Re: [V2 07/11] KVM: selftests: Consolidate boilerplate code in get_ucall()

Peter Gonda
2022-08-02T14:47:21Z

On Tue, Aug 2, 2022 at 3:54 AM Andrew Jones <andrew.jones@linux.dev> wrote:
>
> On Mon, Aug 01, 2022 at 01:11:05PM -0700, Peter Gonda wrote:
> > From: Sean Christopherson <seanjc@google.com>
> >
> > Consolidate the actual copying of a ucall struct from guest=>host into
> > the common get_ucall(). Return a host virtual address instead of a guest
> > virtual address even though the addr_gva2hva() part could be moved to
> > get_ucall() too. Conceptually, get_ucall() is invoked from the host and
> > should return a host virtual address (and returning NULL for "nothing to
> > see here" is far superior to returning 0).
>
> The code does not match this description anymore, now that
> ucall_arch_get_ucall() returns a gva (as a uint64_t), but the description
> is good, the code is wrong. Please restore the spirit of Sean's patch
> (particularly because it still says it's from Sean...)

As discussed in the encrypted ucall patch I'll get this fixed up to
return gva from ucall_arch_get_ucall() and return a vm_addr_t.

>
> Thanks,
> drew
>
> >
> > Use pointer shenanigans instead of an unnecessary bounce buffer when the
> > caller of get_ucall() provides a valid pointer.
> >
> > Signed-off-by: Sean Christopherson <seanjc@google.com>
> > Signed-off-by: Peter Gonda <pgonda@google.com>
> > ---
> > .../selftests/kvm/include/ucall_common.h | 8 ++------
> > .../testing/selftests/kvm/lib/aarch64/ucall.c | 13 +++----------
> > tools/testing/selftests/kvm/lib/riscv/ucall.c | 19 +++----------------
> > tools/testing/selftests/kvm/lib/s390x/ucall.c | 16 +++-------------
> > .../testing/selftests/kvm/lib/ucall_common.c | 19 +++++++++++++++++++
> > .../testing/selftests/kvm/lib/x86_64/ucall.c | 16 +++-------------
> > 6 files changed, 33 insertions(+), 58 deletions(-)
> >
> > diff --git a/tools/testing/selftests/kvm/include/ucall_common.h b/tools/testing/selftests/kvm/include/ucall_common.h
> > index 5a85f5318bbe..c1bc8e33ef3f 100644
> > --- a/tools/testing/selftests/kvm/include/ucall_common.h
> > +++ b/tools/testing/selftests/kvm/include/ucall_common.h
> > @@ -27,9 +27,10 @@ struct ucall {
> > void ucall_arch_init(struct kvm_vm *vm, void *arg);
> > void ucall_arch_uninit(struct kvm_vm *vm);
> > void ucall_arch_do_ucall(vm_vaddr_t uc);
> > -uint64_t ucall_arch_get_ucall(struct kvm_vcpu *vcpu, struct ucall *uc);
> > +uint64_t ucall_arch_get_ucall(struct kvm_vcpu *vcpu);
> >
> > void ucall(uint64_t cmd, int nargs, ...);
> > +uint64_t get_ucall(struct kvm_vcpu *vcpu, struct ucall *uc);
> >
> > static inline void ucall_init(struct kvm_vm *vm, void *arg)
> > {
> > @@ -41,11 +42,6 @@ static inline void ucall_uninit(struct kvm_vm *vm)
> > ucall_arch_uninit(vm);
> > }
> >
> > -static inline uint64_t get_ucall(struct kvm_vcpu *vcpu, struct ucall *uc)
> > -{
> > - return ucall_arch_get_ucall(vcpu, uc);
