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Message-ID: <82a916da-0053-46c6-abfe-faf170cb5a8c@linux.intel.com>
Date: Mon, 16 Dec 2024 09:14:11 +0800
From: Binbin Wu <binbin.wu@...ux.intel.com>
To: Xiaoyao Li <xiaoyao.li@...el.com>
Cc: pbonzini@...hat.com, seanjc@...gle.com, kvm@...r.kernel.org,
rick.p.edgecombe@...el.com, kai.huang@...el.com, adrian.hunter@...el.com,
reinette.chatre@...el.com, tony.lindgren@...ux.intel.com,
isaku.yamahata@...el.com, yan.y.zhao@...el.com, chao.gao@...el.com,
michael.roth@....com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 5/7] KVM: TDX: Handle TDG.VP.VMCALL<ReportFatalError>
On 12/13/2024 5:40 PM, Xiaoyao Li wrote:
> On 12/1/2024 11:53 AM, Binbin Wu wrote:
>> Convert TDG.VP.VMCALL<ReportFatalError> to KVM_EXIT_SYSTEM_EVENT with
>> a new type KVM_SYSTEM_EVENT_TDX_FATAL and forward it to userspace for
>> handling.
>>
>> TD guest can use TDG.VP.VMCALL<ReportFatalError> to report the fatal
>> error it has experienced. This hypercall is special because TD guest
>> is requesting a termination with the error information, KVM needs to
>> forward the hypercall to userspace anyway, KVM doesn't do sanity checks
>> and let userspace decide what to do.
>>
>> Signed-off-by: Binbin Wu <binbin.wu@...ux.intel.com>
>> ---
>> Hypercalls exit to userspace breakout:
>> - New added.
>> Implement one of the hypercalls need to exit to userspace for handling after
>> reverting "KVM: TDX: Add KVM Exit for TDX TDG.VP.VMCALL", which tries to resolve
>> Sean's comment.
>> https://lore.kernel.org/kvm/Zg18ul8Q4PGQMWam@google.com/
>> - Use TDVMCALL_STATUS prefix for TDX call status codes (Binbin)
>> ---
>> Documentation/virt/kvm/api.rst | 8 ++++++
>> arch/x86/kvm/vmx/tdx.c | 50 ++++++++++++++++++++++++++++++++++
>> include/uapi/linux/kvm.h | 1 +
>> 3 files changed, 59 insertions(+)
>>
>> diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
>> index edc070c6e19b..bb39da72c647 100644
>> --- a/Documentation/virt/kvm/api.rst
>> +++ b/Documentation/virt/kvm/api.rst
>> @@ -6815,6 +6815,7 @@ should put the acknowledged interrupt vector into the 'epr' field.
>> #define KVM_SYSTEM_EVENT_WAKEUP 4
>> #define KVM_SYSTEM_EVENT_SUSPEND 5
>> #define KVM_SYSTEM_EVENT_SEV_TERM 6
>> + #define KVM_SYSTEM_EVENT_TDX_FATAL 7
>> __u32 type;
>> __u32 ndata;
>> __u64 data[16];
>> @@ -6841,6 +6842,13 @@ Valid values for 'type' are:
>> reset/shutdown of the VM.
>> - KVM_SYSTEM_EVENT_SEV_TERM -- an AMD SEV guest requested termination.
>> The guest physical address of the guest's GHCB is stored in `data[0]`.
>> + - KVM_SYSTEM_EVENT_TDX_FATAL -- an TDX guest requested termination.
>> + The error codes of the guest's GHCI is stored in `data[0]`.
>> + If the bit 63 of `data[0]` is set, it indicates there is TD specified
>> + additional information provided in a page, which is shared memory. The
>> + guest physical address of the information page is stored in `data[1]`.
>> + An optional error message is provided by `data[2]` ~ `data[9]`, which is
>> + byte sequence, LSB filled first. Typically, ASCII code(0x20-0x7e) is filled.
>> - KVM_SYSTEM_EVENT_WAKEUP -- the exiting vCPU is in a suspended state and
>> KVM has recognized a wakeup event. Userspace may honor this event by
>> marking the exiting vCPU as runnable, or deny it and call KVM_RUN again.
>> diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c
>> index 553f4cbe0693..a79f9ca962d1 100644
>> --- a/arch/x86/kvm/vmx/tdx.c
>> +++ b/arch/x86/kvm/vmx/tdx.c
>> @@ -1093,6 +1093,54 @@ static int tdx_map_gpa(struct kvm_vcpu *vcpu)
>> return 1;
>> }
>> +static int tdx_report_fatal_error(struct kvm_vcpu *vcpu)
>> +{
>> + u64 reg_mask = kvm_rcx_read(vcpu);
>> + u64* opt_regs;
>> +
>> + /*
>> + * Skip sanity checks and let userspace decide what to do if sanity
>> + * checks fail.
>> + */
>> + vcpu->run->exit_reason = KVM_EXIT_SYSTEM_EVENT;
>> + vcpu->run->system_event.type = KVM_SYSTEM_EVENT_TDX_FATAL;
>> + vcpu->run->system_event.ndata = 10;
>> + /* Error codes. */
>> + vcpu->run->system_event.data[0] = tdvmcall_a0_read(vcpu);
>> + /* GPA of additional information page. */
>> + vcpu->run->system_event.data[1] = tdvmcall_a1_read(vcpu);
>> + /* Information passed via registers (up to 64 bytes). */
>> + opt_regs = &vcpu->run->system_event.data[2];
>> +
>> +#define COPY_REG(REG, MASK) \
>> + do { \
>> + if (reg_mask & MASK) \
>> + *opt_regs = kvm_ ## REG ## _read(vcpu); \
>> + else \
>> + *opt_regs = 0; \
>> + opt_regs++; \
>
> I'm not sure if we need to skip the "opt_regs++" the corresponding register is not set valid in reg_mask. And maintain ndata to actual valid number instead of hardcoding it to 10.
Yes, it's better.
>
>> + } while (0)
>> +
>> + /* The order is defined in GHCI. */
>> + COPY_REG(r14, BIT_ULL(14));
>> + COPY_REG(r15, BIT_ULL(15));
>> + COPY_REG(rbx, BIT_ULL(3));
>> + COPY_REG(rdi, BIT_ULL(7));
>> + COPY_REG(rsi, BIT_ULL(6));
>> + COPY_REG(r8, BIT_ULL(8));
>> + COPY_REG(r9, BIT_ULL(9));
>> + COPY_REG(rdx, BIT_ULL(2));
>> +
>> + /*
>> + * Set the status code according to GHCI spec, although the vCPU may
>> + * not return back to guest.
>> + */
>> + tdvmcall_set_return_code(vcpu, TDVMCALL_STATUS_SUCCESS);
>> +
>> + /* Forward request to userspace. */
>> + return 0;
>> +}
>> +
>> static int handle_tdvmcall(struct kvm_vcpu *vcpu)
>> {
>> if (tdvmcall_exit_type(vcpu))
>> @@ -1101,6 +1149,8 @@ static int handle_tdvmcall(struct kvm_vcpu *vcpu)
>> switch (tdvmcall_leaf(vcpu)) {
>> case TDVMCALL_MAP_GPA:
>> return tdx_map_gpa(vcpu);
>> + case TDVMCALL_REPORT_FATAL_ERROR:
>> + return tdx_report_fatal_error(vcpu);
>> default:
>> break;
>> }
>> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
>> index 637efc055145..c173c8dfcf83 100644
>> --- a/include/uapi/linux/kvm.h
>> +++ b/include/uapi/linux/kvm.h
>> @@ -375,6 +375,7 @@ struct kvm_run {
>> #define KVM_SYSTEM_EVENT_WAKEUP 4
>> #define KVM_SYSTEM_EVENT_SUSPEND 5
>> #define KVM_SYSTEM_EVENT_SEV_TERM 6
>> +#define KVM_SYSTEM_EVENT_TDX_FATAL 7
>> __u32 type;
>> __u32 ndata;
>> union {
>
>
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