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Date: Tue, 25 Jun 2024 15:00:59 +0800
From: Binbin Wu <binbin.wu@...ux.intel.com>
To: isaku.yamahata@...el.com, kvm@...r.kernel.org,
linux-kernel@...r.kernel.org
Cc: isaku.yamahata@...il.com, Paolo Bonzini <pbonzini@...hat.com>,
erdemaktas@...gle.com, Sean Christopherson <seanjc@...gle.com>,
Sagi Shahar <sagis@...gle.com>, Kai Huang <kai.huang@...el.com>,
chen.bo@...el.com, hang.yuan@...el.com, tina.zhang@...el.com,
Sean Christopherson <sean.j.christopherson@...el.com>,
Rick Edgecombe <rick.p.edgecombe@...el.com>,
Reinette Chatre <reinette.chatre@...el.com>
Subject: Re: [PATCH v19 110/130] KVM: TDX: Handle TDX PV MMIO hypercall
On 6/25/2024 2:54 PM, Binbin Wu wrote:
>
>
> On 2/26/2024 4:26 PM, isaku.yamahata@...el.com wrote:
>> From: Sean Christopherson <sean.j.christopherson@...el.com>
>>
>> Export kvm_io_bus_read and kvm_mmio tracepoint and wire up TDX PV MMIO
>> hypercall to the KVM backend functions.
>>
>> kvm_io_bus_read/write() searches KVM device emulated in kernel of the
>> given
>> MMIO address and emulates the MMIO. As TDX PV MMIO also needs it,
>> export
>> kvm_io_bus_read(). kvm_io_bus_write() is already exported. TDX PV MMIO
>> emulates some of MMIO itself. To add trace point consistently with x86
>> kvm, export kvm_mmio tracepoint.
>>
>> Signed-off-by: Sean Christopherson <sean.j.christopherson@...el.com>
>> Signed-off-by: Isaku Yamahata <isaku.yamahata@...el.com>
>> Reviewed-by: Paolo Bonzini <pbonzini@...hat.com>
>> ---
>> arch/x86/kvm/vmx/tdx.c | 114 +++++++++++++++++++++++++++++++++++++++++
>> arch/x86/kvm/x86.c | 1 +
>> virt/kvm/kvm_main.c | 2 +
>> 3 files changed, 117 insertions(+)
>>
>> diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c
>> index 55fc6cc6c816..389bb95d2af0 100644
>> --- a/arch/x86/kvm/vmx/tdx.c
>> +++ b/arch/x86/kvm/vmx/tdx.c
>> @@ -1217,6 +1217,118 @@ static int tdx_emulate_io(struct kvm_vcpu *vcpu)
>> return ret;
>> }
>> +static int tdx_complete_mmio(struct kvm_vcpu *vcpu)
>> +{
>> + unsigned long val = 0;
>> + gpa_t gpa;
>> + int size;
>> +
>> + KVM_BUG_ON(vcpu->mmio_needed != 1, vcpu->kvm);
>> + vcpu->mmio_needed = 0;
> mmio_needed is used by instruction emulator to setup the complete
> callback.
> Since TDX handle MMIO in a PV way, mmio_needed is not needed here.
>
>> +
>> + if (!vcpu->mmio_is_write) {
> It's also needed by instruction emulator, we can use
> vcpu->run->mmio.is_write instead.
>
>> + gpa = vcpu->mmio_fragments[0].gpa;
>> + size = vcpu->mmio_fragments[0].len;
>
> Since MMIO cross page boundary is not allowed according to the input
> checks from TDVMCALL, these mmio_fragments[] is not needed.
> Just use vcpu->run->mmio.phys_addr and vcpu->run->mmio.len?
>
>> +
>> + memcpy(&val, vcpu->run->mmio.data, size);
>> + tdvmcall_set_return_val(vcpu, val);
>> + trace_kvm_mmio(KVM_TRACE_MMIO_READ, size, gpa, &val);
>> + }
>
> Tracepoint for KVM_TRACE_MMIO_WRITE is missing when it is handled in
> userspace.
>
> Also, the return code is only set when the emulation is done in
> kernel, but not set when it's handled in userspace.
>
>> + return 1;
>> +}
>
> How about the fixup as following:
>
> @@ -1173,19 +1173,18 @@ static int tdx_emulate_io(struct kvm_vcpu
> *vcpu) static int tdx_complete_mmio(struct kvm_vcpu *vcpu) { unsigned
> long val = 0; - gpa_t gpa; - int size; - - vcpu->mmio_needed = 0; - -
> if (!vcpu->mmio_is_write) { - gpa = vcpu->mmio_fragments[0].gpa; -
> size = vcpu->mmio_fragments[0].len; + gpa_t gpa =
> vcpu->run->mmio.phys_addr; + int size = vcpu->run->mmio.len; + if
> (vcpu->run->mmio.is_write) { + trace_kvm_mmio(KVM_TRACE_MMIO_WRITE,
> size, gpa, &val); + } else { memcpy(&val, vcpu->run->mmio.data, size);
> tdvmcall_set_return_val(vcpu, val);
> trace_kvm_mmio(KVM_TRACE_MMIO_READ, size, gpa, &val); } + +
> tdvmcall_set_return_code(vcpu, TDVMCALL_SUCCESS); return 1; }
>
Sorry for the mess.
