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i386/kvm: Add KVM_EXIT_HYPERCALL handling for KVM_HC_MAP_GPA_RANGE

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KVM_HC_MAP_GPA_RANGE will be used to send requests to userspace for
private/shared memory attribute updates requested by the guest.
Implement handling for that use-case along with some basic
infrastructure for enabling specific hypercall events.

Signed-off-by: Michael Roth <michael.roth@amd.com>
Signed-off-by: Pankaj Gupta <pankaj.gupta@amd.com>
Message-ID: <20240530111643.1091816-31-pankaj.gupta@amd.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Michael Roth 2024-05-30 06:16:42 -05:00 committed by Paolo Bonzini
parent 0765d136eb
commit 47e76d03b1
3 changed files with 57 additions and 0 deletions
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55
target/i386/kvm/kvm.c
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@ -21,6 +21,7 @@
#include <sys/syscall.h>
#include <linux/kvm.h>
#include <linux/kvm_para.h>
#include "standard-headers/asm-x86/kvm_para.h"
#include "hw/xen/interface/arch-x86/cpuid.h"
@ -209,6 +210,13 @@ int kvm_get_vm_type(MachineState *ms)
return kvm_type;
}
bool kvm_enable_hypercall(uint64_t enable_mask)
{
KVMState *s = KVM_STATE(current_accel());
return !kvm_vm_enable_cap(s, KVM_CAP_EXIT_HYPERCALL, 0, enable_mask);
}
bool kvm_has_smm(void)
{
return kvm_vm_check_extension(kvm_state, KVM_CAP_X86_SMM);
@ -5322,6 +5330,50 @@ static bool host_supports_vmx(void)
return ecx & CPUID_EXT_VMX;
}
/*
* Currently the handling here only supports use of KVM_HC_MAP_GPA_RANGE
* to service guest-initiated memory attribute update requests so that
* KVM_SET_MEMORY_ATTRIBUTES can update whether or not a page should be
* backed by the private memory pool provided by guest_memfd, and as such
* is only applicable to guest_memfd-backed guests (e.g. SNP/TDX).
*
* Other other use-cases for KVM_HC_MAP_GPA_RANGE, such as for SEV live
* migration, are not implemented here currently.
*
* For the guest_memfd use-case, these exits will generally be synthesized
* by KVM based on platform-specific hypercalls, like GHCB requests in the
* case of SEV-SNP, and not issued directly within the guest though the
* KVM_HC_MAP_GPA_RANGE hypercall. So in this case, KVM_HC_MAP_GPA_RANGE is
* not actually advertised to guests via the KVM CPUID feature bit, as
* opposed to SEV live migration where it would be. Since it is unlikely the
* SEV live migration use-case would be useful for guest-memfd backed guests,
* because private/shared page tracking is already provided through other
* means, these 2 use-cases should be treated as being mutually-exclusive.
*/
static int kvm_handle_hc_map_gpa_range(struct kvm_run *run)
{
uint64_t gpa, size, attributes;
if (!machine_require_guest_memfd(current_machine))
return -EINVAL;
gpa = run->hypercall.args[0];
size = run->hypercall.args[1] * TARGET_PAGE_SIZE;
attributes = run->hypercall.args[2];
trace_kvm_hc_map_gpa_range(gpa, size, attributes, run->hypercall.flags);
return kvm_convert_memory(gpa, size, attributes & KVM_MAP_GPA_RANGE_ENCRYPTED);
}
static int kvm_handle_hypercall(struct kvm_run *run)
{
if (run->hypercall.nr == KVM_HC_MAP_GPA_RANGE)
return kvm_handle_hc_map_gpa_range(run);
return -EINVAL;
}
#define VMX_INVALID_GUEST_STATE 0x80000021
int kvm_arch_handle_exit(CPUState *cs, struct kvm_run *run)
@ -5417,6 +5469,9 @@ int kvm_arch_handle_exit(CPUState *cs, struct kvm_run *run)
ret = kvm_xen_handle_exit(cpu, &run->xen);
break;
#endif
case KVM_EXIT_HYPERCALL:
ret = kvm_handle_hypercall(run);
break;
default:
fprintf(stderr, "KVM: unknown exit reason %d\n", run->exit_reason);
ret = -1;

1
target/i386/kvm/kvm_i386.h
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@ -33,6 +33,7 @@
bool kvm_has_smm(void);
bool kvm_enable_x2apic(void);
bool kvm_hv_vpindex_settable(void);
bool kvm_enable_hypercall(uint64_t enable_mask);
bool kvm_enable_sgx_provisioning(KVMState *s);
bool kvm_hyperv_expand_features(X86CPU *cpu, Error **errp);

1
target/i386/kvm/trace-events
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@ -5,6 +5,7 @@ kvm_x86_fixup_msi_error(uint32_t gsi) "VT-d failed to remap interrupt for GSI %"
kvm_x86_add_msi_route(int virq) "Adding route entry for virq %d"
kvm_x86_remove_msi_route(int virq) "Removing route entry for virq %d"
kvm_x86_update_msi_routes(int num) "Updated %d MSI routes"
kvm_hc_map_gpa_range(uint64_t gpa, uint64_t size, uint64_t attributes, uint64_t flags) "gpa 0x%" PRIx64 " size 0x%" PRIx64 " attributes 0x%" PRIx64 " flags 0x%" PRIx64
# xen-emu.c
kvm_xen_hypercall(int cpu, uint8_t cpl, uint64_t input, uint64_t a0, uint64_t a1, uint64_t a2, uint64_t ret) "xen_hypercall: cpu %d cpl %d input %" PRIu64 " a0 0x%" PRIx64 " a1 0x%" PRIx64 " a2 0x%" PRIx64" ret 0x%" PRIx64