Re: [kvm-unit-tests PATCH 1/1] s390x: stsi: Define vm_is_kvm to be used in different tests

[Claudio Imbrenda <imbrenda@linux.ibm.com>]

On Tue, 15 Feb 2022 11:46:32 +0100
Pierre Morel <pmorel@linux.ibm.com> wrote:

> Several tests are in need of a way to check on which hypervisor
> and virtualization level they are running on to be able to fence
> certain tests. This patch adds functions that return true if a
> vm is running under KVM, LPAR or generally as a level 2 guest.
> 
> To check if we're running under KVM we use the STSI 3.2.2
> instruction, let's define it's response structure in a central
> header.
> 

sorry, I had replied to the old series, let me reply here too


I think it would look cleaner if there was only one
"detect_environment" function, that would call stsi once and detect the
environment, then the various vm_is_* would become something like

bool vm_is_*(void)
{
	return detect_environment() == VM_IS_*;
}

of course detect_environment would also cache the result with static
variables.

bonus, we could make that function public, so a testcase could just
switch over the type of hypervisor it's being run on, instead of having
to use a series of ifs.

and then maybe the various vm_is_* could become static inlines to be put
in the header.

please note that "detect_environment" is just the first thing that came
to my mind, I have no preference regarding the name.

> Signed-off-by: Pierre Morel <pmorel@linux.ibm.com>
> ---
>  lib/s390x/stsi.h | 32 ++++++++++++++++++++++++++++
>  lib/s390x/vm.c   | 55 ++++++++++++++++++++++++++++++++++++++++++++++--
>  lib/s390x/vm.h   |  3 +++
>  s390x/stsi.c     | 23 ++------------------
>  4 files changed, 90 insertions(+), 23 deletions(-)
>  create mode 100644 lib/s390x/stsi.h
> 
> diff --git a/lib/s390x/stsi.h b/lib/s390x/stsi.h
> new file mode 100644
> index 00000000..bebc492d
> --- /dev/null
> +++ b/lib/s390x/stsi.h
> @@ -0,0 +1,32 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/*
> + * Structures used to Store System Information
> + *
> + * Copyright IBM Corp. 2022
> + */
> +
> +#ifndef _S390X_STSI_H_
> +#define _S390X_STSI_H_
> +
> +struct sysinfo_3_2_2 {
> +	uint8_t reserved[31];
> +	uint8_t count;
> +	struct {
> +		uint8_t reserved2[4];
> +		uint16_t total_cpus;
> +		uint16_t conf_cpus;
> +		uint16_t standby_cpus;
> +		uint16_t reserved_cpus;
> +		uint8_t name[8];
> +		uint32_t caf;
> +		uint8_t cpi[16];
> +		uint8_t reserved5[3];
> +		uint8_t ext_name_encoding;
> +		uint32_t reserved3;
> +		uint8_t uuid[16];
> +	} vm[8];
> +	uint8_t reserved4[1504];
> +	uint8_t ext_names[8][256];
> +};
> +
> +#endif  /* _S390X_STSI_H_ */
> diff --git a/lib/s390x/vm.c b/lib/s390x/vm.c
> index a5b92863..91acd05b 100644
> --- a/lib/s390x/vm.c
> +++ b/lib/s390x/vm.c
> @@ -12,6 +12,7 @@
>  #include <alloc_page.h>
>  #include <asm/arch_def.h>
