Please use "KVM: selftest: ..." for the shortlog.
On Sat, Sep 03, 2022 at 01:28:47AM +0000, Vishal Annapurve wrote:
Modify following APIs for x86 implementation:
- kvm_arch_main : Query the cpu vendor and cache the value in advance.
- kvm_arch_post_vm_load: Populate cpu type in the guest memory so that guest doesn't need to execute cpuid instruction again.
This commit message only describes a subset of the changes in this commit, and does not provide any context on why the changes are being made (other than a clue about avoiding CPUID).
I also think this could be split up into 2 separate commits.
I would suggest first patch changes is_{intel,amd}_cpu() to return a cached result. e.g.
KVM: selftests: Precompute the result for is_{intel,amd}_cpu()
Cache the vendor CPU type in a global variable so that multiple calls to is_intel_cpu() do not need to re-execute CPUID. This will be useful in a follow-up commit to check if running on AMD or Intel from within a selftest guest where executing CPUID requires a VM-exit.
Then add support for AMD to kvm_hypercall():
KVM: selftests: Add AMD support to kvm_hypercall()
Add support for AMD hypercalls to kvm_hypercall() so that it can be used in selftests running on Intel or AMD hosts. This will be used in a follow up commit to ...
As part of this change, sync the global variable is_cpu_amd into the guest so the guest can determine which hypercall instruction to use without needing to re-execute CPUID for every hypercall.
Suggested-by: Sean Christopherson seanjc@google.com Signed-off-by: Vishal Annapurve vannapurve@google.com
.../testing/selftests/kvm/lib/x86_64/processor.c | 15 ++++++++++++--- 1 file changed, 12 insertions(+), 3 deletions(-)
diff --git a/tools/testing/selftests/kvm/lib/x86_64/processor.c b/tools/testing/selftests/kvm/lib/x86_64/processor.c index e22cfc4bf284..ac104653ab43 100644 --- a/tools/testing/selftests/kvm/lib/x86_64/processor.c +++ b/tools/testing/selftests/kvm/lib/x86_64/processor.c @@ -19,6 +19,7 @@ #define MAX_NR_CPUID_ENTRIES 100 vm_vaddr_t exception_handlers; +static int is_cpu_amd = -1;
Should this just be a bool? Since you are initializing it before main(), there is really no way for any code to observe it's pre-initialized value. And nothing even checks if is_cpu_amd -1, it just silently returns false from is_intel_cpu() and is_amd_cpu().
static void regs_dump(FILE *stream, struct kvm_regs *regs, uint8_t indent) { @@ -1019,7 +1020,7 @@ static bool cpu_vendor_string_is(const char *vendor) bool is_intel_cpu(void) {
- return cpu_vendor_string_is("GenuineIntel");
- return (is_cpu_amd == 0);
} /* @@ -1027,7 +1028,7 @@ bool is_intel_cpu(void) */ bool is_amd_cpu(void) {
- return cpu_vendor_string_is("AuthenticAMD");
- return (is_cpu_amd == 1);
} void kvm_get_cpu_address_width(unsigned int *pa_bits, unsigned int *va_bits) @@ -1182,9 +1183,15 @@ uint64_t kvm_hypercall(uint64_t nr, uint64_t a0, uint64_t a1, uint64_t a2, { uint64_t r;
- asm volatile("vmcall"
- if (is_amd_cpu())
asm volatile("vmmcall" : "=a"(r) : "a"(nr), "b"(a0), "c"(a1), "d"(a2), "S"(a3));- else
asm volatile("vmcall": "=a"(r): "a"(nr), "b"(a0), "c"(a1), "d"(a2), "S"(a3));- return r;
} @@ -1314,8 +1321,10 @@ bool vm_is_unrestricted_guest(struct kvm_vm *vm) void kvm_arch_main(void) {
- is_cpu_amd = cpu_vendor_string_is("AuthenticAMD") ? 1 : 0;
} void kvm_arch_post_vm_load(struct kvm_vm *vm) {
- sync_global_to_guest(vm, is_cpu_amd);
}
2.37.2.789.g6183377224-goog