diff options
| author |   Kiryl Shutsemau (Meta) <kas@kernel.org> | 2026-07-13 14:37:53 +0100 |
|---|---|---|
| committer |   Dave Hansen <dave.hansen@linux.intel.com> | 2026-07-13 14:45:07 -0700 |
| commit | 941370fc93cc3474e26811f4d3b062903eefe2cf (patch) | |
| tree | 8293674e577fb4aa25b15d5ae81510b0472b31e3 | |
| parent | x86/insn-eval: Move assign_register() out of KVM as insn_assign_reg() (diff) | |
x86/tdx: Fix zero-extension for 32-bit port I/O
According to x86 architecture rules, 32-bit operations zero-extend the
result to 64 bits. The current implementation of handle_in() only masks
the lower 32 bits, which preserves the upper 32 bits of RAX when a
32-bit port IN instruction is emulated.
Use insn_assign_reg() to write the result back into RAX with proper
partial-register-write semantics: 1- and 2-byte forms leave the upper
bits untouched, the 4-byte form zero-extends to the full register.
Fixes: 03149948832a ("x86/tdx: Port I/O: Add runtime hypercalls")
Reported-by: Borys Tsyrulnikov <tsyrulnikov.borys@gmail.com>
Signed-off-by: Kiryl Shutsemau (Meta) <kas@kernel.org>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Binbin Wu <binbin.wu@linux.intel.com>
Link: https://lore.kernel.org/all/CAKw_Dz96rfSQc6Rn+9QBcUFHhmkK+9zu+P=bxowfZwxrATCBRg@mail.gmail.com/
Cc:stable@vger.kernel.org
Link: https://patch.msgid.link/20260713133753.223947-4-kirill@shutemov.name
| -rw-r--r-- | arch/x86/coco/tdx/tdx.c | 8 |
1 files changed, 3 insertions, 5 deletions
diff --git a/arch/x86/coco/tdx/tdx.c b/arch/x86/coco/tdx/tdx.c index b8bbd715fb62..f904a636d449 100644 --- a/arch/x86/coco/tdx/tdx.c +++ b/arch/x86/coco/tdx/tdx.c @@ -694,8 +694,8 @@ static bool handle_in(struct pt_regs *regs, int size, int port) .r13 = PORT_READ, .r14 = port, }; - u64 mask = GENMASK(BITS_PER_BYTE * size - 1, 0); bool success; + u64 val; /* * Emulate the I/O read via hypercall. More info about ABI can be found @@ -703,11 +703,9 @@ static bool handle_in(struct pt_regs *regs, int size, int port) * "TDG.VP.VMCALL<Instruction.IO>". */ success = !__tdx_hypercall(&args); + val = success ? args.r11 : 0; - /* Update part of the register affected by the emulated instruction */ - regs->ax &= ~mask; - if (success) - regs->ax |= args.r11 & mask; + insn_assign_reg(®s->ax, val, size); return success; } |