- Fixup comment typo

- Prevent unexpected #VE's from:
   - Hosts removing perfectly good guest mappings (SEPT_VE_DISABLE
   - Excessive #VE notifications (NOTIFY_ENABLES) which are
     delivered via a #VE.
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Merge tag 'x86_tdx_for_6.3' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull Intel Trust Domain Extensions (TDX) updates from Dave Hansen:
 "Other than a minor fixup, the content here is to ensure that TDX
  guests never see virtualization exceptions (#VE's) that might be
  induced by the untrusted VMM.

  This is a highly desirable property. Without it, #VE exception
  handling would fall somewhere between NMIs, machine checks and total
  insanity. With it, #VE handling remains pretty mundane.

  Summary:

   - Fixup comment typo

   - Prevent unexpected #VE's from:
      - Hosts removing perfectly good guest mappings (SEPT_VE_DISABLE)
      - Excessive #VE notifications (NOTIFY_ENABLES) which are delivered
        via a #VE"

* tag 'x86_tdx_for_6.3' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/tdx: Do not corrupt frame-pointer in __tdx_hypercall()
  x86/tdx: Disable NOTIFY_ENABLES
  x86/tdx: Relax SEPT_VE_DISABLE check for debug TD
  x86/tdx: Use ReportFatalError to report missing SEPT_VE_DISABLE
  x86/tdx: Expand __tdx_hypercall() to handle more arguments
  x86/tdx: Refactor __tdx_hypercall() to allow pass down more arguments
  x86/tdx: Add more registers to struct tdx_hypercall_args
  x86/tdx: Fix typo in comment in __tdx_hypercall()
This commit is contained in:
Linus Torvalds 2023-02-25 09:11:30 -08:00
commit d8e473182a
4 changed files with 132 additions and 27 deletions