> > -}
> > -
> > #define GUEST_SYNC_ARGS(stage, arg1, arg2, arg3, arg4) \
> > ucall(UCALL_SYNC, 6, "hello", stage, arg1, arg2, arg3, arg4)
> > #define GUEST_SYNC(stage) ucall(UCALL_SYNC, 2, "hello", stage)
> > diff --git a/tools/testing/selftests/kvm/lib/aarch64/ucall.c b/tools/testing/selftests/kvm/lib/aarch64/ucall.c
> > index 1c81a6a5c1f2..d2f099caa9ab 100644
> > --- a/tools/testing/selftests/kvm/lib/aarch64/ucall.c
> > +++ b/tools/testing/selftests/kvm/lib/aarch64/ucall.c
> > @@ -78,24 +78,17 @@ void ucall_arch_do_ucall(vm_vaddr_t uc)
> > uint64_t ucall_arch_get_ucall(struct kvm_vcpu *vcpu, struct ucall *uc)
> > {
> > struct kvm_run *run = vcpu->run;
> > - struct ucall ucall = {};
> > -
> > - if (uc)
> > - memset(uc, 0, sizeof(*uc));
> >
> > if (run->exit_reason == KVM_EXIT_MMIO &&
> > run->mmio.phys_addr == (uint64_t)ucall_exit_mmio_addr) {
> > - vm_vaddr_t gva;
> > + uint64_t ucall_addr;
> >
> > TEST_ASSERT(run->mmio.is_write && run->mmio.len == 8,
> > "Unexpected ucall exit mmio address access");
> > memcpy(&gva, run->mmio.data, sizeof(gva));
> > - memcpy(&ucall, addr_gva2hva(vcpu->vm, gva), sizeof(ucall));
> >
> > - vcpu_run_complete_io(vcpu);
> > - if (uc)
> > - memcpy(uc, &ucall, sizeof(ucall));
> > + return ucall_addr;
> > }
> >
> > - return ucall.cmd;
> > + return 0;
> > }
> > diff --git a/tools/testing/selftests/kvm/lib/riscv/ucall.c b/tools/testing/selftests/kvm/lib/riscv/ucall.c
> > index b1598f418c1f..3f000d0b705f 100644
> > --- a/tools/testing/selftests/kvm/lib/riscv/ucall.c
> > +++ b/tools/testing/selftests/kvm/lib/riscv/ucall.c
> > @@ -51,27 +51,15 @@ void ucall_arch_do_ucall(vm_vaddr_t uc)
> > uc, 0, 0, 0, 0, 0);
> > }
> >
> > -uint64_t ucall_arch_get_ucall(struct kvm_vcpu *vcpu, struct ucall *uc)
> > +uint64_t ucall_arch_get_ucall(struct kvm_vcpu *vcpu)
> > {
> > struct kvm_run *run = vcpu->run;
> > - struct ucall ucall = {};
> > -
> > - if (uc)
> > - memset(uc, 0, sizeof(*uc));
> >
> > if (run->exit_reason == KVM_EXIT_RISCV_SBI &&
> > run->riscv_sbi.extension_id == KVM_RISCV_SELFTESTS_SBI_EXT) {
> > switch (run->riscv_sbi.function_id) {
> > case KVM_RISCV_SELFTESTS_SBI_UCALL:
> > - memcpy(&ucall,
> > - addr_gva2hva(vcpu->vm, run->riscv_sbi.args[0]),
> > - sizeof(ucall));
> > -
> > - vcpu_run_complete_io(vcpu);
> > - if (uc)
> > - memcpy(uc, &ucall, sizeof(ucall));
> > -
> > - break;
> > + return vcpu->vm, run->riscv_sbi.args[0];
> > case KVM_RISCV_SELFTESTS_SBI_UNEXP:
> > vcpu_dump(stderr, vcpu, 2);
> > TEST_ASSERT(0, "Unexpected trap taken by guest");
> > @@ -80,6 +68,5 @@ uint64_t ucall_arch_get_ucall(struct kvm_vcpu *vcpu, struct ucall *uc)
> > break;
> > }
> > }
> > -
> > - return ucall.cmd;
> > + return 0;
> > }
> > diff --git a/tools/testing/selftests/kvm/lib/s390x/ucall.c b/tools/testing/selftests/kvm/lib/s390x/ucall.c
> > index 114cb4af295f..f7a5a7eb4aa8 100644
> > --- a/tools/testing/selftests/kvm/lib/s390x/ucall.c
