[PATCH 05/20] x86/tdx: Convert MSR read handling to use new TDVMCALL_1()

Kirill A. Shutemov
2024-05-17T14:20:00Z

Use newly introduced TDVMCALL_1() instead of __tdx_hypercall() to handle
MSR read emulation.

It cuts code bloat substantially:

Function old new delta
tdx_handle_virt_exception 2052 1947 -105

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
---
arch/x86/coco/tdx/tdx.c | 15 +++++++--------
arch/x86/hyperv/ivm.c | 10 ++--------
2 files changed, 9 insertions(+), 16 deletions(-)

diff --git a/arch/x86/coco/tdx/tdx.c b/arch/x86/coco/tdx/tdx.c
index dce7d6f9f895..32c519d096de 100644
--- a/arch/x86/coco/tdx/tdx.c
+++ b/arch/x86/coco/tdx/tdx.c
@@ -379,22 +379,21 @@ void __cpuidle tdx_safe_halt(void)

static int read_msr(struct pt_regs *regs, struct ve_info *ve)
{
- struct tdx_module_args args = {
- .r10 = TDX_HYPERCALL_STANDARD,
- .r11 = hcall_func(EXIT_REASON_MSR_READ),
- .r12 = regs->cx,
- };
+ u64 val;

/*
* Emulate the MSR read via hypercall. More info about ABI
* can be found in TDX Guest-Host-Communication Interface
* (GHCI), section titled "TDG.VP.VMCALL<Instruction.RDMSR>".
*/
- if (__tdx_hypercall(&args))
+ if (TDVMCALL_1(hcall_func(EXIT_REASON_MSR_READ),
+ regs->cx, 0, 0, 0, val)) {
return -EIO;
+ }
+
+ regs->ax = lower_32_bits(val);
+ regs->dx = upper_32_bits(val);

- regs->ax = lower_32_bits(args.r11);
- regs->dx = upper_32_bits(args.r11);
return ve_instr_len(ve);
}

diff --git a/arch/x86/hyperv/ivm.c b/arch/x86/hyperv/ivm.c
index b4a851d27c7c..3e2cbfb2203d 100644
--- a/arch/x86/hyperv/ivm.c
+++ b/arch/x86/hyperv/ivm.c
@@ -399,18 +399,12 @@ static void hv_tdx_msr_write(u64 msr, u64 val)

static void hv_tdx_msr_read(u64 msr, u64 *val)
{
- struct tdx_module_args args = {
- .r10 = TDX_HYPERCALL_STANDARD,
- .r11 = EXIT_REASON_MSR_READ,
- .r12 = msr,
- };
+ u64 ret;

- u64 ret = __tdx_hypercall(&args);
+ ret = TDVMCALL_1(hcall_func(EXIT_REASON_MSR_READ), msr, 0, 0, 0, *val);

if (WARN_ONCE(ret, "Failed to emulate MSR read: %lld\n", ret))
*val = 0;
- else
- *val = args.r11;
}

u64 hv_tdx_hypercall(u64 control, u64 param1, u64 param2)
--
2.43.0