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x86/virt/tdx: Add tdx_guest_keyid_alloc/free() to alloc and free TDX guest KeyID

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Intel TDX protects guest VMs from malicious host and certain physical
attacks. Pre-TDX Intel hardware has support for a memory encryption
architecture called MK-TME, which repurposes several high bits of
physical address as "KeyID". The BIOS reserves a sub-range of MK-TME
KeyIDs as "TDX private KeyIDs".

Each TDX guest must be assigned with a unique TDX KeyID when it is
created. The kernel reserves the first TDX private KeyID for
crypto-protection of specific TDX module data which has a lifecycle that
exceeds the KeyID reserved for the TD's use. The rest of the KeyIDs are
left for TDX guests to use.

Create a small KeyID allocator. Export
tdx_guest_keyid_alloc()/tdx_guest_keyid_free() to allocate and free TDX
guest KeyID for KVM to use.

Don't provide the stub functions when CONFIG_INTEL_TDX_HOST=n since they
are not supposed to be called in this case.

Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com>
Signed-off-by: Rick Edgecombe <rick.p.edgecombe@intel.com>
Message-ID: <20241030190039.77971-5-rick.p.edgecombe@intel.com>
Acked-by: Dave Hansen <dave.hansen@linux.intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Isaku Yamahata 2024-10-30 12:00:17 -07:00 committed by Paolo Bonzini
parent 4caf32daf0
commit aed4dde24c
2 changed files with 20 additions and 0 deletions
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3
arch/x86/include/asm/tdx.h
View File

@ -122,6 +122,9 @@ int tdx_cpu_enable(void);
int tdx_enable(void);
const char *tdx_dump_mce_info(struct mce *m);
int tdx_guest_keyid_alloc(void);
void tdx_guest_keyid_free(unsigned int keyid);
struct tdx_td {
/* TD root structure: */
struct page *tdr_page;

17
arch/x86/virt/vmx/tdx/tdx.c
View File

@ -28,6 +28,7 @@
#include <linux/log2.h>
#include <linux/acpi.h>
#include <linux/suspend.h>
#include <linux/idr.h>
#include <asm/page.h>
#include <asm/special_insns.h>
#include <asm/msr-index.h>
@ -43,6 +44,8 @@ static u32 tdx_global_keyid __ro_after_init;
static u32 tdx_guest_keyid_start __ro_after_init;
static u32 tdx_nr_guest_keyids __ro_after_init;
static DEFINE_IDA(tdx_guest_keyid_pool);
static DEFINE_PER_CPU(bool, tdx_lp_initialized);
static struct tdmr_info_list tdx_tdmr_list;
@ -1459,6 +1462,20 @@ void __init tdx_init(void)
check_tdx_erratum();
}
int tdx_guest_keyid_alloc(void)
{
return ida_alloc_range(&tdx_guest_keyid_pool, tdx_guest_keyid_start,
tdx_guest_keyid_start + tdx_nr_guest_keyids - 1,
GFP_KERNEL);
}
EXPORT_SYMBOL_GPL(tdx_guest_keyid_alloc);
void tdx_guest_keyid_free(unsigned int keyid)
{
ida_free(&tdx_guest_keyid_pool, keyid);
}
EXPORT_SYMBOL_GPL(tdx_guest_keyid_free);
static inline u64 tdx_tdr_pa(struct tdx_td *td)
{
return page_to_phys(td->tdr_page);