Commit 57a420bb authored by Kai Huang's avatar Kai Huang Committed by Dave Hansen
Browse files

x86/tdx: Pass TDCALL/SEAMCALL input/output registers via a structure 



Currently, the TDX_MODULE_CALL asm macro, which handles both TDCALL and
SEAMCALL, takes one parameter for each input register and an optional
'struct tdx_module_output' (a collection of output registers) as output.
This is different from the TDX_HYPERCALL macro which uses a single
'struct tdx_hypercall_args' to carry all input/output registers.

The newer TDX versions introduce more TDCALLs/SEAMCALLs which use more
input/output registers.  Also, the TDH.VP.ENTER (which isn't covered
by the current TDX_MODULE_CALL macro) basically can use all registers
that the TDX_HYPERCALL does.  The current TDX_MODULE_CALL macro isn't
extendible to cover those cases.

Similar to the TDX_HYPERCALL macro, simplify the TDX_MODULE_CALL macro
to use a single structure 'struct tdx_module_args' to carry all the
input/output registers.  Currently, R10/R11 are only used as output
register but not as input by any TDCALL/SEAMCALL.  Change to also use
R10/R11 as input register to make input/output registers symmetric.

Currently, the TDX_MODULE_CALL macro depends on the caller to pass a
non-NULL 'struct tdx_module_output' to get additional output registers.
Similar to the TDX_HYPERCALL macro, change the TDX_MODULE_CALL macro to
take a new 'ret' macro argument to indicate whether to save the output
registers to the 'struct tdx_module_args'.  Also introduce a new
__tdcall_ret() for that purpose, similar to the __tdx_hypercall_ret().

Note the tdcall(), which is a wrapper of __tdcall(), is called by three
callers: tdx_parse_tdinfo(), tdx_get_ve_info() and tdx_early_init().
The former two need the additional output but the last one doesn't.  For
simplicity, make tdcall() always call __tdcall_ret() to avoid another
"_ret()" wrapper.  The last caller tdx_early_init() isn't performance
critical anyway.

Suggested-by: default avatarPeter Zijlstra <peterz@infradead.org>
Signed-off-by: default avatarKai Huang <kai.huang@intel.com>
Signed-off-by: default avatarDave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: default avatarKirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/all/483616c1762d85eb3a3c3035a7de061cfacf2f14.1692096753.git.kai.huang%40intel.com
parent 5efb9628

arch/x86/coco/tdx/tdcall.S

+18 −29
Original line number Diff line number Diff line
@@ -43,37 +43,10 @@ 
 * __tdcall()  - Used by TDX guests to request services from the TDX

 * module (does not include VMM services) using TDCALL instruction.

 *

 * Transforms function call register arguments into the TDCALL register ABI.

 * After TDCALL operation, TDX module output is saved in @out (if it is

 * provided by the user).

 *

 *-------------------------------------------------------------------------

 * TDCALL ABI:

 *-------------------------------------------------------------------------

 * Input Registers:

 *

 * RAX                 - TDCALL Leaf number.

 * RCX,RDX,R8-R9       - TDCALL Leaf specific input registers.

 *

 * Output Registers:

 *

 * RAX                 - TDCALL instruction error code.

 * RCX,RDX,R8-R11      - TDCALL Leaf specific output registers.

 *

 *-------------------------------------------------------------------------

 *

 * __tdcall() function ABI:

 *

 * @fn   (RDI)	- TDCALL Leaf ID, moved to RAX

 * @rcx (RSI)          - Input parameter 1, moved to RCX

 * @rdx (RDX)          - Input parameter 2, moved to RDX

 * @r8  (RCX)          - Input parameter 3, moved to R8

 * @r9  (R8)           - Input parameter 4, moved to R9

 *

 * @out (R9)           - struct tdx_module_output pointer

 *                       stored temporarily in R12 (not

 *                       shared with the TDX module). It

 *                       can be NULL.

 * @args (RSI)	- struct tdx_module_args for input

 *

 * Return status of TDCALL via RAX.

 */
@@ -81,6 +54,22 @@ SYM_FUNC_START(__tdcall) 
	TDX_MODULE_CALL host=0

SYM_FUNC_END(__tdcall)



/*

 * __tdcall_ret() - Used by TDX guests to request services from the TDX

 * module (does not include VMM services) using TDCALL instruction, with

 * saving output registers to the 'struct tdx_module_args' used as input.

 *

 * __tdcall_ret() function ABI:

 *

 * @fn   (RDI)	- TDCALL Leaf ID, moved to RAX

 * @args (RSI)	- struct tdx_module_args for input and output

 *

 * Return status of TDCALL via RAX.

