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Message-ID: <nvnjhx235xbsrnq3t6zbkgogsdizbigrlgqyx6muyj6k2g34gq@zzn6bqvoha45>
Date: Mon, 17 Mar 2025 11:38:45 +0200
From: "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>
To: Dan Williams <dan.j.williams@...el.com>
Cc: Alexey Gladkov <legion@...nel.org>, x86@...nel.org,
linux-kernel@...r.kernel.org, linux-coco@...ts.linux.dev,
Alexey Gladkov <alexey.gladkov@...el.com>, "H . Peter Anvin" <hpa@...or.com>,
Joerg Roedel <jroedel@...e.de>, Juergen Gross <jgross@...e.com>, Larry.Dewey@....com,
Nikunj A Dadhania <nikunj@....com>, Tom Lendacky <thomas.lendacky@....com>
Subject: Re: [RFC PATCH v1 1/3] x86/tdx: Make TDX metadata available via SYSFS
On Fri, Mar 14, 2025 at 04:42:31PM -0700, Dan Williams wrote:
> Alexey Gladkov wrote:
> > From: "Alexey Gladkov (Intel)" <legion@...nel.org>
> >
> > Expose the TDX module information to userspace. The version information
> > is valuable for debugging, as knowing the exact module version can help
> > reproduce TDX-related issues.
> >
> > Signed-off-by: Alexey Gladkov (Intel) <legion@...nel.org>
> > ---
> > arch/x86/Kconfig | 1 +
> > arch/x86/include/asm/shared/tdx.h | 2 +
> > arch/x86/include/asm/tdx.h | 12 +++++
> > arch/x86/virt/vmx/tdx/tdx.c | 74 +++++++++++++++++++++++++++++++
> > 4 files changed, 89 insertions(+)
> >
> > diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> > index be2c311f5118..516f3539d0c7 100644
> > --- a/arch/x86/Kconfig
> > +++ b/arch/x86/Kconfig
> > @@ -1986,6 +1986,7 @@ config INTEL_TDX_HOST
> > depends on CONTIG_ALLOC
> > depends on !KEXEC_CORE
> > depends on X86_MCE
> > + select SYS_HYPERVISOR
> > help
> > Intel Trust Domain Extensions (TDX) protects guest VMs from malicious
> > host and certain physical attacks. This option enables necessary TDX
> > diff --git a/arch/x86/include/asm/shared/tdx.h b/arch/x86/include/asm/shared/tdx.h
> > index 606d93a1cbac..92ee9dfb21e7 100644
> > --- a/arch/x86/include/asm/shared/tdx.h
> > +++ b/arch/x86/include/asm/shared/tdx.h
> > @@ -18,6 +18,8 @@
> > #define TDG_MEM_PAGE_ACCEPT 6
> > #define TDG_VM_RD 7
> > #define TDG_VM_WR 8
> > +/* TDG_SYS_RD is available since TDX module version 1.5 and later. */
> > +#define TDG_SYS_RD 11
> >
> > /* TDX attributes */
> > #define TDX_ATTR_DEBUG_BIT 0
> > diff --git a/arch/x86/include/asm/tdx.h b/arch/x86/include/asm/tdx.h
> > index e6b003fe7f5e..95d748bc8464 100644
> > --- a/arch/x86/include/asm/tdx.h
> > +++ b/arch/x86/include/asm/tdx.h
> > @@ -31,6 +31,18 @@
> > #define TDX_SUCCESS 0ULL
> > #define TDX_RND_NO_ENTROPY 0x8000020300000000ULL
> >
> > +/*
> > + * TDX metadata base field id, used by TDCALL TDG.SYS.RD
> > + * See TDX ABI Spec Global Metadata Fields
> > + */
> > +#define TDX_SYS_MINOR_FID 0x0800000100000003ULL
> > +#define TDX_SYS_MAJOR_FID 0x0800000100000004ULL
> > +#define TDX_SYS_UPDATE_FID 0x0800000100000005ULL
> > +#define TDX_SYS_INTERNAL_FID 0x0800000100000006ULL
> > +#define TDX_SYS_BUILD_DATE_FID 0x8800000200000001ULL
> > +#define TDX_SYS_BUILD_NUM_FID 0x8800000100000002ULL
> > +#define TDX_SYS_FEATURES0_FID 0x0A00000300000008ULL
> > +
> > #ifndef __ASSEMBLY__
> >
> > #include <uapi/asm/mce.h>
> > diff --git a/arch/x86/virt/vmx/tdx/tdx.c b/arch/x86/virt/vmx/tdx/tdx.c
