lkml.org 
[lkml]   [2022]   [Aug]   [2]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    Date
    From
    SubjectRe: [PATCH Part2 v6 26/49] KVM: SVM: Add KVM_SEV_SNP_LAUNCH_UPDATE command
    On Mon, Jun 20, 2022 at 11:08:05PM +0000, Ashish Kalra wrote:
    > From: Brijesh Singh <brijesh.singh@amd.com>
    >
    > The KVM_SEV_SNP_LAUNCH_UPDATE command can be used to insert data into the
    > guest's memory. The data is encrypted with the cryptographic context
    > created with the KVM_SEV_SNP_LAUNCH_START.
    >
    > In addition to the inserting data, it can insert a two special pages
    > into the guests memory: the secrets page and the CPUID page.
    >
    > While terminating the guest, reclaim the guest pages added in the RMP
    > table. If the reclaim fails, then the page is no longer safe to be
    > released back to the system and leak them.

    From this paragraph I get a picture that reclaimer is failing "all the
    time", and that is totally normal and legit behaviour. Is this the case?

    Stimuli/conditions/something is mandatory if failure is mentioned in any
    context.

    >
    > For more information see the SEV-SNP specification.
    >
    > Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
    > ---
    > .../virt/kvm/x86/amd-memory-encryption.rst | 29 +++
    > arch/x86/kvm/svm/sev.c | 187 ++++++++++++++++++
    > include/uapi/linux/kvm.h | 19 ++
    > 3 files changed, 235 insertions(+)
    >
    > diff --git a/Documentation/virt/kvm/x86/amd-memory-encryption.rst b/Documentation/virt/kvm/x86/amd-memory-encryption.rst
    > index 878711f2dca6..62abd5c1f72b 100644
    > --- a/Documentation/virt/kvm/x86/amd-memory-encryption.rst
    > +++ b/Documentation/virt/kvm/x86/amd-memory-encryption.rst
    > @@ -486,6 +486,35 @@ Returns: 0 on success, -negative on error
    >
    > See the SEV-SNP specification for further detail on the launch input.
    >
    > +20. KVM_SNP_LAUNCH_UPDATE
    > +-------------------------
    > +
    > +The KVM_SNP_LAUNCH_UPDATE is used for encrypting a memory region. It also
    > +calculates a measurement of the memory contents. The measurement is a signature
    > +of the memory contents that can be sent to the guest owner as an attestation
    > +that the memory was encrypted correctly by the firmware.
    > +
    > +Parameters (in): struct kvm_snp_launch_update
    > +
    > +Returns: 0 on success, -negative on error
    > +
    > +::
    > +
    > + struct kvm_sev_snp_launch_update {
    > + __u64 start_gfn; /* Guest page number to start from. */
    > + __u64 uaddr; /* userspace address need to be encrypted */
    > + __u32 len; /* length of memory region */
    > + __u8 imi_page; /* 1 if memory is part of the IMI */
    > + __u8 page_type; /* page type */
    > + __u8 vmpl3_perms; /* VMPL3 permission mask */
    > + __u8 vmpl2_perms; /* VMPL2 permission mask */
    > + __u8 vmpl1_perms; /* VMPL1 permission mask */
    > + };
    > +
    > +See the SEV-SNP spec for further details on how to build the VMPL permission
    > +mask and page type.
    > +
    > +
    > References
    > ==========
    >
    > diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
    > index 41b83aa6b5f4..b5f0707d7ed6 100644
    > --- a/arch/x86/kvm/svm/sev.c
    > +++ b/arch/x86/kvm/svm/sev.c
    > @@ -18,6 +18,7 @@
    > #include <linux/processor.h>
    > #include <linux/trace_events.h>
    > #include <linux/hugetlb.h>
    > +#include <linux/sev.h>
    >
    > #include <asm/pkru.h>
    > #include <asm/trapnr.h>
    > @@ -233,6 +234,49 @@ static void sev_decommission(unsigned int handle)
    > sev_guest_decommission(&decommission, NULL);
    > }
    >
    > +static inline void snp_leak_pages(u64 pfn, enum pg_level level)
    > +{
    > + unsigned int npages = page_level_size(level) >> PAGE_SHIFT;
    > +
