Received-SPF: pass (google.com: domain of linux-kernel+bounces-151728-linux.lists.archive=gmail.com@vger.kernel.org designates 2604:1380:45d1:ec00::1 as permitted sender) client-ip=2604:1380:45d1:ec00::1;
Precedence: bulk
MIME-Version: 1.0
References: <20240418194133.1452059-1-michael.roth@amd.com>
 <20240418194133.1452059-11-michael.roth@amd.com> <CABgObfaj4-GXSCWFx+=o7Cdhouo8Ftz4YEWgsQ2XNRc3KD-jPg@mail.gmail.com>
In-Reply-To: <CABgObfaj4-GXSCWFx+=o7Cdhouo8Ftz4YEWgsQ2XNRc3KD-jPg@mail.gmail.com>
From: Paolo Bonzini <pbonzini@redhat.com>
Date: Fri, 19 Apr 2024 18:12:11 +0200
Message-ID: <CABgObfa9Ya-taTKkRbmUQGcwqYG+6cs_=kwdqzmFrbgBQG3Epw@mail.gmail.com>
Subject: Re: [PATCH v13 10/26] KVM: SEV: Add KVM_SEV_SNP_LAUNCH_UPDATE command
To: Michael Roth <michael.roth@amd.com>
Cc: kvm@vger.kernel.org, linux-coco@lists.linux.dev, linux-mm@kvack.org, 
	linux-crypto@vger.kernel.org, x86@kernel.org, linux-kernel@vger.kernel.org, 
	tglx@linutronix.de, mingo@redhat.com, jroedel@suse.de, 
	thomas.lendacky@amd.com, hpa@zytor.com, ardb@kernel.org, seanjc@google.com, 
	vkuznets@redhat.com, jmattson@google.com, luto@kernel.org, 
	dave.hansen@linux.intel.com, slp@redhat.com, pgonda@google.com, 
	peterz@infradead.org, srinivas.pandruvada@linux.intel.com, 
	rientjes@google.com, dovmurik@linux.ibm.com, tobin@ibm.com, bp@alien8.de, 
	vbabka@suse.cz, kirill@shutemov.name, ak@linux.intel.com, tony.luck@intel.com, 
	sathyanarayanan.kuppuswamy@linux.intel.com, alpergun@google.com, 
	jarkko@kernel.org, ashish.kalra@amd.com, nikunj.dadhania@amd.com, 
	pankaj.gupta@amd.com, liam.merwick@oracle.com, 
	Brijesh Singh <brijesh.singh@amd.com>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable

On Fri, Apr 19, 2024 at 1:56=E2=80=AFPM Paolo Bonzini <pbonzini@redhat.com>=
 wrote:
> > +       ret =3D kvm_gmem_populate(kvm, params.gfn_start, u64_to_user_pt=
r(params.uaddr),
> > +                               npages, sev_gmem_post_populate, &sev_po=
pulate_args);
> > +       if (ret < 0) {
> > +               argp->error =3D sev_populate_args.fw_error;
> > +               pr_debug("%s: kvm_gmem_populate failed, ret %d (fw_erro=
r %d)\n",
> > +                        __func__, ret, argp->error);
> > +       } else if (ret < npages) {
> > +               params.len =3D ret * PAGE_SIZE;
> > +               ret =3D -EINTR;
>
> This probably should 1) update also gfn_start and uaddr 2) return 0
> for consistency with the planned KVM_PRE_FAULT_MEMORY ioctl (aka
> KVM_MAP_MEMORY).

To be more precise, params.len should be set to the number of bytes *left*,=
 i.e.

   params.len -=3D ret * PAGE_SIZE;
   params.gfn_start +=3D ret * PAGE_SIZE;
   if (params.type !=3D KVM_SEV_SNP_PAGE_TYPE_ZERO)
       params.uaddr +=3D ret * PAGE_SIZE;

Also this patch needs some other changes:

1) snp_launch_update() should have something like this:

   src =3D params.type =3D=3D KVM_SEV_SNP_PAGE_TYPE_ZERO ? NULL :
u64_to_user_ptr(params.uaddr),;

so that then...

> +               vaddr =3D kmap_local_pfn(pfn + i);
> +               ret =3D copy_from_user(vaddr, src + i * PAGE_SIZE, PAGE_S=
IZE);
> +               if (ret) {
> +                       pr_debug("Failed to copy source page into GFN 0x%=
llx\n", gfn);
> +                       goto out_unmap;
> +               }

.. the copy can be done only if src is non-NULL

2) the struct should have some more fields

> +        struct kvm_sev_snp_launch_update {
> +                __u64 gfn_start;        /* Guest page number to load/enc=
rypt data into. */
> +                __u64 uaddr;            /* Userspace address of data to =
be loaded/encrypted. */
> +                __u32 len;              /* 4k-aligned length in bytes to=
 copy into guest memory.*/
> +                __u8 type;              /* The type of the guest pages b=
eing initialized. */

__u8 pad0;
__u16 flags;   // must be zero
__u64 pad1[5];

with accompanying flags check in snp_launch_update().

If you think IMI can be implemented already (with a bit in flags) go
ahead and do it.

Paolo