On Tue, Apr 09, 2024, Peter Gonda wrote:
Modifies ucall handling for SEV-ES VMs.
Please follow the preferred changelog style as described in Documentation/process/maintainer-kvm-x86.rst
Instead of using an out instruction and storing the ucall pointer in RDI, SEV-ES guests use a outsb VMGEXIT to move the ucall pointer as the data.
Explain _why_. After poking around, I think I agree that string I/O is the least awful choice, but string I/O is generally unpleasant. E.g. my initial reaction to this addr = *(uint64_t *)((uint8_t *)(run) + run->io.data_offset);
was quite literally, "LOL, what?".
We could use MMIO, because there is no *real* instruction in the guest, it's all make believe, i.e. there doesn't actually need to be MMIO anywhere. But then we need to define an address; it could simply be the ucall address, but then SEV-ES ends up with a completely different flow then the regular magic I/O port.
The changelog should capture explain why string I/O was chosen over the "obvious" alternatives so that readers and reviewers aren't left wondering why on earth we *chose* to use string I/O.
Allows for SEV-ES to use ucalls instead of relying the SEV-ES MSR based termination protocol.
Cc: Vishal Annapurve vannapurve@google.com Cc: Ackerley Tng ackerleytng@google.com Cc: Paolo Bonzini pbonzini@redhat.com Cc: Claudio Imbrenda imbrenda@linux.ibm.com Cc: Sean Christopherson seanjc@google.com Cc: Carlos Bilbao carlos.bilbao@amd.com Cc: Tom Lendacky thomas.lendacky@amd.com Cc: Michael Roth michael.roth@amd.com Cc: kvm@vger.kernel.org Cc: linux-kselftest@vger.kernel.org Signed-off-by: Peter Gonda pgonda@google.com
.../selftests/kvm/include/x86_64/sev.h | 2 + tools/testing/selftests/kvm/lib/x86_64/sev.c | 67 ++++++++++++++++++- .../testing/selftests/kvm/lib/x86_64/ucall.c | 17 +++++ .../selftests/kvm/x86_64/sev_smoke_test.c | 17 +---- 4 files changed, 84 insertions(+), 19 deletions(-)
diff --git a/tools/testing/selftests/kvm/include/x86_64/sev.h b/tools/testing/selftests/kvm/include/x86_64/sev.h index 691dc005e2a1..26447caccd40 100644 --- a/tools/testing/selftests/kvm/include/x86_64/sev.h +++ b/tools/testing/selftests/kvm/include/x86_64/sev.h @@ -109,4 +109,6 @@ static inline void sev_launch_update_data(struct kvm_vm *vm, vm_paddr_t gpa, bool is_sev_enabled(void); bool is_sev_es_enabled(void); +void sev_es_ucall_port_write(uint32_t port, uint64_t data);
#endif /* SELFTEST_KVM_SEV_H */ diff --git a/tools/testing/selftests/kvm/lib/x86_64/sev.c b/tools/testing/selftests/kvm/lib/x86_64/sev.c index 5b3f0a8a931a..276477f2c2cf 100644 --- a/tools/testing/selftests/kvm/lib/x86_64/sev.c +++ b/tools/testing/selftests/kvm/lib/x86_64/sev.c @@ -8,11 +8,18 @@ #include "svm.h" #include "svm_util.h" +#define IOIO_TYPE_STR (1 << 2) +#define IOIO_SEG_DS (1 << 11 | 1 << 10) +#define IOIO_DATA_8 (1 << 4) +#define IOIO_REP (1 << 3)
+#define SW_EXIT_CODE_IOIO 0x7b
struct ghcb_entry { struct ghcb ghcb; /* Guest physical address of this GHCB. */
- void *gpa;
- uint64_t gpa;
/* Host virtual address of this struct. */ struct ghcb_entry *hva; @@ -45,16 +52,22 @@ void ghcb_init(struct kvm_vm *vm) for (i = 0; i < KVM_MAX_VCPUS; ++i) { entry = &hdr->ghcbs[i]; entry->hva = entry;
entry->gpa = addr_hva2gpa(vm, &entry->ghcb);
entry->gpa = (uint64_t)addr_hva2gpa(vm, &entry->ghcb);write_guest_global(vm, ghcb_pool, (struct ghcb_header *)vaddr); } +static void sev_es_terminate(void) +{
- wrmsr(MSR_AMD64_SEV_ES_GHCB, GHCB_MSR_TERM_REQ);