    > + WARN(1, "psc failed pfn 0x%llx pages %d (leaking)\n", pfn, npages);
    > +
    > + while (npages) {
    > + memory_failure(pfn, 0);
    > + dump_rmpentry(pfn);
    > + npages--;
    > + pfn++;
    > + }
    > +}
    > +
    > +static int snp_page_reclaim(u64 pfn)
    > +{
    > + struct sev_data_snp_page_reclaim data = {0};
    > + int err, rc;
    > +
    > + data.paddr = __sme_set(pfn << PAGE_SHIFT);
    > + rc = snp_guest_page_reclaim(&data, &err);
    > + if (rc) {
    > + /*
    > + * If the reclaim failed, then page is no longer safe
    > + * to use.
    > + */
    > + snp_leak_pages(pfn, PG_LEVEL_4K);
    > + }
    > +
    > + return rc;
    > +}
    > +
    > +static int host_rmp_make_shared(u64 pfn, enum pg_level level, bool leak)
    > +{
    > + int rc;
    > +
    > + rc = rmp_make_shared(pfn, level);
    > + if (rc && leak)
    > + snp_leak_pages(pfn, level);
    > +
    > + return rc;
    > +}
    > +
    > static void sev_unbind_asid(struct kvm *kvm, unsigned int handle)
    > {
    > struct sev_data_deactivate deactivate;
    > @@ -1902,6 +1946,123 @@ static int snp_launch_start(struct kvm *kvm, struct kvm_sev_cmd *argp)
    > return rc;
    > }
    >
    > +static bool is_hva_registered(struct kvm *kvm, hva_t hva, size_t len)
    > +{
    > + struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info;
    > + struct list_head *head = &sev->regions_list;
    > + struct enc_region *i;
    > +
    > + lockdep_assert_held(&kvm->lock);
    > +
    > + list_for_each_entry(i, head, list) {
    > + u64 start = i->uaddr;
    > + u64 end = start + i->size;
    > +
    > + if (start <= hva && end >= (hva + len))
    > + return true;
    > + }
    > +
    > + return false;
    > +}
    > +
    > +static int snp_launch_update(struct kvm *kvm, struct kvm_sev_cmd *argp)
    > +{
    > + struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info;
    > + struct sev_data_snp_launch_update data = {0};
    > + struct kvm_sev_snp_launch_update params;
    > + unsigned long npages, pfn, n = 0;
    > + int *error = &argp->error;
    > + struct page **inpages;
    > + int ret, i, level;
    > + u64 gfn;
    > +
    > + if (!sev_snp_guest(kvm))
    > + return -ENOTTY;
    > +
    > + if (!sev->snp_context)
    > + return -EINVAL;
    > +
    > + if (copy_from_user(&params, (void __user *)(uintptr_t)argp->data, sizeof(params)))
    > + return -EFAULT;
    > +
    > + /* Verify that the specified address range is registered. */
    > + if (!is_hva_registered(kvm, params.uaddr, params.len))
    > + return -EINVAL;
    > +
    > + /*
    > + * The userspace memory is already locked so technically we don't
    > + * need to lock it again. Later part of the function needs to know
    > + * pfn so call the sev_pin_memory() so that we can get the list of
    > + * pages to iterate through.
    > + */
    > + inpages = sev_pin_memory(kvm, params.uaddr, params.len, &npages, 1);
    > + if (!inpages)
    > + return -ENOMEM;
    > +
    > + /*
    > + * Verify that all the pages are marked shared in the RMP table before
    > + * going further. This is avoid the cases where the userspace may try
    > + * updating the same page twice.
    > + */
    > + for (i = 0; i < npages; i++) {
    > + if (snp_lookup_rmpentry(page_to_pfn(inpages[i]), &level) != 0) {
    > + sev_unpin_memory(kvm, inpages, npages);
    > + return -EFAULT;
    > + }
    > + }
    > +
    > + gfn = params.start_gfn;
    > + level = PG_LEVEL_4K;
    > + data.gctx_paddr = __psp_pa(sev->snp_context);
    > +
    > + for (i = 0; i < npages; i++) {
    > + pfn = page_to_pfn(inpages[i]);
    > +
    > + ret = rmp_make_private(pfn, gfn << PAGE_SHIFT, level, sev_get_asid(kvm), true);
    > + if (ret) {
    > + ret = -EFAULT;
    > + goto e_unpin;
    > + }
    > +
    > + n++;
