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-rw-r--r--tools/testing/selftests/kvm/include/x86_64/processor.h74
-rw-r--r--tools/testing/selftests/kvm/lib/x86_64/processor.c17
-rw-r--r--tools/testing/selftests/kvm/x86_64/kvm_pv_test.c74
3 files changed, 102 insertions, 63 deletions
diff --git a/tools/testing/selftests/kvm/include/x86_64/processor.h b/tools/testing/selftests/kvm/include/x86_64/processor.h
index 32964d7b2218..79dcf6be1b47 100644
--- a/tools/testing/selftests/kvm/include/x86_64/processor.h
+++ b/tools/testing/selftests/kvm/include/x86_64/processor.h
@@ -15,6 +15,8 @@
#include <asm/msr-index.h>
#include <asm/prctl.h>
+#include <linux/stringify.h>
+
#include "../kvm_util.h"
#define NMI_VECTOR 0x02
@@ -541,6 +543,78 @@ void vcpu_init_descriptor_tables(struct kvm_vcpu *vcpu);
void vm_install_exception_handler(struct kvm_vm *vm, int vector,
void (*handler)(struct ex_regs *));
+/* If a toddler were to say "abracadabra". */
+#define KVM_EXCEPTION_MAGIC 0xabacadabaull
+
+/*
+ * KVM selftest exception fixup uses registers to coordinate with the exception
+ * handler, versus the kernel's in-memory tables and KVM-Unit-Tests's in-memory
+ * per-CPU data. Using only registers avoids having to map memory into the
+ * guest, doesn't require a valid, stable GS.base, and reduces the risk of
+ * for recursive faults when accessing memory in the handler. The downside to
+ * using registers is that it restricts what registers can be used by the actual
+ * instruction. But, selftests are 64-bit only, making register* pressure a
+ * minor concern. Use r9-r11 as they are volatile, i.e. don't need* to be saved
+ * by the callee, and except for r11 are not implicit parameters to any
+ * instructions. Ideally, fixup would use r8-r10 and thus avoid implicit
+ * parameters entirely, but Hyper-V's hypercall ABI uses r8 and testing Hyper-V
+ * is higher priority than testing non-faulting SYSCALL/SYSRET.
+ *
+ * Note, the fixup handler deliberately does not handle #DE, i.e. the vector
+ * is guaranteed to be non-zero on fault.
+ *
+ * REGISTER INPUTS:
+ * r9 = MAGIC
+ * r10 = RIP
+ * r11 = new RIP on fault
+ *
+ * REGISTER OUTPUTS:
+ * r9 = exception vector (non-zero)
+ */
+#define KVM_ASM_SAFE(insn) \
+ "mov $" __stringify(KVM_EXCEPTION_MAGIC) ", %%r9\n\t" \
+ "lea 1f(%%rip), %%r10\n\t" \
+ "lea 2f(%%rip), %%r11\n\t" \
+ "1: " insn "\n\t" \
+ "mov $0, %[vector]\n\t" \
+ "jmp 3f\n\t" \
+ "2:\n\t" \
+ "mov %%r9b, %[vector]\n\t" \
+ "3:\n\t"
+
+#define KVM_ASM_SAFE_OUTPUTS(v) [vector] "=qm"(v)
+#define KVM_ASM_SAFE_CLOBBERS "r9", "r10", "r11"
+
+#define kvm_asm_safe(insn, inputs...) \
+({ \
+ uint8_t vector; \
+ \
+ asm volatile(KVM_ASM_SAFE(insn) \
+ : KVM_ASM_SAFE_OUTPUTS(vector) \
+ : inputs \
+ : KVM_ASM_SAFE_CLOBBERS); \
+ vector; \
+})
+
+static inline uint8_t rdmsr_safe(uint32_t msr, uint64_t *val)
+{
+ uint8_t vector;
+ uint32_t a, d;
+
+ asm volatile(KVM_ASM_SAFE("rdmsr")
+ : "=a"(a), "=d"(d), KVM_ASM_SAFE_OUTPUTS(vector)
+ : "c"(msr)
+ : KVM_ASM_SAFE_CLOBBERS);
+
+ *val = (uint64_t)a | ((uint64_t)d << 32);
+ return vector;
+}
+
+static inline uint8_t wrmsr_safe(uint32_t msr, uint64_t val)
+{
+ return kvm_asm_safe("wrmsr", "A"(val), "c"(msr));
+}
+
uint64_t vm_get_page_table_entry(struct kvm_vm *vm, struct kvm_vcpu *vcpu,
uint64_t vaddr);
void vm_set_page_table_entry(struct kvm_vm *vm, struct kvm_vcpu *vcpu,
diff --git a/tools/testing/selftests/kvm/lib/x86_64/processor.c b/tools/testing/selftests/kvm/lib/x86_64/processor.c