> > index f5e2a937c1e7..89378e2a1f66 100644
> > --- a/arch/x86/virt/vmx/tdx/tdx.c
> > +++ b/arch/x86/virt/vmx/tdx/tdx.c
> > @@ -1869,3 +1869,77 @@ u64 tdh_phymem_page_wbinvd_hkid(u64 hkid, struct page *page)
> > return seamcall(TDH_PHYMEM_PAGE_WBINVD, &args);
> > }
> > EXPORT_SYMBOL_GPL(tdh_phymem_page_wbinvd_hkid);
> > +
> > +#ifdef CONFIG_SYSFS
> > +#define TDX_SYSFS_ATTR(_field, _name, fmt) \
> > +static ssize_t _name ## _show( \
> > + struct kobject *kobj, struct kobj_attribute *attr, char *buf) \
> > +{ \
> > + u64 value = 0; \
> > + read_sys_metadata_field(_field, &value); \
> > + return sprintf(buf, fmt, value); \
> > +} \
> > +static struct kobj_attribute _name ## _attr = __ATTR_RO(_name)
> > +
> > +TDX_SYSFS_ATTR(TDX_SYS_MINOR_FID, minor, "%lld\n");
> > +TDX_SYSFS_ATTR(TDX_SYS_MAJOR_FID, major, "%lld\n");
> > +TDX_SYSFS_ATTR(TDX_SYS_UPDATE_FID, update, "%lld\n");
> > +TDX_SYSFS_ATTR(TDX_SYS_BUILD_NUM_FID, build_num, "%lld\n");
> > +TDX_SYSFS_ATTR(TDX_SYS_BUILD_DATE_FID, build_date, "%lld\n");
> > +TDX_SYSFS_ATTR(TDX_SYS_FEATURES0_FID, features0, "%llx\n");
> > +
> > +static struct attribute *version_attrs[] = {
> > + &minor_attr.attr,
> > + &major_attr.attr,
> > + &update_attr.attr,
> > + NULL,
> > +};
> > +
> > +static const struct attribute_group version_attr_group = {
> > + .name = "version",
> > + .attrs = version_attrs,
> > +};
> > +
> > +static struct attribute *properties_attrs[] = {
> > + &build_num_attr.attr,
> > + &build_date_attr.attr,
> > + &features0_attr.attr,
> > + NULL,
> > +};
> > +
> > +static const struct attribute_group properties_attr_group = {
> > + .name = "properties",
> > + .attrs = properties_attrs,
> > +};
> > +
> > +__init static int tdh_sysfs_init(void)
> > +{
> > + struct kobject *tdx_kobj;
> > + int ret;
> > +
> > + if (!hypervisor_kobj)
> > + return -ENOMEM;
> > +
> > + tdx_kobj = kobject_create_and_add("tdx", hypervisor_kobj);
>
> So this "/sys/hypervisor" proposal is clearly unaware of some other
> discussions that have been happening around sysfs ABI for TEE Security
> Managers like the PSP or TDX Module [1]. That PCI/TSM series discusses
> the motivation for a bus/class + device model, not just raw hand-crafted
> kobjects.
>
> My other concern for hand-crafted kobjects is that it also destroys the
> relationship with other existing objects. A /sys/hypervisor/$technology
> is awkward when ABI like Documentation/ABI/testing/sysfs-driver-ccp
> already exists.
>
> So, no, I am not on board with this proposal. There are already patches
> in flight to have TDX create a 'struct device' object that plays a
> similar role as the PSP device object. For any potential common
> attributes across vendors the proposal is that be handled via a typical
> sysfs class device construction that links back to the $technology
> device. That "tsm" class device is present in the PCI/TSM series [1].
>
> [1]: http://lore.kernel.org/174107245357.1288555.10863541957822891561.stgit@dwillia2-xfh.jf.intel.com
Dan, could you elaborate on what is actual proposal? I am not sure I
understand what 'struct device' can have info on TDX module version be
attached to it.
--
Kiryl Shutsemau / Kirill A. Shutemov
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