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Date:   Tue, 19 Jul 2022 16:42:28 +0200
From:   Andrew Jones <andrew.jones@linux.dev>
To:     Peter Gonda <pgonda@google.com>
Cc:     kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
        marcorr@google.com, seanjc@google.com, michael.roth@amd.com,
        thomas.lendacky@amd.com, joro@8bytes.org, mizhang@google.com,
        pbonzini@redhat.com
Subject: Re: [RFC V1 06/10] KVM: selftests: Consolidate boilerplate code in
 get_ucall()
Message-ID: <20220719144228.txirbh36ezv6fgrj@kamzik>
References: <20220715192956.1873315-1-pgonda@google.com>
 <20220715192956.1873315-8-pgonda@google.com>
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In-Reply-To: <20220715192956.1873315-8-pgonda@google.com>
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On Fri, Jul 15, 2022 at 12:29:52PM -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).
> 
> 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>
> 
> ---
>  tools/testing/selftests/kvm/Makefile          |  1 +
>  .../selftests/kvm/include/ucall_common.h      | 17 +++++++-
>  .../testing/selftests/kvm/lib/aarch64/ucall.c | 36 ++++-------------
>  .../selftests/kvm/lib/perf_test_util.c        |  2 +-
>  tools/testing/selftests/kvm/lib/riscv/ucall.c | 40 ++++---------------
>  tools/testing/selftests/kvm/lib/s390x/ucall.c | 37 ++++-------------
>  .../testing/selftests/kvm/lib/ucall_common.c  | 39 ++++++++++++++++++
>  .../testing/selftests/kvm/lib/x86_64/ucall.c  | 37 ++++-------------
>  8 files changed, 84 insertions(+), 125 deletions(-)
>  create mode 100644 tools/testing/selftests/kvm/lib/ucall_common.c
> 
> diff --git a/tools/testing/selftests/kvm/Makefile b/tools/testing/selftests/kvm/Makefile
> index 4d6753aadfa0..61e85892dd9b 100644
> --- a/tools/testing/selftests/kvm/Makefile
> +++ b/tools/testing/selftests/kvm/Makefile
> @@ -46,6 +46,7 @@ LIBKVM += lib/perf_test_util.c
>  LIBKVM += lib/rbtree.c
>  LIBKVM += lib/sparsebit.c
>  LIBKVM += lib/test_util.c
> +LIBKVM += lib/ucall_common.c
>  
>  LIBKVM_x86_64 += lib/x86_64/apic.c
>  LIBKVM_x86_64 += lib/x86_64/handlers.S
> diff --git a/tools/testing/selftests/kvm/include/ucall_common.h b/tools/testing/selftests/kvm/include/ucall_common.h
> index 98562f685151..cb9b37282701 100644
> --- a/tools/testing/selftests/kvm/include/ucall_common.h
> +++ b/tools/testing/selftests/kvm/include/ucall_common.h
> @@ -23,11 +23,24 @@ struct ucall {
>  	uint64_t args[UCALL_MAX_ARGS];
>  };
>  
> -void ucall_init(struct kvm_vm *vm, void *arg);
> -void ucall_uninit(struct kvm_vm *vm);
> +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);
> +void *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)
> +{
> +	ucall_arch_init(vm, arg);
> +}
> +
> +static inline void ucall_uninit(struct kvm_vm *vm)
> +{
> +	ucall_arch_uninit(vm);
> +}
> +
>  #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 0b949ee06b5e..9c124adbb560 100644
> --- a/tools/testing/selftests/kvm/lib/aarch64/ucall.c
> +++ b/tools/testing/selftests/kvm/lib/aarch64/ucall.c
> @@ -21,7 +21,7 @@ static bool ucall_mmio_init(struct kvm_vm *vm, vm_paddr_t gpa)
>  	return true;
>  }
>  
> -void ucall_init(struct kvm_vm *vm, void *arg)
> +void ucall_arch_init(struct kvm_vm *vm, void *arg)
>  {
>  	vm_paddr_t gpa, start, end, step, offset;
>  	unsigned int bits;
> @@ -64,37 +64,20 @@ void ucall_init(struct kvm_vm *vm, void *arg)
>  	TEST_FAIL("Can't find a ucall mmio address");
>  }
>  
> -void ucall_uninit(struct kvm_vm *vm)
> +void ucall_arch_uninit(struct kvm_vm *vm)
>  {
>  	ucall_exit_mmio_addr = 0;
>  	sync_global_to_guest(vm, ucall_exit_mmio_addr);
>  }
>  
> -void ucall(uint64_t cmd, int nargs, ...)