@@ -1173,19 +1173,18 @@ static int tdx_emulate_io(struct kvm_vcpu *vcpu)
static int tdx_complete_mmio(struct kvm_vcpu *vcpu)
{
unsigned long val = 0;
- gpa_t gpa;
- int size;
-
- vcpu->mmio_needed = 0;
-
- if (!vcpu->mmio_is_write) {
- gpa = vcpu->mmio_fragments[0].gpa;
- size = vcpu->mmio_fragments[0].len;
+ gpa_t gpa = vcpu->run->mmio.phys_addr;
+ int size = vcpu->run->mmio.len;
+ if (vcpu->run->mmio.is_write) {
+ trace_kvm_mmio(KVM_TRACE_MMIO_WRITE, size, gpa, &val);
+ } else {
memcpy(&val, vcpu->run->mmio.data, size);
tdvmcall_set_return_val(vcpu, val);
trace_kvm_mmio(KVM_TRACE_MMIO_READ, size, gpa, &val);
}
+
+ tdvmcall_set_return_code(vcpu, TDVMCALL_SUCCESS);
return 1;
}
>
>
>> +
>> +static inline int tdx_mmio_write(struct kvm_vcpu *vcpu, gpa_t gpa,
>> int size,
>> + unsigned long val)
>> +{
>> + if (kvm_iodevice_write(vcpu, &vcpu->arch.apic->dev, gpa, size,
>> &val) &&
>> + kvm_io_bus_write(vcpu, KVM_MMIO_BUS, gpa, size, &val))
>> + return -EOPNOTSUPP;
>> +
>> + trace_kvm_mmio(KVM_TRACE_MMIO_WRITE, size, gpa, &val);
>> + return 0;
>> +}
>> +
>> +static inline int tdx_mmio_read(struct kvm_vcpu *vcpu, gpa_t gpa,
>> int size)
>> +{
>> + unsigned long val;
>> +
>> + if (kvm_iodevice_read(vcpu, &vcpu->arch.apic->dev, gpa, size,
>> &val) &&
>> + kvm_io_bus_read(vcpu, KVM_MMIO_BUS, gpa, size, &val))
>> + return -EOPNOTSUPP;
>> +
>> + tdvmcall_set_return_val(vcpu, val);
>> + trace_kvm_mmio(KVM_TRACE_MMIO_READ, size, gpa, &val);
>> + return 0;
>> +}
>> +
>> +static int tdx_emulate_mmio(struct kvm_vcpu *vcpu)
>> +{
>> + struct kvm_memory_slot *slot;
>> + int size, write, r;
>> + unsigned long val;
>> + gpa_t gpa;
>> +
>> + KVM_BUG_ON(vcpu->mmio_needed, vcpu->kvm);
>> +
> [...]
>> +
>> + /* Request the device emulation to userspace device model. */
>> + vcpu->mmio_needed = 1;
>> + vcpu->mmio_is_write = write;
> Then they can be dropped.
>
>
>> + vcpu->arch.complete_userspace_io = tdx_complete_mmio;
>> +
>> + vcpu->run->mmio.phys_addr = gpa;
>> + vcpu->run->mmio.len = size;
>> + vcpu->run->mmio.is_write = write;
>> + vcpu->run->exit_reason = KVM_EXIT_MMIO;
>> +
>> + if (write) {
>> + memcpy(vcpu->run->mmio.data, &val, size);
>> + } else {
>> + vcpu->mmio_fragments[0].gpa = gpa;
>> + vcpu->mmio_fragments[0].len = size;
> These two lines can be dropped as well.
>
>> + trace_kvm_mmio(KVM_TRACE_MMIO_READ_UNSATISFIED, size, gpa, NULL);
>> + }
>> + return 0;
>> +
>> +error:
>> + tdvmcall_set_return_code(vcpu, TDVMCALL_INVALID_OPERAND);
>> + return 1;
>> +}
>> +
>
> - /* Request the device emulation to userspace device model. */ -
> vcpu->mmio_needed = 1; - vcpu->mmio_is_write = write;
> vcpu->arch.complete_userspace_io = tdx_complete_mmio;
> vcpu->run->mmio.phys_addr = gpa; @@ -1265,13 +1272,11 @@ static int
> tdx_emulate_mmio(struct kvm_vcpu *vcpu) vcpu->run->mmio.is_write =
> write; vcpu->run->exit_reason = KVM_EXIT_MMIO; - if (write) { + if
> (write) memcpy(vcpu->run->mmio.data, &val, size); - } else { -
> vcpu->mmio_fragments[0].gpa = gpa; - vcpu->mmio_fragments[0].len =
> size; + else trace_kvm_mmio(KVM_TRACE_MMIO_READ_UNSATISFIED, size,
> gpa, NULL); - } + return 0;
>
>
>
- /* Request the device emulation to userspace device model. */
- vcpu->mmio_needed = 1;
- vcpu->mmio_is_write = write;
vcpu->arch.complete_userspace_io = tdx_complete_mmio;
vcpu->run->mmio.phys_addr = gpa;
@@ -1265,13 +1272,11 @@ static int tdx_emulate_mmio(struct kvm_vcpu *vcpu)
vcpu->run->mmio.is_write = write;
vcpu->run->exit_reason = KVM_EXIT_MMIO;
- if (write) {
+ if (write)
memcpy(vcpu->run->mmio.data, &val, size);
- } else {
- vcpu->mmio_fragments[0].gpa = gpa;
- vcpu->mmio_fragments[0].len = size;
+ else
trace_kvm_mmio(KVM_TRACE_MMIO_READ_UNSATISFIED, size,
gpa, NULL);
- }
+
return 0;
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