 */

SYM_FUNC_START(__tdcall_ret)

	TDX_MODULE_CALL host=0 ret=1

SYM_FUNC_END(__tdcall_ret)



/*

 * TDX_HYPERCALL - Make hypercalls to a TDX VMM using TDVMCALL leaf of TDCALL

 * instruction

arch/x86/coco/tdx/tdx-shared.c

+3 −3
Original line number Diff line number Diff line
@@ -5,7 +5,7 @@ static unsigned long try_accept_one(phys_addr_t start, unsigned long len, 
				    enum pg_level pg_level)

{

	unsigned long accept_size = page_level_size(pg_level);

	u64 tdcall_rcx;

	struct tdx_module_args args = {};

	u8 page_size;



	if (!IS_ALIGNED(start, accept_size))
@@ -34,8 +34,8 @@ static unsigned long try_accept_one(phys_addr_t start, unsigned long len, 
		return 0;

	}



	tdcall_rcx = start | page_size;

	if (__tdcall(TDG_MEM_PAGE_ACCEPT, tdcall_rcx, 0, 0, 0, NULL))

	args.rcx = start | page_size;

	if (__tdcall(TDG_MEM_PAGE_ACCEPT, &args))

		return 0;



	return accept_size;

arch/x86/coco/tdx/tdx.c

+25 −19
Original line number Diff line number Diff line
@@ -66,10 +66,9 @@ EXPORT_SYMBOL_GPL(tdx_kvm_hypercall); 
 * should only be used for calls that have no legitimate reason to fail

 * or where the kernel can not survive the call failing.

 */

static inline void tdcall(u64 fn, u64 rcx, u64 rdx, u64 r8, u64 r9,

			  struct tdx_module_output *out)

static inline void tdcall(u64 fn, struct tdx_module_args *args)

{

	if (__tdcall(fn, rcx, rdx, r8, r9, out))

	if (__tdcall_ret(fn, args))

		panic("TDCALL %lld failed (Buggy TDX module!)\n", fn);

}
@@ -89,11 +88,14 @@ static inline void tdcall(u64 fn, u64 rcx, u64 rdx, u64 r8, u64 r9, 
 */

int tdx_mcall_get_report0(u8 *reportdata, u8 *tdreport)

{

	struct tdx_module_args args = {

		.rcx = virt_to_phys(tdreport),

		.rdx = virt_to_phys(reportdata),

		.r8 = TDREPORT_SUBTYPE_0,

	};

	u64 ret;



	ret = __tdcall(TDG_MR_REPORT, virt_to_phys(tdreport),

			virt_to_phys(reportdata), TDREPORT_SUBTYPE_0,

			0, NULL);

	ret = __tdcall(TDG_MR_REPORT, &args);

	if (ret) {

		if (TDCALL_RETURN_CODE(ret) == TDCALL_INVALID_OPERAND)

			return -EINVAL;
@@ -141,7 +143,7 @@ static void __noreturn tdx_panic(const char *msg) 


static void tdx_parse_tdinfo(u64 *cc_mask)

{

	struct tdx_module_output out;

	struct tdx_module_args args = {};

	unsigned int gpa_width;

	u64 td_attr;
@@ -152,7 +154,7 @@ static void tdx_parse_tdinfo(u64 *cc_mask) 
	 * Guest-Host-Communication Interface (GHCI), section 2.4.2 TDCALL

	 * [TDG.VP.INFO].

	 */

	tdcall(TDG_VP_INFO, 0, 0, 0, 0, &out);

	tdcall(TDG_VP_INFO, &args);



	/*

	 * The highest bit of a guest physical address is the "sharing" bit.
@@ -161,7 +163,7 @@ static void tdx_parse_tdinfo(u64 *cc_mask) 
	 * The GPA width that comes out of this call is critical. TDX guests

	 * can not meaningfully run without it.

	 */

	gpa_width = out.rcx & GENMASK(5, 0);

	gpa_width = args.rcx & GENMASK(5, 0);

	*cc_mask = BIT_ULL(gpa_width - 1);



	/*
@@ -169,7 +171,7 @@ static void tdx_parse_tdinfo(u64 *cc_mask) 
	 * memory.  Ensure that no #VE will be delivered for accesses to

	 * TD-private memory.  Only VMM-shared memory (MMIO) will #VE.

