM) { - void *vaddr =3D kmap_local_pfn(pfn); + void *src_vaddr =3D kmap_local_pfn(page_to_pfn(src_page)); + void *dst_vaddr =3D kmap_local_pfn(pfn); =20 - if (copy_to_user(src, vaddr, PAGE_SIZE)) - pr_debug("Failed to write CPUID page back to userspace\n"); + memcpy(src_vaddr, dst_vaddr, PAGE_SIZE); =20 - kunmap_local(vaddr); + kunmap_local(src_vaddr); + kunmap_local(dst_vaddr); } =20 out: - pr_debug("%s: exiting with return code %d (fw_error %d)\n", - __func__, ret, sev_populate_args->fw_error); + if (ret) + pr_debug("%s: error updating GFN %llx, return code %d (fw_error %d)\n", + __func__, gfn, ret, sev_populate_args->fw_error); return ret; } =20 diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c index 4fb042ce8ed1..3eb597c0e79f 100644 --- a/arch/x86/kvm/vmx/tdx.c +++ b/arch/x86/kvm/vmx/tdx.c @@ -3118,34 +3118,21 @@ struct tdx_gmem_post_populate_arg { }; =20 static int tdx_gmem_post_populate(struct kvm *kvm, gfn_t gfn, kvm_pfn_t pf= n, - void __user *src, void *_arg) + struct page *src_page, void *_arg) { struct tdx_gmem_post_populate_arg *arg =3D _arg; struct kvm_tdx *kvm_tdx =3D to_kvm_tdx(kvm); u64 err, entry, level_state; gpa_t gpa =3D gfn_to_gpa(gfn); - struct page *src_page; int ret, i; =20 if (KVM_BUG_ON(kvm_tdx->page_add_src, kvm)) return -EIO; =20 - /* - * Get the source page if it has been faulted in. Return failure if the - * source page has been swapped out or unmapped in primary memory. - */ - ret =3D get_user_pages_fast((unsigned long)src, 1, 0, &src_page); - if (ret < 0) - return ret; - if (ret !=3D 1) - return -ENOMEM; - kvm_tdx->page_add_src =3D src_page; ret =3D kvm_tdp_mmu_map_private_pfn(arg->vcpu, gfn, pfn); kvm_tdx->page_add_src =3D NULL; =20 - put_page(src_page); - if (ret || !(arg->flags & KVM_TDX_MEASURE_MEMORY_REGION)) return ret; =20 diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h index 1d0cee72e560..49c0cfe24fd8 100644 --- a/include/linux/kvm_host.h +++ b/include/linux/kvm_host.h @@ -2566,7 +2566,7 @@ int kvm_arch_gmem_prepare(struct kvm *kvm, gfn_t gfn,= kvm_pfn_t pfn, int max_ord * @gfn: starting GFN to be populated * @src: userspace-provided buffer containing data to copy into GFN range * (passed to @post_populate, and incremented on each iteration - * if not NULL) + * if not NULL). Must be page-aligned. * @npages: number of pages to copy from userspace-buffer * @post_populate: callback to issue for each gmem page that backs the GPA * range @@ -2581,7 +2581,7 @@ int kvm_arch_gmem_prepare(struct kvm *kvm, gfn_t gfn,= kvm_pfn_t pfn, int max_ord * Returns the number of pages that were populated. */ typedef int (*kvm_gmem_populate_cb)(struct kvm *kvm, gfn_t gfn, kvm_pfn_t = pfn, - void __user *src, void *opaque); + struct page *page, void *opaque); =20 long kvm_gmem_populate(struct kvm *kvm, gfn_t gfn, void __user *src, long = npages, kvm_gmem_populate_cb post_populate, void *opaque); diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c index 8b1248f42aae..18ae59b92257 100644 --- a/virt/kvm/guest_memfd.c +++ b/virt/kvm/guest_memfd.c @@ -820,12 +820,48 @@ int kvm_gmem_get_pfn(struct kvm *kvm, struct kvm_memo= ry_slot *slot, EXPORT_SYMBOL_FOR_KVM_INTERNAL(kvm_gmem_get_pfn); =20 #ifdef CONFIG_HAVE_KVM_ARCH_GMEM_POPULATE + +static long __kvm_gmem_populate(struct kvm *kvm, struct kvm_memory_slot *s= lot, + struct file *file, gfn_t gfn, struct page *src_page, + kvm_gmem_populate_cb post_populate, void *opaque) +{ + pgoff_t index =3D kvm_gmem_get_index(slot, gfn); + struct folio *folio; + kvm_pfn_t pfn; + int ret; + + filemap_invalidate_lock(file->f_mapping); + + folio =3D __kvm_gmem_get_pfn(file, slot, index, &pfn, NULL); + if (IS_ERR(folio)) { + ret =3D PTR_ERR(folio); + goto out_unlock; + } + + folio_unlock(folio); + + if (!kvm_range_has_memory_attributes(kvm, gfn, gfn + 1, + KVM_MEMORY_ATTRIBUTE_PRIVATE, + KVM_MEMORY_ATTRIBUTE_PRIVATE)) { + ret =3D -EINVAL; + goto out_put_folio; + } + + ret =3D post_populate(kvm, gfn, pfn, src_page, opaque); + if (!ret) + folio_mark_uptodate(folio); + +out_put_folio: + folio_put(folio); +out_unlock: + filemap_invalidate_unlock(file->f_mapping); + return ret; +} + long kvm_gmem_populate(struct kvm *kvm, gfn_t start_gfn, void __user *src,= long npages, kvm_gmem_populate_cb post_populate, void *opaque) { struct kvm_memory_slot *slot; - void __user *p; - int ret =3D 0; long i; =20 @@ -834,6 +870,9 @@ long kvm_gmem_populate(struct kvm *kvm, gfn_t start_gfn= , void __user *src, long if (WARN_ON_ONCE(npages <=3D 0)) return -EINVAL; =20 + if (WARN_ON_ONCE(!PAGE_ALIGNED(src))) + return -EINVAL; + slot =3D gfn_to_memslot(kvm, start_gfn); if (!kvm_slot_has_gmem(slot)) return -EINVAL; @@ -842,47 +881,38 @@ long kvm_gmem_populate(struct kvm *kvm, gfn_t start_g= fn, void __user *src, long if (!file) return -EFAULT; =20 - filemap_invalidate_lock(file->f_mapping); - npages =3D min_t(ulong, slot->npages - (start_gfn - slot->base_gfn), npag= es); for (i =3D 0; i < npages; i++) { - struct folio *folio; - gfn_t gfn =3D start_gfn + i; - pgoff_t index =3D kvm_gmem_get_index(slot, gfn); - kvm_pfn_t pfn; + struct page *src_page =3D NULL; + void __user *p; =20 if (signal_pending(current)) { ret =3D -EINTR; break; } =20 - folio =3D __kvm_gmem_get_pfn(file, slot, index, &pfn, NULL); - if (IS_ERR(folio)) { - ret =3D PTR_ERR(folio); - break; - } + p =3D src ? src + i * PAGE_SIZE : NULL; =20 - folio_unlock(folio); + if (p) { + ret =3D get_user_pages_fast((unsigned long)p, 1, 0, &src_page); + if (ret < 0) + break; + if (ret !=3D 1) { + ret =3D -ENOMEM; + break; + } + } =20 - ret =3D -EINVAL; - if (!kvm_range_has_memory_attributes(kvm, gfn, gfn + 1, - KVM_MEMORY_ATTRIBUTE_PRIVATE, - KVM_MEMORY_ATTRIBUTE_PRIVATE)) - goto put_folio_and_exit; + ret =3D __kvm_gmem_populate(kvm, slot, file, start_gfn + i, src_page, + post_populate, opaque); =20 - p =3D src ? src + i * PAGE_SIZE : NULL; - ret =3D post_populate(kvm, gfn, pfn, p, opaque); - if (!ret) - folio_mark_uptodate(folio); + if (src_page) + put_page(src_page); =20 -put_folio_and_exit: - folio_put(folio); if (ret) break; } =20 - filemap_invalidate_unlock(file->f_mapping); - return ret && !i ? ret : i; } EXPORT_SYMBOL_FOR_KVM_INTERNAL(kvm_gmem_populate); --=20 2.25.1