+}
static struct ghcb_entry *ghcb_alloc(void) { return &ghcb_pool->ghcbs[0]; struct ghcb_entry *entry;
- struct ghcb *ghcb; int i;
if (!ghcb_pool) @@ -63,12 +76,18 @@ static struct ghcb_entry *ghcb_alloc(void) for (i = 0; i < KVM_MAX_VCPUS; ++i) { if (!test_and_set_bit(i, ghcb_pool->in_use)) { entry = &ghcb_pool->ghcbs[i];
memset(&entry->ghcb, 0, sizeof(entry->ghcb));
ghcb = &entry->ghcb;memset(&ghcb, 0, sizeof(*ghcb));ghcb->ghcb_usage = 0;ghcb->protocol_version = 1;return entry;ucall_failed:
- sev_es_terminate(); return NULL;
} @@ -200,3 +219,45 @@ bool is_sev_es_enabled(void) return is_sev_enabled() && rdmsr(MSR_AMD64_SEV) & MSR_AMD64_SEV_ES_ENABLED; }
+static uint64_t setup_exitinfo1_portio(uint32_t port) +{
- uint64_t exitinfo1 = 0;
- exitinfo1 |= IOIO_TYPE_STR;
- exitinfo1 |= ((port & 0xffff) << 16);
- exitinfo1 |= IOIO_SEG_DS;
- exitinfo1 |= IOIO_DATA_8;
- exitinfo1 |= IOIO_REP;
- return exitinfo1;
+}
+static void do_vmg_exit(uint64_t ghcb_gpa) +{
- wrmsr(MSR_AMD64_SEV_ES_GHCB, ghcb_gpa);
- __asm__ __volatile__("rep; vmmcall");
+}
+void sev_es_ucall_port_write(uint32_t port, uint64_t data) +{
- struct ghcb_entry *entry;
- struct ghcb *ghcb;
- const uint64_t exitinfo1 = setup_exitinfo1_portio(port);
- entry = ghcb_alloc();
- ghcb = &entry->ghcb;
- ghcb_set_sw_exit_code(ghcb, SW_EXIT_CODE_IOIO);
- ghcb_set_sw_exit_info_1(ghcb, exitinfo1);
- ghcb_set_sw_exit_info_2(ghcb, sizeof(data));
- // Setup the SW Stratch buffer pointer.
- ghcb_set_sw_scratch(ghcb,
entry->gpa + offsetof(struct ghcb, shared_buffer));- memcpy(&ghcb->shared_buffer, &data, sizeof(data));
- do_vmg_exit(entry->gpa);
- ghcb_free(entry);
+} diff --git a/tools/testing/selftests/kvm/lib/x86_64/ucall.c b/tools/testing/selftests/kvm/lib/x86_64/ucall.c index 1265cecc7dd1..24da2f4316d8 100644 --- a/tools/testing/selftests/kvm/lib/x86_64/ucall.c +++ b/tools/testing/selftests/kvm/lib/x86_64/ucall.c @@ -5,6 +5,8 @@
- Copyright (C) 2018, Red Hat, Inc.
*/ #include "kvm_util.h" +#include "processor.h" +#include "sev.h" #define UCALL_PIO_PORT ((uint16_t)0x1000) @@ -21,6 +23,10 @@ void ucall_arch_do_ucall(vm_vaddr_t uc) #define HORRIFIC_L2_UCALL_CLOBBER_HACK \ "rcx", "rsi", "r8", "r9", "r10", "r11"
- if (is_sev_es_enabled()) {
No curly braces needed.
sev_es_ucall_port_write(UCALL_PIO_PORT, uc);- }
This will clearly fall through to the standard IN, which I suspect is wrong and only "works" because the only usage is a single GUEST_DONE(), i.e. no test actually resumes to this point.
- asm volatile("push %%rbp\n\t" "push %%r15\n\t" "push %%r14\n\t"
@@ -48,8 +54,19 @@ void *ucall_arch_get_ucall(struct kvm_vcpu *vcpu) if (run->exit_reason == KVM_EXIT_IO && run->io.port == UCALL_PIO_PORT) { struct kvm_regs regs;
uint64_t addr;if (vcpu->vm->subtype == VM_SUBTYPE_SEV_ES) {TEST_ASSERT(
No Google3 style please. I'm going to start charging folks for these violations. I don't know _how_, but darn it, I'll find a way :-)
run->io.count == 8 && run->io.size == 1,"SEV-ES ucall exit requires 8 byte string out\n");addr = *(uint64_t *)((uint8_t *)(run) + run->io.data_offset);
Rather than this amazing bit of casting, I'm tempted to say we should add kvm_vcpu_arch{} and then map the PIO page in vm_arch_vcpu_add(). Then this is more sanely:
return *(uint64_t *)vcpu->arch.pio);
where vcpu->arch.pio is a "void *". At least, I think that would work?
return (void *)addr;}vcpu_regs_get(vcpu, ®s);
Spurious whitespace.