	 */

	td_attr = out.rdx;

	td_attr = args.rdx;

	if (!(td_attr & ATTR_SEPT_VE_DISABLE)) {

		const char *msg = "TD misconfiguration: SEPT_VE_DISABLE attribute must be set.";
@@ -577,7 +579,7 @@ __init bool tdx_early_handle_ve(struct pt_regs *regs) 


void tdx_get_ve_info(struct ve_info *ve)

{

	struct tdx_module_output out;

	struct tdx_module_args args = {};



	/*

	 * Called during #VE handling to retrieve the #VE info from the
@@ -594,15 +596,15 @@ void tdx_get_ve_info(struct ve_info *ve) 
	 * Note, the TDX module treats virtual NMIs as inhibited if the #VE

	 * valid flag is set. It means that NMI=>#VE will not result in a #DF.

	 */

	tdcall(TDG_VP_VEINFO_GET, 0, 0, 0, 0, &out);

	tdcall(TDG_VP_VEINFO_GET, &args);



	/* Transfer the output parameters */

	ve->exit_reason = out.rcx;

	ve->exit_qual   = out.rdx;

	ve->gla         = out.r8;

	ve->gpa         = out.r9;

	ve->instr_len   = lower_32_bits(out.r10);

	ve->instr_info  = upper_32_bits(out.r10);

	ve->exit_reason = args.rcx;

	ve->exit_qual   = args.rdx;

	ve->gla         = args.r8;

	ve->gpa         = args.r9;

	ve->instr_len   = lower_32_bits(args.r10);

	ve->instr_info  = upper_32_bits(args.r10);

}



/*
@@ -799,6 +801,10 @@ static bool tdx_enc_status_change_finish(unsigned long vaddr, int numpages, 


void __init tdx_early_init(void)

{

	struct tdx_module_args args = {

		.rdx = TDCS_NOTIFY_ENABLES,

		.r9 = -1ULL,

	};

	u64 cc_mask;

	u32 eax, sig[3];
@@ -814,7 +820,7 @@ void __init tdx_early_init(void) 
	cc_set_mask(cc_mask);



	/* Kernel does not use NOTIFY_ENABLES and does not need random #VEs */

	tdcall(TDG_VM_WR, 0, TDCS_NOTIFY_ENABLES, 0, -1ULL, NULL);

	tdcall(TDG_VM_WR, &args);



	/*

	 * All bits above GPA width are reserved and kernel treats shared bit

arch/x86/include/asm/shared/tdx.h

+4 −4
Original line number Diff line number Diff line
@@ -76,11 +76,11 @@ static inline u64 _tdx_hypercall(u64 fn, u64 r12, u64 r13, u64 r14, u64 r15) 
void __tdx_hypercall_failed(void);



/*

 * Used in __tdx_module_call() to gather the output registers' values of the

 * Used in __tdcall*() to gather the input/output registers' values of the

 * TDCALL instruction when requesting services from the TDX module. This is a

 * software only structure and not part of the TDX module/VMM ABI

 */

struct tdx_module_output {

struct tdx_module_args {

	u64 rcx;

	u64 rdx;

	u64 r8;
@@ -90,8 +90,8 @@ struct tdx_module_output { 
};



/* Used to communicate with the TDX module */

u64 __tdcall(u64 fn, u64 rcx, u64 rdx, u64 r8, u64 r9,

	     struct tdx_module_output *out);

u64 __tdcall(u64 fn, struct tdx_module_args *args);

u64 __tdcall_ret(u64 fn, struct tdx_module_args *args);



bool tdx_accept_memory(phys_addr_t start, phys_addr_t end);

arch/x86/kernel/asm-offsets.c

+6 −6
Original line number Diff line number Diff line
@@ -68,12 +68,12 @@ static void __used common(void) 
#endif



	BLANK();

	OFFSET(TDX_MODULE_rcx, tdx_module_output, rcx);

	OFFSET(TDX_MODULE_rdx, tdx_module_output, rdx);

	OFFSET(TDX_MODULE_r8,  tdx_module_output, r8);

	OFFSET(TDX_MODULE_r9,  tdx_module_output, r9);

	OFFSET(TDX_MODULE_r10, tdx_module_output, r10);

	OFFSET(TDX_MODULE_r11, tdx_module_output, r11);

	OFFSET(TDX_MODULE_rcx, tdx_module_args, rcx);

	OFFSET(TDX_MODULE_rdx, tdx_module_args, rdx);

	OFFSET(TDX_MODULE_r8,  tdx_module_args, r8);

	OFFSET(TDX_MODULE_r9,  tdx_module_args, r9);

	OFFSET(TDX_MODULE_r10, tdx_module_args, r10);

	OFFSET(TDX_MODULE_r11, tdx_module_args, r11);



	BLANK();

	OFFSET(TDX_HYPERCALL_r8,  tdx_hypercall_args, r8);