Merge tag 'kvm-x86-misc-6.12' of https://github.com/kvm-x86/linux into HEAD

KVM x86 misc changes for 6.12

 - Advertise AVX10.1 to userspace (effectively prep work for the "real" AVX10
   functionality that is on the horizon).

 - Rework common MSR handling code to suppress errors on userspace accesses to
   unsupported-but-advertised MSRs.  This will allow removing (almost?) all of
   KVM's exemptions for userspace access to MSRs that shouldn't exist based on
   the vCPU model (the actual cleanup is non-trivial future work).

 - Rework KVM's handling of x2APIC ICR, again, because AMD (x2AVIC) splits the
   64-bit value into the legacy ICR and ICR2 storage, whereas Intel (APICv)
   stores the entire 64-bit value a the ICR offset.

 - Fix a bug where KVM would fail to exit to userspace if one was triggered by
   a fastpath exit handler.

 - Add fastpath handling of HLT VM-Exit to expedite re-entering the guest when
   there's already a pending wake event at the time of the exit.

 - Finally fix the RSM vs. nested VM-Enter WARN by forcing the vCPU out of
   guest mode prior to signalling SHUTDOWN (architecturally, the SHUTDOWN is
   supposed to hit L1, not L2).

1 files changed, 20 insertions, 1 deletions

diff --git a/tools/testing/selftests/kvm/include/x86_64/apic.h b/tools/testing/selftests/kvm/include/x86_64/apic.h
index 0f268b55fa06..51990094effd 100644
--- a/tools/testing/selftests/kvm/include/x86_64/apic.h
+++ b/tools/testing/selftests/kvm/include/x86_64/apic.h
@@ -11,6 +11,7 @@
 #include <stdint.h>
 
 #include "processor.h"
+#include "ucall_common.h"
 
 #define APIC_DEFAULT_GPA		0xfee00000ULL
 
@@ -93,9 +94,27 @@ static inline uint64_t x2apic_read_reg(unsigned int reg)
 	return rdmsr(APIC_BASE_MSR + (reg >> 4));
 }
 
+static inline uint8_t x2apic_write_reg_safe(unsigned int reg, uint64_t value)
+{
+	return wrmsr_safe(APIC_BASE_MSR + (reg >> 4), value);
+}
+
 static inline void x2apic_write_reg(unsigned int reg, uint64_t value)
 {
-	wrmsr(APIC_BASE_MSR + (reg >> 4), value);
+	uint8_t fault = x2apic_write_reg_safe(reg, value);
+
+	__GUEST_ASSERT(!fault, "Unexpected fault 0x%x on WRMSR(%x) = %lx\n",
+		       fault, APIC_BASE_MSR + (reg >> 4), value);
 }
 
+static inline void x2apic_write_reg_fault(unsigned int reg, uint64_t value)
+{
+	uint8_t fault = x2apic_write_reg_safe(reg, value);
+
+	__GUEST_ASSERT(fault == GP_VECTOR,
+		       "Wanted #GP on WRMSR(%x) = %lx, got 0x%x\n",
+		       APIC_BASE_MSR + (reg >> 4), value, fault);
+}
+
+
 #endif /* SELFTEST_KVM_APIC_H */