On Thu, Dec 22, 2022, Vishal Annapurve wrote:
Add an API to execute hypercall as per the cpu type by checking the underlying CPU. KVM emulates vmcall/vmmcall instruction by modifying guest memory contents with hypercall instruction as per the cpu type.
Confidential VMs need to execute hypercall instruction without it being emulated by KVM as KVM can not modify guest memory contents.
Signed-off-by: Vishal Annapurve vannapurve@google.com
.../selftests/kvm/include/x86_64/processor.h | 3 +++ .../selftests/kvm/lib/x86_64/processor.c | 18 ++++++++++++++++++ 2 files changed, 21 insertions(+)
diff --git a/tools/testing/selftests/kvm/include/x86_64/processor.h b/tools/testing/selftests/kvm/include/x86_64/processor.h index 4d5dd9a467e1..3617f83bb2e5 100644 --- a/tools/testing/selftests/kvm/include/x86_64/processor.h +++ b/tools/testing/selftests/kvm/include/x86_64/processor.h @@ -1039,6 +1039,9 @@ uint64_t *vm_get_page_table_entry(struct kvm_vm *vm, uint64_t vaddr); uint64_t kvm_hypercall(uint64_t nr, uint64_t a0, uint64_t a1, uint64_t a2, uint64_t a3); +uint64_t kvm_native_hypercall(uint64_t nr, uint64_t a0, uint64_t a1, uint64_t a2,
uint64_t a3);void __vm_xsave_require_permission(int bit, const char *name); #define vm_xsave_require_permission(perm) \ diff --git a/tools/testing/selftests/kvm/lib/x86_64/processor.c b/tools/testing/selftests/kvm/lib/x86_64/processor.c index 1e93bb3cb058..429e55f2609f 100644 --- a/tools/testing/selftests/kvm/lib/x86_64/processor.c +++ b/tools/testing/selftests/kvm/lib/x86_64/processor.c @@ -1202,6 +1202,24 @@ uint64_t kvm_hypercall(uint64_t nr, uint64_t a0, uint64_t a1, uint64_t a2, return r; } +uint64_t kvm_native_hypercall(uint64_t nr, uint64_t a0, uint64_t a1, uint64_t a2,
Just do this in kvm_hypercall(). David didn't say "don't do that", he said "don't do that in a single patch". Except for fix_hypercall_test, selftests should always use the native hypercall instruction and not rely on KVM's patching, e.g. patching will go sideways if someone gets clever and makes guest code not-writable.
uint64_t a3)
Align parameters.
+{
- uint64_t r;
- if (is_amd_cpu()) {
Curly brace is unnecessary. Though I think I'd prefer to not duplicate the asm blob (too many darn inputs). It's a little ugly, but I prefer it over duplicating the entire blob. The approach could also likely be macrofied for other hypercall usage (future problem).
asm volatile("test %[use_vmmcall], %[use_vmmcall]\n\t" "jnz 1f\n\t" "vmcall\n\t" "jmp 2f\n\t" "1: vmmcall\n\t" "2:" : "=a"(r) : "a"(nr), "b"(a0), "c"(a1), "d"(a2), "S"(a3), [use_vmmcall] "r" (is_amd_cpu())); return r;