From: James Bottomley <[email protected]> If the SNP boot has a SVSM, probe for the vTPM device by sending a SVSM_VTPM_QUERY call (function 8). The SVSM will return a bitmap with the TPM_SEND_COMMAND bit set only if the vTPM is present and it is able to handle TPM commands at runtime.
If a vTPM is found, register a platform device as "platform:tpm" so it can be attached to the tpm_platform.c driver. Signed-off-by: James Bottomley <[email protected]> [CC] Used SVSM_VTPM_QUERY to probe the TPM Signed-off-by: Claudio Carvalho <[email protected]> [SG] Code adjusted with some changes introduced in 6.11 [SG] Used macro for SVSM_VTPM_CALL Signed-off-by: Stefano Garzarella <[email protected]> --- arch/x86/coco/sev/core.c | 64 ++++++++++++++++++++++++++++++++++++++++ 1 file changed, 64 insertions(+) diff --git a/arch/x86/coco/sev/core.c b/arch/x86/coco/sev/core.c index c5b0148b8c0a..ec0153fddc9e 100644 --- a/arch/x86/coco/sev/core.c +++ b/arch/x86/coco/sev/core.c @@ -21,6 +21,7 @@ #include <linux/cpumask.h> #include <linux/efi.h> #include <linux/platform_device.h> +#include <linux/tpm_platform.h> #include <linux/io.h> #include <linux/psp-sev.h> #include <linux/dmi.h> @@ -2578,6 +2579,51 @@ static struct platform_device sev_guest_device = { .id = -1, }; +static struct platform_device tpm_device = { + .name = "tpm", + .id = -1, +}; + +static int snp_issue_svsm_vtpm_send_command(u8 *buffer) +{ + struct svsm_call call = {}; + + call.caa = svsm_get_caa(); + call.rax = SVSM_VTPM_CALL(SVSM_VTPM_CMD); + call.rcx = __pa(buffer); + + return svsm_perform_call_protocol(&call); +} + +static bool is_svsm_vtpm_send_command_supported(void) +{ + struct svsm_call call = {}; + u64 send_cmd_mask = 0; + u64 platform_cmds; + u64 features; + int ret; + + call.caa = svsm_get_caa(); + call.rax = SVSM_VTPM_CALL(SVSM_VTPM_QUERY); + + ret = svsm_perform_call_protocol(&call); + + if (ret != SVSM_SUCCESS) + return false; + + features = call.rdx_out; + platform_cmds = call.rcx_out; + + /* No feature supported, it must be zero */ + if (features) + return false; + + /* TPM_SEND_COMMAND - platform command 8 */ + send_cmd_mask = 1 << 8; + + return (platform_cmds & send_cmd_mask) == send_cmd_mask; +} + static int __init snp_init_platform_device(void) { struct sev_guest_platform_data data; @@ -2593,6 +2639,24 @@ static int __init snp_init_platform_device(void) return -ENODEV; pr_info("SNP guest platform device initialized.\n"); + + /* + * The VTPM device is available only if we have a SVSM and + * its VTPM supports the TPM_SEND_COMMAND platform command + */ + if (IS_ENABLED(CONFIG_TCG_PLATFORM) && snp_vmpl && + is_svsm_vtpm_send_command_supported()) { + struct tpm_platform_ops pops = { + .sendrcv = snp_issue_svsm_vtpm_send_command, + }; + + if (platform_device_add_data(&tpm_device, &pops, sizeof(pops))) + return -ENODEV; + if (platform_device_register(&tpm_device)) + return -ENODEV; + pr_info("SNP SVSM VTPM platform device initialized\n"); + } + return 0; } device_initcall(snp_init_platform_device); -- 2.47.1
