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KVM: x86/xen: Fix coexistence of Xen and Hyper-V hypercalls

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Disambiguate Xen vs. Hyper-V calls by adding 'orl $0x80000000, %eax'
at the start of the Hyper-V hypercall page when Xen hypercalls are
also enabled.

That bit is reserved in the Hyper-V ABI, and those hypercall numbers
will never be used by Xen (because it does precisely the same trick).

Switch to using kvm_vcpu_write_guest() while we're at it, instead of
open-coding it.

Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
This commit is contained in:
Joao Martins
2021-02-04 14:19:24 +00:00
committed by David Woodhouse
parent 23200b7a30
commit 79033bebf6
3 changed files with 68 additions and 17 deletions
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tools/testing/selftests/kvm/x86_64/xen_vmcall_test.c
+33 -6
View File
@@ -15,6 +15,7 @@
#define HCALL_REGION_GPA 0xc0000000ULL
#define HCALL_REGION_SLOT 10
#define PAGE_SIZE 4096
static struct kvm_vm *vm;
@@ -22,7 +23,12 @@ static struct kvm_vm *vm;
#define ARGVALUE(x) (0xdeadbeef5a5a0000UL + x)
#define RETVALUE 0xcafef00dfbfbffffUL
#define XEN_HYPERCALL_MSR 0x40000000
#define XEN_HYPERCALL_MSR 0x40000200
#define HV_GUEST_OS_ID_MSR 0x40000000
#define HV_HYPERCALL_MSR 0x40000001
#define HVCALL_SIGNAL_EVENT 0x005d
#define HV_STATUS_INVALID_ALIGNMENT 4
static void guest_code(void)
{
@@ -30,6 +36,7 @@ static void guest_code(void)
unsigned long rdi = ARGVALUE(1);
unsigned long rsi = ARGVALUE(2);
unsigned long rdx = ARGVALUE(3);
unsigned long rcx;
register unsigned long r10 __asm__("r10") = ARGVALUE(4);
register unsigned long r8 __asm__("r8") = ARGVALUE(5);
register unsigned long r9 __asm__("r9") = ARGVALUE(6);
@@ -41,18 +48,38 @@ static void guest_code(void)
"r"(r10), "r"(r8), "r"(r9));
GUEST_ASSERT(rax == RETVALUE);
/* Now fill in the hypercall page */
/* Fill in the Xen hypercall page */
__asm__ __volatile__("wrmsr" : : "c" (XEN_HYPERCALL_MSR),
"a" (HCALL_REGION_GPA & 0xffffffff),
"d" (HCALL_REGION_GPA >> 32));
/* And invoke the same hypercall that way */
/* Set Hyper-V Guest OS ID */
__asm__ __volatile__("wrmsr" : : "c" (HV_GUEST_OS_ID_MSR),
"a" (0x5a), "d" (0));
/* Hyper-V hypercall page */
u64 msrval = HCALL_REGION_GPA + PAGE_SIZE + 1;
__asm__ __volatile__("wrmsr" : : "c" (HV_HYPERCALL_MSR),
"a" (msrval & 0xffffffff),
"d" (msrval >> 32));
/* Invoke a Xen hypercall */
__asm__ __volatile__("call *%1" : "=a"(rax) :
"r"(HCALL_REGION_GPA + INPUTVALUE * 32),
"a"(rax), "D"(rdi), "S"(rsi), "d"(rdx),
"r"(r10), "r"(r8), "r"(r9));
GUEST_ASSERT(rax == RETVALUE);
/* Invoke a Hyper-V hypercall */
rax = 0;
rcx = HVCALL_SIGNAL_EVENT; /* code */
rdx = 0x5a5a5a5a; /* ingpa (badly aligned) */
__asm__ __volatile__("call *%1" : "=a"(rax) :
"r"(HCALL_REGION_GPA + PAGE_SIZE),
"a"(rax), "c"(rcx), "d"(rdx),
"r"(r8));
GUEST_ASSERT(rax == HV_STATUS_INVALID_ALIGNMENT);
GUEST_DONE();
}
@@ -73,11 +100,11 @@ int main(int argc, char *argv[])
};
vm_ioctl(vm, KVM_XEN_HVM_CONFIG, &hvmc);
/* Map a region for the hypercall page */
/* Map a region for the hypercall pages */
vm_userspace_mem_region_add(vm, VM_MEM_SRC_ANONYMOUS,
HCALL_REGION_GPA, HCALL_REGION_SLOT,
getpagesize(), 0);
virt_map(vm, HCALL_REGION_GPA, HCALL_REGION_GPA, 1, 0);
2 * getpagesize(), 0);
virt_map(vm, HCALL_REGION_GPA, HCALL_REGION_GPA, 2, 0);
for (;;) {
volatile struct kvm_run *run = vcpu_state(vm, VCPU_ID);