Messages in this thread Patch in this message | | | From | Kuppuswamy Sathyanarayanan <> | Subject | [PATCH v10 11/11] x86/tdx: Handle CPUID via #VE | Date | Fri, 8 Oct 2021 22:37:47 -0700 |
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From: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
When running virtualized, the CPUID instruction is handled differently based on the leaf being accessed. The behavior depends only on the leaf and applies equally to both kernel/ring-0 and userspace/ring-3 execution of CPUID. Historically, there are two basic classes:
* Leaves handled transparently to the guest * Leaves handled by the VMM
In a typical guest without TDX, "handled by the VMM" leaves cause a VMEXIT. TDX replaces these VMEXITs with a #VE exception in the guest. The guest typically handles the #VE by making a hypercall to the VMM.
The TDX module specification [1], section titled "CPUID Virtualization" talks about a few more classes of CPUID handling. But, for the purposes of this patch, the "handled transparently" CPUID leaves are all lumped together because the guest handling is the same.
[1] - https://software.intel.com/content/dam/develop/external/us/en/documents/tdx-module-1.0-public-spec-v0.931.pdf
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Reviewed-by: Andi Kleen <ak@linux.intel.com> Reviewed-by: Tony Luck <tony.luck@intel.com> Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com> ---
Changes since v9: * None
Changes since v8: * Removed zero initialization of struct tdx_hypercall_output in tdx_handle_cpuid(). * Changed return type of tdx_handle_cpuid() to bool.
Changes since v7: * None
Changes since v6: * Fixed commit log as per Dave Hansen comments. * Added extra comments for _tdx_hypercall() usage.
Changes since v5: * Fixed commit log as per review comments. * Removed WARN_ON() in tdx_handle_cpuid(). * Renamed "tdg" prefix with "tdx".
Changes since v4: * None
Changes since v3: * None
arch/x86/kernel/tdx.c | 28 ++++++++++++++++++++++++++++ 1 file changed, 28 insertions(+)
diff --git a/arch/x86/kernel/tdx.c b/arch/x86/kernel/tdx.c index 7c6c84015302..f8f242215dbc 100644 --- a/arch/x86/kernel/tdx.c +++ b/arch/x86/kernel/tdx.c @@ -143,6 +143,31 @@ static bool tdx_write_msr_safe(unsigned int msr, unsigned int low, return ret ? false : true; } +static bool tdx_handle_cpuid(struct pt_regs *regs) +{ + struct tdx_hypercall_output out; + + /* + * Emulate CPUID instruction via hypercall. More info about + * ABI can be found in TDX Guest-Host-Communication Interface + * (GHCI), section titled "VP.VMCALL<Instruction.CPUID>". + */ + if (_tdx_hypercall(EXIT_REASON_CPUID, regs->ax, regs->cx, 0, 0, &out)) + return false; + + /* + * As per TDX GHCI CPUID ABI, r12-r15 registers contains contents of + * EAX, EBX, ECX, EDX registers after CPUID instruction execution. + * So copy the register contents back to pt_regs. + */ + regs->ax = out.r12; + regs->bx = out.r13; + regs->cx = out.r14; + regs->dx = out.r15; + + return true; +} + bool tdx_get_ve_info(struct ve_info *ve) { struct tdx_module_output out; @@ -191,6 +216,9 @@ bool tdx_handle_virtualization_exception(struct pt_regs *regs, case EXIT_REASON_MSR_WRITE: ret = tdx_write_msr_safe(regs->cx, regs->ax, regs->dx); break; + case EXIT_REASON_CPUID: + ret = tdx_handle_cpuid(regs); + break; default: pr_warn("Unexpected #VE: %lld\n", ve->exit_reason); return false; -- 2.25.1
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