| Message ID | 0996e2f1b3e5c72150708b10bff57ad726c69e4b.1724741926.git.kai.huang@intel.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | TDX host: metadata reading tweaks, bug fix and info dump | expand |
On 27/08/24 10:14, Kai Huang wrote: > Old TDX modules can clobber RBP in the TDH.VP.ENTER SEAMCALL. However > RBP is used as frame pointer in the x86_64 calling convention, and > clobbering RBP could result in bad things like being unable to unwind > the stack if any non-maskable exceptions (NMI, #MC etc) happens in that > gap. > > A new "NO_RBP_MOD" feature was introduced to more recent TDX modules to > not clobber RBP. This feature is reported in the TDX_FEATURES0 global > metadata field via bit 18. > > Don't initialize the TDX module if this feature is not supported [1]. > > Link: https://lore.kernel.org/all/c0067319-2653-4cbd-8fee-1ccf21b1e646@suse.com/T/#mef98469c51e2382ead2c537ea189752360bd2bef [1] > Signed-off-by: Kai Huang <kai.huang@intel.com> > Reviewed-by: Nikolay Borisov <nik.borisov@suse.com> Reviewed-by: Adrian Hunter <adrian.hunter@intel.com> > --- > > v2 -> v3: > - check_module_compatibility() -> check_features(). > - Improve error message. > > https://lore.kernel.org/kvm/cover.1721186590.git.kai.huang@intel.com/T/#md9e2eeef927838cbf20d7b361cdbea518b8aec50 > > --- > arch/x86/virt/vmx/tdx/tdx.c | 17 +++++++++++++++++ > arch/x86/virt/vmx/tdx/tdx.h | 3 +++ > 2 files changed, 20 insertions(+) > > diff --git a/arch/x86/virt/vmx/tdx/tdx.c b/arch/x86/virt/vmx/tdx/tdx.c > index fa335ab1ae92..032a53ddf5bc 100644 > --- a/arch/x86/virt/vmx/tdx/tdx.c > +++ b/arch/x86/virt/vmx/tdx/tdx.c > @@ -454,6 +454,18 @@ static int get_tdx_sys_info(struct tdx_sys_info *sysinfo) > return get_tdx_sys_info_tdmr(&sysinfo->tdmr); > } > > +static int check_features(struct tdx_sys_info *sysinfo) > +{ > + u64 tdx_features0 = sysinfo->features.tdx_features0; > + > + if (!(tdx_features0 & TDX_FEATURES0_NO_RBP_MOD)) { > + pr_err("frame pointer (RBP) clobber bug present, upgrade TDX module\n"); > + return -EINVAL; > + } > + > + return 0; > +} > + > /* Calculate the actual TDMR size */ > static int tdmr_size_single(u16 max_reserved_per_tdmr) > { > @@ -1235,6 +1247,11 @@ static int init_tdx_module(void) > > print_basic_sys_info(&sysinfo); > > + /* Check whether the kernel can support this module */ > + ret = check_features(&sysinfo); > + if (ret) > + return ret; > + > /* > * To keep things simple, assume that all TDX-protected memory > * will come from the page allocator. Make sure all pages in the > diff --git a/arch/x86/virt/vmx/tdx/tdx.h b/arch/x86/virt/vmx/tdx/tdx.h > index e7bed9e717c7..831361e6d0fb 100644 > --- a/arch/x86/virt/vmx/tdx/tdx.h > +++ b/arch/x86/virt/vmx/tdx/tdx.h > @@ -154,6 +154,9 @@ struct tdx_sys_info_features { > u64 tdx_features0; > }; > > +/* Architectural bit definitions of TDX_FEATURES0 metadata field */ > +#define TDX_FEATURES0_NO_RBP_MOD _BITULL(18) > + > /* Class "TDX Module Version" */ > struct tdx_sys_info_version { > u16 major;
How about:
Subject: x86/virt/tdx: Require the module to assert it has the NO_RBP_MOD mitigation
...to avoid the double negative.