> +void ucall_arch_do_ucall(vm_vaddr_t uc)
>  {
> -	struct ucall uc = {
> -		.cmd = cmd,
> -	};
> -	va_list va;
> -	int i;
> -
> -	nargs = min(nargs, UCALL_MAX_ARGS);
> -
> -	va_start(va, nargs);
> -	for (i = 0; i < nargs; ++i)
> -		uc.args[i] = va_arg(va, uint64_t);
> -	va_end(va);
> -
> -	*ucall_exit_mmio_addr = (vm_vaddr_t)&uc;
> +	*ucall_exit_mmio_addr = uc;
>  }
>  
> -uint64_t get_ucall(struct kvm_vcpu *vcpu, struct ucall *uc)
> +void *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_MMIO &&
>  	    run->mmio.phys_addr == (uint64_t)ucall_exit_mmio_addr) {
> @@ -103,12 +86,7 @@ uint64_t get_ucall(struct kvm_vcpu *vcpu, struct ucall *uc)
>  		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 addr_gva2hva(vcpu->vm, gva);
>  	}
> -
> -	return ucall.cmd;
> +	return NULL;
>  }
> diff --git a/tools/testing/selftests/kvm/lib/perf_test_util.c b/tools/testing/selftests/kvm/lib/perf_test_util.c
> index 9618b37c66f7..14f88f3ffa80 100644
> --- a/tools/testing/selftests/kvm/lib/perf_test_util.c
> +++ b/tools/testing/selftests/kvm/lib/perf_test_util.c
> @@ -209,7 +209,7 @@ struct kvm_vm *perf_test_create_vm(enum vm_guest_mode mode, int nr_vcpus,
>  		perf_test_setup_nested(vm, nr_vcpus, vcpus);
>  	}
>  
> -	ucall_init(vm, NULL);
> +	ucall_arch_init(vm, NULL);

This change shouldn't be necessary since we have the ucall_init() wrapper
in ucall_common.h

>  
>  	/* Export the shared variables to the guest. */
>  	sync_global_to_guest(vm, perf_test_args);
> diff --git a/tools/testing/selftests/kvm/lib/riscv/ucall.c b/tools/testing/selftests/kvm/lib/riscv/ucall.c
> index 087b9740bc8f..37e091d4366e 100644
> --- a/tools/testing/selftests/kvm/lib/riscv/ucall.c
> +++ b/tools/testing/selftests/kvm/lib/riscv/ucall.c
> @@ -10,11 +10,11 @@
>  #include "kvm_util.h"
>  #include "processor.h"
>  
> -void ucall_init(struct kvm_vm *vm, void *arg)
> +void ucall_arch_init(struct kvm_vm *vm, void *arg)
>  {
>  }
>  
> -void ucall_uninit(struct kvm_vm *vm)
> +void ucall_arch_uninit(struct kvm_vm *vm)
>  {
>  }
>  
> @@ -44,47 +44,22 @@ struct sbiret sbi_ecall(int ext, int fid, unsigned long arg0,
>  	return ret;
>  }
>  
> -void ucall(uint64_t cmd, int nargs, ...)
> +void ucall_arch_do_ucall(vm_vaddr_t uc)
>  {
> -	struct ucall uc = {
> -		.cmd = cmd,
> -	};
> -	va_list va;
> -	int i;
> -
> -	nargs = min(nargs, UCALL_MAX_ARGS);
> -
> -	va_start(va, nargs);
> -	for (i = 0; i < nargs; ++i)
> -		uc.args[i] = va_arg(va, uint64_t);
> -	va_end(va);
> -
>  	sbi_ecall(KVM_RISCV_SELFTESTS_SBI_EXT,
>  		  KVM_RISCV_SELFTESTS_SBI_UCALL,
> -		  (vm_vaddr_t)&uc, 0, 0, 0, 0, 0);
> +		  uc, 0, 0, 0, 0, 0);
>  }
>  
> -uint64_t get_ucall(struct kvm_vcpu *vcpu, struct ucall *uc)
> +void *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 addr_gva2hva(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");
> @@ -93,6 +68,5 @@ uint64_t get_ucall(struct kvm_vcpu *vcpu, struct ucall *uc)
>  			break;
>  		}
>  	}
> -
> -	return ucall.cmd;
> +	return NULL;
>  }
> diff --git a/tools/testing/selftests/kvm/lib/s390x/ucall.c b/tools/testing/selftests/kvm/lib/s390x/ucall.c
> index 73dc4e21190f..0f695a031d35 100644
> --- a/tools/testing/selftests/kvm/lib/s390x/ucall.c
> +++ b/tools/testing/selftests/kvm/lib/s390x/ucall.c
> @@ -6,40 +6,23 @@
>   */
>  #include "kvm_util.h"
>  
> -void ucall_init(struct kvm_vm *vm, void *arg)
> +void ucall_arch_init(struct kvm_vm *vm, void *arg)
>  {
>  }
>  
> -void ucall_uninit(struct kvm_vm *vm)
> +void ucall_arch_uninit(struct kvm_vm *vm)
>  {
>  }
>  
> -void ucall(uint64_t cmd, int nargs, ...)