> > +++ b/tools/testing/selftests/kvm/lib/s390x/ucall.c
> > @@ -20,13 +20,9 @@ void ucall_arch_do_ucall(vm_vaddr_t uc)
> > asm volatile ("diag 0,%0,0x501" : : "a"(uc) : "memory");
> > }
> >
> > -uint64_t ucall_arch_get_ucall(struct kvm_vcpu *vcpu, struct ucall *uc)
> > +uint64_t ucall_arch_get_ucall(struct kvm_vcpu *vcpu)
> > {
> > struct kvm_run *run = vcpu->run;
> > - struct ucall ucall = {};
> > -
> > - if (uc)
> > - memset(uc, 0, sizeof(*uc));
> >
> > if (run->exit_reason == KVM_EXIT_S390_SIEIC &&
> > run->s390_sieic.icptcode == 4 &&
> > @@ -34,13 +30,7 @@ uint64_t ucall_arch_get_ucall(struct kvm_vcpu *vcpu, struct ucall *uc)
> > (run->s390_sieic.ipb >> 16) == 0x501) {
> > int reg = run->s390_sieic.ipa & 0xf;
> >
> > - memcpy(&ucall, addr_gva2hva(vcpu->vm, run->s.regs.gprs[reg]),
> > - sizeof(ucall));
> > -
> > - vcpu_run_complete_io(vcpu);
> > - if (uc)
> > - memcpy(uc, &ucall, sizeof(ucall));
> > + return run->s.regs.gprs[reg];
> > }
> > -
> > - return ucall.cmd;
> > + return 0;
> > }
> > diff --git a/tools/testing/selftests/kvm/lib/ucall_common.c b/tools/testing/selftests/kvm/lib/ucall_common.c
> > index 749ffdf23855..a060252bab40 100644
> > --- a/tools/testing/selftests/kvm/lib/ucall_common.c
> > +++ b/tools/testing/selftests/kvm/lib/ucall_common.c
> > @@ -18,3 +18,22 @@ void ucall(uint64_t cmd, int nargs, ...)
> >
> > ucall_arch_do_ucall((vm_vaddr_t)&uc);
> > }
> > +
> > +uint64_t get_ucall(struct kvm_vcpu *vcpu, struct ucall *uc)
> > +{
> > + struct ucall ucall;
> > + void *addr;
> > +
> > + if (!uc)
> > + uc = &ucall;
> > +
> > + addr = addr_gva2hva(vcpu->vm, ucall_arch_get_ucall(vcpu));
> > + if (addr) {
> > + memcpy(uc, addr, sizeof(*uc));
> > + vcpu_run_complete_io(vcpu);
> > + } else {
> > + memset(uc, 0, sizeof(*uc));
> > + }
> > +
> > + return uc->cmd;
> > +}
> > diff --git a/tools/testing/selftests/kvm/lib/x86_64/ucall.c b/tools/testing/selftests/kvm/lib/x86_64/ucall.c
> > index 9f532dba1003..24746120a593 100644
> > --- a/tools/testing/selftests/kvm/lib/x86_64/ucall.c
> > +++ b/tools/testing/selftests/kvm/lib/x86_64/ucall.c
> > @@ -22,25 +22,15 @@ void ucall_arch_do_ucall(vm_vaddr_t uc)
> > : : [port] "d" (UCALL_PIO_PORT), "D" (uc) : "rax", "memory");
> > }
> >
> > -uint64_t ucall_arch_get_ucall(struct kvm_vcpu *vcpu, struct ucall *uc)
> > +uint64_t ucall_arch_get_ucall(struct kvm_vcpu *vcpu)
> > {
> > struct kvm_run *run = vcpu->run;
> > - struct ucall ucall = {};
> > -
> > - if (uc)
> > - memset(uc, 0, sizeof(*uc));
> >
> > if (run->exit_reason == KVM_EXIT_IO && run->io.port == UCALL_PIO_PORT) {
> > struct kvm_regs regs;
> >
> > vcpu_regs_get(vcpu, &regs);
> > - memcpy(&ucall, addr_gva2hva(vcpu->vm, (vm_vaddr_t)regs.rdi),
> > - sizeof(ucall));
> > -
> > - vcpu_run_complete_io(vcpu);
> > - if (uc)
> > - memcpy(uc, &ucall, sizeof(ucall));
> > + return regs.rdi;
> > }
> > -
> > - return ucall.cmd;
> > + return 0;
> > }
> > --
> > 2.37.1.455.g008518b4e5-goog
> >