>  #include "vm.h"
> +#include "stsi.h"
>  
>  /**
>   * Detect whether we are running with TCG (instead of KVM)
> @@ -26,9 +27,13 @@ bool vm_is_tcg(void)
>  	if (initialized)
>  		return is_tcg;
>  
> +	if (!vm_is_vm()) {
> +		initialized = true;
> +		return is_tcg;
> +	}
> +
>  	buf = alloc_page();
> -	if (!buf)
> -		return false;
> +	assert(buf);
>  
>  	if (stsi(buf, 1, 1, 1))
>  		goto out;
> @@ -43,3 +48,49 @@ out:
>  	free_page(buf);
>  	return is_tcg;
>  }
> +
> +/**
> + * Detect whether we are running with KVM
> + */
> +bool vm_is_kvm(void)
> +{
> +	/* EBCDIC for "KVM/" */
> +	const uint8_t kvm_ebcdic[] = { 0xd2, 0xe5, 0xd4, 0x61 };
> +	static bool initialized;
> +	static bool is_kvm;
> +	struct sysinfo_3_2_2 *stsi_322;
> +
> +	if (initialized)
> +		return is_kvm;
> +
> +	if (!vm_is_vm() || vm_is_tcg()) {
> +		initialized = true;
> +		return is_kvm;
> +	}
> +
> +	stsi_322 = alloc_page();
> +	assert(stsi_322);
> +
> +	if (stsi(stsi_322, 3, 2, 2))
> +		goto out;
> +
> +	/*
> +	 * If the manufacturer string is "KVM/" in EBCDIC, then we
> +	 * are on KVM.
> +	 */
> +	is_kvm = !memcmp(&stsi_322->vm[0].cpi, kvm_ebcdic, sizeof(kvm_ebcdic));
> +	initialized = true;
> +out:
> +	free_page(stsi_322);
> +	return is_kvm;
> +}
> +
> +bool vm_is_lpar(void)
> +{
> +	return stsi_get_fc() == 2;
> +}
> +
> +bool vm_is_vm(void)
> +{
> +	return stsi_get_fc() == 3;
> +}
> diff --git a/lib/s390x/vm.h b/lib/s390x/vm.h
> index 7abba0cc..3aaf76af 100644
> --- a/lib/s390x/vm.h
> +++ b/lib/s390x/vm.h
> @@ -9,5 +9,8 @@
>  #define _S390X_VM_H_
>  
>  bool vm_is_tcg(void);
> +bool vm_is_kvm(void);
> +bool vm_is_vm(void);
> +bool vm_is_lpar(void);
>  
>  #endif  /* _S390X_VM_H_ */
> diff --git a/s390x/stsi.c b/s390x/stsi.c
> index 391f8849..dccc53e7 100644
> --- a/s390x/stsi.c
> +++ b/s390x/stsi.c
> @@ -13,27 +13,8 @@
>  #include <asm/asm-offsets.h>
>  #include <asm/interrupt.h>
>  #include <smp.h>
> +#include <stsi.h>
>  
> -struct stsi_322 {
> -	uint8_t reserved[31];
> -	uint8_t count;
> -	struct {
> -		uint8_t reserved2[4];
> -		uint16_t total_cpus;
> -		uint16_t conf_cpus;
> -		uint16_t standby_cpus;
> -		uint16_t reserved_cpus;
> -		uint8_t name[8];
> -		uint32_t caf;
> -		uint8_t cpi[16];
> -		uint8_t reserved5[3];
> -		uint8_t ext_name_encoding;
> -		uint32_t reserved3;
> -		uint8_t uuid[16];
> -	} vm[8];
> -	uint8_t reserved4[1504];
> -	uint8_t ext_names[8][256];
> -};
>  static uint8_t pagebuf[PAGE_SIZE * 2] __attribute__((aligned(PAGE_SIZE * 2)));
>  
>  static void test_specs(void)
> @@ -91,7 +72,7 @@ static void test_3_2_2(void)
>  	/* EBCDIC for "KVM/" */
>  	const uint8_t cpi_kvm[] = { 0xd2, 0xe5, 0xd4, 0x61 };
>  	const char vm_name_ext[] = "kvm-unit-test";
> -	struct stsi_322 *data = (void *)pagebuf;
> +	struct sysinfo_3_2_2 *data = (void *)pagebuf;
>  
>  	report_prefix_push("3.2.2");
>