> +void ucall_arch_do_ucall(vm_vaddr_t uc)
>  {
> -	struct ucall uc = {
> -		.cmd = cmd,
> -	};
> -	va_list va;
> -	int i;
> -
> -	nargs = min(nargs, UCALL_MAX_ARGS);
> -
> -	va_start(va, nargs);
> -	for (i = 0; i < nargs; ++i)
> -		uc.args[i] = va_arg(va, uint64_t);
> -	va_end(va);
> -
>  	/* Exit via DIAGNOSE 0x501 (normally used for breakpoints) */
> -	asm volatile ("diag 0,%0,0x501" : : "a"(&uc) : "memory");
> +	asm volatile ("diag 0,%0,0x501" : : "a"(uc) : "memory");
>  }
>  
> -uint64_t get_ucall(struct kvm_vcpu *vcpu, struct ucall *uc)
> +void *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 &&
> @@ -47,13 +30,7 @@ uint64_t 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 addr_gva2hva(vcpu->vm, run->s.regs.gprs[reg]);
>  	}
> -
> -	return ucall.cmd;
> +	return NULL;
>  }
> diff --git a/tools/testing/selftests/kvm/lib/ucall_common.c b/tools/testing/selftests/kvm/lib/ucall_common.c
> new file mode 100644
> index 000000000000..c488ed23d0dd
> --- /dev/null
> +++ b/tools/testing/selftests/kvm/lib/ucall_common.c
> @@ -0,0 +1,39 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +#include "kvm_util.h"
> +
> +void ucall(uint64_t cmd, int nargs, ...)
> +{
> +	struct ucall uc = {
> +		.cmd = cmd,
> +	};
> +	va_list va;
> +	int i;
> +
> +	nargs = min(nargs, UCALL_MAX_ARGS);
> +
> +	va_start(va, nargs);
> +	for (i = 0; i < nargs; ++i)
> +		uc.args[i] = va_arg(va, uint64_t);
> +	va_end(va);
> +
> +	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 = 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 e5f0f9e0d3ee..ec53a406f689 100644
> --- a/tools/testing/selftests/kvm/lib/x86_64/ucall.c
> +++ b/tools/testing/selftests/kvm/lib/x86_64/ucall.c
> @@ -8,52 +8,29 @@
>  
>  #define UCALL_PIO_PORT ((uint16_t)0x1000)
>  
> -void ucall_init(struct kvm_vm *vm, void *arg)
> +void ucall_arch_init(struct kvm_vm *vm, void *arg)
>  {
>  }
>  
> -void ucall_uninit(struct kvm_vm *vm)
> +void ucall_arch_uninit(struct kvm_vm *vm)
>  {
>  }
>  
> -void ucall(uint64_t cmd, int nargs, ...)
> +void ucall_arch_do_ucall(vm_vaddr_t uc)
>  {
> -	struct ucall uc = {
> -		.cmd = cmd,
> -	};
> -	va_list va;
> -	int i;
> -
> -	nargs = min(nargs, UCALL_MAX_ARGS);
> -
> -	va_start(va, nargs);
> -	for (i = 0; i < nargs; ++i)
> -		uc.args[i] = va_arg(va, uint64_t);
> -	va_end(va);
> -
>  	asm volatile("in %[port], %%al"
> -		: : [port] "d" (UCALL_PIO_PORT), "D" (&uc) : "rax", "memory");
> +		: : [port] "d" (UCALL_PIO_PORT), "D" (uc) : "rax", "memory");
>  }
>  
> -uint64_t get_ucall(struct kvm_vcpu *vcpu, struct ucall *uc)
> +void *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 addr_gva2hva(vcpu->vm, (vm_vaddr_t)regs.rdi);
>  	}
> -
> -	return ucall.cmd;
> +	return NULL;
>  }
> -- 
> 2.37.0.170.g444d1eabd0-goog
>

Other than the ucall_init() wrapper comment

Reviewed-by: Andrew Jones <andrew.jones@linux.dev>