Messages in this thread | | | Date | Sun, 13 Mar 2022 15:10:38 +0100 | Subject | Re: [RFC PATCH v5 014/104] KVM: TDX: Add a function for KVM to invoke SEAMCALL | From | Paolo Bonzini <> |
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On 3/4/22 20:48, isaku.yamahata@intel.com wrote: > From: Isaku Yamahata <isaku.yamahata@intel.com> > > Add an assembly function for KVM to call the TDX module because __seamcall > defined in arch/x86/virt/vmx/seamcall.S doesn't fit for the KVM use case. > > TDX module API returns extended error information in registers, rcx, rdx, > r8, r9, r10, and r11 in addition to success case. KVM uses those extended > error information in addition to the status code returned in RAX. Update > the assembly code to optionally return those outputs even in the error case > and define the specific version for KVM to call the TDX module. > > SEAMCALL to the SEAM module (P-SEAMLDR or TDX module) can result in the > error of VmFailInvalid indicated by CF=1 when VMX isn't enabled by VMXON > instruction. Because KVM guarantees that VMX is enabled, VmFailInvalid > error won't happen. Don't check the error for KVM. > > Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com> > --- > arch/x86/kvm/Makefile | 2 +- > arch/x86/kvm/vmx/seamcall.S | 55 +++++++++++++++++++++++++++++++++++++ > arch/x86/virt/tdxcall.S | 8 ++++-- > 3 files changed, 62 insertions(+), 3 deletions(-) > create mode 100644 arch/x86/kvm/vmx/seamcall.S > > diff --git a/arch/x86/kvm/Makefile b/arch/x86/kvm/Makefile > index e2c05195cb95..e8f83a7d0dc3 100644 > --- a/arch/x86/kvm/Makefile > +++ b/arch/x86/kvm/Makefile > @@ -24,7 +24,7 @@ kvm-$(CONFIG_KVM_XEN) += xen.o > kvm-intel-y += vmx/vmx.o vmx/vmenter.o vmx/pmu_intel.o vmx/vmcs12.o \ > vmx/evmcs.o vmx/nested.o vmx/posted_intr.o vmx/main.o > kvm-intel-$(CONFIG_X86_SGX_KVM) += vmx/sgx.o > -kvm-intel-$(CONFIG_INTEL_TDX_HOST) += vmx/tdx.o > +kvm-intel-$(CONFIG_INTEL_TDX_HOST) += vmx/tdx.o vmx/seamcall.o > > kvm-amd-y += svm/svm.o svm/vmenter.o svm/pmu.o svm/nested.o svm/avic.o svm/sev.o > > diff --git a/arch/x86/kvm/vmx/seamcall.S b/arch/x86/kvm/vmx/seamcall.S > new file mode 100644 > index 000000000000..4a15017fc7dd > --- /dev/null > +++ b/arch/x86/kvm/vmx/seamcall.S > @@ -0,0 +1,55 @@ > +/* SPDX-License-Identifier: GPL-2.0 */ > +#include <linux/linkage.h> > +#include <asm/export.h> > +#include <asm/frame.h> > + > +#include "../../virt/tdxcall.S" > + > +/* > + * kvm_seamcall() - Host-side interface functions to SEAM software (TDX module) > + * > + * Transform function call register arguments into the SEAMCALL register > + * ABI. Return the completion status of the SEAMCALL. Additional output > + * operands are saved in @out (if it is provided by the user). > + * It doesn't check TDX_SEAMCALL_VMFAILINVALID unlike __semcall() because KVM > + * guarantees that VMX is enabled so that TDX_SEAMCALL_VMFAILINVALID doesn't > + * happen. In the case of error completion status code, extended error code may > + * be stored in leaf specific output registers. > + * > + *------------------------------------------------------------------------- > + * SEAMCALL ABI: > + *------------------------------------------------------------------------- > + * Input Registers: > + * > + * RAX - SEAMCALL Leaf number. > + * RCX,RDX,R8-R9 - SEAMCALL Leaf specific input registers. > + * > + * Output Registers: > + * > + * RAX - SEAMCALL completion status code. > + * RCX,RDX,R8-R11 - SEAMCALL Leaf specific output registers. > + * > + *------------------------------------------------------------------------- > + * > + * kvm_seamcall() function ABI: > + * > + * @fn (RDI) - SEAMCALL Leaf number, 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. > + * > + * Return (via RAX) the completion status of the SEAMCALL > + */ > +SYM_FUNC_START(kvm_seamcall) > + FRAME_BEGIN > + TDX_MODULE_CALL host=1 error_check=0 > + FRAME_END > + ret > +SYM_FUNC_END(kvm_seamcall) > +EXPORT_SYMBOL_GPL(kvm_seamcall) > diff --git a/arch/x86/virt/tdxcall.S b/arch/x86/virt/tdxcall.S > index 90569faedacc..2e614b6b5f1e 100644 > --- a/arch/x86/virt/tdxcall.S > +++ b/arch/x86/virt/tdxcall.S > @@ -13,7 +13,7 @@ > #define tdcall .byte 0x66,0x0f,0x01,0xcc > #define seamcall .byte 0x66,0x0f,0x01,0xcf > > -.macro TDX_MODULE_CALL host:req > +.macro TDX_MODULE_CALL host:req error_check=1
Perhaps name this argument ext_error_out and reverse it (that is, 0 is the current behavior while 1 is what KVM needs).
Paolo
> /* > * R12 will be used as temporary storage for struct tdx_module_output > * pointer. Since R12-R15 registers are not used by TDCALL/SEAMCALL > @@ -51,9 +51,11 @@ > * > * Set %rax to TDX_SEAMCALL_VMFAILINVALID for VMfailInvalid. > * This value will never be used as actual SEAMCALL error code. > - */ > + */ > + .if \error_check > jnc .Lno_vmfailinvalid > mov $TDX_SEAMCALL_VMFAILINVALID, %rax > + .endif > .Lno_vmfailinvalid: > .else > tdcall > @@ -66,8 +68,10 @@ > pop %r12 > > /* Check for success: 0 - Successful, otherwise failed */ > + .if \error_check > test %rax, %rax > jnz .Lno_output_struct > + .endif > > /* > * Since this function can be initiated without an output pointer,
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