Commit dcbcc232 authored by Michael Roth's avatar Michael Roth Committed by Sean Christopherson
Browse files

KVM: SEV: Document/enforce page-alignment for KVM_SEV_SNP_LAUNCH_UPDATE 



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.

Reviewed-by: default avatarVishal Annapurve <vannapurve@google.com>
Tested-by: default avatarKai Huang <kai.huang@intel.com>
Signed-off-by: default avatarMichael Roth <michael.roth@amd.com>
Link: https://patch.msgid.link/20260108214622.1084057-5-michael.roth@amd.com


Signed-off-by: default avatarSean Christopherson <seanjc@google.com>
parent 8622ef05

Documentation/virt/kvm/x86/amd-memory-encryption.rst

+1 −1
Original line number Diff line number Diff line
@@ -523,7 +523,7 @@ Returns: 0 on success, < 0 on error, -EAGAIN if caller should retry 


        struct kvm_sev_snp_launch_update {

                __u64 gfn_start;        /* Guest page number to load/encrypt data into. */

                __u64 uaddr;            /* Userspace address of data to be loaded/encrypted. */

                __u64 uaddr;            /* 4k-aligned address of data to be loaded/encrypted. */

                __u64 len;              /* 4k-aligned length in bytes to copy into guest memory.*/

                __u8 type;              /* The type of the guest pages being initialized. */

                __u8 pad0;

arch/x86/kvm/svm/sev.c

+5 −1
Original line number Diff line number Diff line
@@ -2367,6 +2367,11 @@ static int snp_launch_update(struct kvm *kvm, struct kvm_sev_cmd *argp) 
	     params.type != KVM_SEV_SNP_PAGE_TYPE_CPUID))

		return -EINVAL;



	src = params.type == KVM_SEV_SNP_PAGE_TYPE_ZERO ? NULL : u64_to_user_ptr(params.uaddr);



	if (!PAGE_ALIGNED(src))

		return -EINVAL;



	npages = params.len / PAGE_SIZE;



	/*
@@ -2398,7 +2403,6 @@ static int snp_launch_update(struct kvm *kvm, struct kvm_sev_cmd *argp) 


	sev_populate_args.sev_fd = argp->sev_fd;

	sev_populate_args.type = params.type;

	src = params.type == KVM_SEV_SNP_PAGE_TYPE_ZERO ? NULL : u64_to_user_ptr(params.uaddr);



	count = kvm_gmem_populate(kvm, params.gfn_start, src, npages,

				  sev_gmem_post_populate, &sev_populate_args);