[PATCHv2 1/4] x86/tdx: Introduce tdg_vm_wr()

Kirill A. Shutemov
2024-03-25T10:46:25Z

Add a helper function to write to a TD-scope metadata field and use it
to set NOTIFY_ENABLES.

The helper function will be paired with tdg_vm_rd() and will be used to
manipulate other metadata fields, not just NOTIFY_ENABLES.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
---
arch/x86/coco/tdx/tdx.c | 20 +++++++++++++++-----
1 file changed, 15 insertions(+), 5 deletions(-)

diff --git a/arch/x86/coco/tdx/tdx.c b/arch/x86/coco/tdx/tdx.c
index 59776ce1c1d7..4fb36e5c4e80 100644
--- a/arch/x86/coco/tdx/tdx.c
+++ b/arch/x86/coco/tdx/tdx.c
@@ -77,6 +77,20 @@ 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_wr(u64 field, u64 value, u64 mask)
+{
+ struct tdx_module_args args = {
+ .rdx = field,
+ .r8 = value,
+ .r9 = mask,
+ };
+
+ tdcall(TDG_VM_WR, &args);
+
+ /* Old value */
+ return args.r8;
+}
+
/**
* tdx_mcall_get_report0() - Wrapper to get TDREPORT0 (a.k.a. TDREPORT
* subtype 0) using TDG.MR.REPORT TDCALL.
@@ -902,10 +916,6 @@ static void tdx_kexec_unshare_mem(void)

void __init tdx_early_init(void)
{
- struct tdx_module_args args = {
- .rdx = TDCS_NOTIFY_ENABLES,
- .r9 = -1ULL,
- };
u64 cc_mask;
u32 eax, sig[3];

@@ -924,7 +934,7 @@ 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, &args);
+ tdg_vm_wr(TDCS_NOTIFY_ENABLES, 0, -1ULL);

/*
* All bits above GPA width are reserved and kernel treats shared bit
--
2.43.0