View File

@ -13,6 +13,12 @@
/*
* Bitmasks of exposed registers (with VMM).
*/
#define TDX_RDX BIT(2)
#define TDX_RBX BIT(3)
#define TDX_RSI BIT(6)
#define TDX_RDI BIT(7)
#define TDX_R8 BIT(8)
#define TDX_R9 BIT(9)
#define TDX_R10 BIT(10)
#define TDX_R11 BIT(11)
#define TDX_R12 BIT(12)
@ -27,9 +33,9 @@
* details can be found in TDX GHCI specification, section
* titled "TDCALL [TDG.VP.VMCALL] leaf".
*/
#define TDVMCALL_EXPOSE_REGS_MASK ( TDX_R10 | TDX_R11 | \
TDX_R12 | TDX_R13 | \
TDX_R14 | TDX_R15 )
#define TDVMCALL_EXPOSE_REGS_MASK \
( TDX_RDX | TDX_RBX | TDX_RSI | TDX_RDI | TDX_R8 | TDX_R9 | \
TDX_R10 | TDX_R11 | TDX_R12 | TDX_R13 | TDX_R14 | TDX_R15 )
.section .noinstr.text, "ax"
@ -126,25 +132,38 @@ SYM_FUNC_START(__tdx_hypercall)
push %r14
push %r13
push %r12
push %rbx
/* Free RDI and RSI to be used as TDVMCALL arguments */
movq %rdi, %rax
push %rsi
/* Copy hypercall registers from arg struct: */
movq TDX_HYPERCALL_r8(%rax), %r8
movq TDX_HYPERCALL_r9(%rax), %r9
movq TDX_HYPERCALL_r10(%rax), %r10
movq TDX_HYPERCALL_r11(%rax), %r11
movq TDX_HYPERCALL_r12(%rax), %r12
movq TDX_HYPERCALL_r13(%rax), %r13
movq TDX_HYPERCALL_r14(%rax), %r14
movq TDX_HYPERCALL_r15(%rax), %r15
movq TDX_HYPERCALL_rdi(%rax), %rdi
movq TDX_HYPERCALL_rsi(%rax), %rsi
movq TDX_HYPERCALL_rbx(%rax), %rbx
movq TDX_HYPERCALL_rdx(%rax), %rdx
push %rax
/* Mangle function call ABI into TDCALL ABI: */
/* Set TDCALL leaf ID (TDVMCALL (0)) in RAX */
xor %eax, %eax
/* Copy hypercall registers from arg struct: */
movq TDX_HYPERCALL_r10(%rdi), %r10
movq TDX_HYPERCALL_r11(%rdi), %r11
movq TDX_HYPERCALL_r12(%rdi), %r12
movq TDX_HYPERCALL_r13(%rdi), %r13
movq TDX_HYPERCALL_r14(%rdi), %r14
movq TDX_HYPERCALL_r15(%rdi), %r15
movl $TDVMCALL_EXPOSE_REGS_MASK, %ecx
tdcall
/*
* RAX==0 indicates a failure of the TDVMCALL mechanism itself and that
* RAX!=0 indicates a failure of the TDVMCALL mechanism itself and that
* something has gone horribly wrong with the TDX module.
*
* The return status of the hypercall operation is in a separate
@ -154,30 +173,46 @@ SYM_FUNC_START(__tdx_hypercall)
testq %rax, %rax
jne .Lpanic
pop %rax
/* Copy hypercall result registers to arg struct if needed */
testq $TDX_HCALL_HAS_OUTPUT, (%rsp)
jz .Lout
movq %r8, TDX_HYPERCALL_r8(%rax)
movq %r9, TDX_HYPERCALL_r9(%rax)
movq %r10, TDX_HYPERCALL_r10(%rax)
movq %r11, TDX_HYPERCALL_r11(%rax)
movq %r12, TDX_HYPERCALL_r12(%rax)
movq %r13, TDX_HYPERCALL_r13(%rax)
movq %r14, TDX_HYPERCALL_r14(%rax)
movq %r15, TDX_HYPERCALL_r15(%rax)
movq %rdi, TDX_HYPERCALL_rdi(%rax)
movq %rsi, TDX_HYPERCALL_rsi(%rax)
movq %rbx, TDX_HYPERCALL_rbx(%rax)
movq %rdx, TDX_HYPERCALL_rdx(%rax)
.Lout:
/* TDVMCALL leaf return code is in R10 */
movq %r10, %rax
/* Copy hypercall result registers to arg struct if needed */
testq $TDX_HCALL_HAS_OUTPUT, %rsi
jz .Lout
movq %r10, TDX_HYPERCALL_r10(%rdi)
movq %r11, TDX_HYPERCALL_r11(%rdi)
movq %r12, TDX_HYPERCALL_r12(%rdi)
movq %r13, TDX_HYPERCALL_r13(%rdi)
movq %r14, TDX_HYPERCALL_r14(%rdi)
movq %r15, TDX_HYPERCALL_r15(%rdi)
.Lout:
/*
* Zero out registers exposed to the VMM to avoid speculative execution
* with VMM-controlled values. This needs to include all registers
* present in TDVMCALL_EXPOSE_REGS_MASK (except R12-R15). R12-R15
* context will be restored.
* present in TDVMCALL_EXPOSE_REGS_MASK, except RBX, and R12-R15 which
* will be restored.
*/
xor %r8d, %r8d
xor %r9d, %r9d
xor %r10d, %r10d
xor %r11d, %r11d
xor %rdi, %rdi
xor %rdx, %rdx
/* Remove TDX_HCALL_* flags from the stack */
pop %rsi
/* Restore callee-saved GPRs as mandated by the x86_64 ABI */
pop %rbx
pop %r12
pop %r13
pop %r14

