Messages in this thread Patch in this message | | | From | "Kirill A. Shutemov" <> | Subject | [PATCH 3/4] x86/tdx: Handle PENDING_EPT_VIOLATION_V2 | Date | Sat, 9 Mar 2024 23:02:29 +0200 |
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PENDING_EPT_VIOLATION_V2 allows TD to control whether access to a pending page triggers #VE.
Kernel doesn't want to see any #VEs on accesses to private memory: disable such #VEs.
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> --- arch/x86/coco/tdx/tdx.c | 66 ++++++++++++++++++++++++++++--- arch/x86/include/asm/shared/tdx.h | 18 ++++++++- 2 files changed, 78 insertions(+), 6 deletions(-)
diff --git a/arch/x86/coco/tdx/tdx.c b/arch/x86/coco/tdx/tdx.c index afdaf46cabb9..d9ea82f8772d 100644 --- a/arch/x86/coco/tdx/tdx.c +++ b/arch/x86/coco/tdx/tdx.c @@ -77,6 +77,17 @@ static inline void tdcall(u64 fn, struct tdx_module_args *args) panic("TDCALL %lld failed (Buggy TDX module!)\n", fn); } +static inline u64 tdg_vm_rd(u64 field) +{ + struct tdx_module_args args = { + .rdx = field, + }; + + tdcall(TDG_VM_RD, &args); + + return args.r8; +} + static inline u64 tdg_vm_wr(u64 field, u64 value, u64 mask) { struct tdx_module_args args = { @@ -91,6 +102,17 @@ static inline u64 tdg_vm_wr(u64 field, u64 value, u64 mask) return args.r8; } +static inline u64 tdg_sys_rd(u64 field) +{ + struct tdx_module_args args = { + .rdx = field, + }; + + tdcall(TDG_SYS_RD, &args); + + return args.r8; +} + /** * tdx_mcall_get_report0() - Wrapper to get TDREPORT0 (a.k.a. TDREPORT * subtype 0) using TDG.MR.REPORT TDCALL. @@ -185,7 +207,8 @@ static void tdx_setup(u64 *cc_mask) { struct tdx_module_args args = {}; unsigned int gpa_width; - u64 td_attr; + u64 td_attr, features; + bool sept_ve_disabled; /* * TDINFO TDX module call is used to get the TD execution environment @@ -206,19 +229,52 @@ static void tdx_setup(u64 *cc_mask) gpa_width = args.rcx & GENMASK(5, 0); *cc_mask = BIT_ULL(gpa_width - 1); + td_attr = args.rdx; + /* Kernel does not use NOTIFY_ENABLES and does not need random #VEs */ tdg_vm_wr(TDCS_NOTIFY_ENABLES, 0, -1ULL); + features = tdg_sys_rd(TDCS_TDX_FEATURES0); + /* * The kernel can not handle #VE's when accessing normal kernel * memory. Ensure that no #VE will be delivered for accesses to * TD-private memory. Only VMM-shared memory (MMIO) will #VE. + * + * Check if the TD is created with SEPT #VE disabled. */ - td_attr = args.rdx; - if (!(td_attr & ATTR_SEPT_VE_DISABLE)) { - const char *msg = "TD misconfiguration: SEPT_VE_DISABLE attribute must be set."; + sept_ve_disabled = td_attr & ATTR_SEPT_VE_DISABLE; - /* Relax SEPT_VE_DISABLE check for debug TD. */ + /* + * Check if flexible control of SEPT #VE is supported. + * + * The check consists of verifying if the feature is supported by the + * TDX module (the TDX_FEATURES0 check) and if the feature is enabled + * for this TD (CONFIG_FLAGS check). + * + * If flexible control is supported, disable SEPT #VE. + * + * Disable SEPT #VE regardless of ATTR_SEPT_VE_DISABLE status as + * flexible control allows software running before the kernel to + * enable it. + * + * Skip SEPT disabling for debug TD. SEPT #VE is unsafe but can be + * useful for debugging to produce a stack trace. Known to be useful + * for debugging unaccepted memory problems. + */ + if (features & TDX_FEATURES0_PENDING_EPT_VIOLATION_V2 && + (tdg_vm_rd(TDCS_CONFIG_FLAGS) & TDCS_CONFIG_FLEXIBLE_PENDING_VE) && + !(td_attr & ATTR_DEBUG)) { + tdg_vm_wr(TDCS_TD_CTLS, + TD_CTLS_PENDING_VE_DISABLE, + TD_CTLS_PENDING_VE_DISABLE); + sept_ve_disabled = true; + } + + if (!sept_ve_disabled) { + const char *msg = "TD misconfiguration: SEPT #VE has to be disabled"; + + /* Relax SEPT #VE disable check for debug TD. */ if (td_attr & ATTR_DEBUG) pr_warn("%s\n", msg); else diff --git a/arch/x86/include/asm/shared/tdx.h b/arch/x86/include/asm/shared/tdx.h index fdfd41511b02..29a61c72e4dd 100644 --- a/arch/x86/include/asm/shared/tdx.h +++ b/arch/x86/include/asm/shared/tdx.h @@ -16,11 +16,27 @@ #define TDG_VP_VEINFO_GET 3 #define TDG_MR_REPORT 4 #define TDG_MEM_PAGE_ACCEPT 6 +#define TDG_VM_RD 7 #define TDG_VM_WR 8 +#define TDG_SYS_RD 11 -/* TDCS fields. To be used by TDG.VM.WR and TDG.VM.RD module calls */ +/* TDX Global Metadata. To be used by TDG.SYS.RD */ +#define TDCS_TDX_FEATURES0 0x0A00000300000008 + +/* TDX TD-Scope Metadata. To be used by TDG.VM.WR and TDG.VM.RD */ +#define TDCS_CONFIG_FLAGS 0x1110000300000016 +#define TDCS_TD_CTLS 0x1110000300000017 #define TDCS_NOTIFY_ENABLES 0x9100000000000010 +/* TDCS_TDX_FEATURES0 bits */ +#define TDX_FEATURES0_PENDING_EPT_VIOLATION_V2 BIT_ULL(16) + +/* TDCS_CONFIG_FLAGS bits */ +#define TDCS_CONFIG_FLEXIBLE_PENDING_VE BIT_ULL(1) + +/* TDCS_TD_CTLS bits */ +#define TD_CTLS_PENDING_VE_DISABLE BIT_ULL(0) + /* TDX hypercall Leaf IDs */ #define TDVMCALL_MAP_GPA 0x10001 #define TDVMCALL_GET_QUOTE 0x10002 -- 2.43.0
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