Re: [RFC PATCH v2 02/17] KVM: selftest: Add helper functions to create TDX VMs

[Isaku Yamahata <isaku.yamahata@xxxxxxxxx>]

On Tue, Aug 30, 2022 at 10:19:45PM +0000,
Sagi Shahar <sagis@xxxxxxxxxx> wrote:
...
> diff --git a/tools/testing/selftests/kvm/lib/x86_64/tdx_lib.c b/tools/testing/selftests/kvm/lib/x86_64/tdx_lib.c
> new file mode 100644
> index 000000000000..72bf2ff24a29
> --- /dev/null
> +++ b/tools/testing/selftests/kvm/lib/x86_64/tdx_lib.c
> @@ -0,0 +1,338 @@
> +// SPDX-License-Identifier: GPL-2.0
> +#include <linux/stringify.h>
> +#include "asm/kvm.h"
> +#include "tdx.h"
> +#include <stdlib.h>
> +#include <malloc.h>
> +#include "processor.h"
> +#include <string.h>
> +
> +char *tdx_cmd_str[] = {
> +	"KVM_TDX_CAPABILITIES",
> +	"KVM_TDX_INIT_VM",
> +	"KVM_TDX_INIT_VCPU",
> +	"KVM_TDX_INIT_MEM_REGION",
> +	"KVM_TDX_FINALIZE_VM"
> +};
> +
> +#define TDX_MAX_CMD_STR (ARRAY_SIZE(tdx_cmd_str))
> +#define EIGHT_INT3_INSTRUCTIONS 0xCCCCCCCCCCCCCCCC
> +
> +#define XFEATURE_LBR		15
> +#define XFEATURE_XTILECFG	17
> +#define XFEATURE_XTILEDATA	18
> +#define XFEATURE_MASK_LBR	(1 << XFEATURE_LBR)
> +#define XFEATURE_MASK_XTILECFG	(1 << XFEATURE_XTILECFG)
> +#define XFEATURE_MASK_XTILEDATA	(1 << XFEATURE_XTILEDATA)
> +#define XFEATURE_MASK_XTILE	(XFEATURE_MASK_XTILECFG | XFEATURE_MASK_XTILEDATA)
> +
> +
> +static void tdx_ioctl(int fd, int ioctl_no, uint32_t flags, void *data)
> +{
> +	struct kvm_tdx_cmd tdx_cmd;
> +	int r;
> +
> +	TEST_ASSERT(ioctl_no < TDX_MAX_CMD_STR, "Unknown TDX CMD : %d\n",
> +		    ioctl_no);
> +
> +	memset(&tdx_cmd, 0x0, sizeof(tdx_cmd));
> +	tdx_cmd.id = ioctl_no;
> +	tdx_cmd.flags = flags;
> +	tdx_cmd.data = (uint64_t)data;
> +	r = ioctl(fd, KVM_MEMORY_ENCRYPT_OP, &tdx_cmd);
> +	TEST_ASSERT(r == 0, "%s failed: %d  %d", tdx_cmd_str[ioctl_no], r,
> +		    errno);
> +}
> +
> +static struct tdx_cpuid_data get_tdx_cpuid_data(struct kvm_vm *vm)
> +{
> +	static struct tdx_cpuid_data cpuid_data;
> +	int ret, i;
> +
> +	if (cpuid_data.cpuid.nent)
> +		return cpuid_data;
> +
> +	memset(&cpuid_data, 0, sizeof(cpuid_data));
> +	cpuid_data.cpuid.nent = KVM_MAX_CPUID_ENTRIES;
> +	ret = ioctl(vm->kvm_fd, KVM_GET_SUPPORTED_CPUID, &cpuid_data);
> +	if (ret) {
> +		TEST_FAIL("KVM_GET_SUPPORTED_CPUID failed %d %d\n",
> +		    ret, errno);
> +		cpuid_data.cpuid.nent = 0;
> +		return cpuid_data;
> +	}
> +
> +	for (i = 0; i < KVM_MAX_CPUID_ENTRIES; i++) {
> +		struct kvm_cpuid_entry2 *e = &cpuid_data.entries[i];
> +
> +		/* TDX doesn't support LBR and AMX features yet.
> +		 * Disable those bits from the XCR0 register.
> +		 */
> +		if (e->function == 0xd && (e->index == 0)) {
> +			e->eax &= ~XFEATURE_MASK_LBR;
> +			e->eax &= ~XFEATURE_MASK_XTILE;
> +		}
> +	}
> +
> +	return cpuid_data;
> +}

CET also needs adjust.  How about the followings?

diff --git a/tools/testing/selftests/kvm/lib/x86_64/tdx_lib.c b/tools/testing/selftests/kvm/lib/x86_64/tdx_lib.c
index 1c3e47006cd2..123db9b76f82 100644
--- a/tools/testing/selftests/kvm/lib/x86_64/tdx_lib.c
+++ b/tools/testing/selftests/kvm/lib/x86_64/tdx_lib.c
@@ -25,7 +25,7 @@ char *tdx_cmd_str[] = {
 #define XFEATURE_MASK_XTILECFG (1 << XFEATURE_XTILECFG)
 #define XFEATURE_MASK_XTILEDATA        (1 << XFEATURE_XTILEDATA)
 #define XFEATURE_MASK_XTILE    (XFEATURE_MASK_XTILECFG | XFEATURE_MASK_XTILEDATA)
-
+#define XFEATURE_MASK_CET      ((1 << 11) | (1 << 12))
 
 static int __tdx_ioctl(int fd, int ioctl_no, uint32_t flags, void *data)
 {
@@ -72,12 +72,26 @@ static struct tdx_cpuid_data get_tdx_cpuid_data(struct kvm_vm *vm)
        for (i = 0; i < KVM_MAX_CPUID_ENTRIES; i++) {
                struct kvm_cpuid_entry2 *e = &cpuid_data.entries[i];
 
-               /* TDX doesn't support LBR and AMX features yet.
+               /* TDX doesn't support LBR yet.
                 * Disable those bits from the XCR0 register.
                 */
                if (e->function == 0xd && (e->index == 0)) {
                        e->eax &= ~XFEATURE_MASK_LBR;
-                       e->eax &= ~XFEATURE_MASK_XTILE;
+
+                       /*
+                        * TDX modules requires both CET_{U, S} to be set even
+                        * if only one is supported.
+                        */
+                       if (e->eax & XFEATURE_MASK_CET) {
+                               e->eax |= XFEATURE_MASK_CET;
+                       }
+                       /*
+                        * TDX module requires both XTILE_{CFG, DATA} to be set.
+                        * Both bits are required for AMX to be functional.
+                        */
+                       if ((e->eax & XFEATURE_MASK_XTILE) != XFEATURE_MASK_XTILE) {
+                               e->eax &= ~XFEATURE_MASK_XTILE;
+                       }
                }
        }

-- 
Isaku Yamahata <isaku.yamahata@xxxxxxxxx>