    > + data.address = __sme_page_pa(inpages[i]);
    > + data.page_size = X86_TO_RMP_PG_LEVEL(level);
    > + data.page_type = params.page_type;
    > + data.vmpl3_perms = params.vmpl3_perms;
    > + data.vmpl2_perms = params.vmpl2_perms;
    > + data.vmpl1_perms = params.vmpl1_perms;
    > + ret = __sev_issue_cmd(argp->sev_fd, SEV_CMD_SNP_LAUNCH_UPDATE, &data, error);
    > + if (ret) {
    > + /*
    > + * If the command failed then need to reclaim the page.
    > + */
    > + snp_page_reclaim(pfn);
    > + goto e_unpin;
    > + }
    > +
    > + gfn++;
    > + }
    > +
    > +e_unpin:
    > + /* Content of memory is updated, mark pages dirty */
    > + for (i = 0; i < n; i++) {
    > + set_page_dirty_lock(inpages[i]);
    > + mark_page_accessed(inpages[i]);
    > +
    > + /*
    > + * If its an error, then update RMP entry to change page ownership
    > + * to the hypervisor.
    > + */
    > + if (ret)
    > + host_rmp_make_shared(pfn, level, true);
    > + }
    > +
    > + /* Unlock the user pages */
    > + sev_unpin_memory(kvm, inpages, npages);
    > +
    > + return ret;
    > +}
    > +
    > int sev_mem_enc_ioctl(struct kvm *kvm, void __user *argp)
    > {
    > struct kvm_sev_cmd sev_cmd;
    > @@ -1995,6 +2156,9 @@ int sev_mem_enc_ioctl(struct kvm *kvm, void __user *argp)
    > case KVM_SEV_SNP_LAUNCH_START:
    > r = snp_launch_start(kvm, &sev_cmd);
    > break;
    > + case KVM_SEV_SNP_LAUNCH_UPDATE:
    > + r = snp_launch_update(kvm, &sev_cmd);
    > + break;
    > default:
    > r = -EINVAL;
    > goto out;
    > @@ -2113,6 +2277,29 @@ find_enc_region(struct kvm *kvm, struct kvm_enc_region *range)
    > static void __unregister_enc_region_locked(struct kvm *kvm,
    > struct enc_region *region)
    > {
    > + unsigned long i, pfn;
    > + int level;
    > +
    > + /*
    > + * The guest memory pages are assigned in the RMP table. Unassign it
    > + * before releasing the memory.
    > + */
    > + if (sev_snp_guest(kvm)) {
    > + for (i = 0; i < region->npages; i++) {
    > + pfn = page_to_pfn(region->pages[i]);
    > +
    > + if (!snp_lookup_rmpentry(pfn, &level))
    > + continue;
    > +
    > + cond_resched();
    > +
    > + if (level > PG_LEVEL_4K)
    > + pfn &= ~(KVM_PAGES_PER_HPAGE(PG_LEVEL_2M) - 1);
    > +
    > + host_rmp_make_shared(pfn, level, true);
    > + }
    > + }
    > +
    > sev_unpin_memory(kvm, region->pages, region->npages);
    > list_del(&region->list);
    > kfree(region);
    > diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
    > index 0cb119d66ae5..9b36b07414ea 100644
    > --- a/include/uapi/linux/kvm.h
    > +++ b/include/uapi/linux/kvm.h
    > @@ -1813,6 +1813,7 @@ enum sev_cmd_id {
    > /* SNP specific commands */
    > KVM_SEV_SNP_INIT,
    > KVM_SEV_SNP_LAUNCH_START,
    > + KVM_SEV_SNP_LAUNCH_UPDATE,
    >
    > KVM_SEV_NR_MAX,
    > };
    > @@ -1929,6 +1930,24 @@ struct kvm_sev_snp_launch_start {
    > __u8 pad[6];
    > };
    >
    > +#define KVM_SEV_SNP_PAGE_TYPE_NORMAL 0x1
    > +#define KVM_SEV_SNP_PAGE_TYPE_VMSA 0x2
    > +#define KVM_SEV_SNP_PAGE_TYPE_ZERO 0x3
    > +#define KVM_SEV_SNP_PAGE_TYPE_UNMEASURED 0x4
    > +#define KVM_SEV_SNP_PAGE_TYPE_SECRETS 0x5
    > +#define KVM_SEV_SNP_PAGE_TYPE_CPUID 0x6
    > +
    > +struct kvm_sev_snp_launch_update {
    > + __u64 start_gfn;
    > + __u64 uaddr;
    > + __u32 len;
    > + __u8 imi_page;
    > + __u8 page_type;
    > + __u8 vmpl3_perms;
    > + __u8 vmpl2_perms;
    > + __u8 vmpl1_perms;
    > +};
    > +
    > #define KVM_DEV_ASSIGN_ENABLE_IOMMU (1 << 0)
    > #define KVM_DEV_ASSIGN_PCI_2_3 (1 << 1)
    > #define KVM_DEV_ASSIGN_MASK_INTX (1 << 2)
    > --
    > 2.25.1
    >

    BR, Jarkko

    \
     
     \ /
      Last update: 2022-08-02 14:51    [W:3.999 / U:0.160 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site