View File

@ -19,9 +19,14 @@
#define TDX_GET_VEINFO 3
#define TDX_GET_REPORT 4
#define TDX_ACCEPT_PAGE 6
#define TDX_WR 8
/* TDCS fields. To be used by TDG.VM.WR and TDG.VM.RD module calls */
#define TDCS_NOTIFY_ENABLES 0x9100000000000010
/* TDX hypercall Leaf IDs */
#define TDVMCALL_MAP_GPA 0x10001
#define TDVMCALL_REPORT_FATAL_ERROR 0x10003
/* MMIO direction */
#define EPT_READ 0
@ -37,6 +42,7 @@
#define VE_GET_PORT_NUM(e) ((e) >> 16)
#define VE_IS_IO_STRING(e) ((e) & BIT(4))
#define ATTR_DEBUG BIT(0)
#define ATTR_SEPT_VE_DISABLE BIT(28)
/* TDX Module call error codes */
@ -141,6 +147,41 @@ int tdx_mcall_get_report0(u8 *reportdata, u8 *tdreport)
}
EXPORT_SYMBOL_GPL(tdx_mcall_get_report0);
static void __noreturn tdx_panic(const char *msg)
{
struct tdx_hypercall_args args = {
.r10 = TDX_HYPERCALL_STANDARD,
.r11 = TDVMCALL_REPORT_FATAL_ERROR,
.r12 = 0, /* Error code: 0 is Panic */
};
union {
/* Define register order according to the GHCI */
struct { u64 r14, r15, rbx, rdi, rsi, r8, r9, rdx; };
char str[64];
} message;
/* VMM assumes '\0' in byte 65, if the message took all 64 bytes */
strncpy(message.str, msg, 64);
args.r8 = message.r8;
args.r9 = message.r9;
args.r14 = message.r14;
args.r15 = message.r15;
args.rdi = message.rdi;
args.rsi = message.rsi;
args.rbx = message.rbx;
args.rdx = message.rdx;
/*
* This hypercall should never return and it is not safe
* to keep the guest running. Call it forever if it
* happens to return.
*/
while (1)
__tdx_hypercall(&args, 0);
}
static void tdx_parse_tdinfo(u64 *cc_mask)
{
struct tdx_module_output out;
@ -172,8 +213,15 @@ static void tdx_parse_tdinfo(u64 *cc_mask)
* TD-private memory. Only VMM-shared memory (MMIO) will #VE.
*/
td_attr = out.rdx;
if (!(td_attr & ATTR_SEPT_VE_DISABLE))
panic("TD misconfiguration: SEPT_VE_DISABLE attibute must be set.\n");
if (!(td_attr & ATTR_SEPT_VE_DISABLE)) {
const char *msg = "TD misconfiguration: SEPT_VE_DISABLE attribute must be set.";
/* Relax SEPT_VE_DISABLE check for debug TD. */
if (td_attr & ATTR_DEBUG)
pr_warn("%s\n", msg);
else
tdx_panic(msg);
}
}
/*
@ -617,6 +665,11 @@ static int virt_exception_user(struct pt_regs *regs, struct ve_info *ve)
}
}
static inline bool is_private_gpa(u64 gpa)
{
return gpa == cc_mkenc(gpa);
}
/*
* Handle the kernel #VE.
*
@ -635,6 +688,8 @@ static int virt_exception_kernel(struct pt_regs *regs, struct ve_info *ve)
case EXIT_REASON_CPUID:
return handle_cpuid(regs, ve);
case EXIT_REASON_EPT_VIOLATION:
if (is_private_gpa(ve->gpa))
panic("Unexpected EPT-violation on private memory.");
return handle_mmio(regs, ve);
case EXIT_REASON_IO_INSTRUCTION:
return handle_io(regs, ve);
@ -801,6 +856,9 @@ void __init tdx_early_init(void)
tdx_parse_tdinfo(&cc_mask);
cc_set_mask(cc_mask);
/* Kernel does not use NOTIFY_ENABLES and does not need random #VEs */
tdx_module_call(TDX_WR, 0, TDCS_NOTIFY_ENABLES, 0, -1ULL, NULL);
/*
* All bits above GPA width are reserved and kernel treats shared bit
* as flag, not as part of physical address.

View File

@ -21,12 +21,18 @@
* This is a software only structure and not part of the TDX module/VMM ABI.
*/
struct tdx_hypercall_args {
u64 r8;
u64 r9;
u64 r10;
u64 r11;
u64 r12;
u64 r13;
u64 r14;
u64 r15;
u64 rdi;
u64 rsi;
u64 rbx;
u64 rdx;
};
/* Used to request services from the VMM */

View File

@ -76,12 +76,18 @@ static void __used common(void)
OFFSET(TDX_MODULE_r11, tdx_module_output, r11);
BLANK();
OFFSET(TDX_HYPERCALL_r8, tdx_hypercall_args, r8);
OFFSET(TDX_HYPERCALL_r9, tdx_hypercall_args, r9);
OFFSET(TDX_HYPERCALL_r10, tdx_hypercall_args, r10);
OFFSET(TDX_HYPERCALL_r11, tdx_hypercall_args, r11);
OFFSET(TDX_HYPERCALL_r12, tdx_hypercall_args, r12);
OFFSET(TDX_HYPERCALL_r13, tdx_hypercall_args, r13);
OFFSET(TDX_HYPERCALL_r14, tdx_hypercall_args, r14);
OFFSET(TDX_HYPERCALL_r15, tdx_hypercall_args, r15);
OFFSET(TDX_HYPERCALL_rdi, tdx_hypercall_args, rdi);
OFFSET(TDX_HYPERCALL_rsi, tdx_hypercall_args, rsi);
OFFSET(TDX_HYPERCALL_rbx, tdx_hypercall_args, rbx);
OFFSET(TDX_HYPERCALL_rdx, tdx_hypercall_args, rdx);
BLANK();
OFFSET(BP_scratch, boot_params, scratch);