index 906132e70fa4..1a32b1c75e9a 100644
--- a/tools/testing/selftests/kvm/lib/x86_64/processor.c
+++ b/tools/testing/selftests/kvm/lib/x86_64/processor.c
@@ -1127,6 +1127,20 @@ static void set_idt_entry(struct kvm_vm *vm, int vector, unsigned long addr,
e->offset2 = addr >> 32;
}
+
+static bool kvm_fixup_exception(struct ex_regs *regs)
+{
+ if (regs->r9 != KVM_EXCEPTION_MAGIC || regs->rip != regs->r10)
+ return false;
+
+ if (regs->vector == DE_VECTOR)
+ return false;
+
+ regs->rip = regs->r11;
+ regs->r9 = regs->vector;
+ return true;
+}
+
void kvm_exit_unexpected_vector(uint32_t value)
{
ucall(UCALL_UNHANDLED, 1, value);
@@ -1142,6 +1156,9 @@ void route_exception(struct ex_regs *regs)
return;
}
+ if (kvm_fixup_exception(regs))
+ return;
+
kvm_exit_unexpected_vector(regs->vector);
}
diff --git a/tools/testing/selftests/kvm/x86_64/kvm_pv_test.c b/tools/testing/selftests/kvm/x86_64/kvm_pv_test.c
index 5901ccec7079..feff85e43be3 100644
--- a/tools/testing/selftests/kvm/x86_64/kvm_pv_test.c
+++ b/tools/testing/selftests/kvm/x86_64/kvm_pv_test.c
@@ -12,55 +12,6 @@
#include "kvm_util.h"
#include "processor.h"
-extern unsigned char rdmsr_start;
-extern unsigned char rdmsr_end;
-
-static u64 do_rdmsr(u32 idx)
-{
- u32 lo, hi;
-
- asm volatile("rdmsr_start: rdmsr;"
- "rdmsr_end:"
- : "=a"(lo), "=c"(hi)
- : "c"(idx));
-
- return (((u64) hi) << 32) | lo;
-}
-
-extern unsigned char wrmsr_start;
-extern unsigned char wrmsr_end;
-
-static void do_wrmsr(u32 idx, u64 val)
-{
- u32 lo, hi;
-
- lo = val;
- hi = val >> 32;
-
- asm volatile("wrmsr_start: wrmsr;"
- "wrmsr_end:"
- : : "a"(lo), "c"(idx), "d"(hi));
-}
-
-static int nr_gp;
-
-static void guest_gp_handler(struct ex_regs *regs)
-{
- unsigned char *rip = (unsigned char *)regs->rip;
- bool r, w;
-
- r = rip == &rdmsr_start;
- w = rip == &wrmsr_start;
- GUEST_ASSERT(r || w);
-
- nr_gp++;
-
- if (r)
- regs->rip = (uint64_t)&rdmsr_end;
- else
- regs->rip = (uint64_t)&wrmsr_end;
-}
-
struct msr_data {
uint32_t idx;
const char *name;
@@ -89,14 +40,16 @@ static struct msr_data msrs_to_test[] = {
static void test_msr(struct msr_data *msr)
{
+ uint64_t ignored;
+ uint8_t vector;
+
PR_MSR(msr);
- do_rdmsr(msr->idx);
- GUEST_ASSERT(READ_ONCE(nr_gp) == 1);
- nr_gp = 0;
- do_wrmsr(msr->idx, 0);
- GUEST_ASSERT(READ_ONCE(nr_gp) == 1);
- nr_gp = 0;
+ vector = rdmsr_safe(msr->idx, &ignored);
+ GUEST_ASSERT_1(vector == GP_VECTOR, vector);
+
+ vector = wrmsr_safe(msr->idx, 0);
+ GUEST_ASSERT_1(vector == GP_VECTOR, vector);
}
struct hcall_data {
@@ -165,12 +118,6 @@ static void pr_hcall(struct ucall *uc)
pr_info("testing hcall: %s (%lu)\n", hc->name, hc->nr);
}
-static void handle_abort(struct ucall *uc)
-{
- TEST_FAIL("%s at %s:%ld", (const char *)uc->args[0],
- __FILE__, uc->args[1]);
-}
-
static void enter_guest(struct kvm_vcpu *vcpu)
{
struct kvm_run *run = vcpu->run;
@@ -190,7 +137,9 @@ static void enter_guest(struct kvm_vcpu *vcpu)
pr_hcall(&uc);
break;
case UCALL_ABORT:
- handle_abort(&uc);
+ TEST_FAIL("%s at %s:%ld, vector = %lu",
+ (const char *)uc.args[0], __FILE__,
+ uc.args[1], uc.args[2]);
return;
case UCALL_DONE:
return;
@@ -216,7 +165,6 @@ int main(void)
vm_init_descriptor_tables(vm);
vcpu_init_descriptor_tables(vcpu);
- vm_install_exception_handler(vm, GP_VECTOR, guest_gp_handler);
enter_guest(vcpu);
kvm_vm_free(vm);
generated by cgit v1.2.3 (git 2.39.1) at 2024-06-16 18:46:09 +0000