Kai Huang wrote:
> Old TDX modules can clobber RBP in the TDH.VP.ENTER SEAMCALL. However
> RBP is used as frame pointer in the x86_64 calling convention, and
> clobbering RBP could result in bad things like being unable to unwind
> the stack if any non-maskable exceptions (NMI, #MC etc) happens in that
> gap.
>
> A new "NO_RBP_MOD" feature was introduced to more recent TDX modules to
> not clobber RBP. This feature is reported in the TDX_FEATURES0 global
> metadata field via bit 18.
>
> Don't initialize the TDX module if this feature is not supported [1].
>
> Link: https://lore.kernel.org/all/c0067319-2653-4cbd-8fee-1ccf21b1e646@suse.com/T/#mef98469c51e2382ead2c537ea189752360bd2bef [1]
Trim this to the direct message-id format, but otherwise:
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
On Fri, 2024-09-06 at 16:36 -0700, Dan Williams wrote: > How about: > > Subject: x86/virt/tdx: Require the module to assert it has the NO_RBP_MOD mitigation > > ...to avoid the double negative. Will do. Thanks. > > Kai Huang wrote: > > Old TDX modules can clobber RBP in the TDH.VP.ENTER SEAMCALL. However > > RBP is used as frame pointer in the x86_64 calling convention, and > > clobbering RBP could result in bad things like being unable to unwind > > the stack if any non-maskable exceptions (NMI, #MC etc) happens in that > > gap. > > > > A new "NO_RBP_MOD" feature was introduced to more recent TDX modules to > > not clobber RBP. This feature is reported in the TDX_FEATURES0 global > > metadata field via bit 18. > > > > Don't initialize the TDX module if this feature is not supported [1]. > > > > Link: https://lore.kernel.org/all/c0067319-2653-4cbd-8fee-1ccf21b1e646@suse.com/T/#mef98469c51e2382ead2c537ea189752360bd2bef [1] > > Trim this to the direct message-id format, but otherwise: Will do. If I got it right, the link with message-id should be: https://lore.kernel.org/all/fc0e8ab7-86d4-4428-be31-82e1ece6dd21@intel.com/ > > Reviewed-by: Dan Williams <dan.j.williams@intel.com> Thanks.
diff --git a/arch/x86/virt/vmx/tdx/tdx.c b/arch/x86/virt/vmx/tdx/tdx.c index fa335ab1ae92..032a53ddf5bc 100644 --- a/arch/x86/virt/vmx/tdx/tdx.c +++ b/arch/x86/virt/vmx/tdx/tdx.c @@ -454,6 +454,18 @@ static int get_tdx_sys_info(struct tdx_sys_info *sysinfo) return get_tdx_sys_info_tdmr(&sysinfo->tdmr); } +static int check_features(struct tdx_sys_info *sysinfo) +{ + u64 tdx_features0 = sysinfo->features.tdx_features0; + + if (!(tdx_features0 & TDX_FEATURES0_NO_RBP_MOD)) { + pr_err("frame pointer (RBP) clobber bug present, upgrade TDX module\n"); + return -EINVAL; + } + + return 0; +} + /* Calculate the actual TDMR size */ static int tdmr_size_single(u16 max_reserved_per_tdmr) { @@ -1235,6 +1247,11 @@ static int init_tdx_module(void) print_basic_sys_info(&sysinfo); + /* Check whether the kernel can support this module */ + ret = check_features(&sysinfo); + if (ret) + return ret; + /* * To keep things simple, assume that all TDX-protected memory * will come from the page allocator. Make sure all pages in the diff --git a/arch/x86/virt/vmx/tdx/tdx.h b/arch/x86/virt/vmx/tdx/tdx.h index e7bed9e717c7..831361e6d0fb 100644 --- a/arch/x86/virt/vmx/tdx/tdx.h +++ b/arch/x86/virt/vmx/tdx/tdx.h @@ -154,6 +154,9 @@ struct tdx_sys_info_features { u64 tdx_features0; }; +/* Architectural bit definitions of TDX_FEATURES0 metadata field */ +#define TDX_FEATURES0_NO_RBP_MOD _BITULL(18) + /* Class "TDX Module Version" */ struct tdx_sys_info_version { u16 major;